Roberts v Shimmin - [2024] NSWDC 171 - NSWDC 2023 case summary — Zoe

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Roberts v Shimmin

[2024] NSWDC 171

District Court of NSW|2023-06-09|Before: Bone Joint J, Mr J, Anz J

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At a glance

Source facts

Court

District Court of NSW

Decision date

2023-06-09

Before

Bone Joint J, Mr J, Anz J

Catchwords

(1999) 197 CLR 138 Mason v Demasi [2009] NSWCA 227 Medlin v State GIO (1995) 182 CLR 1
[1995] HCA 5 Onassis and Calogeropoulos v Vergottis [1968] 2 Lloyd's Rep 403 Rogers v Whitaker [1992] HCA 58
(1992) 175 CLR 479 Schneider v Hoechst Schering Agrevo Pty Ltd [2001] FCA 102
(2001) 50 IPR 555 South Western Sydney Local Health District v Gould [2018] NSWCA 69

Source

Original judgment source is linked above.

Catchwords

(1999) 197 CLR 138 Mason v Demasi [2009] NSWCA 227 Medlin v State GIO (1995) 182 CLR 1[1995] HCA 5 Onassis and Calogeropoulos v Vergottis [1968] 2 Lloyd's Rep 403 Rogers v Whitaker [1992] HCA 58(1992) 175 CLR 479 Schneider v Hoechst Schering Agrevo Pty Ltd [2001] FCA 102(2001) 50 IPR 555 South Western Sydney Local Health District v Gould [2018] NSWCA 69

Judgment (44 paragraphs)

[1]

K Yoshino, S Hagiwara, J Nakamura, T Tsukeoka, Y Tsuneizumi and S Ohtori "Intra-and interobserver reliability and agreement in three-dimensional computed tomography measurements of component positions after total knee arthroplasty", (2019) 26 The Knee 1102 M Saffi, S W Yong, M J Spangehi, H D Clarke, "Measuring Tibial Component Rotation Following TKA - What is the Best Method?" (2018) The Journal of Arhtroplasty, doi: https://doi.org/10/1016/j.arth.2018.10.022 S J MacDessi, W Griffith-Jones, I A Harris, J Bellermans and D B Chen, "Coronal Plane Alignment of the Knee (CPAK) classification" (2021) 103-B(2) Bone Joint J 329 Category: Principal judgment Parties: Susan Roberts (plaintiff) Andrew Shimmin (defendant) Representation: Counsel: Mr R O'Keefe with Ms Young (plaintiff) Mr J Downing SC (defendant)

[2]

[3]

JUDGMENT

The plaintiff, Susan Roberts, suffered an injury to her right knee in childhood. In her youth, she had multiple surgeries on her knee, culminating in a patellectomy, the removal of her right knee cap, in 1982. Some years later, in March 2012, Ms Roberts consulted the defendant, Dr Andrew Shimmin (now Associate Professor Shimmin), an orthopaedic surgeon in Melbourne. She sought treatment because she had been suffering increasing pain in her right knee over the previous few weeks.
After considering and attempting other treatments, Dr Shimmin ultimately performed a total knee replacement on Ms Roberts on 18 June 2012 ("the primary TKR"). Ms Roberts since suffered severe pain and loss of function in her knee, which she says was caused by the primary TKR. Eventually, a revision procedure was performed by Associate Professor Paul Stalley on 4 September 2018 ("the revision TKR"), which has stabilised her condition.
Ms Roberts says that the primary TKR was not performed with the requisite degree of care and skill, and that this failure has caused her pain, disability and loss. Specifically, she says that Dr Shimmin implanted the tibial component of the prosthesis in excessive rotation (that is, it was malrotated horizontally) and in excessive varus (that is, it was malaligned vertically), in circumstances where Dr Shimmin was aware that Ms Roberts was particularly vulnerable to error because she did not have a patella.
Dr Shimmin denies any breach of duty on his part and says, to the extent that Ms Roberts has suffered any ongoing pain, disability or loss, that is for reasons unconnected with the primary TKR. He says that the placement of the prosthesis was the intentional outcome of a clinical decision to attain a higher degree of functional alignment in accordance with widely accepted professional practice at the time. He denies that it was placed in excessive varus or excessive external rotation.
In determining whether Dr Shimmin is liable to Ms Roberts, and, if so, to what extent, it is necessary to consider the following issues: 1. What was the pre-operative condition of Ms Roberts' right knee; 2. How was the primary TKR conducted; 3. What was the condition of Ms Roberts' right knee following the primary TKR; 4. Did certain incidents in August 2016 cause injury to Ms Roberts' right knee; 5. What was the condition of Ms Roberts' right knee at the time of the revision TKR in September 2018; 6. Did Dr Shimmin breach his duty of care to Ms Roberts; 7. Has Dr Shimmin established a defence under s 59 of the Wrongs Act 1958 (Vic); 8. Was the condition of Ms Roberts' right knee, at the time of the revision TKR, caused by any breach of duty by Dr Shimmin; and 9. Is Ms Roberts entitled to damages for economic and non-economic loss.
For the reasons that follow, I have found that Dr Shimmin erred, and was in breach of his duty of care to Ms Roberts, in the performance of the primary TKR. I have also found that the breach of duty caused Ms Roberts pain, suffering, disability and economic loss, for which she is entitled to be compensated.

[4]

The anatomy of the knee

I have found it helpful to set out some of the basic elements of the anatomy of the knee, in respect of which I am indebted to the submissions of counsel and the evidence of the experts.
The knee is the largest joint in the body. It is a hinged joint that is subjected to substantial compressive loads. Its major movements are flexion and extension. It is comprised of three bones: the femur, the patella and the tibia. The femur and the tibia articulate to form the knee. There are condyles, akin to knuckles, at the distal end of the femur and at the proximal end of the tibia, which create notches through which the patellar tendon can pass.
The patellar tendon is an important structure, which commences at the distal end of the quadriceps muscles, extends over the joint and attaches at the tibial tubercle, a bony protuberance just below the anterior surface of the tibial condyles. The tendon tracks through the intercondylar notches at both the distal end of the femur and proximal end of the tibia. A knee may become unstable if the patellar tendon does not track precisely.
The patella is a sesamoid bone within the patellar tendon. It protects and stabilises the knee joint and its absence compromises knee function, increasing the risk of subluxation and dislocation.
The knee is a synovial joint with articular cartilage covering the bone surfaces and is contained within a synovial capsule. There are cartilaginous menisci which fill the space and support the joint.
Internal ligaments (the anterior cruciate and posterior cruciate ligaments) and external ligaments (the lateral collateral ligament and medial collateral ligament) connect the femur to the tibia. The extensor mechanism is formed by the quadriceps muscle and tendon, the patella, the patellar tendon and the ligaments that surround and help stabilise the knee.
In a TKR procedure of the type undergone by Ms Roberts in June 2012, the distal femur is cut and reshaped to accept a metal prosthetic femoral component. The tibial plateau (the surface of the proximal tibia) is also cut and reshaped to accept a metal prosthetic tibial component. A polyethylene disc is fixed to the tibial component and provides the surface upon which the femoral component articulates. The metal prosthetics are often cemented into place.
It is the placement of the tibial component in the primary TKR that is in issue in these proceedings. If it is placed at a 90 degree angle to the axis of the tibia, this is described as being in mechanical or neutral alignment. If it is raised on the lateral side (or the outside) of the knee, it is described as being in varus alignment, and if it is raised on the medial side (or inside) of the knee, it is described as being in valgus alignment. The extent of such varus or valgus alignment is measured in degrees from mechanical alignment.
Similarly, the tibial component of the prosthesis may be placed in a position of horizontal (or axial) rotation, that is, it is not placed in that degree of internal or external rotation considered to be neutral. This is less easily articulated than neutral alignment in the vertical (coronal and/or sagittal) planes.
Ms Roberts alleges that the tibial implant in the primary TKR was implanted in about 8 degrees of varus alignment and 8 degrees of external rotation. As a result, she says, there was maltracking of the patellar tendon, resulting in instability within the knee, hemosiderotic synovitis, hemarthrosis (bleeding into the knee joint), pain and disability.

[5]

Approach to evidence

Each of Ms Roberts and Dr Shimmin gave evidence. Although he has since been appointed an Associate Professor, without intending any disrespect, in these reasons I will continue to refer to the defendant as Dr Shimmin.
The Court also heard the evidence of experts called on behalf of each of the parties: Associate Professor Stalley, Dr Stephen Buckley and Mr Reece Jones gave evidence on Ms Roberts' behalf; Dr Myles Coolican and Dr Luba Eikens gave evidence on behalf of Dr Shimmin.
Ms Roberts presented as honest, intelligent, thoughtful, reasonable and not prone to exaggeration. She was an impressive witness, who made concessions where appropriate. It was not suggested that Ms Roberts' evidence was untruthful.
Senior Counsel for Dr Shimmin, however, submitted that I ought treat Ms Roberts' evidence with caution, particularly that evidence which addressed the condition of her knee in the period between the primary TKR, performed by Dr Shimmin, and the revision TKR, performed by Associate Professor Stalley. Senior Counsel referred me to the well-known passage in The Nominal Defendant v Cordin [2017] NSWCA 6 at [100] ff, in which Davies J surveyed approaches in the case law to assessing the evidence of honest witnesses whose evidence may, nevertheless, not be reliable. In particular, Senior Counsel referred me to Onassis and Calogeropoulos v Vergottis [1968] 2 Lloyd's Rep 403 at 431, where Lord Pearce stated: "… though he is a truthful person telling the truth as he sees it, did he register the intentions of the conversation correctly and, if so, has his memory correctly retained them? Also, has his recollection been subsequently altered by unconscious bias or wishful thinking or by overmuch discussion of it with others? Witnesses, especially those who are emotional, who think that they are morally in the right, tend very easily and unconsciously to conjure up a legal right that did not exist. … And lastly, although the honest witness believes he heard or saw this or that, is it so improbable that it is on balance more likely that he was mistaken? On this point it is essential that the balance of probability is put correctly into the scales in weighing the credibility of a witness. And motive is one aspect of probability. All these problems compendiously are entailed when a Judge assesses the credibility of a witness; they are all part of one judicial process. And in the process contemporary documents and admitted or incontrovertible facts and probabilities must play their proper part."
Dr Shimmin gave evidence as to the course of Ms Roberts' treatment, the primary TKR, his usual practice in performing TKR procedures, and his basis for adopting that practice. Like Ms Roberts, he was a careful and truthful witness who made appropriate concessions.
Dr Shimmin was at all times a highly regarded orthopaedic surgeon with particular expertise in hip and knee arthroplasty. He is a past president of the Australian Arthroplasty Society, a member of the International Hip Society, has published close to 100 peer-reviewed publications and given about 500 national and international presentations. He had many years' experience performing TKRs at the time of the primary TKR, likely having conducted about 1,500 such surgeries at the time of the primary TKR.
Dr Shimmin estimated that he had conducted about 1,000 further knee replacements and about 1,000 hip replacements in the period between performing the primary TKR on Ms Roberts and giving evidence in these proceedings.
Notwithstanding the submissions of counsel for Ms Roberts to the contrary, I accept that as at 2012, Dr Shimmin's professional focus was not on hip surgery to the exclusion of knee surgery and that he had extensive experience and expertise in knee arthroplasty.
Significantly, however, Dr Shimmin made the appropriate concession that, while he remembered Ms Roberts and her unusual condition in having undergone a patellectomy, he did not have any actual recollection of how he conducted the primary TKR or his pre- and post-operative consultations with Ms Roberts in 2012. He accepted that he had to reconstruct his account of the primary TKR and his consultations with Ms Roberts from his notes, reports and his recollection of his usual practice at the relevant time. The approach of Davies J in Nominal Defendant v Cordin, therefore, informs my assessment of his evidence, as it does that of Ms Roberts.
Evidence of usual practice can provide some evidence of what a doctor might have done on a particular occasion, even in the absence of an actual recollection. It is not, however, conclusive, and must be weighed with other evidence from which inferences are available: Dhupar v Lee (2022) 107 NSWLR 492 at [106], [151] per Brereton JA.
Counsel for Ms Roberts submitted that the present case is one where the procedure was not routine and, accordingly, evidence of usual practice does not assist. He referred me to Elayoubi v Zipser [2008] NSWCA 335, where Basten JA stated at [86]: "Evidence of usual practice may be of assistance in circumstances where mechanical steps or routine tasks are in issue and the witness who supposedly undertook the task on a particular occasion has no recollection of the occasion. The weight to be given to such evidence will depend upon the possibility or likelihood of departure from such practice. However, the present case was not concerned with a mechanical step or routine task: it was concerned with a quite unusual procedure in professional practice. Nor was the task itself in any sense mechanical: rather, it involved conveying important medical information to a patient in a hospital ward."
That passage concerned a finding that a treating obstetrician had failed to advise the plaintiff of the risks she faced if she were to have another child by vaginal delivery when her ability to do so had been compromised. Basten JA continued at [87]: "Properly understood, Dr Bhardwaj's evidence was a reconstruction of what she would have done on the particular occasion of which she had no memory, based on her professional expertise and understanding of the significance of the particular procedure which had been undertaken. Furthermore, in contrast to the issue with the content of the operation notes, there was express evidence from Mrs Kolled as to what was not said by Dr Bhardwaj."
Each of the experts who gave evidence approached their tasks in assisting the Court conscientiously and honestly. Counsel for Ms Roberts submitted that Dr Coolican slipped into advocacy in giving his evidence and, accordingly, the opinions he expressed, and observations he recorded, ought be given less weight. I will return to this issue when assessing the evidence as to the outcome of the primary TKR, breach of duty, accepted professional practice in 2012 and the cause of Ms Roberts' pain and disability following the primary TKR.
Further, where I am invited to consider the effect of the treating doctors' reports, particularly the reports of Drs David Broe and John Best, I am mindful of the approach taken by the Court of Appeal in Container Terminals Australia Ltd v Huseyin [2008] NSWCA 320. In that case, Basten JA (at [8]) explained the difficulty in discounting a plaintiff's oral testimony on the basis of accounts given to various health professionals which appear inconsistent with each other or with the plaintiff's oral testimony: "In the present case the appellant sought to challenge the acceptance of oral testimony of the plaintiff in part on the basis of inconsistent histories given to medical practitioners. The apparent inconsistencies were put to the plaintiff in cross-examination, without obtaining any significant concession. Her Honour was entitled to discount the inconsistencies, for reasons which might have been repeated, but which are too commonplace to require repetition. They include the following: (a) the medical practitioner who took the history was not cross-examined about the accuracy of what was recorded (often, for good reason, because it is unlikely that he or she will have any real recollection of the circumstances in which the record was made); (b) medical histories were taken in furtherance of a purpose which is not identical with the purpose of establishing liability in tort; (c) the histories did not make reference to the questions which elucidated the replies; (d) the material recorded was a summary of answers rather than a verbatim recording, and (e) there may be a range of factors, including fluency in English, the practitioners knowledge of the background circumstances of the accident and the patient's understanding of the purpose of the question, which will affect the content of the history." In this regard, see also Mason v Demasi [2009] NSWCA 227.
It might be also noted that when considering all medical records (including those of Dr Shimmin), that they are not intended as a verbatim transcript of consultations or a movement by movement record of the manner in which particular procedures were carried out: Bruce v Kaye [2004] NSWSC 277.
Finally, and more generally, where a fact is in issue, a plaintiff must demonstrate that the circumstances raise a more probable inference in favour of the fact alleged: Transport Industries Insurance Co v Longmuir [1997] 1 VR 125. The process of fact finding should be informed as far as possible on the basis of contemporary materials, objectively established, and the apparent logic of events: Fox v Percy (2003) 214 CLR 118 at [30]-[31]. Where proof of a fact is required: "the tribunal must feel an actual persuasion of its occurrence or existence before it can be found. It cannot be found as a result of a mere mechanical comparison of probabilities independently of any belief in its reality": Helton v Allen (1940) 63 CLR 691 at 712; Briginshaw v Briginshaw (1938) 60 CLR 336 at 361.
All evidence, including documentary evidence, must be submitted to rational analysis, including with respect to the drawing of inferences, having regard to the whole of the evidence and the conduct of the trial: State Rail Authority (NSW) v Earthline Constructions Pty Ltd (In Liq) [1999] HCA 3 at [63], [94], [149] and [155].

