Fiber Optic Strain Gage Verification and Polyethylene Hip Liner Testing

Abstract

To optimize stability in total hip arthroplasty, the use of larger femoral heads necessitates a polyethylene liner of reduced thickness. An understanding of the mechanical properties, particularly resistance to fatigue failure, of highly-crosslinked polyethylene is critical to determine the optimal parameters for clinical use. The primary purposes of this study were to characterize the X3^TM highly cross-linked polyethylene (HCLPE) liner peripheral face strain field in multiple orthopaedic acetabular shell constructs under physiological loading and to evaluate the usefulness of fiber optic strain gages in this type of biomedical application. The first phase of this study involved measuring X3 HCLPE material properties in tension and compression using uniaxial fiber optic strain gages and resistance based uniaxial and multi-axial (rosette) strain gages to gain greater insight into the complexities and limitations of the use of fiber optic strain gages with X3 HCLPE. In the second phase, physical testing was used to evaluate the effect of HCLPE thickness on the hoop strain field of liner samples of three different thicknesses at three inclination angles and three head offsets that simulate potential in vivo clinical scenarios occurring in hip replacement. The results from these studies will be presented in this paper.