Revascularization Process of the Bone–Patellar Tendon–Bone Autograft Evaluated by Contrast-Enhanced Magnetic Resonance Imaging 6 and 12 Months After Anterior Cruciate Ligament Reconstruction

Abstract

Revascularization of the graft occurs gradually along its length, with the intra-articular site being the first and the faster part to complete this phase, while both the intraosseous sites are still in progress throughout the first postoperative year. Revascularization is an important link at the intrinsic healing chain of the ACL graft. The surrounding microenvironment does seem to play a significant role in this process, and the differences in its composition along the graft course are reflected at the revascularization progress of the corresponding sites.

Graft bending angle is correlated with femoral intraosseous graft signal intensity in anterior cruciate ligament reconstruction using the outside-in technique

“…They used the SNQ value for the graft evaluated on MRI scans to compare graft revascularization between the two groups. More recently, Ntoulia et al [34] evaluated the biological healing process of the BPTB autografts using the SNQ value calculated on 1.5-T MRI scans; they found that the graft was gradually revascularized along its length, according to SNQ values on MRI six and 12 months after surgery. During the healing process, the microenvironment surrounding the graft plays an important role as it provides the elements necessary for its healing [35,36].…”

Clinical significance of T2*-weighted gradient-echo MRI to monitor graft maturation over one year after anatomic double-bundle anterior cruciate ligament reconstruction: A comparative study with proton density-weighted MRI

“…Previous studies have attributed increments in MRI signals to revascularization of the reconstructed grafts and synovial hypervascular tissue surrounding the grafts [10]. Human studies using Gd-DTPA-enhanced MRI [9,23,24], and an animal study [25] have shown that revascularization of intra-articular graft site was initiated approximately 4 weeks after ACL reconstruction and peaked at approximately 4-6 months. Another animal study reported that graft hyperintensity appeared at 7 Values for SIR and KT arthrometer are expressed as mean ± standard deviation.…”

“…This is usually a plane with about 10-15°internal rotation from the anterior-posterior mechanical axis of the knee joint, and the long axis of the reconstructed AMB and PLB could be depicted. This oblique sagittal plane is frequently used for current MRI studies [9,17], but the long axis of the PLB failed to be depicted in the aforementioned seven cases, who were excluded from the study. Images from MRI were analyzed using image analysis software (Image J version 1.37c; National Institutes of Health, USA) by two independent orthopedic surgeons (Y.K.…”

“…Howell et al advocated the clinical relevance of graft signals on proton density-weighted imaging (PDWI), showing that intercondylar notch impingement resulted in increased graft intensity, and clinical outcomes were poorer when the high-intensity area exceeded N50% of the entire graft [8]. Ntoulia et al reported that MRI with a contrast agent such as gadolinium diethylenetriamine pentaacetic acid (Gd-DTPA) clearly demonstrated that revascularization initiated from the periphery and progressed toward the center of the graft, which may explain part of the increment in graft intensity on conventional PDWI sequences [9,10]. Accordingly, graft intensity changes might reflect not only graft damage, but also neovascularization and matrix synthesis within the graft.…”

Completing the Picture

“…MRI has been used to document the differential survival of the individual components of double-bundle reconstructions, 38 compare the maturation of autografts and allografts, 24 and, with added contrast, evaluate the graft revascularization process. 35 Late development of osteoarthritis following ACL injury has long been a concern, although it is still not clear how much of this risk is contingent upon damage that occurs at the time of the initial injury and how much is secondary to damage from subsequent instability. 7,25 Enhanced MRI techniques, including dGEMRIC, T1 rho, and T2 mapping, promise to provide a noninvasive method of tracking the health of the articular cartilage following ACL injury.…”