[11]

2012 to 2013

After the primary TKR, according to his usual practice concerning a multiply-operated knee, Dr Shimmin prioritised wound healing over mobility.
Dr Shimmin reviewed short leg x-rays of Ms Roberts' knee taken on 21 June 2012. As he did not change his post-operative treatment of Ms Roberts, in his evidence Dr Shimmin inferred that in the immediate post-operative period he was happy with the alignment and bone implant interface. The x-rays themselves were not before the Court and Dr Shimmin's views were not documented at the time.
Ms Roberts' wound healed well and, after a period of immobilisation for the purpose of wound and arthrotomy healing, she progressed through physiotherapy. However, the period of immobilisation contributed to the onset of fibrosis or adhesions between the layers in the knee. This required a manipulation under anaesthetic, which Dr Shimmin performed on 23 August 2012, also at Glenferrie Private Hospital.
Following the manipulation, Ms Roberts experienced some improvement in flexion in her knee. While improving, in her oral evidence Ms Roberts described her return to function as poor in that her range of motion was limited and the knee still could not weight bear. She continued to receive physiotherapy into 2013 and continued to use at least one crutch until at least the time when she saw Dr Best in March 2013.
In late 2012, Ms Roberts and her family returned to Sydney. Knowing that she would soon be moving back to Sydney, Ms Roberts brought forward what would have been her annual review with Dr Shimmin and saw him on 10 December 2012. Her knee was still delicate and painful, she still used a mobility aid as the knee was not strong enough to weight bear and she was experiencing a flicking sensation over her knee. Flexion of the knee continued to improve.
In a contemporaneous file note of the 10 December 2012 consultation, Dr Shimmin noted that they had discussed the flicking of the scar tissue that takes the place of the patella over the femoral component groove. He described this as common, but that it needed to be monitored.
After her return to Sydney, Ms Roberts saw her general practitioner, Dr Felicity Minogue, with whom she discussed a catching sensation in her knee. Dr Minogue referred her to Dr Best, a sports physician, whom she saw in March 2013.
On 20 March 2013, Dr Best recorded, in his report to Dr Minogue, that Ms Roberts' main problem was insecurity of the knee and that she had suffered an acute episode of pain with rotation the previous month. Dr Best recorded a number of observations in his report, the forensic effect of which is the subject of dispute. He noted that Ms Roberts had an unrehabilitated right knee/thigh and that her co-contraction ability was extremely poor with a combination of quadriceps deficiency, hamstring weakness and gluteal dysfunction. He recorded minor patellofemoral change. Dr Best said that a repeat x-ray did not reveal "any abnormality regarding any hint of malalignment or loosening" of the prosthesis.
On 17 May 2013, Dr Best recorded that Ms Roberts was no longer using a walking stick in crowded areas, her walking was more comfortable, her strength was improving and her quadriceps size was increasing.
In a report dated 19 July 2013, Dr Best recorded that Ms Roberts had reduced pain, improved function and improved strength in her knee.
Dr Best was not called as a witness and there are significant aspects of his consultations with, and examination of, Ms Roberts which are not apparent on the face of his reports. In particular, there was no evidence as to how Dr Best conducted his examination of Ms Roberts' knee. Similarly, it is not clear which x-rays he was referring to, whether he examined the x-rays themselves or a radiographer's report, or what, if any, standard of alignment he used as a benchmark against which malalignment could be assessed. He did not expressly refer to axial rotation. Although he noted "insecurity", it is unclear whether he examined for instability of the patellar tendon or whether this is what he meant by reference to "insecurity". Dr Best did not report that Ms Roberts was pain-free.
Ms Roberts undertook the physiotherapy recommended by Dr Best and noticed a considerable improvement in the condition of her knee over the following months.
Ms Roberts said, in evidence, that while her condition improved over this period and the knee had very few symptoms, if she kept it in a state of flexion of 90 degrees or less for a prolonged period of time, it could become painful. She was, however, able to walk for much longer distances and was very confident with the knee. She was, by then, able to cycle, but her walking was still, nevertheless, limited.
Ms Roberts also gave extensive evidence of the instability that she experienced from 2013 to the revision TKR in 2018, and its effect on her day to day life. Ms Roberts described the condition of her right knee in the latter part of 2013 as requiring her to guard against putting weight on it or pivoting on it in certain circumstances, that she was hypervigilant about being knocked over when in crowded places, that she took particular care in ascending or descending stairs, and that she took care to avoid a number of movements that involved putting weight on her right knee. Her evidence included the following: "An example would be a movement that required me to pivot on my right leg or place the majority of my body weight on my right leg. For instance, in getting out of the drivers seat of a car, I wouldn't stick my right leg out and then move from that position, I would turn my whole body so that both my legs were then placed outside the vehicle and then I would alight from the vehicle. Other situations where I was aware of it or concerned about it, was in - after I had been off the knee for a period of time, perhaps in bed or - or sitting, and then went to mobilise on the knee, it - it felt like it had relaxed, I guess, given that I had been relaxing and didn't feel particularly stable and it would take it a period of time to warm up once I then started to mobilise. I was fearful of being knocked over or of being jostled. So, in crowds I was concerned that if I was knocked I could - I wouldn't be able to rely on my right knee to stabilise me and that it might give way so I would often - I'd be very hyper‑vigilant about that or hang onto someone if they were with me. Going down stairs in certain situations even if I was holding onto a handrail, again if there were crowds around I'd want the stability of holding onto someone or I would descend or even ascend the stairs by placing both my feet on the same step as I'd go up. … Always leading with my left leg also. And another situation that I found challenging was turning around or - or being off my - my centre of gravity, I guess. So, I - in turning around perhaps to speak to someone I would move my whole body around rather than turning and keeping my - my legs in a different direction or facing forward. I also found it challenging in terms of my work with the - with NCAT, using a wheelie bag which would have been my preferred way to carry heavy documents because in terms of having an arm, whichever arm it was, behind me pulling something I wasn't confident in that situation in terms of the stability of my knee and I experimented with a range of backpacks to avoid that problem. The other thing that I did is I predominantly during those - that period from 2012 to, it would have been after I recovered from the revision, I would drive an automatic car mainly with my left leg. Sometimes accelerating with my right but being concerned that that movement between the break - the accelerator and the break [brake] - be concerned that the - the stability of my knee was such that I might not be able to execute that smoothly and not wanting to take any risks in doing that. The other thing that I noticed was that for a period - for about eight, 9 months after the first replacement my right knee would hurt and have a - a strange loosening sensation when I was driving and went over speed bumps. And so I would place my hand on my right knee and hold it as I went over bumps or went over a bumpy road. The pain - discomfort resulting from that stopped when in the course probably towards, you know, the second half of 2013 but the very odd sensation which I described as a 'rattling sensation' continued right up until the revision. I actually thought that's just what happens when you have a knee‑joint replacement, I didn't realise that it didn't - it would stop when I had the other one [the revision TKR]. …. If I was unable to get a seat on a - a bus or a train and therefore was standing and swaying with the movement of the form of transport, my - my knee would feel unstable. I was un - I was - was lacking in confidence as to its ability to support me and I would hang on very tightly and I would put the majority of - more than the - 80% of my body weight through my left leg so that I wasn't relying upon my right leg."
Ms Roberts' evidence is not contradicted by the contemporaneous reports of Dr Best in early to mid-2013. The condition of her knee was improving and pain was reducing but it was not pain-free at that time.
In cross-examination, Ms Roberts accepted that by October 2013, she was entirely pain-free, that she was able to walk at a good pace and was able to go about her activities of daily living without any problems with her knee.
On 23 October 2013, Ms Roberts sent an email to Dr Shimmin, as a courtesy, to let him know how she was progressing in circumstances where she was unable to travel to Melbourne to attend a scheduled consultation. In the email, she stated: "Dear Andrew, I feel very guilty that I have not come down from Sydney to see you for my check up but I don't want any more time to go by without letting you know just how brilliantly my new knee is working out. I think you would have heard from Dr John Best in Sydney that while I was still on a stick in March this year, some intense work since then with a rehab physio saw me progress in leaps and bounds. The knee is now strong, can fully straighten and bend (130 degrees on a good day!) and is pain free. I am now able to walk around Centennial Park (3.8 km) non stop at a good clip as well as go about every day activities without really thinking about it. I am so grateful for all your skill and professionalism in getting me through the trials of last year and for the care and compassion you showed me. While there really is no need for me to now think about the knee every day, I still do in wonderment that I have ended up with it working this well and with gratitude for you helping me to get to this point. I will certainly try to pop in one time I am down to show it off but in the meantime thank you so much for giving back me the functionality that this time last year still looked a long long way off. regards Susan".
Senior Counsel for Dr Shimmin submitted that Ms Roberts' evidence as to her condition in and from 2013 was contradicted by her 23 October 2013 email and the reports of Dr Best. Accordingly, it was submitted that her evidence ought not be accepted, by adoption of the approach in Onassis and Calogeropoulos v Vergottis, set out at paragraph 20 above. Further, it was submitted on behalf of Dr Shimmin that the approach in Fox v Percy mitigated against acceptance of Ms Roberts' evidence.
The approach in Container Terminals Australia Ltd v Huseyin requires that care must be taken in drawing conclusions from Dr Best's reports. In particular, it is not clear what questions were asked of Ms Roberts and, critically, how any examination of her knee was undertaken. Given the significance placed by Dr Shimmin on the absence of findings of loosening or malalignment of the prosthesis, the reliability of such findings is open to considerable doubt.
I accept that Ms Roberts' 23 October 2013 email indicates that she had no complaints at all about the condition of her knee and that it accurately records that, at the time, the knee was pain-free, she had recovered strength, mobility, functionality and she did not need to think about it every day. Plainly, she was very happy with it.
In my view, however, whether or not Ms Roberts was subjectively happy with her knee in October 2013 is not conclusive of whether or not she continued to have sensations of instability and pain on prolonged flexion. Ms Roberts' evidence before me went primarily to activities and circumstances which are not expressly addressed in her email to Dr Shimmin. Further, Ms Roberts explained her state of mind when sending the 23 October 2013 email as follows: "The knee, or my knee, following the revision with Associate Professor Stalley feels much more stable, secure, strong than it did following the primary knee replacement up until having the revision done, or - or perhaps a period after that, given that I was very raw from the revision, but yes, there's - there's a considerable difference in the way the knee feels. … The difference has highlighted for me that what I thought was a pretty good outcome in 2014, 2015, up to August 2016, in terms of the primary replacement, and was as good as it might be given my patellectomy, I've realised that it wasn't as good as it could be, and that I was dealing with something that was - felt a lot more unstable and less reliable than I have now."
This was characterised by Senior Counsel for Dr Shimmin as a contrast. It was submitted on Dr Shimmin's behalf that it was difficult to accept that Ms Roberts would not have sought some medical attention if she was experiencing the difficulties she described.
The submission made on Dr Shimmin's behalf had some force. I accept that Ms Roberts was generally positive about the condition of her knee. However, there are two factors which I consider affect the weight of her own, subjective assessment of the condition of her knee.
First, Ms Roberts had accepted that she would have inevitable limitations with respect to her knee, and her expectations were correspondingly constrained. Indeed, Dr Shimmin had told her that she would never have a perfect knee and this, no doubt, conditioned her expectation as to how good it could be.
Secondly, Ms Roberts did not have a point of comparison against which she could assess the condition of her knee following the primary TKR until the revision TKR. As she stated in her evidence, it was only in the light of her subsequent condition that it was possible for her to assess the condition of her knee after the primary TKR. I do not see the correspondence as incompatible with her evidence understood in this context.
Accordingly, I accept both Ms Roberts' above description of her condition and her explanation for the terms of her 23 October 2013 email. I accept that she continued to suffer from instability and pain on prolonged flexion up to and beyond the time of the 23 October 2013 email.

