Ute t2* mri shows evidence of tissue remodeling in acl grafts between 1 and 9 months after surgery

Quantitative measures related to mechanical strength of the anterior cruciate ligament (ACL) graft are needed for timely return-to-sports decisions after the ACL reconstruction surgery (ACLR). Ultra-short echo-time (UTE)-T2* magnetic resonance imaging (MRI) was used to study structural changes in grafts of 9 ACLR patients longitudinally (1, 3, 6, and 9 mos. after surgery) and the results were compared to the native ACL and semitendinosus tendon (SemiT) of the contralateral limb. The grafts were initially well-organized (low T2*), with T2* relaxation times gradually increasing until 6 mos followed by a decrease by 9 mos. after surgery. The rising T2* values suggest increasing tissue disorganization associated with graft remodeling and may reflect compromised mechanical properties of the ACL graft. UTE-T2* shows potential for assessing the remodelling state of the ACL graft, and may have value as a measure for timely return to sports.