The relationship between femoral periprosthetic cortical bone geometry and porosity after total hip arthroplasty

Abstract

Stress shielding from the presence of a femoral component can cause adverse changes to cortical bone geometry and porosity leading to increased fracture risk in the periprosthetic cortical bone. The objectives of this study were to determine if porosity increased after total hip arthroplasty along the principal axes, and to determine if a relationship existed between cortical bone porosity and geometry. Ten postmortem donors allowed comparisons of implanted femurs to the contralateral nonimplanted femurs. Transverse cross-sections of the femur were taken at 25, 45, 65, and 85% along the length of the femoral component. The cortical bone principal axes' location (degrees) and rigidity values (mm(4)) were based on cortical bone geometry by using digitized images of the cortical bone cross-sections. Percent porosity was measured along the principal axes using backscatter electron imaging. Cortical bone porosity increased in the more distal sections of the implanted femurs by approximately 3%, but did not preferentially increase along a particular principal axis. No correlation was found between changes in porosity and rigidity values. In conclusion, the porosity increases in the implanted femurs may have regionally reduced cortical bone strength. The locations of higher porosity did not appear related to the cortical bone geometry.

Design features of implants for direct skeletal attachment of limb prostheses

“…The longevity of the bone‐device bond is also an important issue considering the relatively short hosting bone of the residuum and the high loads associated with operating limb prostheses . An additional concern for longevity of the bone‐device bond is that after replacement surgery, the porosity of the cortical bone hosting the femur implant increases compared to the ipsilateral bone, potentially reducing cortical bone strength …”

New method of fixation of in-bone implanted prosthesis

“…This effect, called stress shielding, increases the porosity of the cortical bone that hosts the implant, relative to the ipsilateral bone [15]. The outcomes of stress shielding are reduction in hosting bone strength [16–17] and cortical thinning in the distal zones, which increases with time [18]. The weaking and thinning increase the risk of failure, especially among young patients who are involved in more active locomotion [19–20].…”

Reorganization of the femoral cortex due to age‐, sex‐, and endoprosthetic‐related effects emphasized by osteonal dimensions and remodeling

“…Although optimization of implant materials and designs have led to considerable improvement of implantation periods, alterations of periprosthetic bone tissue remain in most instances the main reason for prosthesis malfunction 19–22. Besides tissue reactions to implant material and/or wear debris, the new nonphysiological load by the implant is stated as a major reason 22, 24–26. The implanted prostheses stem takes off a part of the stress that is naturally triggered by physical routine load on the proximal femur.…”