The Influence of Perioperative Nerve Block on Strength and Functional Return to Sports After Anterior Cruciate Ligament Reconstruction

Abstract

Background: Patients often have quadriceps or hamstring weakness after anterior cruciate ligament reconstruction (ACLR), despite postoperative physical therapy regimens; however, little evidence exists connecting nerve blocks and ACLR outcomes. Purpose: To compare muscle strength at return to play in patients who received a nerve block with ACLR and determine whether a specific block type affected subjective knee function. Study Design: Cohort study; Level of evidence, 3. Methods: Patients were recruited 5 to 7 months after primary, isolated ACLR and completed bilateral isokinetic strength tests of the knee extensor/flexor groups as a single-session return-to-sport test. Subjective outcomes were assessed with the International Knee Documentation Committee (IKDC) score. Strength was expressed as torque normalized to mass (N·m/kg) and limb symmetry index as involved/uninvolved torque. Chart review was used to determine the type of nerve block and graft used. Nerve block types were classified as knee extensor motor (femoral nerve), knee flexor motor (sciatic nerve), or isolated sensory (adductor canal block/saphenous nerve). A 1-way analysis of covariance controlling for graft type was used. Results: A total of 169 patients were included. Graft type distribution consisted of 102 (60.4%) ipsilateral bone–patellar tendon–bone (BTB) and 67 (39.6%) ipsilateral hamstring tendon. Nerve block type distribution consisted of 38 (22.5%) femoral, 25 (14.8%) saphenous, 45 (26.6%) femoral and sciatic, and 61 (36.1%) saphenous and sciatic. No significant difference was found in knee extensor strength ( P = .113) or symmetry ( P = .860) between patients with knee extensor motor blocks (1.57 ± 0.45 N·m/kg; 70.1% ± 15.3%) and those without (1.47 ± 0.47 N·m/kg; 69.6% ± 18.8%). A significant difference was found between patients with knee flexor motor blocks (0.83 ± 0.26 N·m/kg) and those without (0.92 ± 0.27 N·m/kg) for normalized knee flexor strength ( P = .21) but not knee flexor symmetry ( P = .592). Controlling for graft type, there were no differences in subjective knee function (IKDC score) between all nerve block groups ( P = .57). Conclusion: Our data showed that use of a sciatic nerve block with ACLR in patients with hamstring and BTB grafts influences persistent knee flexor strength deficits at time of return to sports. Although the cause of postoperative muscular weakness is multifactorial, this study adds to the growing body of evidence suggesting that perioperative nerve blocks affect muscle strength and functional rehabilitation after ACLR.