Partial Tears of the Anterior Cruciate Ligament

Abstract

Eight cadaveric lower extremities were examined by three experienced knee surgeons in blinded fashion. The knees were examined with intact anterior cruciate ligaments, sectioned anteromedial bundles, and completely sec tioned anterior cruciate ligaments to evaluate detectable laxity changes. Lachman, anterior drawer, lateral pivot shift, and KT-1000 arthrometer testing were performed. Optimized biplanar radiography using a defined spatial co ordinate reference system was performed with a 30- pound anterior force at 30° of flexion to confirm clinical findings. Physical examination and arthrometertesting de tected no difference between intact and partially sectioned anterior cruciate ligaments; these ligaments were signifi cantly different than completely sectioned ligaments, with the Lachman test being the most sensitive.

Despite consistent clinical detection of complete sec tioning of the anterior cruciate ligament by both physical examination and arthrometer testing, neither method proved accurate in the diagnosis of isolated tears of the anteromedial bundle, but both did show that partially sectioned anterior cruciate ligament closely resembled intact ligament and differed significantly from com pletely sectioned ligament, as confirmed by radiologic data. Clinically diagnosed "partial tear" is likely to be complete rupture of the anterior cruciate ligament. His torically, clinically diagnosed partial tears of the anterior cruciate ligament have tended to "progress" to symp tomatic instability. Our data imply these patients may have had functionally incompetent ligaments from time of injury and, in fact, were demonstrating the expected natu ral history of an anterior cruciate ligament-deficient knee.