Incidence and Etiology of Rare Saphenous Nerve Injury After Knee Surgery with Adductor Canal Block: A Retrospective Observational Study

Abstract

Background: Adductor canal block (ACB) is commonly included in multimodal analgesia regimens for knee surgery. Nonetheless, the incidence, etiology, and procedure-specific risk of saphenous nerve injury after knee surgery with ACB have not been established. Purpose: We sought to identify the risk of saphenous nerve injury during knee surgery with ACB. Methods: We conducted a retrospective cohort study of patients at a single institution who underwent elective knee surgery with ultrasound-guided ACB between January 1, 2014, and December 31, 2018, and had subsequent saphenous nerve injury. The primary outcome was the incidence of saphenous nerve injury within 3 months of surgery, by surgical type and approach. Secondary outcomes included attribution of the most likely etiology and clinical outcome of the injury. Results: In 28,196 cases of knee surgery with ACB, we identified 18 cases (0.06%) of saphenous nerve injury. The most common surgery associated with saphenous nerve injury was anterior cruciate ligament (ACL) reconstruction with autograft (8/18 cases); 3 cases of injury were seen after TKA, 2 after medial patellofemoral ligament reconstruction, 2 after arthroscopy/meniscal surgery, and 1 after patellar fixation. The most likely etiology of nerve injury was attributed to ACB in 5 of 18 cases (28%) and to non-ACB cause in 13 of 18 (72%). Prognosis was rated as unknown in 11 of 18, poor in 2 of 18, favorable in 3 of 18, and full recovery in 2 of 18. Conclusions: This 5-year retrospective, single-institution cohort study found a low overall incidence of saphenous nerve injury after knee surgery with ACB, but the injury likelihood varied based on surgery and approach. Although not statistically significant, ACL reconstruction with hamstring autograft and ACB performed for postoperative rescue analgesia were most frequently associated with nerve injury.