Surgical decompression without transposition for ulnar neuropathy: factors determining outcome. Fifty-one surgical decompressions without nerve transposition for ulnar neuropathy were performed in 46 patients. All of the patients were men with an average age of 59 years at the time of surgery. The follow-up range was between 5 and 32 months (average, 17.8 months). The disease involved the nondominant arm in 24 patients (52%) and was bilateral in 5 (11%). In 23 cases (50%), no predisposing condition could be identified, whereas 15 patients (33%) abused alcohol and 8 patients (17%) had diabetes mellitus. Fifty-seven percent of the patients helped by surgery had symptoms for less than 1 year, whereas only 30% of patients with symptoms for more than 1 year had symptomatic improvement. The relative magnitude of the slowing of ulnar nerve conduction velocity across the elbow was not significantly correlated with the success of decompression in relieving symptoms. Ulnar nerve conduction velocities across the elbow were 36.13 +/- 11.76 m/s in those responding to surgery and 38.97 +/- 13.91 m/s in those not responding (c = 0.06, dF = 50, P less than 0.3). A total of 37 patients showed symptomatic improvement after decompression. Simple decompression of the ulnar nerve was performed under local anesthesia without transposition of the nerve. In all of these cases, compression of the nerve occurred predominantly in the epicondylar groove. Narrowing of the nerve in the groove was present in 28 cases (55%); scar tissue was found adhering to the nerve in 21 cases (41%); and two pseudoneuromas were found (4%). Forty-one operations (80%) resulted in symptomatic improvement, typically noted by the patient within the first month postoperatively. 