A comparison of acute anterior cruciate ligament examinations. Initial versus examination under anesthesia

The preoperative examination, the examination under anesthesia, and the findings at surgery were compared for acutely injured knees that were found at surgery to have anterior cruciate ligament (ACL) tears. The pivot shift was initially positive in only 35% of the knees; however, under anesthesia 98% were positive. The Lachman test was initially positive in 99% of the knees, and under anesthesia, 100%. The anterior drawer sign was present initially in 70% of the knees, and under anesthesia this increased to 91%. Of the 37 patients with isolated ACL tears, only 20 (54%) had initially positive anterior drawer signs. In the knees in which secondary restraints to anterior-posterior motion were injured, this percentage increased to 69% in medial meniscus injury, 82% in lateral meniscus injury and 89.5% in rupture of the medial collateral ligament (MCL). The Lachman test seems relatively unaffected by associated ligamentous or meniscal injuries, but the end point in the Lachman test is absent in all complete ACL tears. The pivot shift phenomenon, which was demonstrable in 98% of patients when tested under anesthesia, may be diminished when there is a MCL injury or absent in partial ACL tears. Experience in performing the Lachman test and in appreciating the quality of the end point will give the examiner a high degree of accuracy in making the diagnosis of an ACL tear without resorting to anesthesia, arthroscopy, or arthrography in most patients.