In reaching its conclusion, the Panel decided that the definition of permanent impairment contained in Section 1.1 of Chapter One of the Guides, quoted above (which is similar to, but not identical with, the definition of permanent impairment contained in the Glossary included in the Guides) required it to assess Mr Taylor's permanent impairment based upon his post-surgery condition. In other words, it resolved what it saw as an "apparent conflict" between the two parts of the Guides referred to by discounting Mr Taylor's assessment because the surgery he underwent appeared to have been successful. In doing so it preferred what it considered Section 1.1 (and the Glossary) meant to the directive in Section 3.3d.
11 The question for this Court is whether, in taking that approach, the Medical Panel was carrying out the statutory function conferred upon it by s 67(1) of the Accident Compensation Act 1985; that is to say whether it was answering the medical question asked of it pursuant to s 104B(9) of that Act according to law. The proper interpretation of the Guides is a question of law, even if the application of their requirements and conclusions reached as a result of that application are questions of fact.[2]
12 To evaluate the correctness of the Medical Panel's approach it is necessary to consider the content of Chapter Three of the Guides (The Musculoskeletal System) and in particular Section 3.3 (the Spine) in more detail.
Chapter Three - The Musculoskeletal System
13 Chapter Three of the Guides provides mechanisms for the assessment of permanent impairment of those parts of the body described as the musculoskeletal system. It has sections which deal with the upper extremities, the lower extremities, the spine and the pelvis. Each of these sections is, itself, divided into sub-sections depending upon the parts of the body being considered.
14 The introduction to Chapter Three directs the reader to a study of Chapters One and Two and the Glossary at page 315 of the Guides before attempting an assessment using Chapter Three. For present purposes it is sufficient to note that in Chapter One and the Glossary there are definitions of "permanent impairment" to which reference has already been made.
15 Chapter Three, Section 3.3 relates to the spine. It commences by offering two different methods of approach to the assessment of permanent injury to the spine. One, which it says applies especially to traumatic injuries is called the "Injury Model". Its use involves assigning a patient to one of eight categories on the basis of objective clinical findings. The Injury Model is sometimes referred to as the "Diagnosis-Related Estimates (DRE) Model". The other is called the Range of Movement model.
16 In its introductory remarks concerning the spine the Guides emphasise that only one of these models should be used to assess permanent impairment. It directs an assessor to the Injury Model if a patient's condition is one of those listed in Table 70 of the Guides. This table, to which reference will be made again, describes a patient's condition and assigns various categories to that condition, which categories lead to an attribution of a "percent" to the patient as being his or her permanent impairment of whole body function. Those remarks also contain a further definition of permanent impairment. Again, it is similar to but not identical with those definitions contained in Chapter One and in the Glossary. These differences are not material in this case.
17 In Mr Taylor's case, no question of which assessment approach should have been used arises. The Medical Panel used the Injury Model as it apparently considered that Mr Taylor's condition could be adequately described by one of the descriptors used in Table 70. As neither party suggested that this determination, which involves a clinical judgment within the particular expertise of the Medical Panel, was erroneous, it need not be considered further.
18 The use of the Injury Model requires the examiner's clinical findings and other medical information to be applied to Table 70 of the Guides to produce a spine impairment category having a number from I to VIII. That spine impairment category is then applied to Table 73 (for cervicothoracic spine impairment) to provide the "percent" whole person impairment resulting from the identified injury to the spine. In some cases further analysis in accordance with the Guides must be undertaken before a final conclusion can be reached and it may even be appropriate in some cases to consider the Range of Movement Model as well. However that is not the case here. The only question is whether, in using the Injury Model the Panel ought to have taken any account of the remedial effect which surgery had had on the condition of Mr Taylor's neck.
19 The Medical Panel recognised that if it ignored the effects of surgery on Mr Taylor it would have determined a whole person impairment of 25% of body function in his case[3]. It said: