A Study to Assess the Effects of Thrombin on Bone Regeneration

Thrombin is occasionally used as a hemostatic agent during bone surgery in humans and animals. Recent evidence from studies in vitro has indicated that thrombin stimulates bone resorption. The effect of 100 units thrombin on bone wound healing and bone resorption in rats was tested in untreated 8-mm circular craniotomy defects and defects treated with 25 mg demineralized rat long bone matrix or 25 mg demineralized calvarial bone matrix. Twentyeight days after treatment, defects were recovered and radiographed. As an indicator of bone, radiopacity within the defect area was quantified using computerized image analysis. In the absence of thrombin, bone resorption occurred in untreated defects 5.3 or - 5.1 sq mm and defects treated with calvarial bone matrix 6.8 or - 5.1 sq mm the use of thrombin had no additional effect on resorption in these groups. Long bone matrix prevented bone resorption and significantly stimulated bone formation by 77, compared with untreated controls, and by 73, compared with defects treated with calvarial bone matrix. Addition of thrombin to long bone matrix diminished the inductive response by 14, though the amount of bone formed in the presence of thrombin was still significantly greater than in untreated control defects. However, thrombin negated the protective effect of long bone matrix on bone resorption. These data indicate that use of thrombin as a hemostatic agent in bone surgery may be counterproductive to bone healing.