The prevalence and treatment impact of the deep lateral femoral notch sign (DLFNS) in skeletally immature patients with anterior cruciate ligament injuries

Objectives: The objective of this study was to investigate the prevalence of the Deep Lateral Femoral Notch Sign (DLFNS) in skeletally immature patients with Anterior Cruciate Ligament (ACL) injuries and its potential impact as it relates to knee trauma and injury.

Methods: This retrospective case-control study included 87 skeletally immature patients with ACL injuries and a minimum follow-up of 1 year, who were matched with 44 controls based on sex and skeletal age. The presence of the DLFNS, defined as a notch depth of >1.5 mm, was assessed on MRI. Intra- and inter-observer reliability were calculated, and prevalence was determined. Associations between the DLFNS and trauma mechanism, trauma-related bone lesions (bone bruises on the lateral femoral condyle or lateral tibial plateau, and posterolateral tibial impression fractures), concomitant injuries, clinical instability, and treatment at both baseline and follow-up were assessed using Fisher’s exact tests.

Results: The prevalence of DLFNS was 11.5% among skeletally immature patients with ACL injuries compared to 0% in controls (p = 0.02). DLFNS depth demonstrated excellent intra- and inter-observer reliability (ICC > 0.90). Furthermore, a significant positive association was identified between the DLFNS and concomitant knee injuries (p = 0.02). All patients presenting with a DLFNS ultimately received operative treatment, either during initial management or follow-up. This revealed a significant positive association between the DLFNS and primary operative treatment (p = 0.02).

Conclusions: The prevalence of the DLFNS in skeletally immature patients with ALC injuries was 11.5%. When present, the DLFNS was associated with concomitant knee injuries and primary ACL reconstruction. The DLFNS may therefore be an important sign to take into consideration on the primary MRI in skeletally immature patients with ACL injuries.