Femoral component loosening in hip arthroplasty Cadaver study of subsidence and hoop strain

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Abstract
To aid in understanding loosening following cemented total hip arthroplasty, we conducted a cadaver study of the proximal femur with implanted cobalt-chromium and titanium femoral components of recent design, loaded through the head of the prosthesis. Stem subsidence and strain in the proximal femur were measured. After proximal support of the implant collar was removed, we found that cobalt-chromium implants had a greater tendency to subside than titanium implants. Subsidence of a femoral component within the cement mantle caused an increase in tensile hoop strain measured in the proximal cortex. When implants were loaded until failure of the cortex, a direct relationship between increase in subsidence and increase in cortical hoop strain was demonstrated. Our data show that implants that resist subsidence into the cement mantle tend to decrease hoop strains in the proximal femoral cortex.