THE INFLUENCE OF MAGNITUDE AND DURATION OF CRUSH LOAD ON FUNCTIONAL RECOVERY OF THE PERIPHERAL-NERVE

This study investigated the effect of crush duration at different loads on motor functional recovery. One hundred and thirty-eight rats were divided into five groups: sham operation, resected sciatic nerve, and 100 g, 500 g, and 15,000 g of sciatic crush load (Groups 1 to 5). According to crush duration, Groups 3 and 5 were divided into 10-min, 2-hr and 6-hr subgroups. In Groups 3 to 5, a 5-mm segment of sciatic nerve was crushed, using a specially-designed crushing device. Motor functional recovery was assessed by calculating a sciatic functional index (SFI). There was no functional deficit in Group 1, and complete dysfunction in Group 2 throughout the experiment. All groups subjected to crush exhibited an initial complete deficit that gradually recovered to normal or near normal. Axonal damage and the speed of motor functional recovery were significantly related to crush duration in the subgroups of the 100 g group, but no marked differences existed between subgroups of the 15,000 g group. There was no obvious difference between the 6-hr subgroup of Group 3 and Groups 4 and 5. Results indicate that crush duration is an important factor in nerve damage and functional recovery at a low crushing level (100 g), and that the mechanical insult is a key factor at a higher crush level (15,000 g). The fact that all crushed nerves recovered, even after the application of a 15,000 g load for 6 hr, suggests the importance of maintaining continuity of the injured nerve in clinical situations.