Abstract
Introduction A prospective, randomised, controlled study has been conducted to compare the clinical outcomes of patients treated with a Presige® artificial cervical disc (Medtronic Sofamor Danek, Memphis, TN) to patients who receive fusion after cervical discectomy for the treatment of primary cervical disc disease. It is hypothesized that maintenance of motion after anterior cervical discectomy will prevent the high rate of adjacent level premature degeneration. The primary purposes of the study are to (1) prove equivalence (non inferiority) of outcome of the disc prosthesis in the short term compared with fusion; and (2) to asses the ability of the prosthesis to maintain motion. Enrolment has closed and this is a report of the data with 50 cases with 6 month follow-up and 9 cases having reached 24 month final follow-up.
Methods In four centres, 52 patients with primary, single level cervical disc disease producing radiculopathy and/or myelopathy were randomised prospectively to receive anterior cervical discectomy with either fusion or artificial cervical disc replacement. The patients were evaluated with pre and postoperative serial flexion-extension cervical x-rays at 6 weeks, 3, 6, 12, and 24 months. At the same intervals, the patients had pre and postoperative 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 At 6 weeks the neck disability index reduced by 34.1 for the investigational group compared to 35.2 for the fusion group. The improvement seen in the treatment groups was statistically equivalent (p < 0.05, non-inferiority margin = 10) up to the 24-month follow-up interval. The pain score had reduced by 7.7 for the investigational group and by 9.7 for the control group. Both groups improved statistically from preoperatively though statistical equivalence could not be shown. This improvement appeared to be maintained until the 12 month follow-up. Mean arm pain scores improved in both groups with statistical equivalence being demonstrated (p < 0.05, non-inferiority margin = 10). The adverse events in both groups were similar. Analysis of range motion showed a mean preoperative range of motion in the arthroplasty group of 5.9 degrees and 6.3 degrees in the fusion group. At twelve months the arthroplasty group had a mean range of motion of 5.9 degrees and the fusion group had a mean range of motion of 1.1 degrees
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 mean time, 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, in the short to medium term, the clinical outcomes appear to be equivalent to fusion. And that range of motion is maintained.
The abstracts were prepared by Professor Bruce McPhee. Correspondence should be addressed to him at Orthopaedics Division, The University of Queensland, Clinical Sciences Building, Royal Brisbane & Women’s Hospital, Herston, Qld, Australia