[12]

2014 to 2016

In late 2013, Ms Roberts applied for a position as a part-time senior legal member of the Guardianship Tribunal, to which she was appointed in 2014, and transitioned from the Guardianship Tribunal to the Guardianship Division of NCAT on the latter tribunal's establishment.
The nature of Ms Roberts' appointment required her to hear matters whilst seated with her right knee flexed for lengthy periods of time. Whilst seated, her thigh was parallel with the floor and her lower leg perpendicular to it. Her knee joints were at an angle of approximately 90 degrees. This appears to have been the first circumstance, following the primary TKR, when Ms Roberts was required to remain seated for extended periods, placing her in a position that did not exist when she sent her email to Dr Shimmin on 23 October 2013.
Nevertheless, between the second half of 2013 and 2016, Ms Roberts did not consult with any medical practitioners in relation to her right knee. In an email to Dr Shimmin's rooms on 31 August 2016, Ms Roberts said that everything had been going well until incidents that occurred that month. I consider that Ms Roberts' 31 August 2016 email must be read in the same light as her 23 October 2013 email, for the reasons set out above.
Ms Roberts developed significant right knee symptoms on three occasions in August 2016. First, while she was walking her dog down a slight incline, her dog pulled on its leash and, as she went to brace, she felt a pain in her knee. She was, however, able to complete the walk. At the end of the walk, there was some swelling, but it was gone by the next day and that pain did not recur.
About a week later, Ms Roberts suffered a second incident when she attended an AFL match at the Sydney Cricket Ground. As she was walking down the stairs at the end of the game, she felt pain, unsteadiness and discomfort in her knee. She was able to finish walking down the stairs and those feelings passed.
Finally, the next day, 28 August 2016, Ms Roberts went on a coastal walk with friends and her dog. As she walked down some stairs, she felt a pain in her knee which became hot, very swollen and extremely painful. There is no suggestion that her dog pulled on its lead or that she had to brace prior to experiencing the sensation on the third occasion.
Following the third incident, Ms Roberts attended on Dr Minogue, again on crutches. Ms Roberts was referred to Dr Best. Ms Roberts' evidence of the consultation, which I accept, was: "Q. At that time, what was your knee like - your right knee like? A. It was still extremely swollen. It felt - it was very difficult to move it - to move my leg without using my hands. And it was extremely painful, and felt very unstable. Q. What do you mean by 'unstable'? A. A feeling that even in using my hands to lift my leg, I had to use my hands to brace it because any slight movement in moving it was going to - well - hurt very much. But also, it - it - it just felt so compromised in terms of its stability. Q. Did - no. Withdraw that. When you went and saw Dr Best, do you recall - did he examine the right knee or right leg? A. I recall sitting on the - the - the side - the - the long side of his examination table, and him asking me if I could straighten my leg. Q. Did you try - A. My right leg. Q. Did you try and do that? A. I tried to and I - I couldn't do it independently. Q. Do you remember: did Dr Best send you for any investigations? A. After the - he gave me a referral to - for an ultrasound, which I had after I saw him. Q. Did he say anything to you during that consultation about the cause for the symptoms and abnormalities for which you had presented? A. Yes. He expressed considerable concern. And he said, 'I think you've ruptured your patella tendon'. And he - sorry. Do you want-- Q. Did he say anything else to you during that consultation? A. He did. He said, 'I think you need to see an orthopaedic surgeon, because you may need to have it repaired - if that's what's occurred'. I said words to the effect of, 'Who would you suggest?' And he said, 'I think David Broe at Prince of Wales Private'. And he, in fact, rang Dr Broe on speakerphone while I was in the rooms with him."
In his subsequent report to Dr Minogue, Dr Best expressed the view that she had disrupted her extensor mechanism (relevantly, her patellar tendon) and said that she had a large hemarthrosis with an extensor lag. Dr Best recorded that Ms Roberts had done very well with her rehabilitation since he had last seen her, and that she suffered "a prodrome [early symptom] of right knee ache some 10 days ago and, 3 days ago, without any major injury, she felt acute discomfort in the knee and a feeling of lack of control". Dr Best consulted x-rays, which excluded peri-prosthesis loosening. The ultrasound, however, suggested to Dr Best that Ms Roberts' tendons were intact.
At Ms Roberts' request, Dr Shimmin provided Ms Roberts' medical information to her to be provided to Dr Broe, an orthopaedic hip and knee surgeon, whom she saw on 9 September 2016.
Dr Broe recorded: "… she underwent total knee replacement in 2012 in Melbourne. She was told that Dr Shimmin was concerned regarding the integrity of her anterior scar tissue. She was kept in knee extension for a period following surgery. As would be expected she stiffened and did require a manipulation under anaesthesia. Her initial recovery was a little slower over the first 6 to 9 months however she turned a corner and for the last few years she has had no problems with her knee and has got back to her more normal life. She has been very happy with her knee replacement. Two weeks ago she was walking the dog down a slope. She felt a sudden pull from the dog and she felt a sharp pain anteriorly over her knee. The pain was across her patella tendon and at the tibial tuberosity. The knee swelled. It felt uncomfortable however it then settled. A couple of days later she was at the Sydney cricket ground watching the Sydney Swans. She climbed a number of stairs and following that she also noted recurrent stiffness and swelling. It then settled. A few days later she was walking downstairs on a coastal walk. It became very swollen and tender once again. She felt her knee give way. When I initially saw her.[sic] She was able to straight leg raise. She is able to straight leg raise against resistance and has a grade 4 to 5 quadriceps power. This reassured me and I also got my colleague Dr Solomon to review her and concur these findings. She was very tender over the mid-patella tendon and at the level of the tibial tuberosity. Her x-ray was well-maintained. There is no evidence of loosening. Her ultrasound did shall [sic - show] partial tears of the extensor mechanism at the level of the tibial tuberosity."
Ms Roberts was cross-examined as to the history taken by Dr Broe, which varied from her account before the Court in some respects. Bearing in mind the approach commended in Container Terminals Australia v Huseyin, and my general acceptance of Ms Roberts as a reliable witness, I do not consider that Dr Broe's record of her history derogates from my reliance on Ms Roberts' evidence as to the condition of her knee or the circumstances that affected her condition.
Ms Roberts recalled the consultation. Her evidence, which I accept, was that Dr Broe examined her knee gently, because of the extreme pain she was still suffering, while she was sitting in a chair next to his desk. He did so whilst also sitting in a chair, which he wheeled over to her, and did not examine her on an examination table. He sought and obtained the views of a colleague, Dr Michael Solomon, who examined her in the same way.
Ms Roberts commenced wearing a brace on her right leg, which she wore for at least four weeks. Dr Broe recommended conservative treatment with the use of a range of motion knee splint (or brace). Thereafter, the knee became more functional, particularly with the support of the brace. Ms Roberts switched to one crutch, rather than two, over the course of the month of September 2016.
Dr Broe saw Ms Roberts again on 7 October 2016. He noted that much of the pain and tenderness around her patellar tendon had resolved. Ms Roberts reported that she was still suffering pain, which he described as lateral retinaculum pain (i.e. pain in a band of thickened deep fascia around tendons on the lateral side of the knee), and a catching sensation as she transitioned from full knee extension to initial flexion. Dr Broe thought the underlying scar tissue might be catching on the femoral implant. Ms Roberts reported that by then the pain was minimal and that she was able to straight leg raise. She could resume her normal day to day activities. Dr Broe thought the catching sensation might mean a knee arthroscopy could be considered.
Dr Broe's report addresses questions of flexion, extension and acute symptoms. Questions of stability were not expressly addressed. Similarly, as was the case with Dr Best's examination, the examination of Ms Roberts' knee did not appear to have been either robust or directed to establishing the degree of the knee's stability. Ms Roberts was not examined by either Dr Best or Dr Broe lying flat on an examination table in 2016.
Between October 2016 and June 2018, however, Ms Roberts' knee felt less stable and less strong. She was less confident with her knee and fearful that the events of 28 August 2016 could recur. She was conscious of instability. She was also conscious that her knee, when flexed or when she was in a sitting position, became painful in a shorter period of time - about 20 minutes - than it had prior to August 2016. This occurred while she was conducting hearings at NCAT, where leg space behind the desk was sometimes compromised by audio boxes or a modesty board, or at the movies. Ms Roberts described the level of pain as annoying, but not sufficient to affect her work in any significant way.
Following the August 2016 episodes, Ms Roberts was unable to sit at NCAT for a number of days. Her best recollection, which I accept as reasonably accurate, is that she lost about 10 to 12 days' work at the then daily NCAT rate for part-time senior Tribunal members.

[13]

Episodes in 2018

No further acute episode was experienced until 2018.
On 7 April 2018, while standing at a checkout register at a grocery store, Ms Roberts developed pain, heat, tingling and swelling in her right knee. She could not weight bear on that knee. She consulted Dr Minogue and returned to wearing a knee brace and using crutches. Over the following weeks, there was slight improvement and, by June 2018, she was usually using only one crutch.
On 8 June 2018, while swinging her right leg to get out of bed in the morning, Ms Roberts felt a sudden onset of pain and swelling. The pain was extreme. She was unable to weight bear on her right leg. A few days later, Ms Roberts again saw Dr Broe, who diagnosed a knee effusion and restricted range of motion. An ultrasound confirmed that Ms Roberts was suffering from a large hemarthrosis.
The pain and swelling in Ms Roberts' knee increased. Ms Roberts was referred to Dr Broe, who aspirated 70 ml of blood from her knee. Steps were taken to discount the risk of infection and a review date four weeks hence was set.
Prior to that date, however, Ms Roberts experienced another episode of the knee becoming extremely painful, swollen and hot. On 22 June 2018, her knee was re-aspirated. Dr Broe referred Ms Roberts to Dr Tim Brighton, the Head of Hematology at Prince of Wales Hospital, and she also made contact with Dr Jim Bertouch, a rheumatologist, who had been treating her for another immune-related condition. Dr Brighton and Dr Bertouch, respectively, excluded bleeding and immune disorders. Dr Broe also arranged for CT scans to be conducted. Ms Roberts' knee was still very tender, painful and difficult to straighten or flex. She could not weight bear on it.
Dr Brighton expressed the view that Ms Roberts was likely suffering chronic pigmented villonodular synovitis (PVNS). In this respect, he mentioned the team at Royal Prince Alfred Hospital (RPA), which was led by Associate Professor Stalley. Ms Roberts knew that a childhood family friend of hers, Dr Amanda Stalley, was married to Associate Professor Stalley, and when she called Dr Stalley, asking who she could get in touch with at RPA, Dr Stalley brought her husband into the conversation and he offered to see Ms Roberts himself.

[14]

Ms Roberts makes contact with Associate Professor Stalley

Ms Roberts attended on Associate Professor Stalley at his home on 8 July 2018. She presented in considerable pain and was unable to walk without aids. Associate Professor Stalley considered her history of a painful, recurrently swollen knee with multiple episodes of giving way and instability, as well as her presentation. He looked at x-rays and scans that Ms Roberts had brought with her by holding them up to the light of an open window. He vigorously examined her knee. His initial view was that she was suffering from instability and recurvatum (backward bending) of the knee of 10 degrees. The images suggested to him that there was some malrotation of the components implanted in the primary TKR.
Associate Professor Stalley made contemporaneous notes, but also had a clear recollection of that first consultation when giving his evidence. On observing Ms Roberts, he formed the view that she was grossly malaligned.
On 8 July 2018, Associate Professor Stalley wrote to Ms Roberts, confirming what had been discussed at their consultation: "Dear Suzi, … It would appear that you have a painful total knee replacement on the right side, and causes of your pain could be multiple. It may be due to the malalignment of the components, although many knees can be quite malaligned and have no symptoms. It could also be due to tendomalacia which is the situation that can develop after chondromalacia, where the knee cap has been removed, and leaving only a tender knee and undergoes degenerative wear and tear changes. The third thing is that you could have infection in this knee, and that has not been ruled out to my satisfaction, unfortunately."
In his letter of 8 July 2018, Associate Professor Stalley went on to describe a course of further investigations which he regarded as necessary to identify and isolate the cause of Ms Roberts' knee pain. He arranged for investigations to exclude infection or other possible causes of the symptoms. In due course, those investigations discounted the possibility of infection.
On 7 July 2021, Associate Professor Stalley retrospectively dictated a file note relating to his initial consultation with Ms Roberts on 8 July 2018. In that file note, he stated: "She had had, in her presentation, a long period of pain in the knee after her total knee replacement with the need for manipulation and a poor result. She had perhaps two episodes of hemarthrosis on reflection in 2016 but had three major episodes in 2018, in the three months prior to coming to see me. They were aspirated and she was thought by her then treating surgeon, to have PVNS. She was referred off to the rheumatology section, I think at Prince of Wales, for this but came to see me because of instability, pain, and recurrent swelling in the knee joint. On that basis when looking at the x-rays, there was clear malrotation, there was clinical malrotation and instability and swelling, and hence the need for revision after investigations to exclude infection."
Associate Professor Stalley eventually recommended that Ms Roberts undergo a revision TKR in which the Stryker Triathlon implant would be replaced with a rotating hinge implant, also known as a distal femoral and proximal tibial tumour prosthesis.
On 17 August 2018, Ms Roberts sent an email to Dr Amanda Stalley for the attention of Associate Professor Stalley as he did not correspond by email directly. In her email, Ms Roberts said: "You might recall when I came to your place and saw Paul, he expressed the view that it appeared to him from my x-ray that the tibial component of my prosthesis when it was inserted in 2012 may have been mal-aligned by up to 10%. If it turns out to be the case (especially once Paul opens my knee up and sees everything in all its glory) that I had a sub-standard procedure done in Melbourne, I am just wondering if I should take any additional steps before I have the 2012 prosthesis removed to record evidence of the state/positioning of the prosthesis in case down the track I have the energy or inclination to consider my legal options re the Melbourne surgeon. … It may be I already have so many x-rays/scans etc that I have a good record of the state of the 2012 TKR and don't need anything further. It may also be that Paul as a matter of course gathers additional information about the primary TKR during the revision procedure. I am cognisant though that Paul may prefer to not be asked to give a formal view as to the quality or standard of the 2012 procedure. If that is the case then I don't want to put Paul in an uncomfortable position by raising it just before or after the operation. For instance, it may be he would prefer me to arrange to get an independent opinion from a radiologist or seek additional imaging about the alignment or positioning of the 2012 prosthesis before he removes it on 4 September?"
On 18 August 2018, Associate Professor Stalley responded: "My responsibility is always to the patient first and although neither of us is litigation prone I will always do the right thing. The gathering of any information at the time of surgery is equally yours as mine. There is nothing further to gather without an operation and I am happy to proceed. Patients always come first. I long ago gave up having any qualms about reporting factual information no matter who may be inconvenienced. Don't worry and don't be embarrassed."
Associate Professor Stalley conducted the revision TKR on 4 September 2018. His observations as to the placement of the tibial component are addressed from paragraph 148 below.

