Background: Although autogenous bone is the most widely used graft
material for spinal fusion, demineralized bone matrix preparations are
available as alternatives or supplements to autograft. They are prepared by
acid extraction of most of the mineralized component, with retention of the
collagen and noncollagenous proteins, including growth factors. Differences in
allograft processing methods among suppliers might yield products with
different osteoinductive activities. The purpose of this study was to compare
the efficacy of three different commercially available demineralized bone
matrix products for inducing spinal fusion in an athymic rat model.
Methods: Sixty male athymic rats underwent spinal fusion and were
divided into three groups of eighteen animals each. Group I received Grafton
Putty; Group II, DBX Putty; and Group III, AlloMatrix Injectable Putty. A
control group of six animals (Group IV) underwent decortication alone. Six
animals from each of the three experimental groups were killed at each of
three intervals (two, four, and eight weeks), and the six animals from the
control group were killed at eight weeks. At each of the time-points,
radiographic and histologic analysis and manual testing of the explanted
spines were performed.
Results: The spines in Group I demonstrated higher rates of
radiographically evident fusion at eight weeks than did the spines in Group
III or Group IV (p < 0.05). Manual testing of the spines at four weeks
revealed variable fusion rates (five of six in Group I, two of six in Group
II, and none of six in Group III). At eight weeks, all six spines in Group I,
three of the six in Group II, and no spine in Group III or IV had fused.
Histologic analysis of the spines in Groups I, II, and III demonstrated
varying amounts of residual demineralized bone matrix and new bone formation.
Group-I spines demonstrated the most new bone formation.
Conclusions: This study demonstrated differences in the
osteoinductive potentials of commercially available demineralized bone
matrices in this animal model.
Clinical Relevance: Comparative clinical testing of demineralized
bone matrices is indicated in order to determine which preparations are best
suited for promoting successful spinal fusion in humans.