Mechanical properties of a hierarchical electrospun scaffold for ovine anterior cruciate ligament replacement.

The anterior cruciate ligament (ACL) acts to stabilize the knee and prevent excessive motion of the tibia relative to the femur. Tears of the ACL are common and can result in pain and damage to surrounding tissues. Thus a torn ACL is often surgically replaced with an autograft or allograft material. Drawbacks to clinically available ACL grafts motivate the development of a tissue engineered ACL replacement. Our group has previously developed a polycaprolactone electrospun scaffold that mimics the hierarchical structure of the ACL. The goal of this study was to investigate the mechanical properties of the electrospun scaffold as an ACL replacement. Scaffold mechanical properties were assessed prior to implantation via stress relaxation and pull to failure testing. Following in vitro characterization, electrospun scaffolds and soft tissue grafts were implanted into ovine cadaver stifle joints as ACL replacements. Stifle joints with ACL replacements were tested via a simulated anterior drawer test as well as in situ stress relaxation and pull to failure tests and compared to stifle joints with the native ACL intact. Prior to implantation the scaffold matched the native ovine ACL well in the range of functional strains as evidenced by stress relaxation measures and the toe region stiffness. After implantation the scaffold was more similar to the native ACL than the soft tissue graft, particularly when it came to reducing joint laxity and matching stress relaxation measures. These results demonstrate that the electrospun scaffold has the potential to be a suitable material for ACL replacement. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 37:421-430, 2019.