Finite Element Analysis of Custom Shoulder Implants Provides Accurate Prediction of Initial Stability

Abstract

<jats:p>Custom reverse shoulder implants represent a valuable solution for patients with large bone defects. Since each implant has unique patient-specific features, finite element (FE) analysis has the potential to guide the design process by virtually comparing the stability of multiple configurations without the need of a mechanical test. The aim of this study was to develop an automated virtual bench test to evaluate the initial stability of custom shoulder implants during the design phase, by simulating a fixation experiment as defined by ASTM F2028-14. Three-dimensional (3D) FE models were generated to simulate the stability test and the predictions were compared to experimental measurements. Good agreement was found between the baseplate displacement measured experimentally and determined from the FE analysis (Spearman’s rank test, p &lt; 0.05, correlation coefficient ρs = 0.81). Interface micromotion analysis predicted good initial fixation (micromotion &lt;150 µm, commonly used as bone ingrowth threshold). In conclusion, the finite element model presented in this study was able to replicate the mechanical condition of a standard test for a custom shoulder implants.</jats:p>

Modified Whiteside’s Line-Based Transepicondylar Axis for Imageless Total Knee Arthroplasty

“…Whiteside's line being a smaller landmark leads to rotational error of up to 10 • , even for small uncertainties [21]. It is a well-known fact that alignment error >3 • from the natural alignment of the knee leads to quick wear and discomfort of the patient, and finite element analysis can accurately predict initial stability of an implant; however, the computational cost increases [15,22,23]. The sTEA, being an inconsistent landmark [24], leaves only aTEA to be a reliable choice for assigning the FCS and setting the rotational alignment of the implant [19,25].…”