DEEP lateral femoral notch sign is associated with lateral meniscus tear and non-spherical lateral femoral condyle in ACL deficient knee

Purpose: This study investigates the relationship between the deep lateral femoral notch sign, lateral meniscus injury, and knee morphology in patients with ACL injuries. Methods: We retrospectively analyzed MRI scans of 74 knees from 73 patients who underwent primary ACL reconstruction. These knees were selected from an initial cohort of 173 knees from 170 patients. We measured the Lateral Femoral Condyle Index, Lateral Femoral Condyle Ratio, Lateral Femoral Condyle Height/Depth Ratio (LFCR H/D), assessed LNS both qualitatively and quantitatively, and evaluated tibial slope and the presence of lateral meniscus injury. We then compared groups based on the following criteria: tibial slope > 12°, LFCI < 0.7 (indicating non-spherical femurs), LNS > 2 mm, presence of lateral meniscus injury, increased average/median LFCR, and decreased average/median LFCR H/D. Results: We found a significant association between LNS > 2 mm and lateral meniscus injury (p = 0.04). This association was also present when comparing knees with LNS > 2 mm to those with absent LNS (p = 0.03). Additionally, LNS > 2 mm was associated with LFCI < 0.7 (p = 0.03) when comparing subgroups with LNS > 2 mm and absent LNS. Decreased median LFCR H/D values were associated with decreased LFCI values (p = 0.04). Finally, knees with both LNS > 2 mm and lateral meniscus injury showed decreased median LFCR H/D values (p = 0.04). Conclusions: In conclusion, our findings indicate that LNS > 2 mm is associated with lateral meniscal injury and LFCI < 0.7. Furthermore, knees exhibiting both lateral meniscus lesions and LNS > 2 mm demonstrate decreased median values of LFCR H/D.