Obturator nerve injury

• obturator nerve takes its origins from L2, L3, and L4
  • divides into an anterior and a posterior branch anterior to the internal obturator muscle
  • gives a motor supply to the gracilis, adductor brevis and longu
  • anterior nerve joins the femoral and saphenous nerves to form a sensory cutaneous plexus

Patient positioning during total hip replacement may result in nerve entrapment in the obturator canal

• other causes include childbirth, pelvic trauma, osteitis pubis and exercise

Clinical features:

• main presenting complaints include hypoaesthesia, paraesthesia or pain in the medial thigh, groin or pubic bone
• patient may also complain of weakness and a feeling of leg instability
• examination findings may reveal a circumducting gait secondary to an externally rotated hip, weakness or wasting of the adductor muscles and a decrease in hip adduction and internal rotation of the hip

Investigation

• radiographic imaging provides limited diagnostic help
• MRI may detect atrophy in the adductors of the leg. However, it is unable to detect any abnormality of the nerve or in the fibro-osseus tunnel
• best test for diagnosis is by electromyography (EMG) and can be confirmed by a local nerve block

Management:

• pharmacologic management of pain and physical therapy can be helpful in the acute phase of injury
• surgical decompression of the nerve should be considered for lesions documented by EMG or local nerve block, for those with predisposing risk factors (prior surgery, pelvic trauma, or hematoma) and with prolonged or severe lesions.

Reference:

• 1) Tipton JS. Obturator neuropathy. Curr Rev Musculoskelet Med 2008; 1: 234-7.