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Reliability and diagnostic accuracy of the Lachman test performed in a prone position
Edward P Mulligan1, Jordan L Harwell, William J Robertson
1University of Texas Southwestern Medical Center, School of Health Professions, Department of Physical Therapy, Dallas, TX, USA. ed.mulligan@utsouthwestern.edu
Study Design:
Prospective, blinded, diagnostic accuracy study.
Objective:
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.
Background:
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.
Methods:
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.
Results:
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.
Conclusion:
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.
Level Of Evidence:
Diagnosis, level 2b.
