The purpose of this study was to evaluate the effect of testosterone deficiency and osteopenia on fracture healing using orchiectomized adult rats.

Fifty-two 3 month old male rats were used. Animals were divided into 3 groups. Group 1 received sham operations and groups 2 and 3 were orchiectomized. At 4 weeks, right tibial shaft fractures were administered in all animals. Afterwards in group 3, testosterone was injected intra-peritoneally for 4 weeks. After 8 weeks of breeding, animals were sacrified for morphometrical, histopathological and biomechanical testing.

No nonunion or delayed union was observed. Differences in tibial volumes and circumferences between the fracture site and the corresponding contralateral site were less in groups 2 and 3 than in group 1, with statistical significance. The yield strength and the trabecular area of the fractured tibiae were significantly lower in group 2, but group 3 and group 1 were similar.

Even though there was no evidence of compromised fracture healing, both of the androgen deficiency and osteopenia induced by orchiectomy negatively influenced callus volume and strength. But osteopenia did not influece callus strength. The above results demonstrate the positive effect of testosterone injection on fracture healing.