Manual Lachman Test Underestimates Tibial Translation Compared to Standardized Generated Force: A Biomechanical Study of Cadaveric Anterior Cruciate Ligament Repair Using Internal Brace (205)

Abstract

Objectives: With an increasing incidence over time, anterior cruciate ligament (ACL) rupture can produce functionally limiting knee instability that requires operative treatment to address the instability as well as prevent the development of osteoarthritis. Anteroposterior instability forms the basis of the most sensitive physical exam maneuver to examine the ACL for rupture, the Lachman test. This investigation has two goals: to assess the precision and accuracy of the manual Lachman test by comparing anterior tibial translation generated to that of a standardized applied force Lachman test, and to compare the anteroposterior stability of cadaver specimens with simulated ACL ruptures which were repaired with and without internal suture tape augmentation. Methods: The tibial plateau in ten cadaveric knees was divided into medial, middle and lateral reference points, which were monitored digitally during testing using Optotrak. Intact knees were subjected to both manual Lachman tests at 30 degrees of flexion and standardized 150N force Lachman tests utilizing a hook and pulley system with force transducer. The ACL's of all specimens were then transected, and the ACL deficient knees were subjected to both the manual and standardized Lachman tests. The specimens were then randomly divided into two groups to be repaired with or without internal suture tape augmentation, and subsequently underwent 100, 250, and 500 cycles from 90 degrees of flexion through full extension with a frequency of .1Hz, after which the same standardized Lachman test was performed on all repaired specimens. Comparison of variances were made using a two-sample F-Test for variances. Comparison of means were made using a two sample t-test assuming unequal variances and one-way ANOVA. Significance was set at p