Murao H, Morishita S, Nakajima M, Abe M
Department of Orthopedic Surgery, Osaka Medical College, 2-7 Daigaku-machi Takatsuki, Osaka 569, Japan.
J Orthop Sci. 1998;3(1):10-7. doi: 10.1007/s007760050016.
Tears of the anterior cruciate ligament (ACL) are often difficult to diagnose on magnetic resonance imaging (MRI), as it is often difficult to interpret the images. We developed a quantitative method for diagnosing ACL tears on MRI; the method involves measuring the angle formed by the intersection between a straight line drawn along the anterior border of the ACL and a straight line drawn along the medial tibial plateau (AT angle) on MRI. The AT angle was measured by two orthopedic surgeons approved by the Japanese Orthopedic Association and one orthopedic resident, none of whom had any prior knowledge of the physical and arthroscopic findings of the patients. Measurements were performed in 30 knees with ACL tears and 57 knees without tears. There was no significant difference between the AT angles measured by the three examiners in either the group with ACL tears or that without ACL tears. The mean value of the AT angle in the torn ACL group (33.9 +/- 1.1 degrees) was significantly smaller than that in the intact ACL group (52.3 +/- 1.0 degrees; mean +/- SE). When 45 degrees or less was set as the criterion defining a tear of the ACL, the diagnostic accuracy of our method was 87.4%; sensitivity was 93.3%, and specificity, 84.2%.
前交叉韧带（ACL）撕裂在磁共振成像（MRI）上往往难以诊断，因为图像通常难以解读。我们开发了一种在MRI上诊断ACL撕裂的定量方法；该方法包括在MRI上测量沿ACL前缘绘制的直线与沿胫骨内侧平台绘制的直线相交形成的角度（AT角）。AT角由两名经日本骨科协会认可的骨科医生和一名骨科住院医生测量，他们均对患者的体格检查和关节镜检查结果一无所知。对30例ACL撕裂的膝关节和57例无撕裂的膝关节进行了测量。在ACL撕裂组和无ACL撕裂组中，三位检查者测量的AT角均无显著差异。ACL撕裂组的AT角平均值（33.9±1.1度）明显小于ACL完整组（52.3±1.0度；平均值±标准误）。当将45度或更小设定为定义ACL撕裂的标准时，我们方法的诊断准确率为87.4%；敏感性为93.3%，特异性为84.2%。
