Abstract
Background: To asses the safety and efficacy of the Wallis Stabilization System in degenerative disorders of the lumbar spine.
Methods: A prospective international multicentre clinical and radiological outcome assessment study. The study is ongoing. The study group comprises 260 consecutive patients meeting inclusion and exclusion criteria with respect to diagnosis (and levels affected), age, medical conditions and prior surgery. 61% were male, 39% female and the mean age was 44 years. The principal diagnosis was massive disc herniation in 37%, degenerative disc disease (with Modic type I change) in 27%, canal stenosis in 13%, recurrent disc herniation in 9% and disc herniation above a transitional segment in 5%. L4/5 was the operated level in 88%. Clinical assessment has been performed using a p atient completed questionnaire incorporating SF-36, JOA (Japanese Orthopaedic Association score), VAS (lumbar pain Visual Analogue Score, 0–100), ODI (Oswestry Disability Index) and Odem’s Criteria. Any adverse or serious adverse events were documented. Pre-operative static and dynamic radiographs and MRI scans have been undertaken, and the radiographs are then repeated at 3 and 6 months post-operatively and yearly thereafter. Post-operative MRI scans are obtained on a yearly basis up to 5 years post-surgery.
Results: Mean operating time has been 74 minutes overall, with mean implantation time of 19 minutes. Blood loss averaged 180 mls. The pre-operative mean VAS of 71 improved to 21 at 3 months (p< 0.01) with further improvement at 6 months (VAS 18) and 1 year (VAS 11). SF-36 scores improved in every category from 3 months onwards, this improvement being statistically significant in all categories except general health. At 1 year SF-36 scores were not distinguishable from an age and sex matched general population. JOA scores improved significantly from 6.1 (15 point scale) pre-operatively to 12.5 at 3 months and 13.7 at 12 months (p< 0.01). Odem’s criteria provide additional evidence of efficacy, with 80% of subjects categorized as ‘good’ or ‘excellent’ at 3 months, this proportion improving to 89% at 1 year. Of those graded as ‘fair’ at 3 months, half had improved to ‘good’ or ‘excellent’ by 1 year.
From the series of 260 cases there were only 3 implant related complications (1.2%).
Conclusion: Previous biomechanical and finite element analysis studies have shown that the Wallis stabilization system off-loads the intervertebral disc and improves the biomechanical characteristics of the degenerative lumbar motion segment. The surgical procedure is simple, minimally invasive and non destructive, preserving surgical options for the future.
This study provides preliminary evidence with respect to the safety and efficacy of the Wallis Stabilization System.
The abstracts were prepared by Mr Colin E. Bruce. Correspondence should be addressed to Colin E. Bruce, Consultant Orthopaedic Surgeon, Alder Hey Children’s Hospital, Eaton Road, Liverpool, L12 2AP.
