Peripheral nerve blockade as an exclusive approach to obturator nerve block in anterior cruciate ligament reconstructive surgery

Abstract

Background: Obturator nerve block plays an additive role on the quality of analgesia for knee surgery. Since the use of dual guidance increases the success rate of nerve blocks, we investigated the feasibility of performing anterior cruciate ligament reconstruction under dual-guided blockade of obturator with femoral and sciatic nerves. Furthermore, we propose a novel method for the assessment of obturator nerve block.

Methods: Fifty-seven patients undergoing anterior cruciate ligament repair were studied. Neurostimulating needles were guided out-of-plane by ultrasound. To induce the obturator nerve block, 10 ml of ropivacaine 0.5% were injected after eliciting contractions of adductor longus, brevis and magnus followed by block assessment for 30 minutes by examining the patient lift and left down the leg.

Results: The sonographic recognition of obturator nerve was easy and quick in all cases. Time for applying the block was 119.9 ± 79.2 sec. Assessing this block with lifting-leaving down the leg gave satisfactory results in 24.0 ± 5.07 min. After performing femoral-sciatic blocks, the inflation of tourniquet resulted in VAS score of > 0 in 2/57 patients and operation in 12/57. Total dose of fentanyl was 120.1 ± 64.6 µg and of midazolam 1.86 ± 0.8 mg. In 6 patients propofol was administered for sedation and 1 of them required ventilation with laryngeal mask airway, converting the anesthesia technique to general anesthesia.

Conclusions: Our data suggest that anterior cruciate ligament reconstruction can be performed under obturator-femoral-sciatic blocks. Identification of obturator nerve with ultrasound is easy and the block can be assessed by observing how the patient lifts and leaves down the leg.

Keywords: Anterior cruciate ligament; Nerve block; Neurostimulation; Obturator nerve; Ultrasonography.

Figures

Fig. 1

Diagram showing decisions and actions concerning anesthetic technique. ON: obturator nerve.

Fig. 2

Position of the ultrasound probe: opposite the angle that is formed by the inguinal crease and adductor longus, with its short diameter in the course of the dichotomous of the angle.

Fig. 3

Ultrasound image where next to pectineus and below adductor longus, a "spider net" image is visualized. Arrows indicate the position of the nerve in the short axis view. P: pectineus, AL: adductor longus, AB: Adductor brevis, AM: adductor magnus.