Abstract
Introduction: The initial promise of stand-alone threaded anterior interbody fusion cages to treat chronic low back pain has not been maintained. In an attempt to overcome some of the problems associated with threaded fusion devices (endplate subsidence, failure to re-establish lordosis and displacement) a two-part ALIF cage was devised. The device consists of a rectangular frame that accommodates a threaded, open-weave cylinder holding bone graft material. The device addresses the biomechanical issues required for successful ALIF whilst providing a large area for bone in-growth and is a less invasive solution than a formal 3600 fusion.
Methods: From August 2001 to December 2002, 41 patients who fulfilled selection criteria for a single or two-level 3600 spinal fusion for low back and leg symptoms underwent ALIF using Stabilis. All patients had failed to improve with all non-invasive and minimally invasive treatments available to them. Prospective follow-up has continued for all cases using the Low Back Outcome Score and a Patient Satisfaction Score. Plain x-rays were taken at 3, 6 and 12 months post-operatively and the 12-month series included flexion and extension films.
Results: Ten patients (24.4%) have completed more than 12 months follow-up; 18 (43.9%) are between six and twelve months post surgery and the rest (31.7%) have less than six months follow-up. LBOS results for the first 10 showed 9 (90%) as excellent or good. LBOS results for the second group of 18 were excellent or good in 15 (83.3%). All but two of the 28 patients, would be prepared to undergo the procedure again and all would recommend the operation to a friend with similar trouble. Radiographic assessment at 6 months showed 16 patients had at least a partial anterior or posterior sentinel sign. Using motion criteria, all 10 cases at one year were fused on flexion and extension lateral x-rays. No devices migrated anteriorly or posteriorly and no lucent lines have been seen around the implants. Three of the two-level procedures showed some subsidence of the L4/5 implant into the L5 vertebral body, but none were symptomatic. No clear reasons have emerged to explain the clinical failure of 14% of the patients given the radiological success. In only one was there a mismatch in the LBOS outcome measure and the satisfaction rating.
Conclusions: Stabilis is a useful standalone ALIF device that not only addresses the theoretical biomechanical failures of anterior threaded interbody fusion cages, but has been shown in this early clinical and radiological evaluation to be effective, objectively and subjectively. It is likely that in the medium term future, fewer patients will require fusion to treat back and leg pain as the results from lumbar spine arthroplasty become established and non-fusion technologies become accepted. Until that time, experience in the UK and USA suggests that Stabilis is a good alternative to 3600 fusion.
The abstracts were prepared by Dr Robert Moore. Correspondence should be addressed to him at Spine Society of Australia, c/o the Adelaide Centre for Spinal Research, Institute of Medical and Veterinary Science, PO Box 14, Rundle Mall, Adelaide SA 500, Australia.
