Total Hip Replacement

Notable Features of Model

• Based on in vivo patient data
• Six structures meshed simultaneously
• Inhomogeneous material properties assigned
• Contact surfaces between stem-cement and head-cup

Segmentation in ScanIP

Hip meshed with +ScanFE

Analysis

Procedure

• CT Scan (Siemens Somatom 16)
  • 42 year old male patient with THR
  • Exeter Hip 44 offset size 1: head 26 mm, cup 52 x 26 mm
  • In-plane Resolution: 0.77 mm x 0.77 mm
  • Slice-to-slice separation: 1 mm
  • Slice-to-slice separation: 1 mm
• Image Processing in ScanIP
  • Resampled: 2 mm x 2 mm x 2 mm
  • MAR (Metal Artefact Reduction) filter applied
  • Six masks segmented: (1) Pelvis, (2) Cement, (3) Cup, (4) Stem, (5) Cement mantle, (6) Proximal Femur
• FE Mesh Generation in ⁺ScanFE
  • Multi-part mesh - 6 structures meshed simultaneously
  • Contact surfaces between stem-cement and head-cup
  • Material properties based on parent Hounsfield numbers for bone (NB different expression applied for bone in cancellous and cortical range)
  • Smooth mesh of segmented structures
  • RP model generated based on FE surfaces
  • Time to mesh: 5 minutes
• Analysis
  • Low density mesh with boundary conditions and loads - includes muscle forces
  • Node sets of top of pelvis and distal part of femur defined in ⁺ScanFE
  • Response under static loading conditions
  • Sliding interface between cup-implant and implant-cement
  • Number of Degress of Freedom: 76,243
  • Solution Time (Intel 2.8 GHz): 3 hours

Special thanks to Stryker Europe, who funded this feasibility study.