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Ulnar Nerve Branches and Anterior Transposition for Cubital Tunnel Syndrome – Surgical Considerations and Possible Complications
University of Glasgow, Glasgow, United Kingdom
Zhi Yang Ng, MBChB1; Prem Ruben Jayaram, MBChB1; Jennifer H. Mitchell, BSc1; Quentin A. Fogg, BSc, (Hons), PhD1; Andrew M. Hart, MD, PhD, FRCS2;
1University of Glasgow, 2Glasgow Royal Infirmary
Introduction: Cubital tunnel syndrome is the second most common nerve entrapment neuropathy. When non-operative measures fail, surgical management is indicated. Options include decompression +/- medial epicondylectomy and forms of anterior transposition. The anatomy of the ulnar nerve branching around the elbow is of technical relevance, but few published details are available. Less is known about the potential effects of sacrificing these branches, if necessary, to facilitate anterior transposition.
Material and Methods: Nine cadaveric upper extremities were dissected to delineate the course and branching pattern of the ulnar nerve into the surrounding musculature (muscular) and elbow capsule (sensory). Branches above the elbow joint were considered “proximal”; those arising at or beyond the joint line, “distal”. Anterior transposition of the ulnar nerve was performed in three cadaveric specimens (two fixed, one fresh). Digital photographs were analyzed using the ImageJ package to provide a quantitative description of the ulnar nerve branches, and to illustrate the effect that these branches might have on ulnar nerve transposition.
Results: Four specimens had a proximal branch – in one specimen this was sensory and in the others, mixed. Specimens also showed a range of one to five distal, mixed branches. With respect to the medial epicondyle (ME) and olecranon (O), measurements of the branching points (range, ME/O: proximal = 78-142/102-165 mm; distal = 21-44/18-38 mm) and likely terminal tissue entry points (range, ME/O: proximal = 18-36/46-61 mm; distal = 39-69/32-59 mm) of ulnar nerve branches showed a distribution towards the olecranon distally.
All three specimens used for transposition were found to have branches from the ulnar nerve around the level of the elbow joint. Additional dissection, including that of the flexor carpi ulnaris (FCU) (mean length cut = 25.2±3.2 mm) allowed further transposition in two specimens but in the third, these branches (two muscular, one sensory) were restricting and had to be sacrificed.
Conclusions: Although anterior transposition is a common procedure, this study suggests that distal ulnar nerve branches in close proximity to the elbow joint may potentially restrict transposition more than has been recognized; proximal branches may also be found to overlap the incision lines of such procedures. There is little published regarding the potential iatrogenous impact upon FCU function should motor branches be divided, or upon pain, local parasthesia, or other sensory symptoms should sensory branches be divided or placed under undue traction. This anatomical study raises a case for more detailed clinical investigation of such potential sequelae.
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