A polymer that expands the boundaries of orthopaedic applications such as joint arthroplasty has been introduced by high-performance biomaterials provider Invibio. So far, the design of arthroscopic devices and their performance capabilities have been limited by the strength and stiffness characteristics of the metals, ceramics and polymers used in their fabrication.
“Motis was formulated to maintain the low wear of metal-on-metal (MoM) constructions while providing enhanced stress distribution, design options and metal-free solutions,” says John Devine, PhD, Strategic Development Director, Invibio Biomaterial Solutions. “The material also addresses manufacturing inefficiencies because it can be directly injection moulded without compromising precision or surface characteristics.” Although MoM technology ensures low wear in medical applications, certain patient populations—people with poor hip mechanics or metal sensitivity issues or who require enhanced design options, for example—are not good candidates for MoM devices.
Motis polymer integrates reinforced fibres within a PEEK matrix, providing a strong, stiff fatigue- and creep-resistant material. Common sterilisation methods will not affect its properties. This material demonstrates excellent wear performance compared with metal and ceramic counter-faces; however, the combination of inherently low wear characteristics and excellent mechanical performance provides design engineers with new options in device design. The advantages of the Motis polymer include fixation and bone conservation enhancement, thin component and part consolidation capabilities, reduced stress shielding and improved distribution of stress. Interest in biomaterials is surging because an ageing yet active population expects advanced performance from joint replacement devices. Joint replacements also are becoming more common in a younger population. The longevity of the replacement and higher activity demands that are placed on the prosthesis mean that the material’s performance is increasingly important.
While Motis initially underwent clinical investigation as an acetabular liner to confirm laboratory-based findings involving biocompatibility and wear performance, the material was recently used for the design of the MITCH PCR acetabular cup. “In terms of bone apposition and long-term stability, these acetabular cups have shown that Motis can be coated with porous titanium and or hydroxyapatite and used as a thin, standalone acetabular cup,” Devine explains.