This study investigates the mechanical behaviour of keeled and pegged implant designs used in shoulder arthroplasty for the first time using multiple 3D models. Thus, this study should provide valuable insights into the preferable use of either of these two controversial implant designs. Three-dimensional models of a scapula were derived from the CT scans of five patients, and an inter-patient-specific finite element analysis with special attention to bone density and boundary conditions was carried out. A distinct decrease in the investigated parameters was evident with the pegged implant in all of the patients, specifically for the implant and the bone cement. The relevance of the stress reduction within the bone is minor, whereas the reduction in the stress of the bone cement contributes to an increase in the bone cement survival. The particular construction of the pegged implant provides better stability and therefore supports bone ingrowth. The large variations between the patients show the necessity of patient-specific simulations and the use of multiple models to derive valuable results. In the conducted inter-patient-specific FEA, the pegged glenoid implants were found to exhibit superior behaviour compared with keeled implants. The results confirm the general clinical findings and demonstrate the FEA as a valuable tool in prosthetic and orthopaedic problems.
Keywords: 3D modelling; Boundary conditions; Finite element analysis; Glenoid implant; Micromotions.