Predegenerated nerve autografts as compared with fresh nerve autografts in freshly cut and precut motor nerve defects in the rat

Abstract

Fresh nerve grafts and predegenerated nerve grafts from a sensory fascicle of the femoral nerve were placed in freshly cut and precut defects in the motor fascicle of the femoral nerve of the opposite side. This allowed us to compare fresh with predegenerated motor nerve grafts in both types of nerve defects. Evaluation was carried out 40 days after graft insertion by axon counts on transverse sections 1 cm proximal and distal to the graft, and the number of axons distal to the grafts was expressed as a percentage of the number proximal. In order to confirm that the axons were functional, muscle tension in the quadriceps muscle was measured at the time the histological specimens were taken, by stimulating the femoral nerve proximal to the graft and by measuring the force of contraction in the quadriceps muscle. This test of muscle contraction confirmed reinnervation of the muscle, but was not used as a quantitative measure. In freshly cut recipient nerve defects, fresh grafts did better (P = 0.01), but when precut defects were grafted, the predegenerated grafts did better (P = 0.05). This experimental design also allowed comparison of the two types of recipient nerve defects. When fresh grafts were inserted in both freshly cut and precut defects, the freshly cut gave a better result (P = 0.10), but when predegenerated grafts were placed in freshly cut and precut defects, the precut defect gave a better result (P = 0.01). These results indicate that the best results were obtained with fresh grafts in fresh defects and precut grafts in precut defects and that in nerve grafting the relationship between the graft and the recipient nerve is important in determining the end result.