Abstract
Introduction: The purpose of this study was to evaluate the design of a titanium/polyolefin artificial disc, assess its safety and measure outcome to determine if a RCT is justified.
Methods: All subjects entered this pilot study with one or two-level disc disruption at l4/l5 and/or l5/s1 and had disabling low back pain for at least 12 months. The diagnosis was confirmed by discography. Independent assessment included physical examination, VAS for pain, Low-Back Outcome Score (LBOS), Oswestry Disability Index (ODI), SF-36, lateral flexion/extension radiographs and MRI. This was carried out preoperatively, at 6 and 12 weeks, 6 months and at 1 and 2 years. Surgery was performed by an anterior retroperitoneal approach.
Results: Twenty-eight cases (14 males; average 41 years) were operated on during 1998–2000. Surgery was performed at L5/S1 in 19, L4/L5 in 5 and both levels in 4. Operating time averaged 130 minutes with 180mls average blood loss. There were no operative complications and average length of stay was 6 days. At 2 years there was 39% average improvement in vas, 15-point average improvement in ODI, 14 point average improvement in LBOS and improvement in 5 of the 8 SF-36 sub-scales. Complications included detection by plain radiographs of early partial displacement of implant in one case and late heterotopic calcification in another. Thin section helical CT, first carried out in early 2001, revealed polyolefin tears in 10 patients, four undergoing revision surgery since 2-year follow-up. CT revealed instances of osteolysis associated with polyolefin failure and hetero-topic bone formation not seen on plain radiographs.
Discussion: Although improvements in clinical outcome comparable to that reported with fusion were obtained at two years, detection of elastomer tears by thin section CT in 36% of patients indicated the prosthesis was not suitable for clinical use. This finding was unexpected given the results of prior extensive mechanical testing1.
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 Serhan H, Lowery G, Fraser RD. Biomechanical characteristics of a new disc prosthesis. Poster presentation at the annual meeting of the International Society for the Study of the Lumbar Spine, Edinburgh, Scotland, 2001. Google Scholar
