Laxity Measurement of the ACL
Introduction
It is well established that the anterior cruciate ligament (ACL) limits anterior translation of the tibia on the femur. Thus, a tear in the ACL has characteristic instability and established physical exam findings. A positive Lachman test has proven to be a sensitive indicator of ACL injury and the pivot shift is highly specific for ACL compromise. The physical exam findings consistent with an ACL rupture are subjective, however, and not quantifiable. They can be classified, but these classifications experience significant inter- and intra-observer variability. This makes it difficult to temporally compare the same subject or cross-compare different subjects. Therefore, arthrometric evaluation of the ACL was developed as a means to standardize the evaluation of ACL injuries.
Several ligament testing devices have been developed in order to establish quantitative measurements for ACL ruptures. These devices have a wide range of cost and complexity. They include the KT-1000 (MEDmetric, San Diego, CA), Stryker Knee Laxity Tester (Kalamazoo, MI), the Genucom (FARO, Lake Mary, FL), KSS Acufex (Norwood, MA), and the Rolimeter (Aircast, Boca Raton, FL). Of these, the KT-1000 has received the most attention and will be the focus of further discussion.
