Femoral Neuropathy: A Curse of Vaginal Hysterectomy

Introduction

With the increase in the trend of performing hysterectomies through the vaginal route, there is a potential risk of developing femoral neuropathy in the lithotomy position. Awareness of this condition is important among gynecologists to prevent morbidity and medicolegal complications. This is especially important when surgery is prolonged. Prolonged lithotomy position under regional anesthesia is blamed for femoral neuropathy and transient neurological symptoms.^1,2 Many reports enumerate injury to the peroneal branch of the sciatic nerve as a complication of vaginal hysterectomy. There are a limited number of reports of femoral neuropathy after vaginal hysterectomy in the lithotomy position. Two (2) patients who developed this complication are described.

Case 1

A 45-year-old woman underwent vaginal hysterectomy for adenomyosis uterus under spinal anesthesia. Results of preoperative medical and neurological examination and laboratory investigations were normal. The surgery lasted for 1 hour 40 minutes. On the 3rd postoperative day, the patients complained of numbness in the right thigh and knee buckling on getting out of bed. Neurological examination revealed loss of sensation from light touch and pin prick over the anterior side of the right thigh and around the knee joint. Ankle jerk was normal, plantars were flexor. There was no other neurological deficit. The clinical diagnosis was femoral neuropathy. Conservative management was started (i.e., oral neurobion [vitamins B₁, B₆, and B₁₂] and physiotherapy). By seventh postoperative day she had recovered completely.

Case 2

A 47-year-old woman underwent vaginal hysterectomy for a 14-week fibroid uterus. Surgery lasted for 1 hour and 30 minutes and the intraoperative period was uneventful. On the 2nd postoperative day the catheter was removed, and when she got up from bed for urination she lost control and fell down. Her vitals signs were within normal limits. Neurological examination revealed gross weakness of the quadriceps femoris muscles (more on the left side), absent knee jerks, and hypoesthesia over the anterior aspect of the left thigh. An opinion was sought from a neurophysician and an anesthetist. An electromyogram (EMG) was done and a diagnosis of femoral neuropathy was made.

The patient was reassured and managed with graded physiotherapy, oral corticosteroids, and methylcobalamine. She gradually responded to treatment, and by the 2nd week she was walking with support and sensations had completely recovered. She was advised to continue physiotherapy and was symptom free by 10 weeks. Later on, she sued the hospital, gynecologist, and anesthetist for reimbursement of damage.

Discussion

Lithotomy positioning during gynecological procedures has been associated with compressive femoral neuropathies. ³ Iatrogenic femoral nerve injury has been documented following abdominopelvic operations, particularly when self-retaining retractors are used. Transverse abdominal incisions and thin body habitus are significant risk factors.^4,5 In the lithotomy position, sharp flexion of the hip can compress the nerve at the inguinal ligament. Excessive hip abduction and external rotation cause additional stretch on the nerve. ⁴ Rarely, bilateral weakness of lower limbs with sensory loss could be caused by epidural hematoma, abscess, injury to the spinal cord, or cauda equina syndrome due to regional anesthesia. ⁶

Knowledge of femoral nerve anatomy is essential to understanding the mechanism of its injury and in localizing the lesion. The femoral nerve is part of the lumbar plexus. It is formed by L2–4 roots and reaches the front of the leg by penetrating the psoas muscle before it exits the pelvis by passing beneath the medial inguinal ligament to enter the femoral triangle just lateral to the femoral artery and vein. Approximately 4 cm proximal to passing beneath the inguinal ligament, the femoral nerve is covered by a tight fascia at the iliopsoas groove. The nerve can be compressed anywhere along its course, but it is particularly susceptible within the body of the psoas muscle, at the iliopsoas groove, and at the inguinal ligament. The main motor component innervates the iliopsoas (a hip flexor) and the quadriceps (a knee extensor). The motor branch to the iliopsoas originates in the pelvis proximal to the inguinal ligament. The sensory branch of the femoral nerve, the saphenous nerve, innervates skin of the medial thigh and the anterior and medial aspects of the calf. The adductor magnus and brevis, which share lumbar innervation with quadriceps and iliopsoas, are spared since they are innervated primarily by the obturator and sciatic nerves.

