Nerve block of the infrapatellar branch of the saphenous nerve in knee arthroscopy: a prospective, double-blinded, randomized, placebo-controlled trial.

BACKGROUND: With the rising use of outpatient knee arthroscopy over the past decade, interest in peripheral nerve blocks during arthroscopy has increased. Femoral nerve blocks are effective but are associated with an inherent risk of the patient falling postoperatively because of quadriceps weakness. We studied blocks of the infrapatellar branch of the saphenous nerve, which produce analgesia in the knee that is similar to that resulting from a femoral nerve block but without associated quadriceps weakness.

METHODS: Thirty-four patients were enrolled into each arm of this prospective, randomized, double-blinded trial comparing 10 mL of 0.25% bupivacaine used as a block of the infrapatellar branch of the saphenous nerve with a placebo during simple knee arthroscopy. Immediate outcome measures included Numeric Rating Scale (NRS) pain scores (0 to 10 points), mobility and discharge times, opioid usage, subjective adverse side effects, and forty-eight-hour anesthesia recovery surveys. Short-term measures included one-week and twelve-week Lysholm knee scores.

RESULTS: No adverse effects or increased quadriceps weakness were observed following use of the nerve block. Improvement in early NRS scores and subjective nausea (p = 0.03) were detected. Patients for whom the block was successful also had improved twelve-week Lysholm knee scores (p = 0.04). No differences in opioid usage, mobility time, forty-eight-hour anesthesia recovery scores, or one-week Lysholm knee scores were found.

CONCLUSIONS: No significant adverse effect or disadvantage was identified for blocks of the infrapatellar branch of the saphenous nerve used in simple knee arthroscopy. In addition to decreased early NRS scores and nausea, blocks of the infrapatellar branch of the saphenous nerve demonstrated potential benefit at twelve weeks after simple knee arthroscopy.