A comparative study of nerve healing in adult, neonatal, and fetal rabbits

This experiment quantitatively compared the human equivalent of a nerve rep air following surgical division in the fetal, adult, and early childhood pe riod of development using a rabbit as an experimental animal model. Twelve time-dated pregnant New Zealand White rabbits at 24 days' gestation (term = 31 days) underwent hysterotomy; one hind limb was delivered through the ut erine opening. The sciatic nerve was divided and repaired by primary neuror rhaphy using mio 11-0 epineural sutures. Sciatic nerve repair was also perf ormed in 10 neonatal and 10 adult New Zealand White rabbits. Following repa ir, each group was assessed using electromyography examination, measuring d istal motor latency and amplitude at 1, 2, 3, and 4 months postrepair. Ther e was no difference in any of the groups in distal motor latency. The ampli tude rose incrementally in all groups, and the fetal group had significantl y higher amplitudes (p < 0.02) at 1, 2, 3, and 4 months in comparison with the adult group. There was no statistically significant difference between fetal and neonatal nerve repairs at ally of the time periods. At the comple tion of the study, the nerve repair sites were harvested for histologic est imation of mean myelinated fiber density and fiber diameter distribution di stal and proximal to the repair site. A greater percentage of myelinated ax ons crossed the repair site in the fetal group (83 percent) in comparison w ith the adult group (63 percent) (p < 0.03). Our study also demonstrated si gnificant increases in the number of larger myelinated fibers crossing the repair site in comparison with the neonatal and adult groups (p < 0.04). Th is study found that fetal nerve healing following surgical repair is superi or to that found in adult animals and results in a higher number of larger myelinated fibers crossing the repair site in comparison with adult and neo natal repairs.