Publication Date

5-2019

Date of Final Oral Examination (Defense)

12-11-2018

Type of Culminating Activity

Thesis

Degree Title

Master of Science in Mechanical Engineering

Department

Mechanical and Biomechanical Engineering

Supervisory Committee Chair

Clare Fitzpatrick, Ph.D.

Supervisory Committee Member

Trevor Lujan, Ph.D.

Supervisory Committee Member

Gunes Uzer, Ph.D.

Abstract

Crouch gait is a musculoskeletal impairment that results in higher than normal stresses at the patellofemoral (PF) joint that can lead to instances of anterior knee pain and loss of ambulation. The impact of commonly implemented surgical procedures to correct for crouch gait can be quantified by evaluating stresses and underlying patellar bone strain during a gait cycle. The aims of this thesis work were (1) to analyze changes in PF mechanics and patellar bone strain between pre- and postoperative conditions; (2) to quantify the variability of predicted patellar strain due to different kinematic/loading profiles or patellar material properties; and (3) to quantify the impact of varying surgical decisions on predicted patellar strain. To accomplish these aims, five finite element (FE) models of the PF joint were developed with density-mapped material properties of patellar bone and appropriate pre- and postoperative kinematic/loading conditions obtained from experimental gait laboratory data. Patients underwent surgical procedures which included patellar advancement, distal femoral extension osteotomy, or a combination of both. These procedures were virtually simulated in the FE environment to predict stresses and strain across the PF joint. It was found that preoperative patellar bone strain and cartilage stresses were consistently higher with approximately two times the variability than their postoperative counterparts. In addition, the variability associated with different kinematic/loading conditions was higher than that of different PF geometries/material properties. A parametric evaluation of surgical decisions found that patellar position and, to a lesser extent, angle of wedge resection for the distal osteotomy influence predicted patellar strain values. Understanding baseline changes in PF loads and patellar strain due to surgical intervention may be used to inform a surgeon on treatment pathways which best alleviate strain in the patella thus reducing the risk of anterior knee pain and early onset osteoarthritis on a patient-specific basis.

DOI

10.18122/td/1551/boisestate

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