A Pilot Study to Evaluate the Effectiveness of Ultrasound Guided Looped Thread Carpal Tunnel Release

Objectives: to evaluate the effectiveness and safety of a minimally invasive ultrasound-guided looped thread technique of carpal tunnel release

Background: Carpal tunnel syndrome (CTS) is the most common peripheral entrapment neuropathy, having a prevalence of 3.7%. CTS is the 2nd leading worktime loss condition. Open surgical decompression of the carpal tunnel is an evidence-based and commonly performed treatment for moderate to severe cases, predictably providing long-term symptom relief. This surgical technique involves placing a 2-5 cm long longitudinal incision at the palm, incising the skin, subcutaneous tissue, palmar fascia, palmaris longus tendon (if present) and transverse carpal ligament under direct visualization. After 3-8 weeks of recovery, most patients experience excellent relief of symptoms and improvement in hand function. On occasion, the procedure is complicated by nerve damage, scar or pillar pain. A variety of strategies have been devised to minimize the invasive nature of carpal tunnel release in hopes to reduce post procedure pain, weakness and recovery time. In the late 1980s, an endoscopic release technique was devised. A recent meta-analysis of existing randomized control trials comparing open to endoscopic release found endoscopic release to provide better early recovery of grip and pinch strength, less scar tenderness and earlier returned to work (~9 days). There was a similar risk of pillar pain and reoperation, and a higher risk of nerve injury (mostly transient neurapraxia). The development of high-resolution ultrasound scanning allows detailed visualization of the carpal tunnel and its contents. Hydrodissection, the injection of fluid during ultrasound visualization, adds to image clarity of both the contents of the carpal tunnel as well as the location of operative instruments. A few minimally invasive ultrasound-guided percutaneous carpal tunnel release techniques have been described. The cutting instruments have included needle tip, knife, saws blades, and thread. Initial results of these techniques suggest that they are feasible, safe, effective and are associated with short recovery times. The most recently described minimally invasive technique involves percutaneously looping a cutting thread around the transverse carpal ligament using a needle under ultrasound guidance. By reciprocally sliding the 2 ends of the thread back and forth like a Gigli saw, the transverse carpal ligament is transected. Only 2 needle puncture site are required. The looped thread carpal tunnel release (TCTR) procedure was initially performed on a single cadaveric hand and dissection demonstrated complete transection of the transverse carpal ligament and no injury to other structures. The authors then performed the same procedure on 34 hands of 20 patients. The primary outcome measure was the Levine-Katz questionnaire completed 3 months postprocedure. The questionnaire scores were compared to those reported in the literature for open and endoscopic release techniques and were found to be similar. No post TCTR complications were reported. Our research group has recently completed a cadaveric evaluation of this technique and found that ultrasound accurately defines the critical boundries and contents of the carpal tunnel in all cases, complete or near-complete transection of the transverse carpal ligament was achieved and no trauma was sustained by any structure within the carpal tunnel other than the transverse carpal ligament.

Procedure/Methods: subjects with clinical and electrophysiologically confirmed CTS from the practice of the principal investigator will be invited to participate. The 1st phase of this study will involve TCTR of 5 carpal tunnels. Within a month prior to and at 3 and 6 months post procedure the following outcome measures will be collected: subjective measure of symptom and functional limitation severity (Boston Carpal Tunnel Questionnaire); monofilament hand sensibility testing, grip and pinch strength; median nerve cross-sectional area measurement at the carpal tunnel inlet using ultrasound; and electrophysiologic function of the median nerve across the carpal tunnel (motor and sensory conduction velocities and amplitudes). At weekly intervals for the 1st month, each subject will also be contacted to report on their recovery (return to everyday activities including work) and any adverse effects/complications. The Boston Carpal Tunnel Questionnaire will also be completed at 1 month post TCTR. Assuming no serious complications are encountered from the initial 5 procedures, and upon approval from the supervising Data and Safety Monitoring Board, 15 additional carpal tunnels will undergo TCTR and the same outcome measures will be recorded. The outcome data will be analyzed using a repeated measures Analysis of Variance (Boston Carpal Tunnel Questionnaire; monofilament hand sensibility;grip and pinch strength; median nerve cross-sectional area; median nerve motor and sensory conduction velocities and amplitudes) and descriptive statistics (recovery duration and adverse effects/complications).