Femoral neuropathy causes weakness predominantly of the quadriceps, which results in difficulty with ambulation. Patients with femoral neuropathy complain of difficulty with stairs and frequent falling secondary to knee buckling. Sensation changes in the thigh, knee, or leg, such as decreased sensation, numbness, tingling, and burning occur. Clinical features includes weakness and wasting of the quadriceps muscle, and sensory impairment over the anteromedian aspect of the thigh and sometimes also of the leg to the medial malleolus, and a decreased or absent patellar reflex.

Femoral neuropathies can also occur secondary to direct trauma, compression, stretch injury, or ischemia. Other problems to be considered are lumbar plexopathies and lumbosacral disk syndromes. ⁷ Isolated femoral neuropathy may occur in patients with diabetes. Risk factors for developing neuropathy are diabetes mellitus, immunologic disorders, body mass index <20, smoking, and radiation exposure. In the present case report, both women did not have any of the abovementioned risk factors.

Occasionally the neuropathy may be severe or prolonged, or both. In these instances, EMG studies are justified, not only to allay the fears of patients and physicians, but to evaluate the progress of the lesion over time. Evaluation for femoral nerve dysfunction includes nerve conduction studies and EMG. EMG (if done at a reputable facility where the physician was formally trained in EMG) should be very helpful in establishing what kind of nerveNerve biopsy Nerve conduction velocity damage there is, and to what degree it was affected. ¹ Depending on the finding, sometimes prognoses can be given. In cases where the etiology is not apparent, magnetic resonance imaging or computed tomography scan of the pelvis may be beneficial to aid in localizing the site of compression and may define the etiology (i.e., tumor, abdominal aneurysm, iliac aneurysm).

Treatment is mostly conservative, mainly reassurance, exercises, and rehabilitation. Treatment is aimed at increasing mobility and independence. All affected patients had significant initial disability. Recovery as a rule occurs usually from a few weeks to months. During this time, physiotherapy may be beneficial. Physiotherapists may use electrical stimulation, hot packs, or ultrasound to relieve pain and reduce swelling. Avoidance of excessive hip abduction and external rotation, and knee bracing to prevent buckling of the knee is advised. However, full functional recovery occurs within 1 postoperative year. In some cases, there may be partial or complete loss of movement or sensation, resulting in some degree of permanent disability.

Various treatment modalities include corticosteroids, methylcyanocobalamin, ⁸ and oral antidepressant drugs. Corticosteroids injected into the area may reduce swelling and pressure on the nerve in some cases. Bilateral femoral nerve blocks with bupivacaine and triamcinolone using a nerve stimulator was also found useful. ⁶

Prevention includes use of specialized legholders such as the Lloyd–Davies leg support instead of stirrups that lead to excessive flexion of the thigh with abduction. ⁹ The general use of adjustable legholders is recommended for exact positioning of legs with a flexion angle of 45 degrees or more and an abduction angle of 45 degrees maximally. Proper lithotomy position is given to the patient by two persons synchronously. Surgical assistants should not lean against the patient's knee. If surgery is expected to become prolonged, then intermittent relaxation of externally rotated legs is advised.

On reviewing the literature, however, we believe that the lithotomy position can cause femoral neuropathy not only by nerve compression at the inguinal ligament, but also by stretching of the nerve by excessive hip abduction and external rotation.

Conclusions

In conclusion, we alert gynecologists to the possibility of femoral neuropathy following vaginal hysterectomy. A thorough understanding of the anatomy and the mechanisms by which operative injuries occur will enable the gynecologic surgeon to reduce the subsequent risk of their occurrence in their surgical practice. There is a need to emphasize preventive measures and to conduct more studies on various treatment modalities.