[15]

Ms Roberts' condition and employment following the revision TKR

Following the revision TKR, Ms Roberts remained an inpatient at RPA and was then discharged to the Wolper Hospital in Woollahra for rehabilitation. She remained there for about 10 days as an inpatient. After her discharge, she continued to receive treatment as an outpatient.
Ms Roberts reached maximal improvement in her knee function about 12 months after she finished her formal course of rehabilitation. By then she had lost the feeling of instability in her knee, which now felt stable and strong.
There has been no recurrence of hemarthrosis. The rattling sensation as she passes over speed bumps in a car has stopped. She still, however, has pain in her right knee that would start after about 15 minutes of sitting with it flexed, the pain only being relieved by extending her leg and moving around. She still has some difficulty with stairs, but otherwise no difficulty walking.
The pain Ms Roberts experiences affects the top of her knee, between the anterior aspect, with pain radiating up the lateral aspect of the right thigh. Some days are worse than others, as was the case during NCAT hearings in 2020 and early 2021. She manages that pain by stretching her leg out.
From 2019, Ms Roberts continued to work at NCAT on a part-time basis, which allowed her to perform other paid work as well. Mostly she sought executive coaching work, which did not conflict with her duties as a senior Tribunal member.
NCAT's conditions for part-time senior members (which were relevantly the same both before and after the revision TKR) remunerated Ms Roberts for days she spent hearing matters as well as for days writing up her reasons for decision. She was paid a daily rate, was not guaranteed a minimum or maximum number of days' work and, as a part-time appointee, received no annual leave or sick leave. Part-time senior members were required to make themselves available to sit for four days per month (which equated to 8 days' work including writing time), with the calendar being set quarterly a few weeks in advance.
Ms Roberts has managed the pain she experiences on flexion of her knee by minimising the periods for which she sits at a desk. She conducts as much work as possible, particularly in the writing of reasons, by sitting sideways on her couch, with her legs extended in front of her and a tray‑table over her lap.
In 2019, Ms Roberts commenced a major consultancy project for the St Vincent de Paul Society, on the basis that she would be paid for a set number of days, for a total remuneration of between $18,000 and $23,000, with any further days to be remunerated at a rate of $1,300 per day. After two or three days, it became clear that the client expected her to perform her duties while physically located at their premises and Ms Roberts formed the view that it was not feasible to try to work in the manner described in paragraph 112 above, at their premises. Accordingly, she terminated the consultancy, after performing a few days' work, and issued a single invoice for about $3,000. She has not undertaken any further consultancy work.
In April 2021, Ms Roberts ceased work and took an unpaid sabbatical from NCAT. She explained her reasons as follows: "By that point I had conducted over 200 hearings from my home office. I had also written approximately 190 decisions in the reclining on the couch position, and by the time I got to April I was exhausted. I was tired of the constant pain in my knee from sitting and conducting hearings. When I wasn't sitting and conducting the hearing, the way in which I needed to write decisions, in order to pain free, was not proving to be great for the rest of my body ergonomically. I also felt about the need - the requirement for me in order to write decisions, to be in that position. I felt resentful about it, and I reached a level of distress, and also I noticed, or realised, that my concentration was being affected by those factors, and I wasn't able to concentrate as well during hearings, particularly those that were, because of the subject matter or the people involved, highly emotional anyhow."
Ms Roberts went on to say that she was "burnt out and distressed". I accept her evidence of her reasons for taking the sabbatical.
At the time of the hearing, Ms Roberts remained on sabbatical but proposed to return to NCAT prior to the expiry of her current appointment, which remains valid until 31 July 2025. Ms Roberts proposed to return to NCAT for two sitting days per month rather than the usual four, so that she could minimise her time spent seated at a desk, and, at the same time, maintain a more physically active schedule. This would mean that she would continue to be remunerated on the basis of four days' work (including writing time) rather than eight, for the balance of her career as a part-time senior Tribunal member. I accept that this accords with the extent of her capacity to work in that role.
But for the issues she continues to experience with her right knee, it had been Ms Roberts' intention to continue to sit as a senior member of NCAT, on the standard NCAT basis of four sitting days per month, with four additional days of remunerated writing time.
I accept that Ms Roberts would have continued to hold the NCAT appointment on NCAT's standard terms for part-time senior members for the balance of her current term. Ms Roberts indicated that her intention was to seek reappointment for a further five-year term as a part-time senior Tribunal member on expiry of her current term in July 2025. There is no reason to doubt that she would have been so reappointed.

[17]

Pre-operative consultations with Dr Shimmin

Following the referral from Dr Zimmerman referred to at paragraph 46 above, Ms Roberts saw Dr Shimmin on 21 March 2012. According to Ms Roberts, Dr Shimmin looked at scans and x-rays that she had brought. At the time, her knee was still tender and she was in a great deal of pain. She did not recall if he performed a physical examination of her knee. If there had been any such examination, it was not robust. Dr Shimmin did not have any direct recollection of those consultations, but his contemporaneous reports were in evidence.
Dr Shimmin was aware from the outset that Ms Roberts had undergone a patellectomy and was suffering from long-term patellofemoral joint instability. Dr Shimmin had always considered that a TKR was likely to be necessary at some point, but as Ms Roberts was only in her mid-40s - considerably younger than most candidates for a TKR procedure - this should be deferred if possible. He, therefore, suggested an arthroscopy as a possible solution. Ms Roberts takes no issue with that judgment or recommendation and makes no complaint about the conduct of the arthroscopy itself.
For the purpose of the arthroscopy, Dr Shimmin examined Ms Roberts' knee, focussing on the structure of the ligaments, although there is no contemporaneous evidence as to what findings were made. Similarly, there is no contemporaneous evidence that he considered the stability of the patellar tendon in any examination preparatory to either the arthroscopy or the primary TKR.
The arthroscopy was performed on 5 April 2012. It did not alleviate Ms Roberts' symptoms and, following further consultations on 12 April 2012 and 21 May 2012 and a course of physiotherapy, Dr Shimmin recommended a total knee replacement. Ms Roberts had, by then, been using crutches since February 2012. Dr Shimmin also saw Ms Roberts again on 12 June 2012.
At the time of the primary TKR, Dr Shimmin was aware of Ms Roberts' prior patellectomy, her tibial tubercle transfer and the need for stability in the implant. In his report to Dr Zimmerman following the consultation of 21 March 2012, he expressed the view that a posterior cruciate stabilised knee design implant ought be used for stability when a TKR was performed.
In his consultation with Ms Roberts on 21 May 2012, Dr Shimmin discussed the peculiarity of a knee replacement in people without a patella and the type of implant he proposed to use, saying that he thought it would be the most appropriate because of Ms Roberts' history. In particular, he said that he would use an implant that would be very stable. Dr Shimmin showed Ms Roberts a model of the prosthesis that he ultimately implanted. In his report of that consultation, Dr Shimmin also referred to her tibial tubercle transfer, which he considered in assessing which type of knee replacement design would be appropriate. He did not, however, say anything to Ms Roberts about adopting a kinematic alignment in the TKR. Further, there was no evidence of any examination, or reference to any images, in connection with any assessment of the degree of varus alignment of Ms Roberts' knee at any pre-operative consultation.
Overall, it appears that Dr Shimmin performed only a limited examination of Ms Roberts' knee in connection with the arthroscopy or prior to the primary TKR. It appears probable that no particular attention was paid to assessing the stability of the patellar tendon or the natural alignment of Ms Roberts' knee.
Prior to the primary TKR, Dr Shimmin told Ms Roberts that she would always experience some limitations with her knee, and it would never be comparable to her friends' knees.

[18]

Dr Shimmin's account of the primary TKR on 18 June 2012

The primary TKR involved the implant of a Stryker Triathlon system prosthesis. At the time, Dr Shimmin had only performed one or two TKRs on patients who had previously undergone patellectomies. Dr Shimmin had available to him a CT scan obtained by the Cabrini Emergency Department, an ultrasound and an MRI arranged by Dr Zimmerman, and a short leg x-ray he, himself, had arranged on 30 May 2012. It was not Dr Shimmin's practice at the time to arrange a long leg radiograph, although such radiographs are now standard practice and he accepted that they were ordered in 2012 to identify any alignment issues a patient may have had. Dr Shimmin did not undertake any pre-operative assessment of the alignment of the knee or of the rotation of the joint in the axial plane.
As indicated above, Dr Shimmin admitted that he had no actual recollection of how he performed the procedure. Dr Shimmin's evidence as to what occurred at particular consultations and what he did during the primary TKR was, for the most part, a reconstruction based on a combination of his contemporaneous records and recollections of what was his usual practice at the time.
Dr Shimmin stated that by 2012, he had adopted the practice of kinematic alignment, rather than mechanical or neutral alignment, of the knee components in performing a TKR. As a generalisation, this requires the components to be aligned anatomically according to the native alignment of the joint, as opposed to mechanical alignment, which requires the components to be set perpendicular to the axis of each bone. He thought that he had moved to this method following the publication of an article in 2006 by Dr Stephen Howells, although the article was not before the Court.
As Dr Shimmin had only performed TKRs on one or two patellicised patients at the time of the primary TKR, it was not contended that he had established a usual practice with respect to such patients at the time. Rather, it was contended that his usual practice with respect to TKRs generally was adopted and that it was appropriate to do so. With reference to his description of his then usual practice, so understood, Dr Shimmin's evidence of how the primary TKR was performed was that he was pursuing an alignment strategy of balancing the knee by having ligaments that were in equal tension between the medial and lateral sides of the knee throughout an arc of motion. He said that, according to his usual practice, he initially cut the tibia at 90 degrees and then assessed ligament balance. He then used a 2 degree cutting guide to cut the tibia in varus or valgus, depending on whether there were tight medial or lateral ligament structures.
The Operation Report refers to use of the "triathlon tibial instrumentation", but does not refer to any other cutting jig being used on the tibia. Dr Shimmin did not have any actual recollection of adopting this course in the primary TKR. He did not recall how many assessments of ligament stability or tibial cuts were made.
With respect to the steps taken with respect to rotation during the primary TKR, Dr Shimmin's evidence was, again, based on his recollection of his then usual practice. He said that he used the posterior condyles of the femur as a reference point and externally rotated the cutting guide 3 degrees from the posterior condyle axis, being the average of the relationship between the posterior condyles and the epicondylar axis. At the end of the process, the distal femur was shaped and trial components were tested through a range of motion.
Other than checking ligament balance, which appears to have been directed primarily to assessing alignment, the evidence did not establish how rotation of the tibial component was checked once the cutting guide had been set to 3 degrees. Dr Shimmin accepted that Ms Roberts' tibial tubercle transfer would have been significant in assessing rotation of the tibial implant. He went on to say that it was standard practice to use the footprint of the posterior cruciate ligament and the medial third of the tibial tubercle as bony landmarks to assess rotation. He did not have any recollection of doing so, however, either in positioning the component or in checking it.
In his Operation Report, the "Operation Performed" is described as a "Right total knee replacement". In the "Operative Findings" section of the Report, Dr Shimmin stated: "Susan was given a combined general and regional anaesthesia. The old medial incision was opened and extended. The incision was used to perform a patellectomy. The old arthrotomy was opened. The knee was exposed. The tibia was cut with the triathlon tibial instrumentation. The femoral instruments were then used to cut the femur to a size 5 with a posterior stabilised femoral component. The tibia was cut to size 4. Trial reduction was done with a size 11 polyethylene insert. Excellent stability was achieved. The femoral component was cementless. The tibial component was cemented with Simplex cement. Ligament balance optimal range of motion and stability optimum. The arthrotomy was closed and the skin closed in layers with a deep drain." [Emphasis added]
There is an apparent error in the Operative Findings section of the Report, which contradicted Dr Shimmin's own description of the Operation Performed, in that Dr Shimmin appears to report that a patellectomy was performed. Notwithstanding the submissions of counsel for Ms Roberts to the contrary, this was likely a reference to the purpose of the existing incision or a typographical error and was of no significance.
The Operation Report is silent on the technique used to shape the tibia to receive the tibial component of the prosthesis. It is silent on the degree of varus or external rotation that was intentional in the placement of the tibial component. It does not provide any explanation as to how alignment and rotation were assessed and determined. There is no mention of the extent to which the native architecture of Ms Roberts' knee was in varus or rotation (if at all). There is no mention of Ms Roberts' prior tubercle transfer. There is no explanation for why 3 degrees of external rotation from the posterior condyle axis was considered appropriate notwithstanding Ms Roberts' tubercle transfer. There is no mention of how the patellar tendon tracked. There is no reference to any assessment of the quality of the ligaments prior to the cutting of the tibia and femur such as would disclose any natural varus alignment.
Dr Shimmin said that the absence of express reference to steps in the Operation Report did not mean that such steps were not taken. He said that it was his practice only to document variations from standard process and to record exceptional, rather than routine, matters.
The absence of any detailed contemporaneous record, together with Dr Shimmin's inability to recall the conduct of Ms Roberts' TKR, diminishes the reliability of his account of the procedure. In particular, Dr Shimmin's evidence of the stages in which the procedure was undertaken and the assessments, he says, were made during the procedure are not supported by any evidence other than Dr Shimmin's evidence as to his usual practice with respect to TKRs generally.
The approach in Dhupar v Lee, as qualified in Elayoubi v Zipser, allows me to consider evidence of usual practice as relevant to, although not determinative of, the question of how the surgery was performed.
In the present case, I accept that Dr Shimmin intentionally placed the tibial component in varus and in some degree of external rotation. This appears to me to accord with the probabilities, and I accept that, in general terms, this was Dr Shimmin's approach at the relevant time.
I also accept that Dr Shimmin checked the tibial prosthesis for stability and ligament balance once it had been implanted. This also accords with the probabilities and with the contemporaneous Operation Report. How he did so, however, and particularly the degree of precision he brought to bear in making any such assessment, remains in issue. Other than the general consideration of stability and ligament balance, there is no evidence that Dr Shimmin considered the tracking of the patellar tendon itself.
Dr Shimmin relied entirely on an intra-operative assessment based on ligament balance and stability on flexion and extension to determine the appropriate degree of varus of the implant. I am not satisfied that he assessed rotation of the implant with reference to bony landmarks, taking into account Ms Roberts' tibial tubercle transfer. I consider it most likely that he relied entirely on his application of an assumption of a 3 degree average external rotation from the posterior condyle axis in setting rotation. I am not satisfied that he had any patient-specific basis for placing Ms Roberts' tibial implant in such degree of external rotation as it was, in fact, placed.
For reasons which include my assessment of the evidence of Associate Professor Stalley and Dr Coolican, I consider it likely that Dr Shimmin failed to take into account Ms Roberts' prior tibial tubercle transfer in assessing rotation.
Dr Shimmin conceded that he could have erred in his conduct of the primary TKR, but did not see any reason to believe that he did so. In his view, the ligaments would not have balanced if he erred.
Dr Shimmin stressed in his evidence before me that he only recorded matters in his contemporaneous records which were out of the ordinary, and his reports and correspondence ought not be treated as a comprehensive report of either his observations or the performance of the procedure. Had he made any assessment of the native architecture of Ms Roberts' knee or taken the tibial tubercle transfer into account, it would accord with this evidence that he would have recorded those matters in some way. Similarly, if he had taken any additional care to ensure that Ms Roberts' patella tendon tracked precisely due to her lack of a patella, in accordance with his own evidence he would have recorded it. He did not.
By reference to the principles in Bruce v Kaye, an operation report ought not be treated as a stroke by stroke record of how a procedure was carried out. Nevertheless, the absence of reference in Dr Shimmin's Operation Report to any particular steps or heightened degree of care resulting from Ms Roberts' particular condition mitigates against a finding that any particular steps were taken, referable to that condition. Aside from the choice of a particular implant, the evidence indicates that Dr Shimmin treated the primary TKR as a routine knee replacement.

