Reliability and Diagnostic Accuracy of the Lachman Test Performed in a Prone Position

Abstract

Prospective, blinded, diagnostic accuracy study. To investigate the reliability and diagnostic accuracy of the Lachman test, performed in a prone position, to detect the presence of an anterior cruciate ligament (ACL) tear. Direct arthroscopic visualization and a consensus of clinical findings, including joint arthrometry and magnetic resonance imaging, were used as the reference standards. An alternative position for evaluating the integrity of the ACL has been proposed as a means for examiners with smaller hands to adequately stabilize the thigh of a larger individual; however, the diagnostic accuracy of this method has not been established. Fifty-two consecutive patients with a complaint of knee pain were independently evaluated in a prone position for the status of their ACL by 2 physical therapists, before any other diagnostic assessment. The 31 men and 21 women ranged in age from 16 to 57 (mean ± SD, 34.3 ± 4.2) years and in acuity of knee injury from 21 to 365 (mean ± SD, 195 ± 130) days. Twenty-three of 52 (44%) of the patients had a torn ACL. The agreement between examiners was 90%, with a kappa coefficient of 0.81. The sensitivity of the prone Lachman test was 70% and the specificity was 97%, resulting in a positive likelihood ratio of 20.17 and a negative likelihood ratio of 0.32. The positive predictive value was 94% and the negative predictive value was 80%. The diagnostic odds ratio was 64.0, with a number needed to diagnose of 1.5. The prone Lachman test is a reliable evaluation technique that can be used to confirm the presence of an ACL tear; however, the test should not be used as the sole criterion to rule out the presence of the injury. Diagnosis, level 2b.