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Strain analysis of human cadaver femora after cemented total hip arthroplasty (THA) has demonstrated a reduction in stress transfer along the proximal femur. The principal objective of this study was to determine the effect of the cementless application of a pressfit, porous-coated prosthesis on the strain experienced by the proximal femur. Using the photoelastic coating technique (PECT), five human cadaver specimens were subjected to strain analysis before and after cementless arthroplasty with a PCA total hip prosthesis. After total hip replacement, the strain magnitudes were reduced for all points along the medial border when the femur was subjected to loading conditions. A reduction of the level of strain experienced by the calcar ranged from 34.7 to 43.7% under loads ranging from 750 to 2000 N—a considerably smaller reduction than that reported by previous investigators. The region of the greater trochanter was the only area of the lateral surface to demonstrate an increase in strain magnitude after THA; the other, more distal points laterally experienced a reduced level of strain. Increases in strain magnitude, although not statistically significant, were detected along the anterior aspect of the femora. Significant decreases in strain were observed at the two more distal points posteriorly, with no significant change proximally. As this investigation is an evaluation only of the immediate effect of the design of the prosthesis in achieving a press fit, and the specimens are without the benefit of bony ingrowth, additional studies are necessary to determine the effect of biologic ingrowth on the distribution of strain within the proximal femur.
porous implants, stress transfer, total hip replacement, porous-coated prostheses, strain analysis, photoelastic coating technique, stress shielding
Medical student, Johns Hopkins University School of Medicine, Baltimore, MD
Research associate, Johns Hopkins University School of Medicine, Baltimore, MD
Associate professorchief, Johns Hopkins University School of MedicineGood Samaritan Hospital, Baltimore, MD