Elasticity Characteristics of Thenar Muscles in Carpal Tunnel Syndrome.

Objective: Measurement of thenar muscle elasticity by ultrasound shear wave elastography (SWE) may be useful for the diagnosis and evaluation of carpal tunnel syndrome (CTS), but there is a paucity of information on SWE of the thenar muscles in patients with CTS. The purpose of this study was to investigate the elasticity of the thenar muscles in patients with CTS.

Methods: Twenty-two adult patients with a referral diagnosis of CTS (27 hands) and 20 healthy volunteers as a control (20 dominant hands) participated in this study. The elastic modulus of the thenar muscles was measured with SWE in two conditions, rest and pinch. The elastic modulus and percent change between the two conditions for each muscle were compared between groups.

Results: The elastic modulus of the abductor pollicis brevis (APB) in the patient group was lower than that in the control group at rest (20.6 ± 5.6 kPa vs. 25.0 ± 8.5 kPa; p = 0.034). However, the elastic modulus (87.9 ± 49.0 kPa vs. 62.5 ± 28.5 kPa; p = 0.044) and percent change (373.3 ± 336.4% vs. 169.2 ± 116.0%; p = 0.006) of the APB in the patient group were higher than those in the control group with pinch. For the opponens pollicis and adductor pollicis, there was no significant difference in the elastic modulus between groups.

Conclusion: Patients with CTS showed differences in SWE of the APB. Future studies need to investigate the accuracy of SWE in diagnosing CTS and assessing prognosis.