Perioperative Ulnar Neuropathy: A Contemporary Estimate of Incidence and Risk Factors.

Background: Retrospective and prospective studies 2 decades ago from the authors' institution reported the incidence of perioperative ulnar neuropathy persisting for at least several months in a noncardiac adult surgical population to be between 30 and 40 per 100,000 cases. The aim of this project was to assess the incidence and explore risk factors for perioperative ulnar neuropathy in a recent cohort of patients from the same institution using a similar definition for ulnar neuropathy.

Methods: We performed a retrospective incidence and case-control study of all adults (≥18 years) undergoing noncardiac procedures with anesthesia services between 2011 and 2015. Each incident case of persistent ulnar neuropathy within 6 months of surgery was matched by age, sex, procedure date, and procedure type to 5 surgical patient controls. For the case-control study, separate conditional logistic regression analyses were performed to assess specific risk factors including the patient's body position and arm position, as well as body mass index (BMI), surgical duration, and selected patient comorbidities.

Results: Persistent ulnar neuropathy of at least 2 months duration was found in 22 of 324,124 anesthetics for patients who underwent these procedures during the study period for an incidence rate of 6.8 (95% confidence interval [CI], 4.3-10.3) per 100,000 anesthetics. The incidence of ulnar neuropathy was higher in men compared to women (10.7 vs 3.0 per 100,000; P = .016). From the matched case-control study, the odds of ulnar neuropathy increased with higher BMI (odds ratio [OR] = 1.67 [1.16-2.42] per 5 kg/m2 increase in BMI; P = .006), history of cancer (OR = 6.46 [1.64-25.49]; P = .008), longer procedures (OR = 1.53 [1.18-1.99] per hour; P = .001), and when 1 or both arms were tucked during surgery (OR = 6.16 [1.85-20.59]; P = .003).

Conclusions: The incidence of persistent perioperative ulnar neuropathy observed in this study was lower than the incidence reported 2 decades ago from the same institution and using a similar definition for ulnar neuropathy. Several of the previously reported risk factors continue to be associated with the development of persistent perioperative ulnar neuropathy, providing ongoing targets for practice changes that might further decrease the incidence of this problem.