We use nerve autograft for complete or partial nerve lacerations that cannot be sutured together without tension. Our choice of nerve graft includes medial antebrachial cutaneous (MABC) nerve and sural nerve. Before surgery, be sure to obtain consent to harvest nerve graft or to use a nerve conduit. Loupe magnification or a dissecting microscope is advocated.

The incision is planned so that it extends into normal tissue at least 2 cm on either end. The median nerve is recognized in the distal forearm straight beneath the palmaris longus tendon. The nerve is traced toward the carpal canal working on the anterior, ulnar margin of the nerve. As the scarred region comes nearer, care is taken to recognize the plane between the nerve and the scar. The existence of perineural fat forms a natural plane except in those occasions when the nerve has been lacerated. If you lose the plane between nerve and scar, proceed with the dissection distal to the carpal tunnel starting in normal tissue. Start on the anterior margin of the third common digital nerve and trace that nerve to the anterior, ulnar margin of the median nerve proper. When there is no clear plane between the nerve and scar, you can infer the line of dissection from the distal and proximal anterior, ulnar margins of the nerve. Dissect just ulnar to this line keeping a cuff of synovial tissue on the nerve. Once the nerve is released from scar, check the nerve for signs of injury such as disruption of fascicles or proximal neuroma (Fig. 16.3a). Identify the motor branch and common digital nerve. Adequate exposure of the median nerve and carpal tunnel is required. The revision CTR begins by extending the previous incision into normal tissue to allow proximal or distal identification of the median nerve to first facilitate exploration.

Dissection of the median nerve from proximal to distal should be performed along the ulnar border of the nerve to avoid damage to the motor branch. If dense scar is encountered during the proximal to distal dissection, stop and find the nerve in normal tissue distal to the densely scarred area. Alternate the exposure from proximal to distal and then distal to proximal until the nerve has been safely mobilized.

Unfortunately, given our limited ability to control scar formation, revision decompression and neurolysis of the median nerve for treatment of perineural fibrosis frequently yield unsatisfactory results [14, 15].

In patients with a significant interval between primary CTR and recurrent symptoms, Mosier et al. [22] treated recurrence of symptoms with simple repeat CTR. They define a “significant interval” as more than 1 year with resolution of carpal tunnel symptoms during this time. Beck et al. [26] demonstrated good relief with repeat decompression at many time intervals.

Interposition of a biologic barrier between the nerve and surrounding tissues may discourage scarring and provide a nutrient bed for axonal regeneration [34]. The advantage of local flaps like the ADQ, pronator quadratus, hypothenar fat flap [35], and palmaris brevis muscle flap [36, 37] is the ease with which they can be used. Unfortunately, length limitations may restrict their utility. Our preference is to use a hypothenar fat flap when possible (Fig. 16.1). After simpler techniques have been ruled out as options, it may be necessary to employ more complex free tissue transfers [12].

When the surgeon feels that the local tissue environment is fibrotic and/or avascular, several procedures may be performed to help protect the nerve from recurrent scarring, including autologous and synthetic nerve wraps and vascularized soft tissue coverage. Other factors to consider are also ease by which the tissue can be obtained and the comorbidities associated with its harvest. There are generally two categories of these procedures, as explained by Abzug et al. [38]:

The hypothenar fat pad flap interposes adipose tissue from the hypothenar eminence between the median nerve, the remnant of the TCL and surrounding scar. First described by Cramer [35] and refined by Strickland et al. [33], the hypothenar eminence includes a generous layer of adipose tissue of sufficient width and thickness to provide coverage for the median nerve within the carpal canal. Dissections of the hypothenar fat pad have demonstrated arterial branches to the fat pad arising from the medial side of the ulnar artery in Guyon’s canal and more distally from branches of the ulnar artery to the small finger and fourth web space. These transverse and somewhat tortuous branches occurr approximately every 1 cm beginning at the distal wrist flexion crease. Additional arterial branches to the fat pad arise from arterial branches to the hypothenar muscles and palmaris brevis muscles [33].

Once sufficient mobilization of the fat pad has been accomplished, it is transposed over the median nerve and sutured to the undersurface of the radial leaflet of the TCL [33] (see Fig. 16.1).

In a retrospective series of 58 patients with 62 hands, Strickland et al. [33] showed excellent results in relieving recurrent symptoms with use of the hypothenar fat pad flap at an average follow-up of 33 months, with 37 of the 43 patients returning to their pre-surgery employment. Subjectively, the vast majority of patients had improvement of proximally referred pain, hypersensitivity, and nocturnal symptoms. There was also significant improvement in the Phalen’s and Tinel’s signs, and relief of dysesthesia and paresthesia was seen in 89% of patients. This relief was not immediate and in some cases took as long as 2.5 years to achieve. Two-point discrimination remained normal in 35 patients, improved from an expanded range to normal (<6 mm) in 21 patients, and remained expanded in 5 patients.

In a retrospective study of 28 patients, Craft et al. [34] showed significant improvement in the average two-point discrimination tests, the grip tests, and in the number of cases with positive Tinel’s sign. Pain resolved in 83% of patients and numbness resolved in 42% of patients. The subjective complaint of “tingling” disappeared in 50% of patients.

Fusetti et al. reported on 20 patients who were treated with a hypothenar fat pad flap. Sixteen patients had adherence of the median nerve to the radial leaf of the divided TCL. The remaining four patients had an unidentifiable plane between the epineurium and the remains of the TCL. Subjectively, 18 of the 20 patients had complete resolution of their hyperesthesia and allodynia by 6 months after surgery. One patient had no improvement and would not recommend the procedure, while the remaining 19 patients stated that they would recommend the procedure. Seventeen of the 20 patients had resolution of provocative signs, including Phalen’s, Durkan’s, and Tinel’s. Seven of the nine workers’ compensation patients returned to work [39].

Wichelhaus et al. [40] conducted a retrospective study of 18 patients with recurrent CTS due to fibrotic adhesions of the median nerve, with scar formation of 3 to 5 cm in length. The hypothenar fat pad flap was used in all the cases, as it covered the entire length of the scarred nerve. Pain disappeared after the surgery in 14 patients, and the Tinel’s sign disappeared in 16 patients. Hand function, grip strength, and pinch strength improved in all patients, as well as two-point discrimination recorded from the fingertips. Fifteen of the 18 patients would elect to have the operation done again if necessary. None of the patients reported hypothenar pain, none deteriorated after surgery, and all of the patients reported complete resolution of nighttime symptoms.

A vascularized synovial flap can be used to supply interposition and neovascularization to a scarred median nerve. This technique has the advantage of being able to be performed over the same incision without the requirement for expanded additional dissection. The synovial flap, raised off of the superficial flexor tendons deep to the median nerve, is a barrier to scar formation. The surgical technique is described in Figs. 16.2 and 16.3.

To make a synovial flap, raise a flap of synovium from the superficial flexors starting on the ulnar aspect of the carpal canal (Fig. 16.3b). Continue raising the flap from the level of the superficial arch to the wrist crease. At the proximal and distal margins of the flap, cut transversely to allow the flap to be mobilized. Continue to raise the flap to the margin of the median nerve (Fig. 16.3c). The flap is then draped over the nerve and sewn to the inner surface of the radial remnant of the TCL (Fig. 16.3d). The wrist is immobilized for 10 to 14 days post-surgery. If there is an associated nerve injury that was repaired or grafted during the procedure, the wrist is immobilized for 4 weeks. Splints and casts are kept low in the palm to permit full and prompt finger motion. Scars are treated with massage and elastomer.