Experimental study of fascicular nerve repair with and without epineurial closure.

Microscopic fascicular repair without closure of epineurium was compared with microscopic epineurial repair in 12 rhesus monkeys. Measurements of evoked nerve action potentials, and responses to repetitive and tetanic stimulation made at one interval 3, 6, 9, or 12 months postoperatively, were compared to baseline preoperative studies. Histological evaluation included light and electron microscopic preparations and studies of distal stump myelinated fiber maturity. Electrical measures of regeneration indicated that recovery was more advanced in the limb with epineurial repair in eight animals, whereas in four there was no difference between fascicular and epineurial repair. Fascicular repair appeared not to fare as well as epineurial repair because, although neuromas developed with both, the length of the neuroma was greater with fascicular than with epineurial repair. The relatively lengthy neuroma in the nerve with fascicular repair was due to axonal disorganization and connective tissue proliferation along the length of the dissection necessary for the repair. Nonetheless, studies of myelinated fiber distribution in the distal stump showed no significant differences. Similar studies were conducted in 11 primates, where epineurial repair was matched with fascicular repair in which the epineurium was closed. Here, regeneration as measured by both electrical and histological studies was comparable. Histological study showed less disorganization at the repair site in the nerve with fascicular suture and epineurial closures than in that with epineurial suture. However, studies of distal stump myelinated fiber maturity demonstrated no significant differences. Thus, there seems to be no advantage in either resecting or closing epineurium in fascicular nerve repair.