Lower-extremity motor neuropathy associated with surgery performed on patients in a lithotomy position

Motor neuropathy of a lower extremity is well-recognized as a potential complication of procedures performed on patients in a lithotomy position. Most of this awareness is based on anecdotal reports, however, and the incidence and risk factors for this complication have not been reported.

We retrospectively reviewed the perioperative courses of 198,461 consecutive patients who underwent 1 of 56 surgical procedures historically performed on patients in a lithotomy position at the Mayo Clinic, Rochester, Minnesota, from 1957 to 1991 inclusive. The medical diagnoses of patients who had procedures in a lithotomy position were scanned for 26 diagnoses associated with neuropathy. Persistent neuropathy of the lower extremity was defined as a motor deficit of at least 3 months' duration. Risk factors anecdotally associated with persistent neuropathy were analyzed by comparing identified cases of neuropathy to controls in a 1:3 case-control study.

Persistent neuropathies after procedures performed on patients in a lithotomy position were identified in 55 cases for a rate of 1 per 3,608. Multivariate risk factors for development of a persistent neuropathy of a lower extremity included duration in lithotomy of 4 h or longer, a body mass index (kilograms per squared meter) of 20 or less, and a history of smoking within 30 days of the procedure. Regional anesthetic techniques were not found to be associated with an increased risk of neuropathy. Of the 53 patients who lived at least 1 yr after their procedure, 24 (45%) required either prosthetic or ambulatory support for persistent foot drop or leg weakness.

These data suggest that prolonged duration in lithotomy and patient risk factors, including very thin body habitus and smoking in the preoperative period, are associated with the development of a lower-extremity neuropathy after procedures performed on patients in a lithotomy position. A reduction of time in the lithotomy position may be particularly worthwhile for patients with these risk factors.