Computational Mechanics Study of A Kinematically Constrained Wrist Arthroplasty Implant
Open Access
- Author:
- Osedeme, Janose
- Graduate Program:
- Mechanical Engineering
- Degree:
- Master of Science
- Document Type:
- Master Thesis
- Date of Defense:
- July 16, 2020
- Committee Members:
- Anilchandra Attaluri, Thesis Advisor/Co-Advisor
Gregory Stephen Lewis, Thesis Advisor/Co-Advisor
Amit Banerjee, Committee Member
Richard Christopher Ciocci, Program Head/Chair
Hwa Bok Wee, Committee Member - Keywords:
- Total Wrist Arthroplasty
Wrist Kinematics
Biomechanics
Wrist Implant - Abstract:
- Pancarpal wrist arthritis is a disease involving most of the wrist joint. The disease is most common among senior populations. Total wrist arthroplasty is an established surgical procedure that has been used to treat pancarpal arthritis because it grants pain relief and restores functionality to the wrist. Although total wrist arthroplasty is one of the most recent and most effective methods of treating pancarpal arthritis, clinical studies show component loosening, hardware failure and dislocation occur in up to 69%, 50% and 22% of cases by 6-year follow-up. This study is a computational study of proposed solutions to the problem of dislocation by innovative implant designs. A new Kinematically Constrained design concept, developed initially at Penn State College of Medicine, was further developed and tested by kinematic analysis and then finite element analysis. Kinematic analysis assumed rigid body components and involved rotating the assembly in flexion and extension and radio-ulnar deviation until limits were reached. This analysis included comparison to several alternative constrained biaxial designs. Finite element analysis involved compression of the assemblies in several different angles including neutral, 5° extension and 15° flexion to simulate the loading occurring during typical wrist activities. Furthermore, the implant was tested at full flexion to simulate loading at the extreme with a pin constraining further flexion. These analyses included comparison to a model of a commercially available, less constrained traditional toroidal ball-and-shallow socket type implant. The Kinematically Constrained implant consists of three articulating components, (Cobalt Chromium alloy proximal and distal arms, and an ultrahigh molecular weight polyethylene ball with grooves for articulation) and stainless-steel locking screws which make up the implant embodiment. The design consists of 2 coplanar axes that intersect at the center of rotation. In this embodiment rotation axes for flexion and extension and for ulnar and radial deviations are created by sliding of the articulating arms with the polyethylene articulation grooves. This implant was selected as the best among several alternatives because near-full wrist range of motion is achieved through combined rotation about the two rotational axes. The results from the finite element analysis shows that through conditions simulating activities of daily living the Kinematically Constrained wrist implant has higher peak stresses of 94.7 MPa compared to the unconstrained ReMotion wrist implant with peak stresses of 72.0 MPa. The higher stresses in the Kinematically constrained wrist implant are attributed to the constrained articulation. Loading in the Kinematically Constrained implant was also considered in the functional range of motion of 5° Extension and 15° flexion and the results show that peak stresses begin to exceed the allowable stresses at 400 N loading, which is twice the typical loads passing through the wrist during functional activities of daily motion. From the load/angle analysis it is shown that although the initial relationship between load and peak stress is not linear, this relationship is linear at moderate and higher loads, over the functional range of motion. From analysis of loading with the Kinematically Constrained wrist implant fully flexed against the constraining pin, theoretically, yield failure is predicted to occur in the pin when loads of 550 N are applied. Future work will include design iterations and revisions of the implant design to limit component loosening, enhance osseointegration, and incorporate component size variations.