To investigate the effects of tumor necrosis factor-alpha on calcium sulfate, as a bone graft substitute, in terms of achieving inter-transverse fusion in experimental rabbits.

Twenty adult New Zealand white rabbits were used in our study. 0.4 mg of calcium sulfate was mixed with 0.4 mg of autogenous iliac bone and grafted on the left intertransverse space of L4-5 or L5-6, and then 0.8 mg of autogenous iliac bone was grafted on the right side at the same level. Thus, the experimental rabbits served as their own control. At postoperative 0, 4, 8, 12, and 16 weeks, plain roentgenography was performed to evaluate the bony union. At 16 weeks, all rabbits were sacrificed and histologic evidences of the bony union observed by H and E and trichrome staining. Computed tomography was also used to evaluate the union state. An immuno-histochemical study for TNF-alpha was to investigate the union.

Bone graft, mixed with calcium sulfate was resorbed completely radiologically and histologically in 20 rabbits (100%). In contrast, a graft using autogenous cancellous bone showed complete bony union in 15 of 20 rabbits (75%). By immuno-histochemical staining, TNF-alpha was detected at the calcium sulfate mixed autogenous bone graft site.

Union was not showed at the bone graft site, mixed with calcium sulfate. Therefore, TNF-alpha plays an important role causing subsequent calcium resorption.