Date Approved

8-19-2025

Graduate Degree Type

Thesis

Degree Name

Engineering (M.S.E.)

Degree Program

School of Engineering

First Advisor

Wendy Reffeor

Second Advisor

Yunju Lee

Third Advisor

Sung-Hwan Joo

Academic Year

2024/2025

Abstract

Hip fractures are a significant public health issue as they are a commonly encountered problem and have a high rate of mortality. The fracture of the femoral neck is difficult to treat due to the geometry of the proximal femur and the weight-bearing capacity that the structure must comply with. Internal fixation of the femoral neck is often accomplished with three screws inserted along the axis of the femoral neck. The optimal configuration and number of these screws is not agreed upon in the literature. The purpose of this study was to conduct a pilot investigation on the biomechanical performance of a novel, divergent triangle screw construct for internal fixation of femoral neck fractures using experimental methods and finite element analysis (FEA) in comparison to the standard inverted triangle construct. For the experimental portion, composite femur models were osteotomized using a custom-made cutting jig to simulate a Pauwels angle of 50 degrees, and the distal portion of the femur was removed. Specimens were placed at 20 degrees of adduction to simulate one-legged stance in the MTS material testing machine. Four specimens from each group were cyclically loaded for 10,000 cycles at 1 Hz with a force of 1000 N. Additionally, four specimens from each group were loaded cyclically at 1 Hz, then subsequently subjected to 10,000 cycles at 4.3 kN. All specimens surviving cyclic loading were loaded till failure. FEA was used to quantify the stress distribution and displacement of the divergent and inverted triangle constructs, providing an additional insight into their biomechanical stability. The experimental results showed that the inverted triangle had lower displacements during cyclic loading and on average a higher failure load, suggesting an advantage in construct stability and load bearing, however, due to a small sample size there was no statistical difference between the two groups. The FEA model revealed comparable equivalent stress distribution and deformation between the two fixation constructs, with the divergent triangle showing advantages in cancellous bone stress distribution but higher screw stresses, while the inverted triangle demonstrated reduced fracture surface displacement. Both constructs provided sufficient stability to support primary bone healing.

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