Abstract
Currently available focal knee resurfacing implants (FKRIs) are fully or partially composed of metals, which show a large disparity in elastic modulus relative to bone and cartilage tissue. Although titanium is known for its excellent osseointegration, the application in FKRIs can lead to potential stress-shielding and metal implants can cause degeneration of the opposing articulating cartilage due to the high resulting contact stresses. Furthermore, metal implants do not allow for follow-up using magnetic resonance imaging (MRI).To overcome the drawbacks of using metal based FKRIs, a biomimetic and MRI compatible bi-layered non-resorbable thermoplastic polycarbonate-urethane (PCU)-based FKRI was developed. The objective of this preclinical study was to evaluate the mechanical properties, biocompatibility and osteoconduction of a novel Bionate® 75D - zirconium oxide (B75D-ZrO 2) composite material in vitro and the osseointegration of a B75D-ZrO 2 composite stem PCU implant in a caprine animal model. The tensile strength and elastic modulus of the B75D-ZrO 2 composite were characterized through in vitro mechanical tests under ambient and physiological conditions. In vitro biocompatibility and osteoconductivity were evaluated by exposing human mesenchymal stem cells to the B75D-ZrO 2 composite and culturing the cells under osteogenic conditions. Cell activity and mineralization were assessed and compared to Bionate® 75D (B75D) and titanium disks. The in vivo osseointegration of implants containing a B75D-ZrO 2 stem was compared to implants with a B75D stem and titanium stem in a caprine large animal model. After a follow-up of 6 months, bone histomorphometry was performed to assess the bone-to-implant contact area (BIC). Mechanical testing showed that the B75D-ZrO 2 composite material possesses an elastic modulus in the range of the elastic modulus reported for trabecular bone. The B75D-ZrO 2 composite material facilitated cell mediated mineralization to a comparable extent as titanium. A significantly higher bone-to-implant contact (BIC) score was observed in the B75D-ZrO 2 implants compared to the B75D implants. The BIC of B75D-ZrO 2 implants was not significantly different compared to titanium implants. A biocompatible B75D-ZrO 2 composite approximating the elastic modulus of trabecular bone was developed by compounding B75D with zirconium oxide. In vivo evaluation showed an significant increase of osseointegration for B75D-ZrO 2 composite stem implants compared to B75D polymer stem PCU implants. The osseointegration of B75D-ZrO 2 composite stem PCU implants was not significantly different in comparison to analogous titanium stem metal implants.
Original language | English |
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Pages (from-to) | 1424-1435 |
Number of pages | 12 |
Journal | Journal of Biomedical Materials Research Part A |
Volume | 112 |
Issue number | 9 |
Early online date | 11 Mar 2024 |
DOIs | |
Publication status | Published - Sept 2024 |
Keywords
- coating
- composite
- implant
- osseointegration
- polycarbonate-urethane