3D printed and punched porous surfaces of a non-resorbable, biphasic implant for the repair of osteochondral lesions improves repair tissue adherence and ingrowth

Summary: The objective of this study was to evaluate a non-resorbable implant for the focal repair of osteochondral defects. Enhanced adherence of repair cartilage overgrowing the implants was the secondary goal and was tested by introducing porosities on the articular surface of the implant. This study evaluated four versions of the construct composed of a polycarbonate-urethane-urea biomaterial (elastomer) and a bone anchor. In order to induce porosities on the surface of the implant, either vertical holes were punched into it, or the chondral component was 3D-printed onto the implant. Fabrication, biomechanical characterization and cell infiltration of the implant were evaluated in-vitro. Subsequently the implants were tested in an in-vivo study in four Shetland ponies for 5 weeks. Enhanced porosity was successfully obtained for all implants. The 3D-printing of the elastomeric material produced pore diameters of 775μm and 690μm whilst the micro-punched pores had a diameter of 319μm. The elastic modulus of the elastomer decreased with the introduction of porosity but stayed above values of native cartilage in all versions of the implant. Clinically the implant was well tolerated. The over-growing repair tissue was mostly flush with surrounding cartilage and attached to the elastomer through ingrowth of the tissue into the pores. Overall the tested implants all showed good mechanical performance in vitro and subjectively also in vivo. The repair cartilage was solidly attached to the porous surface of the implant. The printing approach potentially enables fine-tuning of the biomechanical properties of the implant depending on the specific requirements for a given location.