Dynamic Hip Screw Side-Plate Configurations Minimally Influence Predicted Failure Loads by CT-Based Finite Element Analysis

Student Researcher:
Nicholas Yee

Supervisor / Principle Investigator:
Dr. Steven K. Boyd

Additional Authors:
Andrew Michalski

MD Class of 2021

ABSTRACT

Femoral neck fractures are common and present a high one-year mortality rate in older adults. Many adults over 50 years old have high hip fractures risks, even without an osteoporosis diagnosis. Current fracture reduction surgical practices are based on evidence to implant dynamic hip screws (DHS) with either two- or four-hole side-plates. There exist minimal computational studies in the literature examining the differences in predicted failure loads between different DHS side-plates. This project examined the potential mechanical compressional strength offered by the DHS with two- and four-hole side-plates.

Eight cadaveric left femurs were scanned using clinical computed tomography (CT; Revolution CT, GE Healthcare, USA) and resampled into 1 mm voxels. Simulated DHS with two- and four-hole side-plates (DePuy Synthes, USA) were manually aligned to each femur. In order to comply with current surgical practices, the lag screw was placed within 25 mm of the apex of the femoral head. A single limb stance finite element compression was performed to predict fracture regions using Mohr-Coulomb failure theory. Garden fracture classification were qualitatively identified. Statistical analysis used a paired t-test (alpha criterion = 0.05).

Under a simulated compression, the DHS redistributes the load from the femoral neck to the head and diaphysis. Both DHS configurations resolved a Garden type 1 fracture compared to the femurs without the DHS. They tolerated higher predicted failure loads (p<0.01). Between the DHS side-plate configurations, no differences in the predicted failure loads were observed. However, the DHS with four-hole side-plates exhibited more stress redistribution towards the femoral head and diaphysis. Despite this difference, both DHS models tolerated similar failure loads, which suggest that the side-plates offered minimal additional compressional strength. Future efforts will be directed towards computationally assessing mechanical benefits of different surgical strategies based on bone properties of the femoral head, neck, and diaphysis.

 
 

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