[19]

Associate Professor Stalley's intraoperative observations; Dr Coolican's critique and alternative assessment

Associate Professor Stalley conducted the revision TKR on 4 September 2018, following his communications with Ms Roberts as set out at paragraphs 97 to 105 above. When conducting the revision TKR, he made an intraoperative observation of the positioning of the tibial prosthesis and, on removing it, of the degree of alignment in which Ms Roberts' tibia had been cut. He paid particular attention to assessing the extent of any malalignment or malrotation of the existing prosthesis.
Associate Professor Stalley's observation on 4 September 2018 was that the tibial component was in 8 degrees of external rotation and 8 degrees of varus. Associate Professor Stalley made a number of other observations which are significant. He found no evidence of PVNS. The patellar tendon had a tendency to slide laterally and was easily displaced. There was insufficiency and attenuation of the medial ligamentous structures of the knee. It was mobile to physical examination under anaesthetic.
For the reasons which follow, I accept that Associate Professor Stalley's observations were accurate and, accordingly, that Dr Shimmin had placed the tibial component in 8 degrees of varus and 8 degrees of external rotation.
The revision TKR involved the removal of the existing prosthesis and its replacement with a rotating hinge prosthesis. The rotating hinge replaced the mechanism of the knee joint with an entirely artificial joint in which the prosthesis connected the femur to the tibia via a mechanical hinge. Such prostheses are commonly used in tumour surgery but also in the reconstruction of grossly unstable knee and hip replacements where there is considerable bone loss.
A rotating hinge prosthesis is inherently stable to varus and valgus movements of the knee joint and prevents hyperextension. Stability of the joint derives from the prosthesis itself, rather than the surrounding soft tissues. The nature of the prosthesis used in the revision TKR was such that it was essential that it be implanted in neutral, or very nearly neutral, alignment. Accordingly, accuracy of measurement of the alignment of the prosthesis is essential in ensuring a satisfactory clinical outcome, which was achieved in the case of the revision TKR.
There was a vigorous debate between Associate Professor Stalley and Dr Coolican as to the reliability of Associate Professor Stalley's technique in assessing vertical alignment and horizontal rotation of the primary TKR. Associate Professor Stalley examined the knee under anaesthesia and found it to be grossly unstable. There was clear lateral displacement of the patellar tendon. He then divided the medial, lateral and posterior cruciate ligaments, so that the only significant remaining tissue was the quadriceps mechanism.
Associate Professor Stalley then removed the existing prosthesis, taking particular care not to damage the existing top of the tibia. He then assessed vertical alignment, using an insertion jig and a goniometer or protractor.
The insertion jig is an intermedullary device necessary for the implant of the rotating hinge prosthesis. Exhibit P42 shows how the insertion jig is inserted into the tibia and that an alignment handle and a tibial resection guide abut the tibial plateau. When the alignment handle is in neutral alignment, any part of the proximal tibia, which is in varus or valgus alignment, will sit proud of the alignment guide. The proximal part of the jig passes through the position of the intercondylar notch and that part of the proximal tibia, which is in varus or valgus alignment, will be observable and measurable. On that basis, Associate Professor Stalley observed that the tibia was in 8 degrees of varus, measured with a goniometer or protractor.
Associate Professor Stalley also measured the external rotation with a goniometer or protractor. He considered the assessment of external rotation was a more difficult observation to make. However, in implanting a rotating hinge prosthesis, all the collateral ligaments are removed and "the tibia sits out like a pylon sticking out of the sea, and you can actually see it beautifully". On Associate Professor Stalley's own account, rotation was difficult to assess in Ms Roberts' case because she had had the tubercle transfer and the native architecture of her knee had been altered. He considered there was scope for large degrees of error. Nevertheless, he assessed it as 8 degrees externally rotated from a neutral rotation.
Associate Professor Stalley then cut the tibia back to neutral alignment by performing a series of cuts to the tibia and using the jig to ensure that the tibial component was at 90 degrees to the long axis of the tibia. He then put in femoral and tibial trials to ensure that the knee aligned and rotated properly.
Associate Professor Stalley took particular care to record the extent of malalignment, not just because of his correspondence with Ms Roberts the previous month, but also because he was assembling data for a paper he proposed to write concerning the use of rotating hinge implants in revision surgery.
Dr Coolican was critical of the means by which Associate Professor Stalley measured varus alignment and external rotation and considered Associate Professor Stalley's conclusions to be unreliable. Dr Coolican considered that the use of an intramedullary device, visual intraoperative inspection and the use of a protractor or goniometer did not provide an accurate means of determining alignment and rotation.
Further, Dr Coolican challenged the conclusion of malalignment and malrotation on the basis that Ms Roberts' post-operative course was, in his view, inconsistent with such a surgical outcome and more likely caused by trauma suffered in August 2016. My assessment of Ms Roberts' post-operative course is set out at paragraphs 48 to 105 above.
I accept Associate Professor Stalley's observations as reliable. I do not accept Dr Coolican's criticisms of Associate Professor Stalley's methodology or his conclusions.
The use of an intramedullary device to measure vertical alignment was a key component of both Associate Professor Stalley's assessment and the successful revision TKR. Because the rotating hinge prosthesis required a high degree of conformity with neutral alignment, there was a clinical imperative to assessing vertical alignment accurately. This had been achieved by the revision TKR. The fact that Ms Roberts also had a straight tibia, as was acknowledged by Dr Coolican, adds to the reliability of the jig being used to assess vertical alignment.
Associate Professor Stalley's assessment of axial rotation, as recorded in Exhibit P38, was achieved by displaying the whole of the proximal tibia, reflecting the capsule off it and identifying the tibial tubercle exactly. It was that bony landmark, in particular, that he relied on in determining that axial rotation was 8 degrees externally.
I did not find that Dr Coolican provided an adequate explanation for his contrary view with respect to the use of an intramedullary jig. This is particularly so in circumstances where the jig was used with precision to achieve neutral alignment in the revision implant.
Similarly, while Associate Professor Stalley agreed rotation was a more difficult assessment to make, it is difficult to accept Dr Coolican's view that it would be more, rather than less, difficult to make an assessment where the tubercle can be located visually on when the proximal tibia "sticks out like a pylon", as described by Associate Professor Stalley.
Dr Coolican considered that imaging studies, such as a long leg radiograph, were the best means by which both the alignment of the implant and the natural architecture of Ms Roberts' knee could be assessed. With reference to long leg films taken after the revision TKR, Dr Coolican considered that there was a slight varus alignment of the implant.
Dr Coolican's own measurements, however, were not consistent. He, himself, measured varus angulation variously at 4.5 degrees and 2 degrees, as recorded in the Joint Report signed by him and Associate Professor Stalley, which he thought was likely explained by his having used different radiographs. This demonstrates the unreliability of the alternative means of assessing vertical alignment that was propounded by Dr Coolican.
Assessments based on x-rays are subject to distortion, rotation and magnification errors and intra-operator variability over time, as well as inter-operator variability. Associate Professor Stalley considered at least some of the same images that Dr Coolican relied on and disagreed as to what they disclosed. Dr Coolican's own experience with variable results only serves to emphasis this conclusion. I do not accept that assessment by way of x-ray is superior to invasive, visual inspection, at least when such an inspection was conducted by an experienced surgeon such as Associate Professor Stalley. Indeed, Associate Professor Stalley, perhaps immodestly, described visual inspection as the gold standard in his hands.
Finally, Dr Coolican considered that Associate Professor Stalley's use of a goniometer was not reliable. There was no real foundation for this criticism. Essentially, Dr Coolican regarded the method as idiosyncratic and he had not heard of it done before. This does not undermine its reliability.
Medical literature was adduced in support of Dr Coolican's view, however, it did not make good the contention that a goniometer was inherently unreliable. Comparisons were drawn between various non-invasive forms of assessment in E J De Valk, J C A Noorduyn and E L A R Mutsaerts, "How to assess femoral and tibial component rotation after total knee arthroplasty with computed tomography: a systematic review" (2016) 24 Knee Surg Sports Traumatol Arthrosoc 3517, and the consensus appears to be that 3D scans are, in that context, the "gold standard" and are superior to 2D scans.
In my view, direct visual inspection, unmediated by imaging, is more accurate and provides less scope for variation than at least 2D scanning. It is both three-dimensional and not prone to distortion or to magnification that imaging can impart. It also obviates unreliability borne out of the positioning of the knee at the time of the scan, which can affect the conclusion. A goniometer or protractor, placed on the tibial plateau or resection guide, is a simple and, to my mind, perfectly acceptable means of determining angulation and rotation.
Dr Coolican's view was that the images taken of Ms Roberts' knee over time did not support the conclusion that it was either malaligned or malrotated as a result of the primary TKR.
With particular reference to horizontal rotation, Dr Coolican conducted his own analysis using three methodologies, each of which was based primarily on his assessment of 2D scans. Those methodologies were to determine the extent to which the implant was parallel to the transepicondylar axis; to draw a line at a right angle to the Akagi line (a line drawn from the medial border of the tibial tubercle to the centre of the posterior cruciate ligament facet) as a reference point for rotation; and to assess rotation from the anterior margin of the implant and assess its relation to the anterior margin of the tibial cortex at the level of the joint line. By reference to each of these methods, Dr Coolican considered that the tibial component was not malrotated.
The difficulty with Dr Coolican's analysis, however, is that each method suffers from the same vice, which is that each is dependent on the reliability of 2D scans taken in circumstances where it is not established that Ms Roberts' knee was ever in a consistent or appropriate position against which rotation could be measured. Ms Roberts' evidence was that she had difficulty maintaining a consistent position when scans and x-rays were taken. This was not disputed.
It was submitted for Dr Shimmin that the "gold standard" for assessment of alignment in the sagittal and coronal planes (which together are the relevant planes for vertical alignment) is, according to the literature, 3D scanning. This was also a point repeatedly made by Dr Coolican in his various reports. Accepting that to be true, the first difficulty with this evidence, however, is that 3D scans were never taken of Ms Roberts' knee and were not in evidence before the Court. This was eventually conceded by Dr Coolican, although the impression left by his reports was that the scans on which he based his assessment of the alignment of the tibial component were according to the gold standard, whereas in reality they were 2D scans.
With respect to the assessment of rotation, it was submitted that 2D scans are sufficient. As a general proposition, this may well be the case. The difficulty, however, lies in the uncertainty of the circumstances in which they were recorded, the variability in assessment between operators and by a single operator at different times and the risk of rotation, magnification and distortion errors.
According to the medical literature before me (M Saffi, S W Yong, M J Spangehi, H D Clarke, "Measuring Tibial Component Rotation Following TKA - What is the Best Method?" (2018) The Journal of Arhtroplasty), measurement of tibial component rotation is challenging. It is essential in drawing conclusions based on the position of the femoral epicondyles relative to the proximal tibia that the limb be kept in a standard position when the scan is taken, which the evidence did not establish. This derogates from the reliability of Dr Coolican's conclusions.
This difficulty is compounded in the present circumstances by the tibial tubercle transfer. In Saffi et al, the authors excluded patients who had had a prior tibial tubercle osteotomy. This was because, where the location of the tibial tubercle is unclear, all rotation measurements are affected. Those such as that which require a line to be drawn from the Akagi line, particularly, become unreliable.
In the present case, I am not satisfied that the location of the tibial tubercle could be assessed accurately from the scans because of the prior tibial tubercle transfer.
Unlike vertical alignment, assessing rotation is complicated by the absence of standardised reference values or grading systems for measuring rotation of TKR components. As recorded in A M Suchowersky, D Dickison and LA Ashton, "Current variability in the assessment of component position for the unhappy knee replacement", (2019) ANZ J Surg 1, some radiological firms regard tibial rotation measurement as intrinsically unreliable because of excessive variability in measurement and at least one reputable firm regards it as incapable of being accurately measured using radiology. In K Yoshino, S Hagiwara, J Nakamura, T Tsukeoka, Y Tsuneizumi and S Ohtori "Intra-and interobserver reliability and agreement in three-dimensional computed tomography measurements of component positions after total knee arthroplasty", (2019) 26 The Knee 1102, it was noted that 2D CT scans risk inaccuracy because differences in the position of the leg when scanning may affect positioning of anatomical landmarks.
In my view, the difficulties associated with ensuring a consistent basis for assessment based on CT scans, particularly where the subject, as was the case with Ms Roberts, had difficulty in maintaining her leg in a constant position during each scan, causes assessment of rotation to be unreliable when based on them. Dr Coolican described them as "the best we have", however, I am not satisfied that the materials available to Dr Coolican can provide a sufficient basis to prefer his assessment to Dr Stalley's intraoperative assessment.
Accordingly, I prefer Associate Professor Stalley's evidence, based on his intraoperative observations, to that of Dr Coolican, based on his review of imaging, with respect to the positioning of the tibial component.

