The Depth of the Lateral Femoral Notch Sign: Its Significance in Acute Anterior Cruciate Ligament Tears with Concomitant Posterior Root Tears of the Lateral Meniscus

Abstract

Background: Anterior cruciate ligament (ACL) tears are frequently accompanied by lateral meniscus posterior root tears (LMPRT), which worsen prognosis. The lateral femoral notch sign (LFNS), a radiographic depression on the lateral femoral condyle, has been linked to ACL injury, yet its association with LMPRT and post-operative function remains unclear. This study examined whether LFNS depth predicts LMPRT and influences short-term functional outcomes after ACL reconstruction. Purpose: To investigate the relationship between the LFNS and functional outcomes in patients with acute ACL tears undergoing surgery and to explore the potential of LFNS as a predictive sign for ACL injuries combined with LMPRT. Methods: A total of 89 patients with ACL tears were enrolled in this retrospective pilot study between December 2020 and December 2023. All enrolled patients were divided into two groups based on LMPRT: the ACL group (ACL tear alone) and the LMPRT group (ACL tear combined with concomitant LMPRT). In addition to demographic data, the following parameters were compared: the incidence and depth of LFNS, functional results (Lysholm score) at 6 and 12 months, VAS score, and ROM before and after surgery. A logistic regression model was used to identify potential risk factors for ACL injury with concurrent LMPRT. Results: Among the 89 enrolled patients, 64 patients (71.9%) were in the ACL group, whereas 25 patients (28.1%) were in the LMPRT group. LMPRT was found to be correlated with the depth of LFNS (P < 0.001), and logistic regression analysis demonstrated that age, depth of LFNS, and LMPRT were correlated with the 12-month functional results (P = 0.001, P = 0.035, P = 0.010). The 12-month functional results were better in the LMPRT group (P < 0.001); however, no significant difference was found in the 6-month functional results between the ACL group and the LMPRT group (P = 0.272). The ROM in the ACL group was 118.44 ± 10.35 at 12 months post-operatively (P = 0.031), which was significantly greater than that in the LMPRT group (113.20 ± 9.45). However, no significant differences were observed at any other time points. Conclusion: LFNS may be a potential indicator of the LMPRT in patients with ACL tears. LFNS had an impact on the 12-month functional results in the LMPRT group but not on the 6-month functional results. Age, depth of LFNS, and LMPRT are risk factors for 12-month functional results.