Date of Award

5-2026

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Bioengineering

Committee Chair/Advisor

John DesJardins

Committee Member

Joseph Singapogu

Committee Member

Jordan Gilmore

Abstract

Total elbow arthroplasty (TEA) remains a valuable intervention for end-stage elbow pathology, yet its long-term success is limited by fundamental biomechanical mismatches between implant design and physiological loading. Current TEA systems require lifelong lifting restrictions, often below 10 lbs, due to their inability to tolerate forces generated during routine activities of daily living (ADLs), leading to functional limitations and high complication rates. Revision rates approach 15-30% within 10 years, with failure modes including aseptic loosening, instability, polyethylene wear, and periprosthetic fracture. Surgical approach poses a significant impact on functional outcome, as “triceps-off” techniques often leave patients with compromised triceps function and potential disability. Conversely, elbow arthrodesis provides superior load tolerance and stability at the expense of elbow joint motion, significantly impairing function. This trade-off highlights a critical unmet clinical need for a solution that balances mobility with load-bearing capacity.

This thesis presents the design and evaluation of an indexed, variable-constraint TEA system intended to function as a mechanical and clinical intermediate between conventional TEA and arthrodesis. The proposed system incorporates a ratcheting, locking mechanism that enables incremental adjustment of constraint across the range of motion, allowing the joint to selectively increase stability in flexion while preserving mobility for low-demand activities. By modulating constraint rather than maintaining a fixed mechanical state, the design aims to reduce torque transmission to the bone-implant interface, mitigate wear at articulating surfaces, and improve functional performance under physiologic loading. 

A design history file (DHF)-driven methodology was employed to translate clinical needs into engineering specifications, incorporating surgeon input, biomechanical analysis, and established regulatory frameworks. Design inputs were derived from identified limitations in existing TEA systems, including dependence on soft tissue integrity, poor load-bearing activity, and an inability to accommodate high-demand patients or revision scenarios. The proposed mechanism was developed through iterative prototyping and evaluated using mechanical testing methods adapted from orthopedic implant standards, including assessments of constraint behavior, load transfer, and cyclic durability. 

Results demonstrate that the indexed locking mechanism provides controlled, repeatable modulation of joint constraint with limited reliance on triceps and biceps function. The system achieves approximately 110° of flexion-extension, allows 3-8° of varus-valgus play to accommodate physiological laxity, and sustains loading at 10 Nm of applied torque. These findings suggest that the mechanism can maintain functional motion while stabilizing the joint under load and reducing dependence on compromised soft tissues as a novel solution for revision and salvage cases.

This work establishes the feasibility of a variable-constraint approach to elbow arthroplasty and introduces a new design paradigm that bridges the gap between mobility and stability. The findings support further development and validation of adaptive, load-response implant systems aimed at improving functional independence in individuals with severe elbow pathology.

Author ORCID Identifier

0009-0001-8764-2107

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