[21]

Conclusion as to the positioning of the tibial component in the primary TKR

I am satisfied that the tibial component was malaligned and malrotated by Dr Shimmin in 8 degrees of varus and 8 degrees of external rotation for the reasons set out below.
First, the evidence does not show that Dr Shimmin made any assessment of the native architecture of Ms Roberts' knee prior to the primary TKR. It may well be, in light of the comparative unreliability of short leg x-rays and 2D CT scans to disclose alignment and rotation, that this would have made little practical difference, although Dr Shimmin did accept that long leg x-rays were in use in 2012 to assist with assessment of patients' vertical alignment. Nevertheless, while not of itself indicative of breach, the absence of any pre-operative consideration of the native alignment and rotation of Ms Roberts' knee is a factor in elevating the risk that error might have occurred in the surgery.
Secondly, Dr Shimmin's account of the surgery did not disclose that he took any particular precaution or paid any additional regard to Ms Roberts' prior patellectomy or tibial tubercle transfer. He had no recollection of the procedure and his contemporaneous records, which should at least have recorded any matters that were not routine, do not recall any such precautions or additional consideration.
Accepting that he used a 2 degree block to guide the making of cuts in the proximal tibia, Dr Shimmin was unable to say how many cuts were made and his contemporaneous records do not record what steps were taken to ensure that the patellar tendon tracked precisely. While he did record that stability was excellent and ligament balance achieved an optimal range of motion, I am not satisfied that this records that any particular attention was paid to Ms Roberts' particular condition, nor does it record the standard of stability and balance that Dr Shimmin considered acceptable in this particular case.
Accordingly, Dr Shimmin's evidence of the procedure itself carries little weight in determining the factual question of whether the tibial component was malpositioned.
Thirdly, I have had great regard to the expert evidence as to whether, on intraoperative assessment by Associate Professor Stalley, the tibial component was found to be malpositioned, or whether, relying on a review of x-rays and CT scans by Dr Coolican, it was not.
Associate Professor Stalley was an impressive witness, who alone had the benefit of conducting an invasive assessment of Ms Roberts' knee. His evidence was challenged on the basis that his assessment technique was unreliable, that his initial conclusions were expressed more tentatively than was the case in his evidence, and that he may have placed his wish to help Ms Roberts above his duty to the Court in giving his evidence. I have rejected each of these challenges to his credit and reliability.
Dr Coolican, like Associate Professor Stalley, is an eminent and vastly experienced surgeon. I was troubled by his frequent references to 3D scans as the gold standard in assessment in circumstances where no such scans were in evidence. Nevertheless, I accept that he gave his evidence honestly and the views he expressed were genuine.
I have preferred the evidence of Associate Professor Stalley over that of Dr Coolican. Associate Professor Stalley had the singular benefit of conducting an invasive assessment, which allowed him a 3D view of the tibial component and, on its removal, the proximal tibia itself. He did so in circumstances where he was conscious of the need accurately to record the extent of any malpositioning. His view was unmediated by the process of recording an image, which has its own difficulties of distortion, magnification and rotation. The use of a protractor or goniometer to measure the angle of varus alignment or external rotation might be considered by Dr Coolican to be idiosyncratic, but I do not find that it was unreliable when used by Associate Professor Stalley.
I accept that Associate Professor Stalley found gross instability of Ms Roberts' knee at the commencement of the revision TKR, lateral displacement of the patellar tendon and soft tissue changes consistent with instability and malpositioning of the tibial component in the course of the revision TKR. He did not find PVNS or tendomalacia.
While Dr Coolican contended that the gold standard for assessment of alignment and rotation was a 3D CT scan, this ultimately was irrelevant as no such scans were taken and were not considered by the experts. He conceded that there was scope for variation in assessment of all images, even in the case of 3D scans, as between operators and even by the same operator over different times. Much depends on the circumstances in which the image is taken and, in this case, the evidence was clear that Ms Roberts had difficulty in keeping her leg in position at the time. The images in this case are, accordingly, an unreliable basis for assessment.
Even on the assessment of the experts before the Court, there were differences as to what the images disclosed. Associate Professor Stalley did not agree with Dr Coolican's findings as to the positioning of the tibial component. Even Dr Coolican found variation in his results, assessing alignment by over 2 degrees of difference on different occasions.
Fourthly, I have taken into account Associate Professor Stalley's successful conduct of the revision TKR, which required a high degree of precision in the alignment of the rotating hinge prosthesis. The assessments necessary to align the new prosthesis were clearly made correctly in light of the significant improvement in Ms Roberts' condition. This degree of precision fortifies my conclusion that Associate Professor Stalley's measurements were correct and his techniques were sound.
Fifthly, the medical literature relied on by Dr Coolican was, at best, inconclusive. I did not understand any of the papers put before the Court to prefer imaging over invasive assessment as the more accurate means of assessment and the use of imaging, particularly with respect to assessing rotation, has considerable difficulty in terms of its reliability.
Finally, the symptoms experienced by Ms Roberts were consistent with malpositioning of the tibial component. Malpositioning of the tibial component in a patient with a prior patellectomy can cause progressive instability and pain. Ms Roberts experienced instability, pain on prolonged flexion and episodes of hemarthrosis in the period between the primary TKR and the revision TKR.
There was a debate as to whether the onset of particular symptoms from August 2016, which I consider below, were too remote in time from the primary TKR to have been caused by it. To some extent, Dr Coolican based his conclusions as to the positioning of the tibial component on his assessment of Mr Roberts' treating doctors, Dr Best and Dr Broe. I have reached the conclusion, for reasons set out elsewhere in these reasons, that Dr Coolican's reliance on the reports of these doctors was misplaced, and that Ms Roberts' symptoms were not too remote from the primary TKR or likely caused by an intervening event, or series of events, in August 2016.
I have found that Ms Roberts' symptoms prior to August 2016 and between August 2016 and the revision TKR in September 2018 to be consistent with instability, subluxation and dislocation of the patellar tendon resulting from malpositioning of the tibial component. Similarly, the resolution of many of those symptoms following the revision TKR is also consistent with malpositioning of the tibial component having been the cause of all of them.
Accordingly, I consider it most likely that Dr Shimmin did position the tibial component in 8 degrees of varus and 8 degrees of external rotation, and I find that he did so.

[23]

Relevant principles

The parties broadly agree on the relevant principles that govern Ms Roberts' cause of action. Dr Shimmin owed Ms Roberts a "single comprehensive duty covering all the ways in which a doctor is called upon to exercise his skill and judgment; it extends to the examination, diagnosis and treatment of the patient": Rogers v Whitaker [1992] HCA 58; (1992) 175 CLR 479 at [5].
The primary TKR procedure was conducted in Melbourne and, accordingly, the governing legislation is the Wrongs Act 1958 (Vic).
Section 48 relevantly provides: 48 General principles (1) A person is not negligent in failing to take precautions against a risk of harm unless- (a) the risk was foreseeable (that is, it is a risk of which the person knew or ought to have known); and (b) the risk was not insignificant; and (c) in the circumstances, a reasonable person in the person's position would have taken those precautions. (2) in determining whether a reasonable person would have taken precautions against a risk of harm, the court is to consider the following (amongst other relevant things) - (a) the probability that the harm would occur if care were not taken; (b) the likely seriousness of the harm; (c) the burden of taking precautions to avoid the risk of harm; (d) the social utility of the activity that creates the risk of harm. (3) For the purposes of subsection (1)(b) - (a) insignificant risks include, but are not limited to, risks that are far-fetched or fanciful; and (b) risks that are not insignificant are all risks other than insignificant risks and include, but are not limited to, significant risks. [Emphasis in original].
Section 58 relevantly provides: 58 Standard of care to be expected of persons holding out as possessing a particular skill In a case involving an allegation of negligence against a person (the defendant) who holds himself or herself out as possessing a particular skill, the standard to be applied by a court in determining whether the defendant acted with due care is, subject to this Division, to be determined by reference to - (a) what could reasonably be expected of a person possessing that skill; and (b) the relevant circumstances as at the date of the alleged negligence and not a later date.
Dr Shimmin relies on s 59 of the Wrongs Act, whereas Ms Roberts contends that that does not apply on the facts of this case.
Section 59(1) of the Wrongs Act provides: 59 Standard of care for professionals (1) A professional is not negligent in providing a professional service if it is established that the professional acted in a manner that (at the time the service was provided) was widely accepted in Australia by a significant number of respected practitioners in the field (peer professional opinion) as competent professional practice in the circumstances.
Both parties referred to the decision of the Court of Appeal in Dean v Pope [2022] NSWCA 260, which considered s 5O of the Civil Liability Act 2002 (NSW). Section 5O provides that: 5O Standard of care for professionals (1) A person practising a profession (a professional) does not incur a liability in negligence arising from the provision of a professional service if it is established that the professional acted in a manner that (at the time the service was provided) was widely accepted in Australia by peer professional opinion as competent professional practice. …
In Dean v Pope, the Court of Appeal held that "professional practice", as used in s 5O, refers to the manner in which professionals practice their profession and not to a particular protocol, procedure or process. "[C]ompetent professional practice" refers to what a significant body of professionals would have done. The relevant inquiry is directed towards what professionals would have done at the time of the conduct in question, rather than at the time of the hearing.
The parties also agree that it is necessary for a defendant to establish the elements of the statutory formulation of the standard of care for professionals before he, she or they can rely on s 5O, or s 59, as the case may be.
For the purpose of s 59(1) of the Wrongs Act, "competent professional practice" must be established by evidence for it to apply: Boxell v Peninsula Health [2019] VSC 830 per Keogh J; South Western Sydney Local Health District v Gould [2018] NSWCA 69; (2018) 97 NSWLR 513 at [30(1)] per Leeming JA. It could be a practice in a general, rather than specific, sense. Nevertheless, it is incumbent on a defendant affirmatively to establish a standard of care which was widely accepted in Australia at the time as competent professional practice in order to avail himself, herself or themselves of s 59. The plaintiff's obligation remains to establish breach by reference to the test in s 58, and not to disprove compliance with s 59 (see Boxell at [297]-[299]).
As to causation, s 51 of the Wrongs Act relevantly provides: 51 General principles (1) A determination that negligence caused particular harm comprises the following elements - (a) that the negligence was a necessary condition of the occurrence of the harm (factual causation); and (b) that it is appropriate for the scope of the negligent person's liability to extend to the harm so caused (scope of liability). (2) In determining in an appropriate case, in accordance with established principles, whether negligence that cannot be established as a necessary condition of the occurrence of harm should be taken to establish factual causation, the court is to consider (amongst other relevant things) whether or not and why responsibility for the harm should be imposed on the negligent party. … (4) For the purpose of determining the scope of liability, the court is to consider (amongst other relevant things) whether or not and why responsibility for the harm should be imposed on the negligent party.

[26]

Conduct of the surgery and positioning of the tibial component: was there a breach of Dr Shimmin's duty to Ms Roberts?

The duty of care alleged by Ms Roberts was a duty to place the tibial component in the correct position by exercising reasonable care and skill, investigating properly Ms Roberts' post-operative symptoms, taking specific precautions, such as using jigging techniques and visual inspection at the time of placement of the tibial component, avoiding cementing the tibial component in external rotation by carefully positioning the prosthesis by reference to anatomical landmarks and avoiding cementing the tibial component in varus by carefully cutting the tibia in the correct alignment.
It was common ground that it was important to take extra precautions with respect to the stability of a TKR in a patient who has previously undergone a patellectomy. Whatever the margin for error may have been in relation to patients with a patella, the peculiar circumstances of Ms Roberts having had her patella removed meant, to Dr Shimmin's knowledge, that a higher degree of accuracy in the placement of the tibial component was required. Associate Professor Stalley considered that more than 3 or 4 degrees of malalignment would be excessive in the circumstances. Dr Coolican did not agree.
Associate Professor Stalley and Dr Coolican agreed that Ms Roberts' condition made her more vulnerable to any malalignment in the primary TKR. Associate Professor Stalley added that there is no leeway for error in rotational stability in a patient who does not have a patella. Dr Coolican accepted that Ms Roberts' prior patellectomy made her vulnerable to issues with malalignment if there is instability within the sagittal plane because the extensor mechanism does not work normally. Accordingly, Ms Roberts needed an implant that was stable in the coronal plane and the sagittal plane, and malalignment in the axial plane could also cause problems with the extensor mechanism.
In my view, the positioning of the tibial component in 8 degrees of varus and 8 degrees of external rotation resulted from a failure by Dr Shimmin to take sufficient precautions and take sufficient care in the primary TKR to ensure stability of the patellar tendon and that it tracked precisely through the centre of the axis of the knee. This was a breach by Dr Shimmin of his duty to Ms Roberts. Dr Shimmin admitted that placement in more than 7 degrees of varus would be indicative of error. As I have found the positioning of the tibial component to be in more than 7 degrees of varus, I am satisfied that Dr Shimmin, on his own description of the relevant duty, was in breach of his duty of care to Ms Roberts. In reaching this conclusion, I have had regard to the following matters.
First, Ms Roberts' prior patellectomy was a key factor in determining the content of Dr Shimmin's duty, in that she was, to Dr Shimmin's knowledge, in a position of particular vulnerability. In a patient who had undergone such a procedure, there was a particular need to ensure that the patellar tendon tracked accurately through the intercondylar notches. If it did not do so, there was a heightened risk of subluxation and/or dislocation, resulting in instability, pain, hemarthroses and hemosiderotic synovitis. What was, or may have been, perfectly acceptable practice in the case of non-patellicised patients with respect to alignment and rotation, was not necessarily going to be true in Ms Roberts' case. A higher degree of precision in achieving accurate tracking of the patellar tendon was necessary.
Secondly, the native architecture of Ms Roberts' knee was not in varus, or at least not significantly so. As Associate Professor Stalley noted, and Dr Coolican acknowledged with reference to long leg radiographs, Ms Roberts had straight limbs, and if there was any varus in her knee, it was very slight. This was consistent with the history of Ms Roberts' consultations with all relevant medical specialists, including Dr Shimmin: at no stage was there any comment on her stance or gait, which would have been suggestive of any significant varus alignment of her knee.
In these circumstances, any positioning of the tibial component would have needed to be either in neutral alignment or in accordance with Ms Roberts' native anatomy, which was, at most, very slight varus. I consider that 8 degrees of varus was not consistent with such positioning.
Although it was not expressly pleaded, Dr Shimmin did not make any pre-operative assessment of the extent of varus or rotation of Ms Roberts' knee. Such an omission, while not necessarily of itself indicative of a breach of duty, increases the likelihood of surgical error, in that there was no benchmark against which intraoperative assessment could be considered. The lack of any pre-operative assessment is also relevant to Dr Shimmin's defence under s 59 of the Wrongs Act, considered below.
As Dr Coolican did not accept the factual premise that the prosthesis was in 8 degrees of varus and 8 degrees of external rotation, much of his evidence as to breach - which assumed no more than 2 to 4.5 degrees of varus and 3 degrees of rotation - became irrelevant.
At one point, Dr Coolican did express the view, however, that it would not necessarily be a breach of duty if the implant was in 8 degrees of varus and 8 degrees of external rotation. I do not accept that view, at least insofar as it applies to Ms Roberts as a patient who had undergone a prior patellectomy. Dr Shimmin admitted that placement in excess of 7 degrees of varus would be in error. Associate Professor Stalley also disagreed with Dr Coolican's view. I do not accept that it would have been conformable with Dr Shimmin's duty of care to have permitted such a degree of varus alignment and external rotation, at the same time, in the case of a patellicised patient.
Accordingly, I consider Ms Roberts has established breach within the meaning of s 58 of the Wrongs Act.

