Abstract
Introduction: The Wallis implant was developed as a minimally invasive and anatomically conserving method of addressing the various biomechanical derangements associated with lumbar degenerative changes without recourse to rigid fixation.1 The Wallis implant evolved from successful clinical experience in over 300 patients with a first generation implant, supported by detailed biomechanical and finite element studies. These demonstrated that the implant improves the stability of the degenerate motion segment, reduces loads transmitted through the intervertebral disc and facet joints and improves the dimensions of the spinal canal, lateral recesses and root foramina. The purpose of the present ongoing study is to demonstrate the tolerance of this implant and its efficacy against low back pain and functional disability in patients with degenerative disc disease.
Methods: A prospective multi-centre international observational study was commenced 2 years ago. The inclusion criteria were degenerative disc disease without disc herniation, recurrence of herniated disc, voluminous herniated disc (corresponding to a complete loss of the nucleus) and herniated disc accompanying the transitional anomaly, sacralisation of L5. Assessment includes SF-36, JOA, VAS and Oswestry Disability Index, and all patients undergo pre-operative radiographs and MRI scans with interval radiographs and scans post-operatively. The study will be continued for a minimum of five years.
Results: Thus far 210 patients have been recruited and 1-year review is available for 51. Preliminary 1-year results confirm the clinical efficacy of this procedure in the management of low back pain and as an adjunct in the treatment of radicular and stenotic symptoms. Furthermore, in some instances MRI evaluation has shown re-hydration of the disc nucleus.
Discussion: The procedure involves no additional exposure or muscle dissection compared with simple flavectomy decompression. The supraspinous ligament and facet joints are preserved and no bony fixation is required. As such the procedure can potentially be reversed and all options for future procedures, if required, are preserved. There is no adverse effect on adjacent segments.
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 Sénégas J. Mechanical supplementation by non-rigid fixation in degenerative intervertebral lumbar segments: the Wallis system. Eur Spine J. 2002; 11Suppl 2:S164–9. Google Scholar
