Plaster of Paris as bone substitute in spinal surgery

In order to assess the effectiveness of calcium sulphate (plaster of Paris; POP) as a substitute for autologous bone graft, we performed lumbar interv ertebral fusion in mature sheep using POP and a variety of other graft mate rials, and reviewed the literature. The osteoconductivity of the POP grafts was compared to that of grafts carried out with autogenous iliac crest, fr ozen allogeneic bone, and ProOsteon 500 coralline bone. We also compared th e osteogenicity of POP to admixtures of autogenous iliac crest bone with PO P and coralline bone, and to an osteoinductive demineralized sheep bone pre paration (DBM). The substrates were loaded into tubular titanium mesh, impl anted into excavated disc spaces and recovered after a period of 4 months. Fusion mass segments tested in flexion and tension showed that POP was equa l to autogenous bone and most other substrates. The POP fusions were signif icantly tougher than the DBM fusions, even though histomorphometry failed t o reveal differences in the amount of trabecular bone. We conclude that POP can be used to achieve a biomechanically stable interbody lumbar vertebral fusion. In addition, our literature review indicated that POP can be used as a vehicle for local delivery of antibiotics in bone infections.