Carpal tunnel syndrome (CTS) is a common compressive neuropathy in which the median nerve is compressed at the level of the carpal tunnel [1, 2]. CTS can occur in one or both hands, and is either idiopathic (spontaneous) or dynamic (only during certain movements). The compression leads to numbness and tingling in the first three fingers and the radial side of the ring finger, paresthesia, pain, and (in severe cases) weakness. The symptoms are often worse at night or after use of the hand . Prevalence is estimated to be about 4% in the general population  and up to 10% in the working population . Although CTS can occur at any age, it most commonly occurs between 40 to 60 years and its prevalence is higher in women compared to men . Obesity, diabetes mellitus, and alcohol abuse are risk factors for developing CTS . Occupation has been identified as an environmental risk factor: vibration, hand force, and repetition are associated with increased risk for developing CTS . Furthermore, there is a psychological component to the experience of CTS symptoms: depression has been reported as a predictor of pain in CTS patients .
CTS can be diagnosed using electromyography (EMG). Compression of the median nerve can lead to damage and dysfunction of the myelin sheath, resulting in slowed conduction velocity, which can be detected using EMG . Treatment options to reduce the compression and relieve symptoms can be roughly divided into surgical and non-surgical procedures. Non-surgical, less invasive treatment options are numerous, including oral medication, corticosteroid injections, splinting, exercise, and mobilization interventions [8–12]. However, there is only short-term or limited evidence of benefit for these interventions. Many (non-steroidal) drugs did not prove to be significantly superior compared to placebo . There is only limited evidence for the effectiveness of splinting, exercise, and mobilization interventions [10, 11]. Local corticosteroid injections provide considerable symptom relief and therefore show the best results of the non-surgical treatments [8, 9]. However, corticosteroids seem to merely suppress CTS symptoms and the positive effects do not last [8, 13]. The treatment effect diminishes over time and half of patients who receive corticosteroid injections experience recurrence of symptoms within a year .
Compared to non-surgical treatment, surgery is the only known treatment option that shows long-term positive effects . The principle of the procedure, called carpal tunnel release (CTR), is to decompress the nerve by dividing the transverse carpal ligament . Evidence suggests that CTR is a more effective treatment for CTS than splinting or oral medication, especially long-term . However, up to 30% of patients who underwent CTR experience persistence or recurrence of CTS symptoms in the long-term or suffer from complications [16, 17]. Therefore, there is still a clear need for an alternative non-invasive therapy, possibly making surgery redundant for a sub-category of patients.
Another promising non-surgical treatment for CTS is mechanical wrist traction using the Phystrac traction device. The Phystrac applies repeated traction movements to the wrist in different positions using gravitational force. Brunarski et al. described four case studies using mechanical traction that showed promising results . In an observational study, physical therapists reported a success rate of 70% with mechanical traction immediately post-treatment , and 60% after two years follow-up . However, until now, no randomized controlled trial (RCT) has been performed to show clinical evidence for the effectiveness of mechanical traction as compared to care as usual (surgical and non-surgical intervention).
Hypothesis and objectives
The purpose of this study is to evaluate the effectiveness of mechanical traction in alleviating symptoms and improving hand function in patients with CTS compared to care as usual. The primary outcome is the change from baseline in symptom severity and functional status at 12 months, which is measured using the Boston Carpal Tunnel Questionnaire (BCTQ). Change from baseline in functional status and symptom severity at three and six months will be used as covariates. As secondary outcomes, we will assess quality of life, health related resource utilization, and absenteeism from work. Tertiary outcome is the impact of psychological distress on treatment outcome. We hypothesize that hand function and symptom severity will significantly improve more in CTS patients receiving 12 treatments with mechanical traction compared to CTS patients who receive care as usual after 12 months. Moreover, 12 treatments with mechanical traction will result in less absenteeism from work, a higher quality of life, and less health related resource utilization compared to care as usual in CTS patients after 12 months follow-up. Furthermore, a higher degree of depression and anxiety at baseline will result in a lower treatment effect in CTS patients.