24 Recurrent Ulnar Neuropathy
24.1 Patient History Leading to the Specific Problem
A 54-year-old man is referred with persistent ulnar neuropathy following decompression and transposition over 1 year ago. His symptoms began about 1.5 years ago when he began to notice weakness and clumsiness in his right hand. A diagnosis of severe cubital tunnel syndrome was made, followed by ulnar nerve transposition. Postoperatively, however, he has continued to experience progressive loss of ulnar nerve function and severe ulnar nerve pain for which he takes nortriptyline. He complains of hypersensitivity along the ulnar aspect of his forearm, hand, and ring and small fingers.
24.2 Anatomic Description of the Patient’s Current Status
The patient has a well-healed longitudinal curvilinear scar behind the left medial epicondyle extending approximately 6 cm. He has marked ulnar intrinsic atrophy of the left hand, very little ulnar intrinsic function, and a very positive Froment’s sign (▶Fig. 24.1). He has very weak ulnar extrinsic function as well. His pinch and grip strengths on the right are 9 and 55 lb, respectively, compared to 20 and 110 lb, respectively, on the left. His 2-point discrimination in the median nerve distribution is between 4 and 5 mm, but no detectable 2-point discrimination or even light touch sensation in the ulnar nerve distribution. He has a strong Tinel’s sign at the right elbow and especially at the distal end of his scar where it seems his enlarged ulnar nerve is almost palpable.
Fig. 24.1 Intrinsic wasting secondary to ulnar nerve neuropathy. The first dorsal interosseous muscle is most notably deficient.
24.3 Recommended Solution to the Problem
A common problem after ulnar nerve transposition is insufficient release and mobilization of the nerve at the most proximal and distal extent of dissection that leads to an acute angle of turn of the nerve both proximally and distally after transposition. Insufficient soft tissue and fascial release will also cause a firm edge against which the nerve will press as its course changes in its transposed location. All of these areas will need to be released and the ulnar nerve further mobilized both proximally and distally so its course is more gradual and smooth as it transitions from its anatomic location to the transposed position. His symptoms are also suspect for injury to one or more branches of the medial antebrachial cutaneous (MBAC) nerve, which will need neuroma excision and proximal transposition into muscle away from the scar.
Finally, he has significant muscle atrophy after a prolonged period of chronic denervation. An appropriate and thorough decompression at this point will be helpful, especially for his pain and sensation, but muscle reinnervation may be more limited because of the chronic duration of his problem. As such, a nerve transfer from the distal anterior interosseous nerve (AIN) should be considered to provide a source of motor axons in closer proximity to the intrinsic muscles and allow faster reinnervation. If done in a reverse end-to-side (RETS) or supercharge end-to-side (SETS) fashion, any reinnervation from his recovering ulnar nerve would still be possible and additive.
24.3.1 Recommended Solution to the Problem
• MABC nerve branches and neuromas need to be identified, excised, and the proximal nerve transposed proximally away from scar.
• The ulnar nerve should be more extensively mobilized to release all scar and existing or potential compression points, including all fascial and septal edges.
• There should be easy transposition of the nerve without sharp bends or pressure points at the proximal and distal endpoints of dissection.
• SETS nerve transfer from the distal AIN should be done to optimize intrinsic muscle reinnervation and supplement the recovering ulnar nerve.
His previous scar is excised, reopened, extended both proximally and distally, and skin flaps re-elevated. Branches of the MABC should be identified and any neuromas excised, mobilized, and transposed proximally into innervated muscle to minimize the risk of recurrent neuroma formation. The transposed ulnar nerve is identified, and any overlying scar is released, especially if a fascial sling was constructed to keep it in a transposed position and is now causing any compression. At the proximal and distal exposures, the nerve is remobilized, and the muscle and fascial planes dissected and released to ensure that the nerve takes a smooth curving course to and from its transposed position without any kinking or palpable fascial edges against it. If a submuscular transposition was done before or is being done, intermuscular septa between the forearm muscles under the transposed nerve should also be excised to provide a smooth, soft bed for the nerve without ridges or firm edges that may become more pronounced with scarring. If a new fascial sling needs to be constructed to keep the nerve transposed, it should be very loose and ideally any fascial suturing should be kept away from the nerve and not directly over it if possible (▶Fig. 24.2). Nerve branches coming off the nerve within the cubital tunnel, usually articular and flexor carpi ulnaris (FCU) branches, should be neurolysed from the nerve proximally to gain sufficient length to allow easy anterior transposition without tethering.