The Effect of Skeletal Fixation on Nerve Healing in a Rat

Abstract

Objective To investigate the effect of rigid internal skeletal fixation of a rat femoral shaft fracture on the healing of an induced sciatic nerve crush injury as assessed by functional outcomes. Methods Thirty-six male Lewis rats were divided into two groups. A unilateral sciatic nerve crush injury and a same-level transverse femur fracture were created in all animals. Animals in the first group underwent immediate open reduction internal fixation (ORIF) with a stainless steel plate and screws. Animals in the second group were treated non-operatively (NON) without internal or external fixation or bracing. At each of the six-time points relevant to different nerve degeneration and regeneration stages, three animals in each group underwent bilateral limb assessments of electrophysiology, muscle mass, and nerve histomorphometry. Results Outcome measurements of the ORIF group (n=17) and NON group (n=16) showed the ORIF group to have both significantly greater tibialis anterior muscle force generation and sciatic nerve conduction velocity across the zone of injury for the overall groups. Force and conduction velocity measurements were greater for the ORIF group at selective time points in the subgroup analysis. Histologic analysis confirmed a greater cross-sectional area of the sciatic nerve in the ORIF group. Conclusion This study provides information about the influence of the stability of the skeletal and soft tissue environment on the nerve healing process. The significantly greater maximum force generation and conduction velocity and the increased cross-sectional areas with greater axon counts observed in our ORIF group support our hypothesis that rigid internal skeletal fixation of a fracture promotes superior recovery of a concomitant peripheral nerve injury. The findings of this study suggest that superior healing of the peripheral nerve injury may occur with stable skeletal fixation.