Biomechanical evaluation of novel concepts in soft tissue knee reconstruction

Abstract

Anterior cruciate ligament (ACL) rupture is a common injury associated with a failure to return to sport and early osteoarthritis. The optimal technique for ACL reconstruction (ACLR) is yet to be determined. The aim of this PhD was to investigate novel concepts in ACL anatomy and reconstruction, and thus provide quantifiable data to help clinicians choose the correct graft type, configuration, preparation and augmentation technique. A robotic testing system was utilised to perform cadaveric experiments. The load bearing characteristics of the fibres of the native ACL tibial attachment were quantified and compared to a blinded anatomical assessment. It was found that the most important fibres in resisting tibial displacements attach to the ‘C’-shaped anterior-medial area of the native ACL tibial attachment. The femoral attachment site has the most effect on ACL graft isometry, so a simplified 3-socket (3S) construct utilising two femoral sockets is attractive. The ability of 3S, single- and double-bundle surgery to restore native knee kinematics was assessed. No significant benefit was observed over single-bundle surgery. Smaller tunnels for compressed grafts reduce bone loss. Instron materials testing machines were used to test non-irradiated allograft tendons following graft compression. Graft compression did not cause adverse mechanical effects. The grafts significantly increased in size during joint simulation with no effect on graft stability. Lateral extra-articular tenodesis (LEAT) is a popular adjunct to ACLR. It was not known whether closing the ilio-tibial band (ITB) defect overconstrains tibial rotation. Robotic testing found this was not the case. Therefore, it is advised that surgeons use a ribbon-like single-bundle reconstruction aligned with the anteromedial border of the tibial attachment. Graft compression downsizing should be used if bone loss is to be minimised. When considering an LEAT, the ITB defect can be left open or closed depending on patient or surgeon specific factors.