Deep lateral femoral sulcus: study of 124 patients with anterior cruciate ligament tear

Abstract

Abnormal deepening of the lateral femoral sulcus has been proposed as a potential indirect sign allowing the diagnosis of an anterior cruciate ligament (ACL) tear on conventional lateral knee radiographs. We studied a large group of patients with proven ACL tears during the acute injury and at 5-year follow-up to determine (a) the normal range of the depth of this sulcus and (b) the sensitivity, specificity, and positive predictive value of a deepened lateral sulcus. One hundred fifty patients with suspected ACL tears after sustaining unilateral injuries to their knees were referred to a specialty clinic for further evaluation. The injury was based on the presence of hemarthrosis, pathologic joint motion, and/or instability of the tibiofemoral joint. From this group, 124 patients were diagnosed with complete ACL tears (112 cases confirmed by arthroscopy, 12 cases diagnosed by the presence of pathologic motion with a KT-1000 arthrometer). Conventional radiographs of the injured knee were obtained in all 150 patients at the time of the acute injury. Five years later, radiographs of both the injured knee and the uninjured contralateral knee were evaluated. The lateral femoral condylopatellar sulcus, or notch, was measured on the acute injury and 5-year follow-up radiographs, and this measurement was compared to that on radiographs of the uninjured contralateral knee. The depth of the lateral sulcus consistently was noted to be similar in both knees in a given patient. Two groups of patients were identified: one group consisted of 124 patients with torn ACLs with a mean notch depth on the injured side of 0.57 mm [range, 0.0–3.3 mm; standard deviation (SD), 0.57 mm] and on the uninjured contralateral side of 0.43 mm (range, 0.0–2.0 mm; SD, 0.42 mm); and a second group consisted of those 26 injured patients with intact ACLs with a mean notch depth on the injured side of 0.31 mm (range, 0.0–1.0 mm; SD, 0.35 mm) and on the uninjured contralateral side of 0.27 mm (range, 0.0–0.8 mm; SD, 0.26 mm). Four of the 124 patients with a proven ACL tear had lateral notch measurements greater than 2.0 mm in depth. No patient with an intact ACL demonstrated a lateral sulcus that exceeded 2.0 mm in depth. A depth greater than 2.0 mm had a specificity of 100%, sensitivity of 3.2%, accuracy of 60%, and a positive predictive value of 100% for complete ACL tear.