Incidence and Characterization of Hypoesthesia in the Distribution of the Infrapatellar Branch of the Saphenous Nerve after Anterior Cruciate Ligament Reconstruction: A Prospective Study of Patient-Reported Numbness

Abstract

AbstractThe purpose of this study was to determine the incidence of patient-reported numbness following anterior cruciate ligament reconstruction (ACLR), if postoperative numbness dissipates with time, and how the graft type affects numbness severity. A total of 218 patients undergoing ACLR were prospectively enrolled. At 6 weeks, 6 months, and 1 year postoperatively, patients completed a questionnaire assessing numbness severity and location. Each time, patients rated their sensory deficit from 0 to 10 (0 = no deficit; 10 = complete lack of sensation) and indicated the location of their sensory deficit by marking a picture of a knee divided into nine rectangular segments. A mixed effect linear regression model was used to identify predictors for the patient-reported numbness severity. Overall, 69.8% (150/218) of patients reported numbness at 6 weeks, 50.0% (97/194) at 6 months, and 42.2% (78/185) at 1 year. Allograft patients reported a mean numbness severity of 2.9 ± 0.3 (mean ± standard error), 1.7 ± 0.2, and 1.4 ± 0.3 at 6 weeks, 6 months, and 1 year, respectively. The 6-week, 6-month, and 1-year averages were 4.7 ± 0.4, 2.7 ± 0.4, and 1.7 ± 0.4 for bone-patellar tendon-bone (BTB) autograft patients and 4.3 ± 0.4, 2.9 ± 0.4, and 2.5 ± 0.4 for hamstring autograft patients. The model indicated that the use of hamstring autografts increased patient-reported numbness by an average of 1.4 ± 0.5 across all time points, and the use of a BTB autograft increased patient-reported numbness by 1.2 ± 0.4 across all time points. Time from surgery decreased the severity of patient-reported numbness for all graft types (−1.3 ± 0.2 at 6 months and −1.7 ± 0.2 at 1 year). Hypoesthesia in the distribution of the infrapatellar branch of the saphenous nerve is common after ACLR but is likely to dissipate with time. Patients undergoing ACLR with allograft may be less likely to develop sensory deficits, and these deficits may be less severe.