High-resolution ultrasound in the diagnosis of failed carpal tunnel decompression: a study of 35 cases.

We used high-resolution ultrasound to examine 35 median nerves (35 patients) with failed carpal tunnel decompression to identify the cause of failure. The carpal tunnel was examined before revision surgery, and the results were correlated with surgical findings. The cross-sectional area was measured, and nerve morphology was analysed at the sites of compression. We found persistent median nerve compression in 30 out of 35 patients. In 20 patients, the compression was caused by a residual transverse carpal ligament, in four by perineural fibrosis, in five by both of these causes and in one by tenosynovitis. In four patients, evidence of median nerve injury with an epineural/fascicular lesion was detected; and in one, no abnormalities were found. Surgical findings were consistent with the ultrasound findings except in one patient where tenosynovitis was associated with a giant cell tumour, which was missed by ultrasound. High-resolution ultrasound can provide helpful information in preoperative diagnosis of failed carpal tunnel decompression with good correlation between the ultrasound and surgical findings.Level of evidence: IV.