Abstract
BackgroundTunnel widening after anterior cruciate ligament (ACL) reconstruction (ACLR) is commonly reported without a clear understanding of the mechanism. This study aimed to quantify the spatiotemporal change of the newly formed bone mass, bone tunnel diameter, and area along both bone tunnels using micro-computed tomography (μCT) and correlated the result with histology. MethodsACLR was performed in 24 rabbits. At baseline and weeks 2, 6, and 12, the juxta-articular, middle, and exit segments of both tunnels were harvested for μCT and histological evaluation. ResultsμCT and histology revealed signifi cant bone tunnel and graft–bone tunnel healing, respectively, only at week 6 after reconstruction. Despite this, the mean tunnel diameter and area remained relatively unchanged with time. The newly formed bone mass [new bone volume/total bone volume (BV/TV) ratio] and its bone mineral density (BMD) were both higher, whereas the mean tunnel diameter and area were signifi cantly smaller at the femoral tunnel compared to those at the tibial tunnel at weeks 6 and 12 and at week 12, respectively. These were consistent with histological fi ndings, which showed inferior graft remodeling and integration at the tibial tunnel at weeks 6 and 12. The BV/TV increased, whereas the mean tunnel diameter and area decreased toward the exit segment of both tunnels. However, whereas better histological healing occurred at the femoral exit segment, poorer graft remodeling and Sharpey’s fi ber formation occurred at the tibial exit segment. ConclusionsPoor healing was observed during the initial 6 weeks, particularly that of the tibia, after ACLR. Bone resorption was rapid during healing, resulting in unchanged tunnel diameter and area with time.
Published Version
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