The First Clinical Trial of Beta-Calcium Pyrophosphate as a Novel Bone Graft Extender in Instrumented Posterolateral Lumbar Fusion

BACKGROUND: Porous β-calcium pyrophosphate (β-CPP) was developed to improve the fusion success of posterolateral lumbar fusion (PLF). The possibility of accomplishing PLF using a mixture of porous β-CPP and iliac bone was studied. This paper reports the radiologic results of PLF using the β-CPP plus autograft for lumbar degenerative disease as a bone graft extender. METHODS: A prospective, case-matched, radiographic study evaluating the results of short segment lumbar fusion using a β-CPP plus autograft was performed to compare the efficacy of β-CPP plus autograft with that of an autograft alone for short segment lumbar fusion. Thirty one consecutive patients (46 levels) underwent posterolateral fusion with pedicle screw fixation and additional posterior lumbar interbody fusion. In all patients, 3 mL of β-CPP plus 3 mL of autogenous bone graft was placed randomly in one side of a posterolateral gutter, and 6 mL of autogenous iliac bone graft was placed on the other. The fusion rates, volumes of fusion masses, and bone absorption percentage were evaluated postoperatively using simple radiographs and 3 dimensional computed tomography (3D-CT) scans. RESULTS: The control sides treated with an autograft showed significantly better Lenke scores than the study sides treated with β-CPP at 3 and 6 months postoperatively, but there was no difference between the two sides at 12 months. The fusion rates (confirmed by 3D-CT) were 87.0% in the β-CPP group and 89.1% in the autograft group, which were not significantly different. The fusion mass volumes and bone absorption percentage at 12 months postoperatively were 2.49 mL (58.4%) and 1.89 mL (69.5%) for the β-CPP and autograft groups, respectively, and mean fusion mass volume was significantly higher in the β-CPP group. CONCLUSIONS: β-CPP combined with an autograft is as effective as autologous bone for grafting during instrumented posterolateral spinal fusion. These findings suggest that β-CPP bone chips can be used as a novel bone graft extender for short-segment posterolateral spinal fusion.