Fracture callus engulfing a peripheral nerve does not affect its function: an experimental study in rabbits

The fate of a peripheral nerve engulfed in fracture callus is not known. We investigated the impact of envelopment of the sciatic nerve by fracture callus using a New Zealand rabbit femoral fracture model. The sciatic nerve was mobilized and coiled around the ipsilateral femur, which was surgically fractured, shortened, and osteosynthesized. Bony union was achieved, and callus engulfed the sciatic nerve in all animals. Nerve function was evaluated clinically and by conduction studies preoperatively and postoperatively. Although the nerve function in terms of clinical evaluation, amplitude, motor latency, and spontaneous activity deteriorated immediately postoperatively, recovery was evident in the following weeks indicating that the detected nerve dysfunction was attributable to the surgical mobilization. In addition, histologic and quantitative histomorphometric analyses proved that in none of the animals did the callus compress the sciatic nerve whereas an impressive process of axonal regeneration took place despite callus maturation. Results of our study suggest that callus, engulfing a peripheral nerve, does not compress it and the nerve appears to be intact in an osseous canal. This results in preservation of the integrity and function of the nerve, which may have significant clinical applications.