Background: The semitendinosus tendon graft with an intact tibial insertion has a sustainable blood supply and might be beneficial for graft maturation after anterior cruciate ligament reconstruction (ACLR); however, its potential advantages for graft tendon-bone healing is still unclear.
Hypothesis: Intact tibial insertion of the hamstring tendon can preserve enough blood supply to keep the harvested tendon alive, which can improve tendon-bone healing and the biomechanical strength of the graft.
Study design: Controlled laboratory study.
Methods: Sixty-four healthy New Zealand White rabbits underwent unilateral ACLR with a semitendinosus tendon autograft after random enrollment into 2 groups (study group, n = 32 rabbits with semitendinosus tendon-preserved tibial insertions; control group, n = 32 rabbits with free semitendinosus tendons). At weeks 3, 6, 12, and 24, 8 rabbits in each group were sacrificed to evaluate tendon-bone healing by histologic staining, micro-computed tomography (micro-CT) examination, and biomechanical test.
Results: The grafts in the study group maintained a similar cell count with no signs of necrosis or hypocellularity across all time points, but the grafts in the control group underwent a characteristic stage of necrosis at weeks 3 and 6. Sharpey-like fibers were observed from postoperative 3 weeks at the tendon-bone interface in the study group, and a normal insertion-like structure was formed at week 12, which became more mature at week 24. In the control group, however, Sharpey-like fibers could not be observed until week 12, and a normal transition through cartilage from bone to tendon was not observed at any time point. Histologic scores of the tendon-bone interface in the study group were significantly higher than those in the control group at week 6 ( P = .04), week 12 ( P < .001), and week 24 ( P = .04). As compared with the control group via micro-CT, the study group had a significantly smaller bone tunnel area at week 6 ( P = .01) and larger bone volume/total volume at week 3 ( P = .0026) and week 6 ( P = .01). Also, the study group had a significantly higher failure load at weeks 12 and 24 (both P = .03) and a significantly higher stiffness at week 24 ( P < .001) versus the control group.
Conclusion: The semitendinosus tendon graft with an intact tibial insertion in ACLR would bypass the graft avascular necrosis stage, which improves tendon-bone healing and biomechanical strength.
Clinical relevance: An alive graft in ACLR could improve tendon-bone healing and the biomechanical strength of the graft, which might be beneficial to early and intensive rehabilitation after ACLR.
Keywords: ACL; semitendinosus tendon; tendon-bone healing; tibial insertion; vascularized graft.