PhD Thesis Defense: Kathleen Lewicki

Wednesday, May 24, 2017, 2:00–4:00pm

Jackson Conference Room, Cummings Hall

“Damage and Wear of Reverse Shoulder Arthroplasty: Patient, Implant, and Design Considerations”

Abstract

Reverse shoulder arthroplasty (RSA) is an increasingly popular procedure that re-establishes a stable joint and restores range of motion for patients with significant shoulder pain. To accommodate patients with deficient rotator cuff structures, the RSA prosthesis and procedure alter the biomechanics of the shoulder to provide a mechanical advantage for the deltoid. However, due to this change in biomechanics, several failure mechanisms and complications unique to RSA have presented. These include unpredicted wear behavior and its impact on the host, as well as fracture of the attendant bony structures supporting the shoulder musculature. The overarching objectives of this work are to (1) quantify the clinical failure modes of clinically retrieved shoulder prostheses, (2) validate a suite of analytical failure analysis tools and (3) develop predictive biomechanical and finite element models for RSA-specific bone fractures.

A cohort of failed RSA devices was assessed for damage features and failure mode prevalence. Because commonly-observed articular- and impingement-related wear indicate a biomechanical environment outside of the range of expected motions and loads, development of a measurement tool for material loss was warranted. A manufacturer- and design-independent computational tool was designed and validated. The technique was applied to cohorts of failed devices to demonstrate the strength of the wear analyses approach.

In response to clinical observations of wear, manufacturers have changed designs and surgical techniques to reduce polymer-on-bone contact. These changes further alter the biomechanics of the joint, likely predisposing the scapula and acromion to fracture. The final objective of this work is to determine how biomechanical changes affect the muscle load vectors, joint reaction forces, and the scapular bone strain. The resulting musculoskeletal simulations and predictive finite element models can be used by decision makers to improve patient outcomes.

Thesis Committee

For more information, contact Daryl Laware at daryl.a.laware@dartmouth.edu.