Selection of optimal axon ratio for nerve regeneration.

The traditional teaching that "nerve fibers are lost at the suture line" after a nerve repair was investigated by asking the question, "Can the number of nerve fibers distal to a nerve repair site be increased by increasing the number of nerve fibers proximally?" Ratios of proximal to distal nerve fibers were increased from 1:1 to 2.5:1 to 3.5:1 by suturing peroneal or posterior tibial or sciatic nerve proximally to peroneal nerve distally. At one year following the repair, distal nerve fiber numbers increased to twice normal as the ratio increased to 2.5:1, and then nerve fiber numbers plateaued. Nerve function, as judged by walking track analysis, was best in the peroneal:peroneal group (1:1 ratio), suggesting that appropriateness rather than number of proximal fibers was more critical in this nerve repair model.