SUBCUTANEOUS TRANSPOSITION OF THE ULNAR NERVE FOR TREATMENT OF CUBITAL TUNNEL SYNDROME

Subcutaneous transposition of the ulnar nerve has been widely reported as a successful surgical treatment for ulnar neuropathy at the elbow attributable to a variety of causes. Accepted indications for anterior transposition include any anatomic lesion that interferes with or impinges on the nerve along its native course. This may include a tumor, ganglion, osteophyte, valgus deformity or instability, or subluxation of the nerve, as listed previously. The surgical technique of ASCT also was described thoroughly earlier in this article. Points that warrant emphasis include thorough decompression along the entire course of the nerve, an attempt to preserve the venous plexus that accompanies the nerve, identification and preservation of branches of the medial antebrachial cutaneous nerve, and resection of a 3 to 6 cm segment of the medial intramuscular septum. Poor prognostic indicators include age over 50 years; relatively advanced neuropathy, as noted by electrical evidence of demyelination; or aggravating medical conditions, such as diabetes or alcoholism. Complications include neuroma of the medial antebrachial cutaneous nerve and resubluxation posterior to the medial epicondyle. In cases of reoperation for recurrent or persistent symptoms, inadequate release, most commonly at the medial intramuscular septum, was sited as the cause of failure in over 90% of cases. In a few cases, compression was found at the site of a fasciodermal sling. The majority of complications therefore were technical in nature and probably could have been avoided by strict attention to basic principles. Controversy surrounds the appropriate treatment for approximately half of patients in whom no clearly definable cause can be found. These cases are either attributed to "repetitive strain" or lumped into the "idiopathic" category. The pathophysiology leading to neuropathy in these groups is poorly understood, so the rationale for choosing one surgical procedure over another remains somewhat obscure. In the absence of an anatomic lesion, proponents of in situ decompression believe transposition involves unnecessary dissection, with attendant risks of devasularization or injury to the nerve or surrounding structures. Advocates of ASCT point out that the nerve may be compressed at any of several points along its course, as outlined in Fig. 1. Unlike in situ decompression, therefore, a properly performed anterior transposition assures adequate decompression at all points along its course. Indications for subcutaneous versus submuscular transposition are even less clear. Some believe submuscular transposition should be performed for more severe neuropathy, when muscular atrophy is present. Other authors point out that thin patients will be susceptible to repeated minor trauma if the nerve is left in a subcutaneous position. Neither of these contentions is supported consistently by available published data. In most cases of failed subcutaneous transposition, submuscular transposition has been used as a salvage procedure simply to place the nerve in an unscarred bed. Answers to the unresolved issues await well-designed studies. Nevertheless, there is ample cause for optimism given that adherence to basic principles has resulted in satisfactory results for 85% to 95% of patients regardless of the procedure chosen.