To the Editor:—I read the recent article by Warner et al.  with great interest. The Mayo Clinic's early adoption of computerized medical records provides an especially large data base within which to assess the frequency of rare complications, in this case, lower extremity motor neuropathy.
Warner et al. identified only four cases of femoral neuropathy, none of which was associated with either common peroneal or sciatic neuropathy. This low incidence is in agreement with the early report by Dhuner  in which all four cases of perioperative lower extremity neuropathy (in 30,000 anesthetics) involved the common peroneal nerve. One potential cause (often present in patients undergoing laparotomy in the lithotomy position) of isolated femoral neuropathy is direct pressure from the metal blade of an abdominal wall retractor. Is it possible that the four patients who suffered femoral nerve injuries had undergone intraabdominal procedures, possibly distinguishing them from patients with injury either to the common peroneal or sciatic nerves?.
John Butterworth, M.D., Associate Professor Department of Anesthesia, Bowman Gray School of Medicine of Wake Forest University, Winston-Salem, North Carolina 27157–1009.
(Accepted for publication December 5, 1994).