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The Reliability and Diagnostic Accuracy of Assessing the Translation Endpoint during the Lachman Test.

Authors: Mulligan EP, McGuffie DQ, Coyner K, Khazzam M

Interpretation of Lachman testing when evaluating the status of the anterior cruciate ligament (ACL) typically includes a numerical expression classifying the amount of translation (Grade I, II, III) in addition to a categorical modifier (Grade A [firm] or B [absent]) to describe the quality of the passive anterior tibial translation endpoint. Most clinicians rely heavily on this tactile sensation and place value in this judgment in order to render their diagnostic decision; however, the reliability and accuracy of this endpoint assessment has not been well established in the literature. The purpose of this study was to determine the intertester reliability of endpoint classification during the passive anterior tibial translation of a standard Lachman test and evaluate the classification's ability to accurately predict the presence or absence of an ACL tear.  The authors found that the agreement between examiners on A versus B endpoint classification was 91% with a kappa coefficient of 0.72. In contrast, classification agreement based on the translational amount or grade had an agreement of 65% with a weighted kappa coefficient of 0.52. The sensitivity of the endpoint grade alone was 0.81 with perfect specificity resulting in a positive likelihood ratio of 6.2 and a negative likelihood ratio of 0.19.  The overall accuracy of the Lachman test using the endpoint assessment grade alone was 93% with a number needed to diagnose of 1.2. Therefore, the authors concluded that the nominal endpoint classification (A or B) from a Lachman test is a reliable and accurate reflection of the status of the ACL. The true dichotomous nature of the test's interpretation (positive vs. negative) is well-served by the quality of the endpoint during passive anterior tibial translation.

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