Hemiarthroplasty implants should have very low stiffness to optimize cartilage contact stress

Abstract

Hemiarthroplasty is often preferred to total arthroplasty as it preserves native tissue; however, accelerated wear of the opposing cartilage is problematic. This is thought to be caused by the stiffness mismatch between the implant and cartilage‐bone construct. Reducing the stiffness of the implant by changing the material has been hypothesized as a potential solution. This study employs a finite element model to study a concave‐convex hemiarthroplasty articulation for various implant materials (cobalt‐chrome, pyrolytic carbon, polyether ether ketone, ultra‐high‐molecular‐weight polyethylene, Bionate‐55D, Bionate‐75D, and Bionate‐80A). The effect of the radius of curvature and the degree of flexion‐extension was also investigated to ensure any relationships found between materials were generalizable. The implant material had a significant effect (P < .001) for both contact area and maximum contact pressure on the cartilage surface. All of the materials were different from the native state except for Bionate‐80A at two of the different flexion angles. Bionate‐80A and Bionate‐75D, the materials with the lowest stiffnesses, were the closest to the native state for all flexion angles and radii of curvature. No evident difference between materials occurred unless the modulus was below that of Bionate‐55D (288 MPa), suggesting that hemiarthroplasty materials need to be less stiff than this material if they are to protect the opposing cartilage. This is clinically significant as the findings suggest that the development of new hemiarthroplasty implants should use materials with stiffnesses much lower than currently available devices.

In Vivo Biocompatibility of an Innovative Elastomer for Heart Assist Devices

“…No effect of implanted materials on peripheral blood count parameters and CRP levels were noticed, thus confirming their biocompatibility [ 14 ]. Conversely, Berkmortel et al [ 17 ], when using Bionate-55D, Bionate-75D, and Bionate-80A biomaterials, noted that, in the case of hemiarthroplasty materials, the use of materials with significantly lower stiffness than those currently used was requested [ 17 ]. This confirms the continuous need to search for new solutions in biomaterial implantology.…”

Decoding the “Fingerprint” of Implant Materials: Insights into the Foreign Body Reaction

“…However, the mismatch of stiffness between the implant surface and surrounding tissue leads to the damage of the opposing cartilage. [ 154 ] Therefore, in order to maintain the balance between mechanical properties and clinical function, the stiffness of biomedical implants must be optimized to avoid FBR while facilitating adaption between implant and tissue, simultaneously. The relationship between stiffness, porosity, and biocompatibility has been intensively studied, Kelly et al, revealed that both the strength and modulus of the porous Ti implants decreased with the increase of porosity.…”