This is a multidisciplinary, single-blinded, three-arm randomized controlled trial, comparing perineural hydrodissection and steroid injection for the treatment of CTS. Patients are screened based on pre-established eligibility criteria and randomized to one of the three study groups. Patients are followed at 6-week, 3-month, 6-month, and 12-month time points to assess the primary and secondary outcomes of the study, which include both patient-reported outcome measures and objective clinical assessments.

This study aims to examine the effect of perineural hydrodissection (PNH), a novel treatment for CTS. PNH is a minimally invasive, ultrasound-guided, percutaneous technique in which the median nerve is released by injecting fluid (local anesthetic and corticosteroid) circumferentially, using larger fluid volumes and higher pressure to target areas of adhesion between the median nerve and its surrounding structures. In chronic CTS, a rind of perineural fibrosis develops, tethering the median nerve to the overlying flexor retinaculum and to the adjacent flexor tendons. Theoretically, the removal of tethering to adjacent structures, via perineural hydrodissection, should allow circumferential bathing of the median nerve with the local anesthetic and corticosteroid, thus reducing inflammation and prolonging symptom relief.

The primary outcome is pain as measured by the Boston Carpal Tunnel Questionnaire (BCTQ). Secondary outcomes include health-related quality of life measures using the Disabilities of the Arm, Shoulder, and Hand (DASH) questionnaire and the Visual Analog Scale (VAS) for pain.

The selected questionnaires have been shown to correlate well with domains of the International Classification of Functioning, Disability, and Health (ICF) (3). Other secondary measures include the ultrasound appearance (cross-sectional index) of the median nerve, and electromyography (EMG) measurements (including sensory and motor conduction velocities, and amplitudes), before and after the injection.

The study hypothesis is that PNH will show greater benefits in terms of pain, function, and patient quality of life when compared to corticosteroid injection in patients with CTS. The null hypothesis is that there is no difference. The study is powered to address the primary outcome and will also be powered to identify minimally important differences in functional, sonographic, and electromyographic outcomes.

Inclusion Criteria:

1. Adult men or women aged 18 years or greater.
2. Clinical and electromyographic diagnosis of Carpal Tunnel Syndrome.
3. Persistent symptoms from Carpal Tunnel Syndrome after at least three months of appropriate splinting.
4. Ability to consent for study.

Exclusion Criteria:

1. Acute symptom onset (less than 3 months).
2. Bifid median nerve
3. Anticoagulation with International Normalized Ratio (INR) > 1.4, or platelets <150.
4. Anomalous muscles (eg. inverted palmaris longus).
5. Patients requiring anti-platelet medication for the treatment of heart attack, stroke, or other medical condition.
6. Previous surgery for Carpal Tunnel Syndrome.
7. Previous local injections, including steroids within the past 6 months.
8. Allergy to any of the injection agents.

Care provider is performing a specific type of injection and therefore cannot be blinded. Those investigators responsible for collecting, managing, and analyzing data will be blinded to treatment randomization.