Biomechanical Response of Glenoid Prostheses During the Use of Mobility Aids - A Finite Element Analysis

Glenohumeral conformity, defined as the quotient of the radius of the humeral head and the radius of a glenoid implant, has been shown to be a critical factor of implant survivability following total shoulder arthroplasty (TSA). Several Studies have investigated the impact of glenohumeral conformity on stress-strain profiles, glenohumeral contact pressure, cement stress, and micromotions at the bone-cement interface. Biomechanical studies have centered around cyclic loading from low-force movements to make predictions regarding loosening of the implant and fixation failure. Total shoulder arthroplasty tends to be performed, however, on an aging demographic, subject to unique loading conditions regarding the shoulder complex. Specifically, the use of mobility aids, such as canes and walkers, function by transferring forces typically experienced by the lower limbs, to the upper limb. My Thesis will explore the mechanical effect of cane or walker usage on the fixation parameters that have been previously investigated, using an anatomically detailed finite element model of the shoulder. The results of this study could provide insight on optimal glenohumeral conformity in patients who use mobility aids, which may be different from the degree of conformity suggested based on generic shoulder movements. Varying degrees of conformity will be examined in two commercially available glenoid prostheses (Implant A, Implant B). Osteoarthritic shoulders often present moderate to severe retroversion, which is corrected by augmented material on the backside of the glenoid implant. The Implant A and Implant B implants vary in their augmentation geometry (Stepped vs Wedged) which may also impact the fixation criteria investigated by this study.