The surgeon should be aware of the strengths and weaknesses of each clinical test and should consider the use of reasonable test-combinations to improve accuracy.
Anterior drawer test, Lachman test including evaluation of the endpoint, and pivot shift test have been commonly applied in diagnosing anterior cruciate ligament (ACL) injury but how they function in the appraisal of partial ACL tears is less known. The purposes of this study were to examine the diagnostic values of the commonly used knee function tests on patients in detecting partial injury patterns of the ACL and to assess if using multiple tests collectively for the diagnosis of the injury could improve diagnostic accuracy.
Examination under anesthesia was performed prior to surgery. The rupture pattern was confirmed by arthroscopy. We evaluated 36 consecutive patients with a partial rupture of the ACL. Out of these 36 patients, 9 patients presented with an isolated tear of the anteromedial (AM) bundle and 27 patients with an isolated tear of the posterolateral (PL) bundle. Those patients were matched by gender and age to 36 patients with a complete rupture of the ACL. Sensitivity, specificity, positive, and negative likelihood ratio values were used to evaluate the diagnostic value for each knee function test. The prediction of specific ACL injury pattern for each individual test and the tests collectively were investigated by using binary and multinomial logistic regression. Significance was set at p<0.05.
Clinical exam of the endpoint had the highest sensitivity in diagnosing the rupture pattern of the ACL (complete rupture vs. partial tear: 100%, complete rupture vs. PL bundle tear: 100%, complete rupture vs. AM bundle tear: 100%, AM bundle tear vs. PL bundle tear: 89%), followed by Lachman test (81%, 89%, 78%, 56%, respectively). Pivot shift test (81%, 78%, 81%, 81%, respectively) and anterior drawer test (78%, 56%, 85%, 85%, respectively) had higher specificity comparing the different types of ACL injuries. The pivot shift test was the test with the highest positive likelihood ratio (complete rupture vs. PL bundle tear: 2,8; CI 95% (1,17;6,69)). The Lachman test had the smallest negative likelihood ratio (complete rupture vs. partial tear: 0,39; CI 95% (0,19; 0,82)). When using the results of both Lachman test and pivot shift tests, the Odds ratio was increased 200% in predicting a complete rupture versus a partial tear. The pivot shift test was significant in predicting a partial PL tear vs. a complete rupture with an Odds ratio of 0,20, CI 95% (0,06; 0,66), (p<0.05).
Collectively using both Lachman test and pivot shift test increases ability to distinguish between partial tears and complete ruptures. When comparing PL tears and complete ruptures the pivot shift test is more important than the Lachman test. In diagnosing AM tears among patients with partial tears and in diagnosing a complete rupture, the evaluation of the endpoint is more sensitive than the Lachman test. The surgeon should be aware of the strengths and weaknesses of each clinical test and should consider the use of reasonable test-combinations to improve accuracy.