Biphasic Calcium Phosphate Bone Graft with Submicron-Sized Needle-Shaped Surface Topography is Favorable in an Intra-patient Controlled Trial

Introduction: Pseudoarthrosis after spinal fusion is an important complication leading to revision spine surgeries. Iliac Crest Bone Graft is considered the gold standard, but with limited availability and associated co-morbidities, spine surgeons often utilize alternative bone grafts. This study serves to determine the non-inferiority of a novel submicron-sized needle-shaped surface biphasic calcium phosphate (BCP<µm) as compared to autograft in instrumented posterolateral spinal fusion (PLF).

Methods: Adult patients indicated for instrumented PLF of one to six levels from T10-S2 were enrolled at five participating centers. The randomized allocation side of the graft type was disclosed after preparation of the bone bed. One side was grafted with 10 cc of autograft per level containing a minimum of 50% iliac crest bone. The other side was grafted with 10 cc of BCP<µm granules standalone. In total, 71 levels were treated. Prospective follow-up included a fine-cut ( < 1mm) Computerized Tomography (CT) at one year. Fusion was systematically scored as fused or not fused per level per side by two spine surgeons blinded for the procedure.

Results: The first fifty patients enrolled are included in this analysis. Average age was 57 years old, with 60% female and 40% male. The diagnoses included deformity (56%), structural instability (28%), and instability from decompression (20%). The fusion rate determined by fine-cut CT for BCP<μm was 76.1% (54/71 levels), which compared favorably to the autograft fusion rate of 43.7% (31/71 levels). Fusion of the BCP<μm side was not contingent upon fusion of the autograft side, as 36.6% (26/71) of levels fused on the BCP<μm side but did not fuse on the autograft side. In contrast, 4.2% (3/71) of levels fused on the autograft side but not on the BCP<μm side. Statistical analysis through binomial modeling showed that the odds of fusion of BCP<μm was 2.54 times higher than that of autograft.

Conclusion : These data, aiming to determine non-inferiority of standalone BCP<μm compared to autograft for posterior spinal fusions, are promising. Ongoing studies to increase the power of the statistics with more patients are forthcoming.