A favorable suture method for size-mismatched nerve transfer: comparison with standard perineural suture in an experimental rat study

In nerve transfer for peripheral nerve injury, it is sometimes necessary to suture size-mismatched nerves. In 1993, a favorable suture method called the Ochiai suture method for size-mismatched nerve transfer was reported. However, there is currently a lack of substantial evidence beyond the original report. Therefore, this study aimed to verify the advantages of using the Ochiai suture method for size-mismatched nerve transfer. A total of 18 rats were evaluated in this study and randomly divided into two groups. All rats underwent femoral to sciatic nerve transfer. Specifically, group A (n = 10) underwent the Ochiai suture method, while group B (n = 8) underwent the perineural suture method. After 12 weeks postoperatively, we conducted the sciatic functional index (SFI) test, measured muscle wet-weight, and performed histological evaluations. All data were compared between the two groups, with Welch's t test for normally distributed data and Mann-Whitney's U test for non-normally distributed data. Statistical significance was set at p < 0.05. The mean number of axons was significantly greater in group A than in group B at 5 mm distal to the stump (p = 0.04). Additionally, the average axonal diameter was significantly greater in group A than in group B at 5 mm and 10 mm distal to the stump (p < 0.01 and p < 0.01, respectively). However, the SFI test and measured muscle wet-weight values showed no significant differences between the two groups. Our study revealed that the Ochiai suture method for size-mismatched nerve transfer in rats increases the regenerative axon numbers and diameters. These findings suggest that the Ochiai suture method could be a valuable approach for achieving effective motor function restoration in cases of size-mismatched nerve transfer.