Abstract
<title>Abstract</title> <p>Objectives The primary objective of this study is to evaluate the diagnostic properties of measuring the lateral femoral notch on lateral knee radiographs in cases of acute trauma for the diagnosis of anterior cruciate ligament (ACL) tears. Materials and Methods This is a monocentric retrospective study assessing the diagnostic properties of a test based on data from patients who presented with knee trauma at the emergency trauma department from October 2020 to December 2022. Inclusion criteria included the performance of knee radiographs (anteroposterior and lateral views) in primary care and subsequent MRI. A group with confirmed ACL tear diagnosed via MRI was compared to a control group where MRI ruled out any central pivot lesions. Radiographic analysis evaluated the presence of a notch and, if present, its depth. Results A total of 412 patients were included in our study. Patients with ACL tears had a deeper lateral femoral notch (LFNS) on average (0.677 ± 0.613 mm) compared to injury-free patients (0.214 ± 0.206 mm). A notch depth threshold of 1 mm exhibited interesting and discriminative diagnostic characteristics, with a calculated specificity of 98.5% and a positive likelihood ratio of 21.3. This sign was present in 31.1% of patients with ACL tears. For a threshold set at ≥ 1 mm notch depth, we found no statistically associated peripheral ligament, meniscal, or chondral lesions linked to ACL tears. However, among patients with ACL tears and an LFNS ≥ 1 mm, contact pivot sports were significantly overrepresented. Finally, the evaluation of a composite criterion combining initial clinical suspicion and the presence of an LFNS ≥ 1 mm further enhanced the test's discriminatory capacity, yielding a specificity of 99.5%. Conclusion The measurement of LFNS ≥ 1 mm confirms with 99.5% specificity the diagnosis of anterior cruciate ligament (ACL) tear when clinical hemarthrosis is present in the context of acute knee trauma.</p>