In vitro osteoblast proliferation as a predictor for spinal fusion mass.

Abstract

The biological factors determining a successful spinal fusion have not yet been fully determined. To determine the influence of graft cell vigor on fusion rate and fusion mass using in vitro osteoblast proliferation as a predictor. Animal study randomizing to posterolateral fusion with autograft with or without pedicle-screw instrumentation. Twenty adult Göttingen mini-pigs. Fusion rate measured both with X-ray and computed tomography (CT) as well as amount of fusion mass determined with three-dimensional CT. Animals underwent posterolateral fusion with autograft either with or without pedicle-screw instrumentation. Additional graft was harvested for osteoblastlike cell culture. Cells were counted after 3 weeks, and their proliferative capacity was correlated to fusion rate and fusion amount. Cell count was significantly higher in the fused animals (p<.011). Furthermore, a tendency toward a positive correlation to fusion mass amount was observed (p<.091). The achievement of a solid spinal fusion using autograft is related to properties of the bone-forming cells in the graft and fusion bed. Most likely it is the number of cells and not their proliferative capacity that is the most important factor.