To assess radiological fusion rates in posterolateral fusions using SiS-CaP. Retrospective, radiological follow-up study. Single surgeon series of 76 consecutive patients were evaluated, in a regional spinal unit. All patients had clinical and radiological (MRI) spinal canal stenosis secondary to degenerative spondylosis or spondylolisthesis. Surgery consisted of instrumentation, decompression and meticulous preparation of the posterolateral graft bed by removal of all soft tissues posterior to the inter-transverse membrane and decortication of transverse processes (TPs). SiS-CaP putty was injected into this gutter and moulded around the instrumentation. Good quality, well prepared bone chips from the posterior decompression were seeded into the putty. Patient radiographs were reviewed at 3-6 months, 1 year and 2 years. Radiographs were assessed using a protocol to examine granularity, bone formation and evidence of pseudarthrosis, based upon previously reported literature 1 and our personal experience. Of the 76 patients, 26 were excluded. M:F was 21:29. Mean age was 58yrs. Average number of motion segments fused per case was 2.2. There was one pseudarthrosis with metalwork fracture, and thus a total fusion rate of 98%. In addition, one patient had scanty bridging of TPs, and one patient had lucency around the S1 screws. SiS-CaP, as a bone graft substitute in posterolateral instrumented fusions, gives comparable results to published fusion rates using autologous iliac crest grafting and/or Bone Morphogenic Protein 2. Moreover, it avoids the associated morbidity of iliac bone harvest.
