Neural involvement in post-traumatic osteopenia: an experimental study in the rat.

The effect of sciatic nerve resection on post-traumatic bone loss and mechanical strength of the ipsilateral (IL) and contralateral (CL) femoral shafts and necks was studied 25 days after a tibial fracture. We subjected 45 male rats to a standardized tibial fracture, stabilized it with a modular intramedullary nail and then randomly allocated the animals to two groups: right sciatic nerve resection (SNR group) or sham operation (sham group). All of the operated hindlimbs were further immobilized in a plaster cast to avoid unequal loadbearing between the two groups. After 25 days of healing, 85Sr incorporation in the IL femora was 10% lower in the SNR group compared to the sham group, indicating a lower bone mineralization after sciatic nerve resection. The bone mineral content was 15% higher in the SNR group ipsilaterally. Accordingly, the bending moment and energy absorption in the femoral midshaft were higher in the SNR group compared to the sham group. The sciatic nerve resection protected the femoral shaft against the normally occurring post-traumatic bone loss after a tibial fracture. This protective effect of the neurectomy also occurred in the femoral neck, but not to the same extent. A protective effect was also present in the CL femur, suggesting additional systemic effects of the sciatic nerve resection.