Influence of Local Anesthetic Techniques on Patient-Reported Lateral Numbness Following Total Knee Arthroplasty

Total knee arthroplasty (TKA) results in significant postoperative pain, requiring effective analgesia to enable early mobilization and reduce complications. While local infiltration analgesia (LIA) is effective, it may cause prolonged lower limb numbness if sensory nerves are affected. This study evaluated the incidence of patient-reported inferolateral knee numbness at 2 and 6 weeks and 3 months post-TKA using different LIA techniques. A retrospective cohort study of 1,142 patients undergoing TKA (2021-2024) compared two LIA techniques. Group 1 (n = 471) received a conventional multisite periarticular injection, while Group 2 (n = 671) underwent a modified protocol avoiding the inferolateral knee region to minimize sensory nerve injury. All patients received a standardized cocktail (ropivacaine 0.25%, ketorolac, dexmedetomidine, epinephrine, dexamethasone). The primary outcome was the incidence of patient-reported inferolateral knee numbness at 2, 6, and 12 weeks. Secondary outcomes included patient demographics, comorbidities, Charlson Comorbidity Index, fixation method, numbness duration, Visual Analog Scale (VAS) scores, analgesic use, anesthetic volume, and early complications, including local anesthetic systemic toxicity (LAST), allergic reactions, and hospital stay. A total of 1,142 patients were included (471 Conventional, 671 Modified). Groups were demographically comparable, except for a higher body mass index (BMI) in the Conventional group (p  <  0.001). Inferolateral knee numbness was significantly more common in the Conventional group at all time points: At 2 weeks, numbness was reported in 8.28% of the Conventional group versus 0.44% of the Modified group (p  <  0.001); the difference remained significant at 6 and 12 weeks (2.33% vs. 0.14%, p  <  0.001). VAS scores were slightly lower in the Conventional group postoperatively, though differences were minimal. Analgesic use and complication rates were similar. No cases of LAST, thromboembolism, or transfusion occurred. Hospital stay was slightly shorter in the Conventional group (p  <  0.001), with similar follow-up duration. A modified LIA technique that avoids the inferolateral knee region significantly reduced postoperative numbness without compromising pain control or safety. This targeted approach may enhance sensory outcomes following TKA.