Background and objectives: The antiepileptic drug Phe-nytoin (Diphenyl hydantoin) has been documented to have a beneficial effect on wound healing. Its effect on fracture healing has been investigated to a much lesser extend. In this study we have combined histology, his-tomorphometry and radiology in analyzing the effect of phenytoin on fracture healing, following its local administration.

Methods: Twenty-four Wistar strain rats of 8-9 months age were assigned into two groups of 12 each, which had been matched for age, sex and weight. In one group, selected as the study group phenytoin 20 mg/kg was administered through a 24 gauge needle directly on to the fracture site every 72 hours, while in the controls an equivalent volume of normal saline was administered at the same interval. At 28 days radiographic and histo-logical analysis was done.

Results: Radiographic and histological scoring across the control and test animals did not show any statistical difference. Histomorphometric analysis of the callus however showed that the total periosteal callus on either side of the central bridging callus was mineralized to a greater extend in the phenytoin group animals as compared to the control group animals (p= 0.011).

Conclusion: After analyzing our data, we concluded that phenytoin does have an influence in fracture healing, albeit small, which is primarily on the hard callus region. The hard callus region is the high oxygen tension region and the first region to differentiate. It appears that the effect of phenytoin is probably exerted at the early mesenchymal differentiation stage. However our preliminary work shows that the effect is small and it is not justifiable at this stage to advocate the use of phe-nytoin clinically to augment fracture healing.