Diagnostic performance of the Francophone Arthroscopic Society (SFA) score for anterior cruciate ligament rupture and intra-articular knee lesions in the emergency department: a prospective multicenter study

BACKGROUND: The Francophone Arthroscopic Society (SFA) score was designed to identify patients with anterior cruciate ligament (ACL) rupture in the immediate post-traumatic period, based on history alone (pain intensity, immediate post-traumatic functional impairment, history of a "pop," feeling of instability, and knee swelling). The aim of this multicenter study was to assess the external validity of the SFA score for ACL injury screening in the emergency department and to evaluate its ability to predict other significant intra-articular knee lesions. HYPOTHESIS: The SFA score is a reliable screening tool for ACL rupture in emergency departments and can also help identify patients at high risk of severe intra-articular knee injuries. PATIENTS AND METHODS: This prospective multicenter observational study enrolled 150 consecutive patients aged 18-55 years who presented to the emergency department within 9 days after a knee trauma and had no fracture on standard radiographs. Patients were excluded if the trauma required immediate surgical management or if they had a history of trauma or surgery on the same knee. The SFA score was assessed by the emergency physician at first presentation. The reference diagnosis (ACL rupture, other intra-articular lesions or no lesion) was established at follow-up by an orthopedic surgeon, based on clinical examination or MRI. RESULTS: Of the 150 included patients, 115 completed follow-up and were analyzed; 48 had an ACL rupture and 67 an intact ACL. For ACL injury screening, the SFA score showed an AUC of 0.759 (95% CI 0.673-0.845). A score ≤4 demonstrated a sensitivity of 100% and a NPV of 100% for ruling out ACL rupture, whereas a score ≥8 indicated a high probability of ACL tear (specificity 77.6%, PPV 67.4%). For severe intra-articular knee lesions as a whole, the AUC was 0.82 (95% CI: 0.745-0.895). DISCUSSION: This study supported the external validity of the SFA score for screening ACL rupture and other significant intra-articular knee lesions in the emergency department setting. The score appears to be a useful decision-making tool to guide triage, imaging, and orthopedic referral in patients presenting with acute knee trauma. LEVEL OF EVIDENCE: III; prospective observational multicenter study.