Electronic Theses and Dissertations

Date

2022

Document Type

Dissertation

Degree Name

Doctor of Philosophy

Department

Biomedical Engineering

Committee Chair

John Williams

Committee Member

Amy L de Jongh Curry

Committee Member

Carl Herickoff

Committee Member

Aaryani Sajji

Abstract

The capital femoral physis is a growth plate located between the head of the femur and the femoral neck and forms a temporary joint where growth cartilage differentiates into bone by endochondral ossification during development. A slip occurs when a shear stress across the physis overcomes the mechanical integrity of the bone-cartilage-bone interface, known as slipped capital femoral epiphysis. Though this disorder is widely studied the etiology is not completely understood. Joint morphology may play a critical role in stability, until the joint closes in early adulthood. During development morphological changes in the joint emerge and provide natural mechanical mechanisms resistant to shear: At first a large, eccentrically located epiphyseal tuberosity (tubercle), which projects into a corresponding metaphyseal fossa followed by epiphyseal cupping, which envelops the metaphysis. These features have also been observed in the domestic pig where the tubercle starts as an elongated ridge in early development, decreasing in length to a peaked structure in the caudal-lateral region as age increases. A shear component of the hip joint force acting in a plane parallel to the growth plate, through the center of the femoral head, could produce a moment around the pivot point provided by the tubercle and induce rotation of the femoral head relative to the neck unless the joint develops additional structures for stability. This work examined the development of domestic pig joint morphology from birth to adolescence through a comprehensive analysis of biomodels created from laser scans of pig femoral bones. Finite element models of idealized geometries were developed to examine the structure-function relationship of the peripheral secondary mammillary processes. The comprehensive analysis showed secondary mammillary processes in the periphery developed in a radial pattern with a degree of periodicity, well suited to resist torsional loading by interlocking the joint. Computational results showed that the radial mammillary processes acted to limit the translations and tilting of the head but had reduced effectiveness when the growth plate thickness was doubled. This suggests their radial pattern develops specifically to resist torsion and enhance stability of the joint, protecting the growth plate against torsional loading during development.

Comments

Data is provided by the student

Library Comment

Dissertation or thesis originally submitted to ProQuest.

Notes

Open Access

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