[27]

Section 59 of the Wrongs Act

It was contended on Dr Shimmin's behalf that the means by which he conducted the primary TKR, described at paragraphs 131 and 133 above, provides a basis upon which to find that the critical elements of s 59 of the Wrongs Act are made out.
I am not satisfied that Dr Shimmin has made out the elements of the statutory defence.
First, I do not consider there to be any real issue in these proceedings as to whether the adoption of kinematic principles in knee replacement surgery was appropriate in 2012. The issue with respect to the s 59 defence is whether, in the particular circumstances of Ms Roberts having undergone a prior patellectomy, the positioning of the tibial component in 8 degrees of varus and 8 degrees of external rotation constituted provision of a service in a manner that was widely accepted in Australia by a significant number of respected practitioners in the field as competent professional practice.
Dr Coolican considered that Dr Shimmin's technique of checking ligament balance was consistent with the kinematic philosophy that knee surgeons were using in 2012. Dr Coolican primarily based his view that Dr Shimmin was pursuing an alignment strategy on the Operation Report. However, while Dr Coolican thought that Dr Shimmin had approached the surgery in a manner consistent with the philosophy of kinematic alignment, he did not accept that Dr Shimmin's technique was actually the application of kinematic technique as at 2012. He said: "… reading Dr Shimmin's operation report, … his philosophy at that point in time, and bearing in mind, it's … our philosophies on alignment strategy are changing, was more towards balancing the knee, that is having ligaments that are equal tension throughout an arc of motion between the medial and lateral sides to the knee. And in order to achieve that I suspect he placed the tibia in slight varus. I don't think he was doing what we would call kinematic alignment at that point in time, but you'd have to discuss that with him."
It might also be noted that Dr Shimmin did not conduct any pre-operative assessment of Ms Roberts' knee and the question of malrotation was not addressed in Dr Shimmin's submissions in this context.
In S J MacDessi, W Griffith-Jones, I A Harris, J Bellermans and D B Chen, "Coronal Plane Alignment of the Knee (CPAK) classification" (2021) 103-B(2) Bone Joint J 329, it was emphasised that without knowing an individual's constitutional alignment, replication of native anatomy with kinematic techniques is not easily achieved.
In my view, the evidence to support the s 59 defence does not establish that the positioning of the tibial component in 8 degrees of varus and 8 degrees of external rotation constituted provision of a service in a manner that meets the test in s 59. This is for two principal reasons.
First, I am not satisfied that Dr Shimmin's description of the technique he adopted, and Dr Coolican's consideration of it as competent professional practice, meets that standard in the present case. At its highest, it describes a practice that has elements of kinematic technique, being the focus on ligament balance. It does not, however, take any account of the particular circumstances of Ms Roberts' knee, which required a focus on the tracking of the patellar tendon. The consideration of ligament balance obscures the significance of the patellar tendon, which appears simply to be assumed to track correctly if the ligaments balance. If this is indeed the case, I am not satisfied that the evidence demonstrates it to be so or that competent professional practice would permit such an assumption.
Secondly, even if I am wrong as to the relationship between ligament balance and the tracking of the patellar tendon, Associate Professor Stalley stated that a patient was entitled to a higher degree of stability in a TKR in 2012 than was achieved in Ms Roberts' case. The outcome of the surgery was not satisfactory and the knee was unstable, with the patellar tendon prone to subluxation and dislocation, with the consequence of instability, recurring hemarthroses and hemosiderotic synovitis. The outcome of the surgery, in circumstances where Dr Shimmin was aware of Ms Roberts' particular vulnerability, resulted in the tibial component being positioned in a degree of varus that Dr Shimmin accepted as indicative of error and in a degree of rotation that was not described in the evidence as being consistent with competent professional practice. Regardless of the conformity of the technique with then current surgical philosophy, the outcome spoke of error in its application.
In the circumstances, therefore, I am not satisfied that Dr Shimmin has made out his s 59 defence.

[29]

Principles for determination of factual causation

Ms Roberts must, of course, establish factual causation, in the sense that Dr Shimmin's negligence was a necessary condition of the occurrence of the harm. She must also establish that it is appropriate for the scope of his liability to extend to the harm so caused. However, this was not in issue in these proceedings.
Section 51 of the Wrongs Act requires the establishment of a factual, causal link between a defendant's negligence and the harm suffered. It is a retrospective enquiry in which the counterfactual of the probable course of events if the negligent act or omission had not been committed is considered: Strong v Woolworths Ltd t/as Big W (2012) 246 CLR 182; [2012] HCA 5. It may be established by a process of inferential reasoning from circumstantial evidence. The evidence must justify an inference of probable, rather than possible, connection: Transport Industries Insurance Co v Longmuir; Schneider v Hoechst Schering Agrevo Pty Ltd [2001] FCA 102; (2001) 50 IPR 555. See also Adelaide Stevedoring Co Ltd v Forst (1940) 64 CLR 538, Tubemakers of Australia Limited v Fernandez (1976) 50 ALJR 720 and Forder v Hutchinson [2005] VSCA 281 at [47].
In Tabet v Gett (2010) 240 CLR 537 at [111], Kiefel J stated: "All that is necessary is that, according to the course of common experience, the more probable inference appearing from the evidence is that a defendant's negligence caused the injury or harm. More probable means no more than that, upon a balance of probabilities, such an inference might reasonably be considered to have some greater degree of likelihood; it does not require certainty."
Counsel for both parties also referred to the comments of Basten JA in Elbourne v Gibbs [2006] NSWCA 127 at [75]: "Where it is demonstrated that a defendant has breached a duty owed to a plaintiff, and harm has followed, it would be understandable that the law might impose an onus on the defendant to show that his or her breach of duty had not caused the harm. However, that course has not been taken and it is clear beyond doubt that the burden of establishing causation lies on the plaintiff. On the other hand, in some circumstances the law has accepted that an inference of causation will arise from the existence of a temporal connection, together with other slender support. Thus, where medical science is unable to confirm or deny a causal connection between exposure to a potentially harmful agent and a particular medical condition, courts have been willing to infer on the basis of 'common sense' that a connection is established on the balance of probabilities."
It was submitted for Dr Shimmin that the present case does not raise the need for inferential reasoning. Senior Counsel submits that this is a case where the Court has before it a reasonable body of treating and expert evidence so as to permit findings as to whether, on the balance of probabilities, Ms Roberts' tibial component was malaligned and malrotated and whether that led to her deteriorating condition and need for further surgery. The question of whether a probable connection can be inferred, it was submitted, can be determined on the evidence. I agree.

[30]

Assessment of factual causation

As indicated at paragraph 149 above, Associate Professor Stalley found, during the revision TKR, that the patellar tendon was easily displaced laterally, and there was insufficiency and attenuation of the medial ligament structures such that the knee was quite mobile when physically examined under general anaesthetic.
I accept that this establishes that, at the time of the revision TKR, the knee was, in Associate Professor Stalley's words, "grossly unstable".
There was no real challenge to this finding. The issue between the parties was whether it was caused by the malpositioning of the tibial component in the primary TKR or whether there was some other cause or causes.
Associate Professor Stalley considered that the symptoms suffered by Ms Roberts were well described as consequences of malpositioning of the tibial component, particularly given Ms Roberts' lack of a patella to act as a restraining force against dislocation of the patellar tendon. The symptoms had developed over time, as a result of soft tissue changes in the knee, which accommodate the maltracking of the tendon.
Dr Coolican disagreed as to the cause of Ms Roberts' condition. In his view, the most likely cause was trauma suffered in August 2016, which caused a tear in the patellar tendon, leading to synovitis and hemarthroses. This conclusion was also bound up with his assessment of the question of whether Dr Shimmin had malpositioned the tibial component, as Dr Coolican considered the alternative explanation for Ms Roberts' condition to be the explanation most consistent with the imaging, with his reading of the reports of Dr Best and Dr Broe and with Ms Roberts' email communications with Dr Shimmin's rooms.
Dr Coolican explained, with particular reference to the August 2016 incident where Ms Roberts was walking her dog, that the absence of a patella meant that there was less restraining force on the femur sliding forward when Ms Roberts was walking down hill or forced to brace, in circumstances where she had a weak quadriceps. Due to the absence of a patella, he believed the femur pushed forward and Ms Roberts suffered a tear to her patellar tendon, which in turn caused synovitis. The synovitis then caused the hemarthroses, which were unrelated to the positioning of the implants. He also suggested that there may have been some loosening of the femoral component which contributed to the symptoms.
Put another way, Dr Coolican considered the episodic swelling in the knee was likely to be associated with synovitis, and the reason for the gradual onset of difficulty was that Ms Roberts' extensor mechanism did not work as well as it should, likely because of the prior patellectomy and prior tibial tubercle transfer. Her symptoms likely related to extensor mechanism problems and synovitis but not to any malalignment.
In determining the issue of causation, I have taken into account the approach commended by Tabet v Gate and the other cases referred to above. For the reasons which follow, I have concluded that the most likely cause of Ms Roberts' symptoms to be the malpositioning of the tibial component in the primary TKR and not any trauma suffered in August 2016.
Among Dr Coolican's principal criticisms was his view that, if the implant had been malpositioned, it would have caused Ms Roberts' problems immediately on completion of her rehabilitation after the primary TKR. On his reading of the reports of Dr Best in 2013 and of Dr Best and Dr Broe in 2016, together with Ms Roberts' email to Dr Shimmin's rooms on 23 October 2013, he considered that Ms Roberts had, in fact, had a good outcome from the primary TKR.
As set out above, I have concluded, on the basis of the whole of the relevant evidence before me, that Ms Roberts was not symptom-free in the period 2013 to August 2016. I have accepted Ms Roberts' account that she had experienced symptoms of instability and pain on prolonged flexion. My findings on the facts are, accordingly, inconsistent with a key assumption on which Dr Coolican's analysis rests. I have also accepted Ms Roberts' explanations as to her state of mind when corresponding with Dr Shimmin's rooms and in her consultations with Dr Best and Dr Broe, as set out above.
However, it remains the case that Ms Roberts did not suffer any acute symptoms, such as a hemarthrosis, until August 2016. If I am wrong about the existence of symptoms prior to that time, or if it were the case that such symptoms were only minor and unrelated to Ms Roberts' later symptomology, Associate Professor Stalley, whose evidence on this point I accept, explained why this would not derogate from a finding that Ms Roberts' symptoms after August 2016 were caused by the malpositioning of the tibial component: "malrotation, malalignment does not always present with symptomatology immediately. In the group of patients that I've - I was suggesting I was going to write up, many of them have been asymptomatic and had gradual onset of symptoms and have had malrotation, and it is my opinion that you can have malrotation early in knee replacement, which is asymptomatic, and becomes symptomatic with the passage of time. I felt that that applied here because the physical findings of the examination were most suggestive of that. DOWNING: would you agree that more typically when someone has a significant malalignment, and a malrotation, that they have some degree of symptoms and problems with function right through after the initial total knee replacement? WITNESS STALLEY: No, that is not the case. I have seen many patients, and patients of my own, that have been put in incorrectly, slightly malaligned by my fellows and registrars, and they don't necessarily have symptoms immediately, but you look at some of them, and I know they are going to have symptoms later on, and I make that a point - I make that comment to the patient. So, I have seen patients who have had malalignment, and I've suggested to them that this may be progressive in terms of beginning of symptoms, and progression of symptoms, and that I should see them should they get any of these symptoms. So yes, I do do that. DOWNING: Accepting that you've had patients that you've managed in that way, would you accept that the more typical presentation is of some degree of symptomology which then builds over time, rather than having a period of being entirely pain-free and having good function? WITNESS STALLEY: No, I would not. Most of these people are asymptomatic to start off with. They may actually not be symptomatic, I don't believe everything that the patients tell me, and they've had a terrible pain, and they may be 80% improved, and they think they're perfect, and if you really want to push it hard, you can get some symptoms out of them. So, often, a patient will say, 'I'm asymptomatic,' and in actual fact, there are some niggling things going on, and they become progressive with time. That would be the most common thing that I would see."
Accordingly, I am satisfied that Ms Roberts experienced some symptomology in the period prior to August 2016 and that the onset of symptoms from that time was, nevertheless, still likely to be caused by the maltracking of the patellar tendon.
Secondly, I consider the reports of Dr Best and Dr Broe to be unreliable to establish either Ms Roberts' condition with respect to instability, which was not in issue at that time, or her state of mind and subjectively experienced symptoms. Ms Roberts may well have been happy at the time with the primary TKR, given her reduced expectations and lack of any post-TKR point of comparison. In any event, I am reluctant to place much weight on such medical reports in light of Container Terminals Australia Ltd v Huseyin. I also consider the imaging inconclusive for the reasons described above.
Thirdly, I accept Associate Professor Stalley's view that malalignment is well described as an episodic cause of catching and the reconstructed knee giving way following a TKR. This is consistent with Ms Roberts' evidence from the period immediately following her rehabilitation after the manipulation in 2012, the catching sensation being recorded by Dr Shimmin in December 2012. It is also well described as a cause of pain. Malalignment is not, however, the only cause of catching. At best, the evidence of catching lends a small amount of additional support to the conclusion that Ms Roberts' knee was malaligned following the primary TKR.
Fourthly, the revision TKR resolved much of Ms Roberts' symptomology, even though the patellar tendon and quadriceps muscle structure remained intact. This suggests that it was the removal and replacement of the primary TKR prosthesis with the rotating hinge prosthesis that achieved such resolution.
Senior Counsel for Dr Shimmin, however, pointed out that there was some evidence of a tear in the patellar tendon in August 2016 and that, as a matter of mechanics, external rotation and tight medial ligament structures ought mitigate against the risk of lateral subluxation.
I have taken these matters into account but, on balance, have found the weight of evidence in support of a finding that Ms Roberts' symptoms were caused by malpositioning of the tibial component of the primary TKR. This would be so even if I were persuaded that Ms Roberts did suffer a tear in her patellar tendon in August 2016. However, I consider that the evidence of a tear in Ms Roberts' patellar tendon to be inconclusive. I am not satisfied on the evidence that external horizontal rotation mitigates against lateral subluxation where there is simultaneously a vertical malalignment in 8 degrees of varus.
On balance, I have preferred the conclusions of Associate Professor Stalley on the question of causation, which I have found to be more conformable with the evidence as to Ms Roberts' condition from 2013, the intraoperative findings of September 2018 and Dr Shimmin's acceptance that varus alignment of more than 7 degrees would be in error.
Finally, Ms Roberts' absence of a patella is a key distinguishing feature in considering the evidence concerning her condition and that which relates to post-TKR patients in general. As I have already noted, in the circumstances of a patellicised knee, subluxation or dislocation of the tendon is more likely if the tendon does not track precisely through the middle of the axis of the knee. As I have found excessive varus and external rotation in the primary TKR, it is, on the whole, more likely than not that such malalignment and malrotation was the cause of the subluxation, dislocation, instability and subsequent hemarthroses suffered by Ms Roberts, and I so find. This, in turn, caused the need for the revision TKR as a corrective to a failed TKR which, if successful, would have given Ms Roberts 20 years or more of pain-free, functional use.

