Ulnar Nerve Release Technique

Current surgical strategies for treatment of cubital tunnel syndrome include the following ^{[20, 21]} :

• In-situ decompression
• Simple decompression
• Anterior subcutaneous transposition
• Anterior submuscular transposition
• Medial epicondylectomy
• Endoscopic cubital tunnel release

Intraoperative magnification with loupes and headlight or microscope is required, and intraoperative neuromonitoring is a valuable adjunct for localizing the nerve.

A well-defined and widely accepted algorithm for choosing among the various surgical treatment options for cubital tunnel syndrome has not been established. ^[22]

A 6- to 8-cm curvilinear incision centered over the course of the ulnar nerve is made between the medial epicondyle and the olecranon. The dissection includes the two heads of the flexor carpi ulnaris (FCU) distally and proximally to the arcade of Struthers. It is safer to identify the nerve proximal to the ligament of Osborne. The ligament becomes tighter as the elbow is brought into flexion, confirming a dynamic compression of the ulnar nerve.

The ligament is incised proximally to distally to minimize the chances of injury. The nerve is then followed along the postcondylar groove and between the two heads of the FCU to exclude other sites of compression. The nerve should not be mobilized from the groove; doing so would increase the risk of subluxation.

Another dynamic test of flexion of the elbow is performed to ensure that the nerve is not compressed or does not tend to subluxate from the cubital tunnel during flexion; in these cases, an anterior transposition would ensure a better long-term result.

Among the postoperative morbidities easily avoided with the minimalist approach are lesions to the medial antebrachial cutaneous (MABC) nerve. ^[23] The terminal branches of the MABC nerve usually lie medial to the elbow; therefore, a curvilinear skin incision is directed toward the MABC branches, volar and distal to the medial epicondyle, but not beyond, in order to avoid injuries to the MABC nerve. The ulnar nerve is localized proximal to the cubital tunnel under the medial epicondyle before it passes beneath the Osborne band.

The fascia is divided, and the nerve is followed to the arcuate ligament between the two heads of the FCU. The FCU is also divided to free the nerve. If an anomalous epitrochleoanconeus muscle stretches the nerve in the cubital tunnel instead of the thickened fascial roof, ^{[24, 25]} it has to be divided.

The arcade of Struthers cannot be explored during this approach, because it is too distant from the skin incision. A smooth blunt probe can be inserted along the course of the ulnar nerve subcutaneously to evaluate the resistance to its passage proximally at the intermuscular septum and at the arcade of Struthers. If resistance is encountered, the incision can be extended.

The skin incision is centered between the medial epicondyle and the medial aspect of the olecranon. The structures exposed with this approach include the arcade of Struthers, the medial triceps, the cubital tunnel retinaculum, the Osborne fascia, and the two heads of the FCU.

The medial triceps could also represent a site of compression, with the nerve being compressed between the belly of the muscle and the medial intermuscular septum (MIS). In this case, the MIS is dissected and excised. The FCU is also partially divided. The fascia of the flexor pronator origin is used to contain the mobilized nerve and attached to the superficial subcutaneous layer.

A variant of this technique has been described in which the ligament of Osborne is used as a ligamentofascial or ligamentodermal sling to create a smooth gliding surface without causing compression and thereby to avoid subluxation. ^[26]

Anterior transposition may also be accomplished via a submuscular approach (see below); the evidence to date has not indicated that eaither approach is superior to the other. ^[27]

The skin incision is centered along the posterior condylar groove of the humerus. The proximal cubital tunnel is opened and the ulnar nerve identified. The MIS is excised as described above. The two heads of the FCU are separated, and a musculofascial incision or Z-plasty is made on the common flexor-pronator fascia. The fascia is cut at a length of 1.5-2 cm to provide enough length to avoid tension once the ulnar nerve is transposed.

Two flaps are made—one based on the medial humeral epicondyle and the other on the muscle bellies of the pronator teres and the FCU. The FCU is detached from the ulna, and the nerve is mobilized from its groove on the condyle over the MIS and the ulnar attachment of the FCU and placed back under the FCU. The flaps prepared at the beginning are sutured to the superficial layers.

A skin incision centered over the medial epicondyle is made, and the ulnar nerve is identified before it enters the Osborne band and the cubital tunnel. The FCU is prepared as described above, and the medial epicondyle is exposed with care to leave the origin of the flexor and the pronator with the periosteum in one layer. An osteotomy of 1.5 cm of the medial epicondyle is performed, and the stump is drilled with a diamond burr to accommodate the ulnar nerve on a smooth surface. This procedure may be combined with in-situ decompression.

A standard 30° Perneczky scope is used, traveling into a specific trocar with a flat inferior surface that helps both mobilization and safe dissection along the nerve. A retractor system mounted on the cannula facilitates separation from the surrounding structures.

The skin incision is made just over the cubital tunnel behind the medial epicondyle, and the initial dissection is carried out with a spatula so as to establish a plane between the roof of the canal and the nerve. The trocar is then introduced in the same plane with the retractor system, keeping superficial nerves away from the ulnar nerve. The endoscope is inserted with the visor window pointing inferiorly though its entire course. After this is done, the roof of the canal is sectioned and the ulnar nerve followed again to confirm its release.

In a systematic review and meta-analysis of 20 studies (17 observational and three comparative) comprising a total of 981 patients with idiopathic cubital tunnel syndrome, Aldekhayel et al found endoscopic cubital tunnel release (n = 556) to be similar to open cubital tunnel release (n = 425) with respect to outcomes, complication profiles, and reoperation rates. ^[28]

The following are potential complications of ulnar nerve release ^[29] :

• Postoperative persistence of symptoms caused by incomplete or inadequate decompression of the nerve and/or entrapment at a different location ^[30]
• Scar formation around the nerve due to insufficient/inadequate hemostasis
• Subluxation of the nerve to or across the medial epicondyle
• Direct injury or traction injury to the ulnar nerve during dissection
• Lesion of the MABC nerve or of its terminal branches (hyperesthesia, hyperalgesia due to painful neuromas formed from disorganized regeneration of sensory nerve fibers)
• Local postoperative hematomas due to inadequate hemostasis
• Cosmetic problems in wound healing
• Wound infection or dehiscence