Mechanical function of muscle reinnervated by end-to-side neurorrhaphy

End-to-side neurorrhaphy is a surgical technique for peripheral nerve recon struction when end-to-end neurorrhaphy is not an option. To define the effe ctiveness of end-to-side neurorrhaphy as a method of nerve repair, the auth ors tested the null hypothesis: there is no difference in the mechanical fu nction of skeletal muscle denervated and reinnervated by end-to-side versus end-to-end neurorrhaphy. Adult Lewis rats underwent either transection and end-to-end epineurial repair of the left peroneal nerve (n = 9) or end-to- side repair of the distal stump of the peroneal nerve to the side of the ti bial nerve (n = 8). After a B-month recovery period, isometric force (F-o) was measured, and specific force (sF(o)) was calculated for the extensor di gitorum longus muscle of each animal. Immunohistochemical staining for neur al cell adhesion molecule (NCAM) was performed to identify populations of d enervated muscle fibers. The mean extensor digitorum longus muscle mass in the end-to-end group (195 +/- 32 g) was significantly greater than that of the end-to-side group (146 +/- 55 g) (P < 0.05). A significantly greater pe rcentage of denervated fibers was identified in the extensor digitorum long us muscles of animals in the end-to-side group (9.4 +/- 3.2 percent) than i n those in the end-to-end group (3.8 +/- 1.0 percent) (p < 0.05). Despite a lower muscle mass and a higher percentage of denervated fibers, neither F- o nor sF(o) was significantly different in the two groups. These data suppo rt the null hypothesis that, under appropriate circumstances, there is no d ifference in the recovery of whole muscle force and specific force producti on in muscles reinnervated by end-to-side versus end-to-end neurorrhaphy.