Correlation between preoperative Kimura inching studies and intraoperative findings during endoscopic-assisted decompression of the ulnar nerve at the elbow.

Background: During the evolution of the senior author's technique of ulnar nerve transposition to in situ decompression for ulnar neuropathy at the elbow, nerve conduction studies (NCS) including the Kimura inching method were performed preoperatively in an effort to ensure that all potential sites of compression were investigated intraoperatively. The purpose of this study is to compare the results of the Kimura inching technique with the intraoperative findings noted during decompression of the ulnar nerve at the elbow.

Methods: The medical records of consecutive patients who underwent in situ decompression of their ulnar nerves combined with endoscopic examination between March and December of 2009 were retrospectively reviewed. The site of ulnar nerve compression noted using the Kimura inching technique was compared with the intraoperative findings.

Results: Twelve consecutive patients (four with bilateral symptoms) underwent endoscopic ulnar nerve compression in the study period for a total of 16 cases analyzed. In 12 cases, the Kimura method localized the site of compression to Osborne's bands and/or the aponeurosis of the flexor carpi ulnaris (FCU). Intraoperatively, compression was noted at Osborne's bands, the FCU aponeurosis, and/or the FCU) muscle proper in all 16 patients. There was partial or full correlation between the nerve conduction data and intraoperative findings in 13/16 cases.

Conclusions: There was good but not perfect agreement between the NCS and intraoperative findings, perhaps because transcutaneous NCS are less accurate when a nerve is surrounded by muscle. The information obtained in this study is valuable when planning surgery to address ulnar nerve compression.