Examiner Proficiency in Performing the Anterior Drawer and Lachman Tests

Abstract

The anterior drawer and Lachman tests are frequently used for determining anterior cruciate ligament (ACL) instability. The Lachman test is considered to be the most accurate, yet it is difficult to perform on a large person, especially by an examiner with small hands. One procedure, the alternate Lachman test, has been used with some success by examiners who have difficulty performing the Lachman test. The purpose of this study was to compare these three manual tests with respect to predicting ACL stability. These findings were compared with those of the KT-1000 knee arthrometer. Seventy-four subjects (mean age = 22 years) volunteered for the study. Girth measurements were recorded for each subject at 8 cm above and below the midpoint of the patella. An examiner with small hands (21-cm span) performed each of the three tests on both knees of the subjects and then recorded which knee he believed was the most lax of the two with respect to each test. Another examiner then tested each subject's knees with the KT-1000. A log-linear model with terms for manual test type, category, and thigh girth was used for statistical analysis. The alternate Lachman test significantly outperformed the other two tests. Subjects with > 2.5 mm bilateral laxity difference were correctly evaluated 100% of the time using the alternate Lachman test. In subjects with large thigh girth (> 43 cm), 1) the alternate Lachman test was correct 78% of the time; 2) the anterior drawer test was correct 59% of the time; and 3) the Lachman test produced only 28% correct examinations. Based upon these results, the alternate Lachman test should be included in the regimen of manual ACL tests, especially for athletes with large thigh circumference or when performed by examiners with small hands.