[32]

Economic loss: lost income

Ms Roberts must demonstrate a diminution of earning capacity likely to cause financial loss: Husher v Husher [1999] HCA 47; (1999) 197 CLR 138 at [7] and Medlin v State GIO [1995] HCA 5; (1995) 182 CLR 1 at [2].
Ms Roberts' right knee symptoms have affected, and will continue to affect, her ability to work and her productivity by reason of the pain and discomfort it has caused and her method for alleviating it. This has affected both her work as a senior part-time member of NCAT and also her ability to undertake private consultancy work. It was submitted for Dr Shimmin that since 2021 Ms Roberts has had a residual capacity to earn, had she chosen to exercise it.
Mindful of the approach in Medlin v State GIO, I accept that the condition of Ms Roberts' knee has also impacted on her ability to perform work beyond the creation of physical impediments to her hearing matters and writing up reasons for decision. I accept that the emotional effect on Ms Roberts was such that the effects of her injury were a principal cause of her decision to take her unpaid sabbatical and her continued intention to sit two days, rather than four days, per month as a senior Tribunal member at NCAT.
Ms Roberts calculates her loss with respect to the lost net earnings from the St Vincent de Paul consultancy ($12,988 net of tax and Medicare levy), 11 lost days at NCAT from August 2016 ($6,043 net), 12 lost days at NCAT from April 2018 ($6,593 net) and 30 lost days at NCAT from August 2018 to January 2019 ($16,483 net). This amounts to $42,107.
Ms Roberts also claims lost income from April 2021, being the commencement of her unpaid sabbatical, to June 2023 in the sum of $64,561 net. I accept Ms Roberts' reasons for taking the sabbatical were as described above, and that this falls within the principles of Medlin v State GIO.
The total claim in respect of NCAT work and the St Vincent de Paul consultancy is, therefore, $106,668. I accept this figure.
Ms Roberts also seeks a buffer in respect of past lost consultancy fees. According to the Further Amended Statement of Particulars, Ms Roberts' income from her consultancy work has been modest, including during the period from 2012 to 2016. The high point was the 2018-19 financial year, in which she earned $4,912, which corresponds with the St Vincent de Paul project, which was initially for a fee of between $18,000 and $23,000, but which had to be abandoned because of difficulties associated with her knee.
It was submitted for Dr Shimmin that the evidence was insufficient to establish a pattern of such earnings from consultation work in the past. I accept the substance of this submission. Whereas Ms Roberts sought a buffer of $70,000 in respect of past lost consultancy income, it was submitted for Dr Shimmin that it ought be reduced by at least 50%. I accept Dr Shimmin's submissions in this respect and will therefore award $35,000 for the loss of consulting work from 2018.
Total past loss of earnings, therefore, are assessed at $141,668.
In addition, Ms Roberts is entitled to interest on past lost earnings, which I will ask the parties to calculate and agree on before making final orders. My own tentative calculation is $53,125.50 (being $70,834 x 10% x 7.5 years).

[33]

Economic loss: impairment of earning capacity

Ms Roberts' appointment to NCAT is on the basis of five-year terms, which to date have been renewed at the end of each term. Her present term expires in July 2025. She has indicated that will seek reappointment for another five-year term if her preference to sit for two days per month, rather than the customary four days, can be accommodated. But for the difficulties she has experienced with her knee, she would have sought reappointment to a further five-year term on the basis of four sitting days per month, and then a further term to follow that. At the conclusion of that putative further term, Ms Roberts will be 70 years old, retiring in 2035.
I accept Ms Roberts' evidence as to her intentions with respect to seeking reappointment to NCAT and see no reason to discount her claim on the basis of any doubt that she would, in fact, have been reappointed on that basis. I am satisfied that Ms Roberts' most likely future circumstance but for the breaches of duty by Dr Shimmin is that she would have continued as a part-time senior member of NCAT until the expiry of her next 5-year term, retiring at age 70 in 2035.
I also consider that Ms Roberts may have continued to conduct private executive coaching or other consultancy work, although any assessment of how much work she would have performed but for the breaches of duty by Dr Shimmin are more difficult to quantify.
Ms Roberts seeks a buffer of $150,000 in respect of lost earning capacity on the basis that she proposes to carry half the normal load of an NCAT senior member, in terms of sitting days, and her capacity to work is limited to that extent. I accept that she is so limited and that a buffer in respect of lost earning capacity is appropriate in the circumstances.
The defendant submits a buffer of $75,000 would be appropriate. It was submitted that this would reflect the likelihood that, in the future, Ms Roberts could continue working for NCAT four days per month, and possibly more, subject to being able to position herself so as to relieve pain. It was also submitted that she retains the prospect of obtaining further alternative work on a part-time basis.
In my view, the most likely outcome for Ms Roberts is that she will work as a senior Tribunal member at NCAT sitting two days per month and spending two days per month writing up her reasons for two further terms of appointment on the completion of her current term. She may continue to hold herself out as available for consultancy work if it can be performed according to her particular mode of working. In my view, taking account of the parties' respective submissions, the appropriate sum by way of a buffer for impairment of future earning capacity is $120,000.

[35]

Future out of pocket expenses

Ms Roberts' claim for future medical care, includes further consultations with Dr Stalley and general practitioners (both of which are agreed in the sum of $7,170), revision surgery in due course, physiotherapy and gym membership that would enable Ms Roberts to undertake waterborne exercises all year round.
There was no dispute that Ms Roberts is entitled to the cost of physiotherapy, although there was a dispute as to its extent. The relevant test is neither what was "ideal" treatment nor "necessary" treatment but what is reasonable treatment: in this regard see Arthur Robinson (Grafton) Pty Ltd v Carter (1968) 122 CLR 649 at 662.
Ms Roberts' claim is for 78 physiotherapy sessions in the first year, followed by 12 sessions per year for 18 years. In light of Ms Roberts' extensive history of physiotherapy, and what I consider to be her ability to take direction, I consider 78 sessions in the first year to be excessive. The more appropriate course would be that suggested by Dr Buckley in his 29 March 2022 report, which was 12 sessions annually. On the basis of $100 per session for 18 years (subject to the appropriate multiplier), according to my tentative calculation, this amounts to $14,418. I will give the parties an opportunity to revisit these calculations, however, before entering final orders.
Ms Roberts' claim for future gym membership was based on her need for waterborne exercise. As she is able to perform such activities in outdoor pools in the summer months, she has reduced her claim in this regard by half. I will allow the balance of the claim in the sum of $12,018.50.
Further, I do not see any proper basis for any further revision surgery being an expense referable to any breach of duty by Dr Shimmin. The evidence in this regard was that Ms Roberts could have expected up to 20 years of service from the TKR and she was deprived of this by needing the revision TKR some 6 years later. Any further TKR would have followed in either case. Accordingly, I do not allow the claim for revision surgery in 10 years' time, quantified in the Further Amended Statement of Particulars at $17,217.

[38]

Non-economic loss

Ms Roberts' claim for non-economic loss has two components: limitation of right knee function, pain and multiple hemarthroses prior to the revision TKR on 4 September 2018; and continued ongoing flexion pain and difficulty using stairs since the revision TKR.
On 21 December 2021, Ms Roberts was issued with a certificate under s 28LN of the Wrongs Act by Professor Love, certifying that she had suffered a significant injury within the meaning of s 28G of the Wrongs Act and therefore, has satisfied the threshold to recover damages for non-economic loss provided in s 28LE. Non-economic loss is defined in 28B as meaning any one or more of pain and suffering, loss of amenities of life, and loss of enjoyment of life.
Section 28G provides that the maximum sum allowable for non-economic loss under the Wrongs Act was, in 2016, $577,050 and, by reason of indexation, is now well over $660,000. Section 28G does not provide that the maximum amount is reserved for the worst cases and does not impose a scaling exercise but the appropriate amount is determined as a common law assessment, with the amount to be reduced if it would otherwise exceed the cap: see Harold Luntz and Sirko Harder, Assessment of Damages for Personal Injury and Death (5th ed, 2021, LexisNexis) at [3.6.46].
Ms Roberts' claim in this regard was for $200,000 plus interest. For Dr Shimmin, it was submitted that $100,000 was a more appropriate figure, given Ms Roberts' pre-existing and underlying knee condition, leading to an earlier patellectomy, and evidence of her improvement since the revision TKR.
On the evidence before me, I consider that Ms Roberts' pain and suffering, loss of amenities of life, and loss of enjoyment of life during the period from the completion of her rehabilitation from the primary TKR to the conduct of the revision TKR to have been substantial, particularly from August 2016. She suffered pain and instability in her knee, which affected her day to day life and recurrent, painful hemarthroses. In the period since the revision TKR, Ms Roberts has recovered much of her prior mobility and condition. However, she continues to suffer pain and difficulty and will do so for the rest of her life.
In the circumstances, I consider the sum of $175,000 to be an appropriate award for non-economic loss.
Interest on past non-economic loss is assessed at 2% per annum on half of this sum, which is $11,500 to date.

[41]

Section 44(3) application for increased jurisdiction

Ms Roberts also makes an application under s 44(3) of the District Court Act 1973 to increase the jurisdictional limit applicable to this claim to the present jurisdictional limit of the Court of $1,2450,000.
At the time that these proceedings were commenced, pursuant to s 44(1) of the District Court Act, the jurisdictional limit was $750,000. Ms Roberts' claim, as quantified at the commencement of the trial, was in the sum of $838,365.
In light of my findings above with respect to quantum, any need for the application does not arise. Nevertheless, if either my findings or my calculations are incorrect, I consider Ms Roberts' application below.
Section 44(3) provides: (3) Where - (a) an amendment to subsection (1) which is enacted after, or was enacted before the commencement of Schedule 3 to the District Court (Procedure) Amendment Act 1984 has or had the effect of increasing the amount specified in paragraph (a) or (b) of that subsection, and (b) an action in which an amount of money is claimed is pending at the time when the amendment has effect or, as the case may be, an action in which an amount of money is claimed was pending at the time when the amendment had effect and has not been finally determined, the Court may, on the application of the claimant, make an order altering the amount specified in the claim to an amount not exceeding that specified in paragraph (a) or (b) of that subsection, as in force immediately after the amendment has or had effect.
Counsel for Ms Roberts referred me to Csalar v Cirosta (2002) 55 NSWLR 212 at [27], where O'Keefe J took the approach that the relevant time at which regard is to be had to the amount in the statute is the time of hearing rather than the date of institution of the action. Senior Counsel for Dr Shimmin submitted that Csalar v Cirosta did no more than stand for the obiter proposition that where there is an increase in the jurisdictional limit, it should be applicable in actions commenced before the amendment, subject to the determination of any particular application on its merits.
In this case, I consider that the merits would have justified an order under s 44(3). The sum sought was a comparatively small amount in excess of the jurisdictional limit at the time of commencement, and includes the calculation of interest. The conduct of Ms Roberts in commencing in this Court was reasonable and it would have been an unnecessary and unreasonable requirement that she either seek to have the proceedings transferred to the Supreme Court or disclaim part of her claim because the final quantification of her claim exceeded the jurisdictional limit at the time of commencement by about 11%.
In the circumstances, however, the question does not arise.

Roberts v Shimmin

At a glance

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Judgment (44 paragraphs)

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Cases Cited (31)