Carpal tunnel syndrome was first described by Sir James Paget in 1854, and carpal tunnel syndrome is the most common compressive neuropathy of the upper extremity. Carpal tunnel release is one of the most frequently performed surgical interventions by hand surgeons today [1]. Recurrent carpal tunnel is defined as symptom resolution after surgery with subsequent recurrence after a set time interval [2]. Failed carpal tunnel surgery accounts for approximately 10% of cases and is most often attributed to incomplete release [3]. A second operation to divide the accumulated scar tissue and “re-release” the ligament is often required and considered a secondary carpal tunnel release [4]. Secondary carpal tunnel surgery can have unfavorable results with up to 95% of patients having persistent symptoms [5]. Furthermore one must differentiate between unrelieved carpal tunnel syndrome and recurrent carpal tunnel being that in recurrent carpal tunnel syndrome, there is complete resolution of symptoms for a period of at least 3 months [6]. Postoperative outcomes for recurrent carpal tunnel syndrome surgery produce up to 40% of patients with poor result, being either those who experienced no symptom relief, new related symptoms, or worse symptoms [1]. This is likely why no procedure remains superior, and many approaches have been purposed. However, there are two main principles that remain central to the treatment of recurrent carpal tunnel. These are neurolysis with restoration of median gliding and coverage of the median nerve with a native tissue flap to prevent internal scar recurrence. It is the author’s proposal that the extent of the neurolysis should include intrafasicular release to the bands of Fontana with accompanied vascularized flap coverage for prevention of adhesions and allowing for neovascularization of the perineural tissue [7]. Good to excellent results are reproducible and acceptable, as defined by some relief of symptoms to allow for daily activity, and thus it should be considered the procedure of choice in recurrent carpal tunnel [8].

The normal median nerve longitudinally slides several millimeters in its bed with wrist flexion and extension [9]. Through biomechanical and cadaveric studies, a common pathology for recurrent carpal tunnel syndrome, was elucidated as a “traction neuropathy” that was purposed to prevent median nerve gliding through the tunnel, leading to increased load transmission on the median nerve with wrist motion [10]. This also has been characterized by the findings intraoperatively of the adherence of the nerve to the radial leaflet of the transverse carpal ligament. Additionally, there was a complete encasement of the median nerve by fibrosis [8]. In an undefined period of time, the nerve then experiences pathological changes indicating decreased bands of Fontana with exposure to tensile forces [11].

Patients with recurrent carpal tunnel syndrome typically report a prior carpal tunnel release with at least 3 months of partial clinical relief and then subsequent return of symptoms that are similar before surgery or worse. Patient symptoms are reported to consist of paresthesia in median nerve distribution, numbness, aching pain, and nocturnal awakening due to pain. Although these symptoms are often associated with primary carpal tunnel syndrome, a noted difference is pain with active extension of wrist and fingers. Since only approximately 50% of patients with recurrent carpal tunnel have a positive Phalen’s or Tinel’s sign [1], recurrent carpal tunnel is diagnosed through symptoms consisting of median nerve hypersensitivity at the wrist and scar, without damage to the palmar cutaneous branch [3]. The physical diagnosis is further supported with noted physical compression of the nerve just proximal to the carpal tunnel, while holding the forearm in maximum supination, with resulting paresthesias in the median nerve distribution. Other forms of provocation such as resisted pronation and resisted superficialis muscle strain may also produce symptoms if entrapment of the nerve exists just proximal to the carpal tunnel [12]. The thenar muscle abduction test is another method used to clinically detect recurrent carpal tunnel syndrome. This involves detected weakening of the abduction of the thumb against resistance in a position of forearm supination, wrist and finger extension, and thumb abduction in setting of prior carpal tunnel release [7].

Conservative measures of splinting, stretching therapy, scar massage, and activity modifications may provide temporary relief; however, symptoms frequently recur with cessation of therapy or return despite these significant measures. More aggressive therapy solutions promote a “work hardening” program with compensatory activities that can themselves lead to competing compressive neuropathies such as radial nerve compression from supination exercises [7]. Furthermore, limitation of forearm activities persuades one to use more shoulder and neck motion that can lead to “brachial plexus traction problem” exercises [7]. This leads patients to consider surgery as a potentially longer-lasting solution.

Electromyography results in recurrent carpal tunnel syndrome are often variable. Some nerve conduction velocity studies show abnormal conduction velocity and prolonged latency in both motor and sensory values [13]. Other studies note EMG/NCV studies with high patient variability ranging from unchanged conduction velocities to worsening velocities, to signs of denervation of the thenar muscles [14]. In other instances while the initial EMG may be normal, it can become positive after exercise and positional stress testing [7]. It is notable that the variability in electromyography depends on the prior median nerve compression and scarring that occurs after surgery. Often comparison of pre- and post-initial carpal tunnel release EMG/NCV studies shows continued decreased sensory and motor latencies in setting of prior improvement [15].