PARTIAL ACL RUPTURE - AN MR DIAGNOSIS

Purpose. We sought to clarify the ability of magnetic resonance imagin g (MR) to show partial anterior cruciate ligament (ACL) ruptures and t o allow distinction of partial from complete ACL ruptures. Materials a nd methods. Eighty-eight patients were studied by arthroscopy and MR ( 36 with normal ACLs, 21 with partial ACL ruptures, and 31 with complet e ACL ruptures). MR studies were interpreted by an experienced, blinde d reader. MR examinations were also independently scored with respect to four primary and seven secondary signs, and these data were analyze d using discriminant analysis. Results. The sensitivity of MR is lower for partial than for complete ACL ruptures. Most detected partial ACL ruptures resemble complete ruptures on MR. Secondary signs do not sig nificantly improve detection of partial ACL ruptures, but they do help to distinguish partial from complete ACL ruptures. Displacement of th e posterior horn of the lateral meniscus and popliteus muscle injury a re indicative of complete ACL rupture. Conclusions. The majority of pa rtial ACL ruptures are shown by MR, but MR is less sensitive for parti al than for complete ACL rupture. The distinction of partial from comp lete ACL rupture on MR examination, while problematic, is slightly imp roved by assessment of secondary signs.