Comparison of postoperative biomechanical function between anatomic double-bundle and single-bundle ACL reconstructions using calcium phosphate-hybridized tendon grafts in goats

Abstract Background Calcium phosphate (CaP)-hybridized tendon grafts improved biomechanical function compared with untreated grafts after single-bundle (SB) anterior cruciate ligament (ACL) reconstruction.The purpose of this study was to compare the biomechanical functionbetweenanatomic double-bundle (DB)and single-bundle (SB)ACL reconstructions using CaP-hybridized tendon grafts at 6 months postoperativelyin goats. Hypothesis We hypothesized that the postoperativebiomechanicalfunctioninthe DBgroupwill bebetterthan that inthe SB group. Materials and Methods Knee kinematics and in situ forces in the graftsunder applied anterior tibial load of 50 N (ATL) and internal tibial torque of 2.0 Nm (ITT) at fullextension,and 60° and 90° of knee flexion,and the histology of the tendon-bone interfacewere compared between the DB group (n = 6)and SB group(n = 6). Results The in situ forces under ATL in the DB group at full extension and 90°of knee flexionwere greater than those in the SB group.The in situ forcesunder ITT in the DB group at full extension and 60°of knee flexionwere greater than those in the SB group. The in situ forcesonthe posterolateral bundle of the grafts under ATLand ITTin the DB group at full knee extensionwere greater than thoseonthe posterior halfof the grafts in the SB group.The histologydidnot differ significantly between the groups. Conclusions AlthoughCaP-hybridized tendon grafts were used in both groups,the in situ forces under ATL and ITT in the DB group were greater than those in the SB group at 6 months postoperatively. The posterolateral bundle of the grafts in the DB group acted effectively against both ATL and ITT at full extension.The tendon-to-bone healing was similar in the both groups. Study Design Controlled laboratorystudy. Level 2