Abstract
Introduction: Following a systematic review of the literature, de Kleuver1 concluded that there was insufficient data to assess the performance of total disc replacement. In the absence of controlled trials, the relative merits and efficacy of artificial disc replacement as a treatment option for degenerative disc disease was unproven. Observational studies reported a moderate success rate (50-81%), but a relatively high complication rate (3%–50%). In particular, 4% of the operated levels fused spontaneously or after revision surgery.
Methods: Using the research methodology of the above study, all subsequent published studies of artificial lumbar disc replacement were identified and reviewed by meta-analysis. In the two years (2002–2003) since the above study, a further nine case series and three controlled studies have been reported. The three randomised controlled trials compared disc replacement with spinal fusion. Seven prospective studies (include the randomised controlled studies) had defined indications, exclusions and outcome measures.
Results: A total of 623 disc replacements were performed in 510 patients. The outcomes were classified as “good” or “excellent”, ranged from 70–93% (mean=83%). Complications were observed in up to 35% (mean=3%) of patients. Eight patients subsequently underwent spinal arthrodesis at the level of the disc replacement. Two patients were reported to have heterotopicossification.
The outcomes for the 2002–2003 publications were better (MWp=0.02) than for the de Kleuver study. Fewer patients had disc replacement at more than one level (FEp< 0.01). The number of patients undergoing secondary surgery (FEp< 0.01) and arthrodesis (FEp=0.04) was less and the incidence of prosthetic subsidence or migration was lower (FEp=0.28). This overall improvement in recent studies highlights the importance of patient selection and the use of a disc replacement of appropriate size.
Following disc replacement, there was a significant improvement in outcome measures at six-week follow-up. This improvement was maintained at two years. While disc replacement reported significantly less pain and disability in the early period following surgery compared with the fusion, the difference was not significant by six months.
Discussion: In the short to medium term, disc replacement is as effective as spinal fusion in the treatment of degenerative disc disease in critically selected patients. Although the number of complications has been reduced, some serious complications were reported.2 A satisfactory salvage procedure for failed disc replacement is yet to be found. The long-term biological effects of disc replacement are unknown. Late failure of disc replacement is predictable in a substantial number of patients. Long-term studies of ten or more years are necessary to adequately define the place of disc replacement in the treatment of lumbar disc disorders. Because the numbers of disc replacement patients is likely to be small, protocols and outcome measures should be standardised and data centrally recorded.
The abstracts were prepared by I. B. McPhee. Correspondence should be addressed to the Spine Society of Australia Secretariat, The Adelaide Centre for Spinal Research, Institute of Medical and Veterinary Science, PO Box 14, Rundle Mall, Adelaide SA 5000, Australia.
References:
1. de Kleuver M, Oner FC, Jacobs WC. Total disc replacement for chronic low back pain: background and a systematic review of the literature. Eur Spine J.2003;12:108–16. Google Scholar
2. van Ooij A, Oner FC, Verbout AJ. Complications of artificial disc replacement: a report of 27 patients with Charitédisc. J Spinal Disord Tech.2003;16:369–83. Google Scholar
