A submuscular ulnar nerve transposition is performed to decompress the ulnar nerve in the cubital tunnel at the elbow.
Siegel from the Tucson Orthopaedic Institute, Arizona generally reserve submuscular transposition for patients who have failed previous anterior subcutaneous transposition and those who are very thin, in which case the nerve may be prominent immediately beneath the skin, resulting in an area of uncomfortable sensitivity. In patients who are candidates for reoperation following failed anterior submuscular transposition, it is common to find an area of compression that was not released during the initial operation. Most importantly, failure to release the arcade of Struthers, the arcuate ligament, and the flexor carpi ulnaris muscle fascia; excise the medial intermuscular septum; or provide ample room for the ulnar nerve beneath the flexor-pronator muscles will result in failure of surgical treatment. Range-of-motion exercises and hand strengthening facilitate early return of function 1).
The medial antebrachial cutaneous nerve is identified and protected. Proximally, the medial intermuscular septum is resected. A step-lengthening of the fascia of the flexor-pronator muscles is performed. The ulnar nerve is placed in a transmuscular location. More importantly, the distal fascial septum between the flexor carpi ulnaris and the flexor-pronator muscles is removed.
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Submuscular transposition (SMT) for ulnar nerve entrapment treatment is commonly performed, however, published comparisons of surgical techniques exclude a high proportion of the at-risk population encountered in real-world practice. To examine the influence of risk factors on the clinical outcome following SMT Davis et al. performed a retrospective review of all patients who underwent SMT, including patient self-reported outcome and Louisiana State University Medical Centre ulnar nerve grading scale. A total of 403 ulnar nerves were operated on, with follow-up data available for 385 cases (359 patients). Risk factors (including smoking, diabetes, previous elbow trauma/pathology, subluxation, workers' compensation) were reported in 266 of 385 surgeries (69.09%). SMT was the primary procedure in 339 nerves (88.05%), revision procedure in 46 nerves (11.95%). At last follow up 91.05% reported symptomatic improvement. Nerve grade improvement in 71.09% of primary and 67.39% revision surgery (p = 0.605). No significant difference in improvement was identified between demographic and risk categories, except for patient-reported improvement in those without peripheral neuropathy (90.59% vs 73.33%, p = 0.027), and those not improved were on average older than those improved (62.94 vs. 55.68 years, p = 0.012). Superficial infection occurred in 2.6% and there were no deep infections. Application of published exclusion criteria would have resulted in the exclusion of ½-⅔ of the cohort. SMT in patients with a history of elbow trauma, diabetes, workers compensation, smoking history, nerve subluxation or revision surgery have similar outcomes compared to those without these factors, whilst improved results were observed in younger patients and those without peripheral neuropathy 2).
A retrospective study of 26 submuscular ulnar nerve transpositions was performed with the specific use of grip and pinch analysis to evaluate this form of objective testing. Twenty-six patients were treated by submuscular transposition of the ulnar nerve between 1981 and 1985 and were followed an average of 21 months. Preoperative and postoperative analysis consisted of subjective questioning, clinical examination, quantitative two-point discrimination, quantitative pinch and grip analysis, and electromyographic (EMG) and nerve conduction velocity (NCV) evaluation. Many of the patients suffered from associated problems such as alcohol abuse, diabetes mellitus, and concurrent Guyon's canal compression, which adversely affected the outcome. Subjectively, 62% were improved, 31% were no better, and 7% were worse. Clinical examination demonstrated 46% improved, 35% no better, and 19% worse. Quantitative two-point discrimination was better in 59%, unchanged in 26%, and worse in 15%. Quantitative pinch and grip analysis revealed 28% improved, 56% with little improvement, or the same, and 16% worse, while EMG/NCV showed one-third of the patients in each category postoperatively. Quantitative pinch and grip analysis provided good preoperative and postoperative documentation, which is absent from previous studies in the literature concerning ulnar nerve transportation 3)