Efficacy of a needle-shaped Biphasic Calcium Phosphate ceramic versus autograft in instrumented posterolateral spinal fusion-a multicenter randomized noninferiority trial with intra-patient design

Introduction: Successful spinal fusion with a solid bone bridge between the vertebrae is traditionally achieved by grafting with autologous iliac bone. However, the disadvantages of autograft and unsatisfactory fusion rates have prompted the exploration of alternative bone grafts. A novel polymer embedded biphasic calcium phosphate bone graft with a submicron needle-shaped topography (BCP<µm) was developed to predictably form bone in spinal fusion.

Methods: Adults indicated for PLF (one to six levels) were enrolled at five centers. After bilateral instrumentation and fusion-bed preparation, the randomized allocation side was disclosed. Per segment 10cc of BCP<μm granules (1-2 mm) was placed in the posterolateral gutter on one side and 10cc autograft on the contralateral side. Fusion was systematically scored on one-year follow-up CT scans. The study was powered to detect >15% inferiority with binomial paired comparisons of the fusion performance score per treatment side. At segment level, a Generalized Estimating Equations (GEE) model was used accounting for clustering of fusions within segments and within patients.

Results: Out of 100 patients (57 ±12.9 years, 62% female), 91 subjects and 128 segments were analyzed. The overall posterolateral fusion rate per segment (left and/or right) was 83%. For the BCP<μm side the fusion rate was 79% vs. 47% for the autograft side (difference 32 percentage points, 95% CI = 23 to 41). Analysis of the primary outcome confirmed the non-inferiority of BCP<μm with an absolute difference in paired proportions of 39.6% (95% CI = 26.8 to 51.2%, p< 0.001).

Conclusion : This clinical trial demonstrates superiority of BCP<μm as a standalone ceramic compared to autograft for spinal fusion and supports the use of a novel bone graft for spinal fusion without the need for added cells, growth factors, or autologous bone. These findings may influence the standard of care and gold standard treatment for patients undergoing spinal fusion.