Comparisons of Early MRI Patterns with Arthroscopic Findings of Possible Acute ACL Tears

Yoon, Kyoung Ho; Ahn, Jin Hwan; Kim, Seung Ho; Han, Kye Young; Ha, Kwon Ick

Abstract

Early MRI and arthroscopic findings were compared to evaluate the efficacy of the former for patients, who upon physical examination, were diagnosed with possihle acute ACL tears. MRI, taken between 1-21 days after injury, had to reveal complete ACL tears and arthroscopic surgery should have taken place 3-12 weeks after the injury for patients of this prospective study. Fifty such cases were initially catagorized according to five MRI patterns. Types I to V were separated by the following ACL tear characteristics: Enlarged and diffusely increased in signal, horizontally oriented, non-visualized, discontinuous and vertically oriented. The cases were then divided into two groups of arthroscopic findings; Group A included cases of complete ACL tearing and group B included those with intact or minimally torn ACLs. Of MRI types I through V, there were 31, 9, 5, 4, and I cases of each respectively. 37 cases resulted in complete ACL tears (21 type I, 6 type II, 5 type III, 4 type IV and 1 type V) and 13 cases were catagorized into group B, 10 of which had pattern type I and 3 of which had pattern type II. As result, types III, IV and V had a 100% Positive Predictive Value (PPV) whereas types I and II together had a 67% PPV vaiue. Division of the cases into the five pattern types in early MRI proved valuble for possible cases of acute ACL tears. MRI pattern types III, IV and V were correlated with definite complete ACL tears. However, caution must be taken for types I and II, the majority of the cases, for which there exists a significant possibility for misdiagnosis and consequently unnecessary arthroscopic surgery.