Summary
MRI-based observation of graft remodelling and maturation cycle provides valuable insight, relevant for post-op decision-making process especially in terms of physical activity and RTS
Abstract
Background
Anatomical "ribbon" ACL reconstruction (ACLRR) cases were evaluated both clinically and through imaging. The following data relate to the part of the study focusing on analysis of ACL graft signal measured on MRI scans compared to a native ACL signal intensity (SI) to establish the pattern of structural changes it undergoes over time.
Methods
A total of 51 cases (34 males and 17 females,) following ACLRR using an autologous quad tendon graft, were assessed on 3Tesla MRI scans done at 3, 6, 9,12, and 18 months post-op. A control group included 84 healthy adults with intact ACL (35 males and 49 females). SI was manually measured on PDWI sagittal sequences in four regions of interest (ROI): proximal, middle, distal intra-articular portions of the graft, and PCL. ACL:PCL ratio named "APR" was calculated and compared over time (from 3 to 18 months) to intact ACL SI.
Results
Median signal intensity (MSI) has changed significantly in the proximal (p<0,001), mid-substance (p<0,001), and distal (p<0,001) portions of ACL graft over study period, however the change was nonlinear. The most hyper-intensive signal period was recorded at 6 months for all the portions of the graft (p<0,01). The APR of the distal section was significantly higher in all periods compared to proximal and mid-substance, except for 6 months post-op when the proximal part achieved the highest value (p<0,01). At 18 months post-op, the SI did not reach the levels of native-ACL MSI. Compared to the native ACL, the quadriceps graft reached approximately 85% MRI-SI.
The period between 3 to 6 months post-op, with recorded hyper-intensity levels indicating an intensive graft remodelling process, seems crucial for the entire remodelling and subsequent maturation cycle that continues after 6 months post-op.
Conclusions
After 6 months the remodelling process continues at a notably slower rate and the maturation can take up to 18 months after the surgery. With that in mind, it is important to consider MRI as a useful assessment tool, complementing clinical evaluation of patients after ACLRR. Data gathered through MRI observation enables surgeons to make relevant, patient-specific adjustments to the post-op protocol translating into improved surgery outcomes and increased patient safety, especially in terms of their readiness for return to physical activity and sports. To reduce the risk of re-rupture and/or early-onset osteoarthritis, both function (through physical examination) as well as structure (through proper imaging diagnostics) should be considered when making decisions meant to optimise patient's post-op recovery, rehabilitation, and final outcome.