Effects of Prosthesis Shape and Material on the Contact Mechanics of Elbow Joints Following Radial Head Arthroplasty: An In-Silico Investigation.

Objectives: Radial head fractures often require prosthetic replacement, but post-surgical complications like radial neck osteolysis, capitellum osteopenia, and ulnohumeral osteoarthritis can arise due to altered elbow biomechanics. This study used the finite element method to evaluate how radial head prostheses (RHPs) shape and material affect elbow joint biomechanics.

Methods: A 3D elbow model was developed, including bones, ligaments, and cartilage. Implants featuring two geometries (anatomical vs. axisymmetric) and three materials (polymethylmethacrylate [PMMA], polyether ether ketone [PEEK], and Cobalt) were tested. Bones were considered isotropic and heterogeneous, ligaments and implants linear elastic, and cartilages were considered hyperplastic materials. Stress distributions, contact stresses, and contact areas were assessed during elbow flexion and forearm rotation.

Results: During forearm rotation, Cobalt RHPs exhibited lower stresses in the radial neck, indicating higher stress shielding, and all axisymmetric implants showed increased edge loadings. In rotation, only the PMMA anatomic RHP showed close contact stresses to the intact model, while all other models resulted in lower stress levels. In flexion, anatomical designs produced more uniform stress distributions in the radial neck that resembled intact conditions and matched intact capitellum contact stresses, in contrast to axisymmetric designs. The reduction in the contact area in the ulnohumeral cartilage was most noticeable with all axisymmetric RHPs in flexion.

Conclusion: The lower contact areas, higher contact stresses, and lower stresses at the radial neck observed in the presence of most axisymmetric RHPs and anatomic Cobalt RHP can be correlated to postoperative complications. The findings suggest that polymeric anatomical RHPs may be superior to conventional metallic axisymmetric options in preserving elbow biomechanics and reducing postoperative complications. However, their long-term effects need to be further explored.