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Magnetic resonance imaging follow-up study of bone bruises associated with anterior cruciate ligament ruptures.

PURPOSE
The purpose of this study was to perform a magnetic resonance imaging (MRI) follow-up study of bone bruises in a group of patients with acute anterior cruciate ligament (ACL) ruptures that were reconstructed and followed-up for a minimum of 2 years.


TYPE OF STUDY
Cohort study.


METHODS
The study group included 21 patients with a mean age of 31 years whose initial MRI scans showed associated bone bruises. Patients were included if they had an acute isolated ACL tear, no documentation of an episode of repeated injury to the affected knee during the follow-up period, and no evidence of cartilaginous injury at the time of arthroscopy. All patients had preoperative MRI scans and underwent arthroscopic ACL reconstruction using a bone-patellar tendon autograft an average of 2 months after injury. The preoperative MRI scans were analyzed using a 3-level grading system based on the appearance and location of bone bruises. A second MRI of the knee was obtained from 24 to 64 months postoperatively (average 34 months). The presence of resolution of bone bruises was determined and correlation with clinical scoring established.


RESULTS
This study showed resolution of all type I lesions and 91% of type II lesions (10 of 11). In all type III lesions, an articular cartilage thinning and depression was observed after 2 years of follow-up. In 15 patients (71%), MRI showed that the bone bruises had resolved without apparent sequelae. In the remaining 6 patients (29%), sequelae of the osteochondral lesion were evident on MRI.


CONCLUSIONS
According to our clinical data, there was no correlation between scores obtained from patients with resolved lesions against those with osteochondral sequelae. Although long-term clinical implications of these findings are uncertain, a severe occult osteochondral lesion sustained at the time of ACL rupture seems to be persistent on MRI even after a successful reconstruction.