Abstract
INTRODUCTION: A prospective, randomised, controlled study has been conducted to compare the clinical outcomes of patients treated with an Artificial Cervical Disc to patients who receive fusion after cervical discectomy for the treatment of primary cervical disc disease. It is hypothesised that maintenance of motion after anterior cervical discectomy will prevent the high rate of adjacent level premature degeneration. The primary purpose of the study is to prove equivalence (non inferiority) of outcome of the disc prosthesis in the short term compared with fusion.
METHODS: In four centres, 60 patients with primary, single level cervical disc disease producing radiculopathy and/or myelopathy are randomised prospectively to receive anterior cervical discectomy with either fusion or artificial cervical disc placement. The patients are evaluated with pre- and post-operative serial flexion-extension cervical X-rays at six weeks, three, six, 12, and 24 months. At the same intervals, the patients have pre- and post-operative neck disability indexes, visual pain analogue scales, European myelopathy scores, SF-36 general health scores, and neurological status examinations assessing the patient’s reflex, motor and sensory function.
RESULTS: Data are presented for the first 47 patients. At six weeks the neck disability index reduced by 36.1 for the investigational group compared to 34.8 for the fusion group. The pain score had reduced by 8.2 for the investigational group and by 9.9 for the control group. This improvement appeared to be maintained until the 12 month follow-up. In general there appeared to be a slightly better outcome for the investigational group. Both pain score and disability scores improved statistically significantly compared to the pre-operative scores (p< 0.001 all comparisons). Analysis of non inferiority of outcome for the investigational group using ANCOVA with the pre-operative score as the covariate and a non inferiority margin of five points showed statistical significance at six and 12 weeks for Neck disability index. Operative time appeared slightly less (2.3 hours) for the investigational group compared to the fusion group (2.5 hours). Blood loss also appeared higher in the fusion group (165 mls compared to 91 mls). Hospital stay was equivalent (2.8 days and 2.9 days).
DISCUSSION: Anterior cervical discectomy and fusion has a good short term outcome though there is a high incidence of failure at adjacent levels over time. It is hypothesised that the maintenance of motion of a segment will prevent adjacent premature degeneration. It will take long term follow-up studies however to prove this. In the meantime, the justification to insert artificial cervical prostheses rests on being able to prove equivalence of outcome between fusion and prosthesis in the short term. This paper shows that the outcomes appear to be equivalent. Early statistical evidence is available for some of the outcome measures at early post-operative follow-up. Further statistical power will be available when the full 60 cases are available for study and this may give further weight to the hypothesis of equivalence of outcome.
These abstracts were prepared by Dr Robert J. Moore. Correspondence should be addressed to him at Spine Society of Australia, Institute of Medical and Veterinary Science, The Adelaide Centre for Spinal Research, Frome Road, Adelaide, South Australia 5000.
