Effect of Exercise on Ultrasound SWV in CTS Patients

Overview

Carpal tunnel syndrome (CTS) is the most common peripheral neuropathy, and studies suggest exercises can be used for symptom management. Purpose: The study evaluated the impact of exercise protocols on the ultrasound shear wave velocity (SWV) of the median nerve and 3rd flexor digitorum superficialis (3rd FDS) in participants with mild to moderate CTS. Methods: Ninety-one CTS participants (79 females) were divided into control group, nerve and tendon gliding exercise group, and strength exercise group. The participants followed a three-week daily exercise plan. The SWV measurements were conducted using Canon Aplio i800 ultrasound and linear probe (LX18i5). Regions of interest were positioned within the nerve epineurium and hyperechogenic borders of the 3rd FDS tendon. The pre- and post-intervention SWV values were recorded. Results: In preliminary results on a smaller sample, trends indicated reduced SWV in both the median nerve and 3rd FDS in the nerve and tendon gliding group and reduced SWV in the median nerve in the strengthening group. No measurable change was observed in the 3rd FDS in strength group and in the control group. Conclusion: Trends suggest specific exercises may decrease stiffness in the median nerve and 3rd FDS in CTS participants.

The aim of the study is to evaluate the impact of exercise protocols on the US SWV of the median nerve and 3rd FDS in the carpal tunnel in participants with mild to moderate CTS. The investigators aim to establish US SWE as a potential method to monitor nerve and tendon SWE changes due to exercise intervention and consequently show the effect of different exercise interventions on mechanical changes within the carpal tunnel. This study was conducted in accordance with the ethical principles of the Declaration of Helsinki and Good Clinical Practice guidelines. The study protocol adhered to the CONSORT guidelines for reporting randomized trials and received approval from the National Medical Ethics Committee of the Republic of Slovenia (protocol number 0120-25/2023/3). Written informed consent was obtained from all participants prior to enrolment. Participants with suspected CTS were prospectively recruited from April 2025 to October 2025 at a single tertiary referral centre: the Institute of Clinical Neurophysiology, University Medical Centre Ljubljana, Slovenia. The inclusion criteria were as follows: (1) age between 24 and 78 years; (2) affirmative responses to at least two of the following three questions: (a) tingling in at least two of the first four digits; (b) symptoms worsening at night or in the morning; (c) symptom relief with hand flicking (flick sign); and (3) electrodiagnostic (EDx) confirmation of mild to moderate median nerve entrapment neuropathy at the wrist. Exclusion criteria were: (1) previous wrist fracture or surgery; (2) polyneuropathy, motor neuron disease, cervical radiculopathy, or brachial plexopathy; (3) structural abnormalities within the carpal tunnel; and (4) tenosynovitis. The investigators conducted a prospective, randomized, three-arm, parallel-group trial with a 1:1:1 allocation ratio to Gliding, Strength, and Control groups. Outcome measures were assessed before and after the intervention. Randomization of participants into two intervention groups and one control group was performed using the Clinical Trial Randomization Tool developed by the National Cancer Institute. The same tool was applied in participants with bilateral CTS to randomly determine which hand was assessed and included in the study. The intervention lasted for 3 weeks and was performed once daily. The control group did not participate in any training program and was instructed to continue with their usual daily and work-related activities. Ultrasound SWV measurements were performed by the primary investigator, who was blinded to participants' CTS diagnoses. A second investigator conducted the randomization process and scheduled participants' appointments; consequently, the primary investigator remained unaware of participant details prior to the SWV assessment. Participants randomized to Gliding or Strength group received written description of exercises supported with images. Nerve and tendon gliding exercises targeted flexion and extension of the index and ring fingers, complemented by wrist flexion and extension movements. These exercises were taken from literature and designed to promote median nerve and tendon gliding through the carpal tunnel, thereby reducing entrapment of the median nerve and the 3rd FDS tendon. Strengthening exercises involved movement patterns (finger and wrist flexion and extension) similar to the nerve and tendon gliding exercises; however, external resistance was introduced through the use of hand therapy resistance balls or low-weight dumbbells ranging from 0.5 to 2.0 kg depending on the participant. A contact phone number was provided in case of any difficulties. The first session was demonstrated and supervised by a kinesiologist with 8 years of experiences. After 7 days, participants were contacted by phone to assess their progress and discuss the potential symptoms issues related with exercise plan. Participants were seated with their forearms supinated, wrist in neutral position and fingers relaxed. Measurements were performed by a researcher with 3 years of experiences with ultrasound elastography using US system Canon Aplio i800 (Canon Medical Systems Europe BV, Zoetermeer, The Netherlands) with a i18Lx5 linear probe. Cross-sectional area (CSA) of the median nerve at the carpal tunnel inlet and at the forearm was measured. Thereafter, SWV of the median nerve and 3rd FDS tendon at the wrist was measured with the probe oriented longitudinally. Generous amount of gel was used to assure minimal pressure. Circular ROI was used and positioned within the epineurium of the median nerve and hyperechoic borders of the 3rd FDS tendon. SWV measurements were acquired only when the motion stability index (M-STB Index) displayed five consecutive green stars, indicating low or absent motion interference and stable image acquisition. The minimal time interval between two consecutive measurements was 10 seconds. Three consecutive SWV measurements were performed and median value in m/s was used for further analysis. A sample size estimation was conducted for this randomized controlled trial, which included two intervention groups and one control group. Continuous outcomes were planned to be analyzed using pairwise comparisons between each intervention group and the control group. A two-sided significance level of 0.025 was applied to account for multiple comparisons using the Bonferroni correction. Assuming a statistical power of 0.80, an expected mean difference of 1.0, and a standard deviation of 1.25, the required sample size was estimated to be 30.14 participants per group. The calculation was performed using G\*Power 3.1 software (Heinrich Heine University, Düsseldorf, Germany), based on effect sizes reported in previous randomized trials investigating exercise interventions for carpal tunnel syndrome. Statistical analyses were performed using SPSS 29.0 (IBM Corp, Armonk, NY). Shapiro Wilk test was used to determine the variables normality distribution. For normal distributed variables, pre and post intervention SWV data was compared using ANOVA with within-subjects effect and interaction time vs. intervention. For group comparison, the investigators compared individual pairs of data with Paired sample T-test. Non-normally distributed variables were analysed using non-parametric Wilcoxon test. All statistical tests were two-tailed, with a p-value \< 0.05 considered statistically significant.