Development of testing systems to analyze strength of hormonally treated ligaments and stability of fixation devices

This thesis presents the results of two distinct research projects. The first project involved an investigation into the causes of injuries to anterior cruciate ligaments (ACL), while the second study dealt with the methods for treating hip fractures. Both studies involved developing a methodology for experimental testing, which included the design of the test apparatus, the test parameters, and the data acquisition system. The methodologies were designed to accurately simulate the physiological behavior of bones and ligaments.

In the first project, the objective was to develop a method to analyze whether estrogen had a detrimental effect on the strength of the ACL. This would help to explain why female athletes are 3 to 10 times more likely to injure their ACL than their male counterparts. Initially, strain rates of 117%/s, 273%/s, and 490%/s were utilized to determine the strength of the ACL. It was determined that the strength tended to decrease with irrcreasing strain rate; however, only strain rates of 117%/s and 490%/s showed a statistical significance in strength reduction of 28.8%. More importantly, a comparison of an estrogen treated group to a control group showed a statistically significant decrease of 37.7% in the strength of the ACL. In addition, the study showed that the implants used to treat the specimens with estrogen had no significant effect on the properties of the ACL. Furthermore, the modes of ACL failure were consistent with the cases observed in clinical studies. That is, all specimens in the strain rate study underwent ligamentous tears and/or bone-ligament interface tears, as did 83% of the estrogen controlled specimens.

The second project involved the development of the methodology to quantify the stability of fixation devices used to treat reverse obliquity intertrochanteric hip fractures. Determination of the optimal implant design to treat these types of fractures might help to decrease the high rate of unsuccessful recovery typically seen with these types of injuries. The objective of this research was to design a test apparatus and procedure to simulate the physiological behavior of human femurs. In addition, a data acquisition system for recording displacements and strains experienced by the femur was developed.