Calcium phosphate-hybridized tendon grafts reduce femoral bone tunnel enlargement in anatomic single-bundle ACL reconstruction

Purpose This study aimed to clarify the effect of calcium phosphate (CaP)-hybridized tendon grafting versus unhybridized tendon grafting on the morphological changes to the bone tunnels at the aperture 1 year after anatomic single-bundle anterior cruciate ligament (ACL) reconstruction. Methods Seventy-three patients were randomized to undergo the CaP (n = 37) or the conventional method (n = 36). All patients underwent computed tomography (CT) evaluation 1 week and 1 year post-operatively. The femoral and tibial tunnels at the aperture were evaluated on reconstructed 3D CT images. Changes in the cross-sectional area (CSA) and diameters of the femur and the tibia, and the translation rate of the tunnel walls and the morphological changes of both tunnels were assessed. Results There was a significant reduction in the increase in the CSA and the anterior-posterior and proximal-distal tunnel diameters on the femoral side in the CaP group as compared with the conventional group. On the femoral side, the translation rate of the posterior wall was significantly larger in the CaP group than in the conventional group, whereas the translation rate of the distal wall was significantly smaller in the CaP group than in the conventional group. Conclusions As compared with the conventional method, the CaP-hybridized tendon graft reduced bone tunnel enlargement on the femoral side 1 year after anatomic single-bundle ACL reconstruction due to an anterior shift of the posterior wall and reduced distal shift in the femoral bone tunnel. Clinically, the CaP-hybridized tendon grafts can prevent femoral bone tunnel enlargement in anatomic single-bundle ACL reconstruction.