The purpose of this retrospective study, is to demonstrate the survivorship and clinical effectiveness of the Wallis implant, against low back pain and functional disability in patients with degenerative lumbar spine disease. The Wallis Interspinous implant, was developed as a minimally invasive and anatomically conserving procedure, without recourse to rigid fusion procedures. The initial finite element analysis and cadaver biomechanical studies showed that the Wallis ligament improves stability in the degenerate lumbar motion segment. Unloading the disc and facet joints reduces intradiscal pressures at same and adjacent levels allowing for the potential of the disc to repair itself. A total of 157 patients who had wallis ligament insertion between 2003 and 2009 were reviewed, with a mean age of 54 and were followed for 48 months on average. Patients were assessed pre-operatively and post-operatively every 6 months by VAS pain score, Oswestry Disability Index and SF-36. 90% of patients improved, to show a minimal clinical difference, compared to the pre-operative evaluation. There is overall 75-80% good clinical outcome. Low infection rate of 1.1%. Two cases of prolapsed discs at the same level requiring further discectomy, 7 required fusion. No fractures or expulsions. The Wallis implant represents a safe non-fusion stabilisation device in the treatment of degenerative lumbar spine disease with canal stenosis. There is less soft tissue damage, quick rehabilitation, less morbidity and associated low complication rate

Introduction. Lumbar spondylolysis is a fatigue fracture of the pars interarticularis and correlates with Spina Bifida Oculta (SBO) in 67%. Hpothesis. Load is normally transferred across the arch in axial rotation. Bifid arch results in increased strain across the isthmus of the loaded inferior articular process. Aim of investigation. Finite element (FE) analysis of altered load transfer in combined axial rotation and anteroposterior shear in SBO potentially predisposing to fatigue fracture of the pars interarticularis. Methods. FE models of natural and SBO (L5-S1) including ligaments were axially load to 1kN and an axial rotation of 3° applied. Bilateral stresses and strains on intact and SBO lateral inferior lines of the L5 isthmus were assessed and compared. Results. Under 1000N axial load: Maximum von Mises stress observed on left and right lateral inferior lines of L5 isthmus were 0.13 and 0.24 MPa, with maximum equivalent strain values of 1.56 and 2.91 (strain, for natural spine and SBO, respectively. Combined with 3° axial rotation (rotation of spinal processes toward right lateral side): Left lateral L5 isthmus stresses increased to 0.49 and 0.77 MPa for natural spine and SBO, respectively. Right lateral L5 isthmus values increased to 0.67 and 0.95 MPa for natural spine and SBO, respectively. The percentage increase in SBO strains compared to the natural spine on the L5 isthmus were +57.9 and +40.2%. Conclusion. Significant load transfer occurs through the vertebral arch in axial rotation. In SBO this load transfer is lost and mechanical demand on the isthmus is significantly increased. Strain increases across the L5 isthmus in axial rotation by +40.2% to +57.9% compared to normal and may predispose to fatigue fracture

This study prospectively compared the efficacy of kyphoplasty using a Jack vertebral dilator and balloon kyphoplasty to treat osteoporotic compression fractures between T10 and L5. Between 2004 and 2009, two groups of 55 patients each underwent vertebral dilator kyphoplasty and balloon kyphoplasty, respectively. Pain, function, the Cobb angle, and the anterior and middle height of the vertebral body were assessed before and after operation. Leakage of bone cement was recorded. The post-operative change in the Cobb angle was significantly greater in the dilator kyphoplasty group than in the balloon kyphoplasty group (−9.51° (sd 2.56) vs −7.78° (sd 1.19), p < 0.001)). Leakage of cement was less in the dilator kyphoplasty group. No other significant differences were found in the two groups after operation, and both procedures gave equally satisfactory results in terms of all other variables assessed. No serious complications occurred in either group.

These findings suggest that vertebral dilator kyphoplasty can facilitate better correction of kyphotic deformity and may ultimately be a safer procedure in reducing leakage of bone cement.