Postoperative diagnostic potentials of median nerve strain and applied pressure measurement after carpal tunnel release

BAKGROUND: The objective of this study is to investigate the prognostic values of median nerve strain and applied pressure measurement for the assessment of clinical recovery after carpal tunnel release. METHODS: Forty-five wrists, from 45 idiopathic carpal tunnel syndrome patients who treated with open carpal tunnel release, were evaluated by ultrasound. Median nerve strain, pressure applied to the skin, and ratio of pressure-strain were measured at the proximal part of the carpal tunnel. In addition, distal latencies in the motor and sensory nerve conductions studies and cross-sectional area of median nerve were measured. The parameters were compared before and after the open carpal tunnel release. According to patient recovery, the receiver operating characteristic curves were generated to evaluate the prognostic values of the parameters. The areas under the receiver operating characteristic curves were compared among parameters. RESULTS: There was a significant increase in the median nerve strain, and significant decreases in the pressure applied to the skin and ratio of pressure-strain after carpal tunnel release (P < 0.01). There were significant decreases in the distal latencies and the cross-sectional area after carpal tunnel release (P < 0.01). The areas under the curves were 0.689, 0.773, 0.811, 0.668, 0.637, and 0.562 for the pressure, strain, pressure-strain ratio, motor latency, sensory latency, and area, respectively. CONCLUSIONS: The results suggest that elasticity of the median nerve and pressure around the nerve recover quickly after carpal tunnel release. Pressure-strain ratio was the most reliable parameter to reflect clinical recovery. The measurement of strain and applied pressure can be useful indicators to evaluate effectiveness of the carpal tunnel release. TRIAL REGISTRATION: Registered as NCT04027998 at ClinicalTrials.gov. Retrospectively registered on July 22, 2019.