Postoperative MR findings of the healthy ACL grafts: correlation with second look arthroscopy

To evaluate the postoperative MR findings of healthy anterior cruciate ligament (ACL) grafts, which were confirmed by second look arthroscopic examination.

We evaluated 33 MR scans of 29 patients who underwent postoperative MR scans and second look arthroscopic examination (four patients underwent postoperative MRI twice) between June 1996 and January 2001. There were 18 male and 11 female patients, and their ages ranged from 16 to 59 years old (mean 29.7). There were 15 cases of autogenous bone-patellar tendon-bone (BPTB) grafts, 13 cases of autogenous double-loop hamstring grafts, and 1 case of allogenous BPTB graft. Thirty-three MRIs were divided into three groups according to the time interval between operation and postoperative MR examination: less than 6 months, 7-12 months, and 13 or more months. The following MR findings of ACL grafts--signal intensity, morphology, continuity, orientation, and diameter--were analyzed.

Increased signal intensity was found in 29 ACL grafts (87.7%). The most common pattern of the graft morphology was a longitudinal streak-increased signal intensity band (27 cases, 81.8%). A partial rupture was seen in nine cases (27.3%) and lax orientation in four cases (12.1%). The signal intensity score of the ACL graft tended to decrease with time after operation, and the sagittal diameter of the graft tended to increase with time after operation.

The main postoperative MR findings of the healthy ACL graft was a longitudinal streak-increased signal intensity band. The graft signal intensity seemed to decrease and the sagittal diameter of the graft seemed to increase as time passed after operation.