gms | German Medical Science

Objectives/Interrogation: Characterization of the changes of ultrasound parameters after carpal tunnel release may be useful for clarifying recovery process of the carpal tunnel syndrome (CTS) treatment. We hypothesized that the strain and pressure around the median nerve may differ before and after carpal tunnel release in CTS patients. The aim of this study was to evaluate the diagnostic significance of median nerve strain and applied pressure measurement for clinical recovery after carpal tunnel release.

Methods: Twenty-six wrists from 23 idiopathic carpal tunnel syndrome patients (17 females and 6 males; age range 37-89, mean age 67.2 years), who underwent open carpal tunnel release, were evaluated by ultrasound. The pressure monitor ultrasound system were developed to apply pressure to the tissue with a pre-determined cycle and displacement of the transducer. Median nerve strain, applied pressure to the skin, and pressure-strain ratio were measured at the proximal carpal tunnel level. In addition, distal motor latency in an electrophysiological test was measured. The parameters were compared before and after carpal tunnel release. According to patient recovery, the receiver operating characteristic curves were calculated to determine the diagnostic value of the parameters. The areas under the receiver operating characteristic curves were compared among parameters.

Results and Conclusions: Before carpal tunnel release, the median nerve strain, pressure, and pressure-strain ratio were 0.15+/-0.04%, 87.1+/-13.0 gf, and 538.1+/-134.6 gf/%, respectively. After carpal tunnel release, the median nerve strain, pressure, and pressure-strain ratio were 0.23+/-0.09%, 73.8+/-11.9 gf, and 331.9+/-153.6 gf/%, respectively. There was a significant increase of strain after carpal tunnel release (P<0.01), and significant decreases of pressure and pressure-strain ratio (P<0.05: pressure, P<0.01: pressure-strain ratio) after carpal tunnel release. Before carpal tunnel release, distal latency was 7.3+/-2.6ms. After carpal tunnel release, distal latency was 5.6+/-1.9ms. There was a significant decrease in distal motor latency (P<0.01). The areas under the curves were 0.762, 0.691, 0.746, and 0.709 for the strain, pressure, pressure-strain ratio, and distal motor latency, respectively.

The median nerve strain and the pressure-strain ratio showed relatively higher relevance with clinical recovery after carpal tunnel release. The results of this study may be useful when considering median nerve recovery after carpal tunnel release.