Predictors of Functional Outcome Change 18 Months After Anterior Ulnar Nerve Transposition

OBJECTIVE: To determine which variables derived from the electrodiagnostic examination were predictive of patient self-reported symptoms and disability at 18 months after anterior ulnar nerve transposition. DESIGN: Retrospective cohort study. SETTING: Electrodiagnostic laboratories affiliated with a tertiary care center. PARTICIPANTS: Patients (N=73) with cubital tunnel syndrome (CuTS). INTERVENTIONS: Patients were randomly assigned to one of the anterior transpositions of the ulnar nerve (subcutaneous or submuscular). MAIN OUTCOME MEASURES: Outcome was a patient-rated ulnar elbow evaluation (PRUNE). Predictors were all variables derived from the electrodiagnostic examination and characteristics of participants, as well as the preoperative clinical status. A stepwise multivariable linear regression analysis was used to determine the relative importance of the selected variables on the change in PRUNE scores. RESULTS: Above-elbow compound muscle action potentials amplitude and proportional compound muscle action potentials amplitude decreasing from above elbow to below elbow were predictors of change score of the PRUNE at 18 months after operation (R(2)=16%). Sex and preoperative PRUNE also showed predictive information (R(2)=14% and 15%, respectively). CONCLUSIONS: CuTS is predominantly a clinical diagnosis. Electrophysiologic studies are important supplemental examinations for the diagnosis of CuTS because they not only contribute to diagnosis, but are also important prognostic features. Females may have more improvement with regard to functional outcomes than males when undergoing surgical intervention.