Chapter 82B: Obturator Nerve Block

INTRODUCTION

Selective obturator nerve block was first described by Gaston Labat in 1922.¹ More interest in obturator nerve block emerged a few years later when Victor Pauchet, Sourdat, and Gaston Labat stated, “obturator nerve block combined with blocks of the sciatic and femoral nerves, anesthetized the entire lower limb.” However, a lack of clear anatomic landmarks, the block complexity, and inconsistent results were the reasons why this block had been used infrequently. Historically, Labat’s classic technique remained forgotten until 1967, when it was modified by Parks.² In 1993, the interadductor approach was described by Wassef,³ which was further modified by Pinnock in 1996.⁴ In 1973, Alon Winnie introduced the concept of the “3-in-1 block,” an anterior approach to the lumbar plexus using a simple paravascular inguinal injection to anesthetize the femoral, lateral cutaneous and obturator nerves.⁵ Since its description however, many studies have refuted the ability of the 3-in-1 block to reliably block the obturator nerve with this technique. With the introduction of modern nerve stimulators, and particularly ultrasound guidance selective blockade of the obturator nerve has become more reliable.

Indications

Obturator nerve block is used to treat hip joint pain and is also used in the relief of adductor muscle spasm associated with hemiplegia or paraplegia. Muscle spasticity is a relatively common problem among patients suffering from central neurologic problems, such as cerebrovascular pathology, medullar injuries, multiple sclerosis, and cerebral palsy. Spasticity of the adductor muscle induced via the obturator nerve plays a major role in associated pain problems and makes patient hygiene and mobilization very difficult. Tenotomies, cryotherapy, botulinum toxin infiltration, surgical neurolysis, and muscle interpositions have been suggested to remedy this problem.^6,7,8,9 Common clinical practice is to combine a sciatic nerve block with the femoral nerve block for surgical procedures distal to the proximal third of the thigh. When deemed necessary, addition of a selective obturator nerve block may reduce intraoperative discomfort, improve tourniquet tolerance, and improve the quality of postoperative analgesia in these cases.

Obturator nerve block is also occasionally used in urologic surgery to suppress the obturator reflex during transurethral resection of the lateral bladder wall. Direct stimulation of the obturator nerve by the resector as it passes in close proximity to the bladder wall results in a sudden, violent adductor muscle spasm. This is not only distracting to the surgeon, but may increase the risk of complications such as bladder wall perforation, vessel laceration, incomplete tumor resection, and obturator hematomas.^10,11 Prevention strategies include muscle relaxation, reduction in the intensity of the resector, the use of laser resectors, shifting to saline irrigation, periprostate infiltrations, and/or endoscopic transparietal blocks.^{12,13,14,15,16} A selective obturator nerve block remains an effective remedy to this problem.^17-22