Reply: Femoral Nerve Injury may be Related to Abdominal Wall Retractor

In Reply:—We appreciate Butterworth's interest and the opportunity to describe in more detail our experience with femoral neuropathies associated with surgery performed on patients in a lithotomy position. [1] Unilateral femoral neuropathies developed in all four of the patients. Three of these patients underwent vaginal hysterectomies with or without cystoccle or rectoccle repairs (Table 1). The remaining patient underwent resection of a rectal carcinoma and ilcoanal anastomosis while in a low lithotomy (synchronous) position in which both abdominal and rectal incisions are made. In this patient, a self-retaining retractor that exerted bilateral lateral abdominal wall traction via a set of 10-cm wide blades placed at the level of the umbilicus was used. A separate, hand-held retractor with a 7-cm-wide blade was used at the suprapubic end of the abdominal incision to lift the rectus abdominis muscle and bladder toward the symphysis pubis.

Abdominal wall retractors often are reported to be associated with perioperative femoral neuropathies, although many other factors also may be implicated. When related to retractors, the assumption is that retractors place continuous pressure on the iliopsoas muscle and either stretch the nerve or cause it to become ischemic by occluding the external iliac artery or penetrating vessels of the nerve as it passes through the muscle (Figure 1). Rosenblum et al. [2] have speculated that self-retaining retractors that exert continuous pressure are more likely to produce a femoral neuropathy than hand-held retractors, which usually exert pressure intermittently. Although a self-retaining abdominal wall retractor was used in one of our patients, its placement at the umbilical level (not in the pelvis) and use on only the abdominal wall muscles and peritoneum makes it an unlikely contributor to the femoral neuropathy. A bladder retractor could affect the femoral nerve, especially if turned laterally, but the use of hand-held pressure also makes it unlikely to have contributed to the neuropathy. Vaginal retractors in nonparturients [2] and forceps in parturients [3] also have been implicated in femoral neuropathies, but their role in the development of neuropathies in our patients is unknown.

There may be factors other than retractors associated with perioperative femoral neuropathies. [4] As we have shown, a variety of patient factors, such as very thin body habitus and smoking in the preoperative period, may be associated with lower extremity neuropathies. [1] Three of these four patients had one or more of these factors. Two of the women undergoing vaginal hysterectomy had body mass indexes 20 kg/m [2] or less and were smokers. The man undergoing resection of a rectal carcinoma was in the low lithotomy position for approximately 5 h and was a smoker. Extremes of either hip flexion or extension also may be associated with femoral neuropathies. [5,6] Hemorrhage in the iliopsoas muscle and subsequent compression or ischemia of the femoral nerve also have been reported to occur during the perioperative period. [7].

Mark A. Warner, M.D., Associate Professor of Anesthesiology, Mayo Clinic Rochester, Minnesota 55905.

John T. Martin, M.D., Professor Emeritus of Anesthesiology Medical College of Ohio at Toledo, 30OO Arlington Avenue, Toledo, Ohio 43614.

(Accepted for publication December 5, 1994).