Orthopaedic Research Laboratory Alumni Council

Alumni Laboratories

Visit the research laboratories of the alumni of Dr. Woo.

Board of Directors

Richard Debski, Ph.D. President
Caroline Wang, M.S. Secretary
Jamie Pfaeffle, M.D., Ph.D. Treasurer
Doug Boardman, M.D.
Thay Lee, Ph.D.
Patrick McMahon, M.D.
Karen Ohland, M.S.
Christos Papgeorgiou, M.D.
Masataka Sakane, M.D.
Sven Scheffler, M.D.
Jennifer Wayne, Ph.D.

2003 Erin McGurk Grant Recipient

Susan Moore
University of Pittsburgh

Development of Subject-Specific Finite Element Models


Susan in the Lab

Acknowledgement

I would like to extend my gratitude and my appreciation to Erin McGurk. Without her generosity, this experience would not have been possible. The grant money provided by Ms. McGurk has greatly enhanced my experience as a graduate student researcher by providing me with the initial training necessary to start bridging the gap between experimental and computation data. I would also like to thank Dr. Jeffrey A. Weiss, his students, and staff for their willingness to instruct and guide me during my visit.

Final Report

The glenohumeral joint is the most commonly dislocated diarthrodial joint in the body with 80% of the dislocations occurring in the anterior direction.   Redislocation rates are as high as 12 and 23% following open and arthroscopic surgical repairs, respectively and return to normal function remains inadequate. Unsatisfactory results have been reported in 20-25% of patients who suffer from pain, chronic instability, rotator cuff injury, joint stiffness, and osteoarthritis.

The glenohumeral capsule is a complex construct with multiple regions. Previously, these regions have been treated as uniaxial elements. These studies helped to develop clinical exams for anterior instability, performed with the arm abducted and externally rotated, that generally assess which regions of the capsule are not functioning as they would in a normal joint.   Recent experimental data has suggested that substantial interactions at the interface of the capsular regions exist as their strain and force distributions are not uniaxial. The regions that interact with one another and the location of these interactions within the region remain largely unknown, making clinical evaluation impossible. Recently, we modeled the anterior and posterior bands of the inferior glenohumal ligament and the axillary pouch using 3D finite element methods. Our results indicated that in order to predict accurate magnitudes, directions, and locations of strains and stresses within the capsular regions, all regions of the glenohumeral capsule should be modeled.  

We propose using a combined experimental and computational approach whereby one subject-specific finite element model of all regions of the normal glenohumeral capsule will be constructed and validated using experimental data. To understand the interactions of the regions, the validated model will then be used to determine the magnitude, direction, and location of the strains and stresses in and at the interface of the capsular regions during a simulated clinical exam. This study will represent the final aspect of my PhD dissertation work. The overall goal of this study is to identify those capsular regions that interact with one another and the location of these interactions within the region during a simulated clinical exam for anterior instability in a normal joint. The overall hypothesis is that substantial interactions occur at the interface of all adjacent capsular regions near the glenoid, where the capsular regions are frequently ruptured.

The previously described finite element models of select capsular regions were generated in collaboration with Dr. Jeffrey A. Weiss at the University of Utah. Therefore, in order to advance our modeling expertise here at the University of Pittsburgh, it was necessary to travel Dr. Weiss' laboratories.   Dr. Weiss gave instructional meetings regarding the appropriate manner in which to both construct and validate finite element models. Dr. Weiss demonstrated the methodologies his laboratory has mastered on how to accurately segment bony geometry from CT datasets, generate quality meshes, select element type and constitutive relation, and perform finite element analyses using NIKE3D software. Furthermore, discussions were held regarding how to perform and evaluate sensitivity analyses for our input parameters.  

Since leaving Dr. Weiss' laboratories, we have acquired all of the necessary software and have purchased a high powered PC for the purpose of performing all the analyses. To date, I have successfully segmented several previously existed CT datasets to obtain the bony, capsular, and articular cartilage geometry.  Moreover, I have begun performing simple analyses with the meshing and finite element analysis software packages. Once the subject-specific finite element model is constructed and validated, the data obtained in this study can be utilized to improve clinical exams that assess normal joint function.  A better understanding of normal joint function is a necessary step to improve surgical repairs. In the future, the methodology developed can also be utilized to develop multiple subject-specific models that describe the normal, injured, and surgically repaired populations.   The state-of-the-art methodologies developed can also be used to assess the function of the other capsular and ligamentous structures such as the hip.


Susan with her advisor Dr. Rich Debski

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