Preliminary study of bipolar hip prosthesis - influence of acetabular bone interactions on bone morphology

Periprosthetic bone changes following hip arthroplasty are yet to be completely described. The material consisted of imagistic records (X-ray films, CT and MRI scans) and of acetabular bone tissue sampled from 14 cases with femoral head prosthesis and revision of the prosthesis fixed and decalcified in Duboscq-Brazil solution and stained with Hematoxylin and Eosin, trichrome van Gieson and trichrome Masson. Acetabular bone is home of a great variety of morphological changes that can be divided in degenerative and regenerative changes seen in both compact and trabecular components but only inside the maximal pressure area of the acetabular roof. Our preliminary morphological study revealed the existence of an adaptation effort to the mechanical stress materialized through a dynamic process of bone remodeling in the maximal pressure area.

Morphological experimental study of bone stress at the interface acetabular bone/prosthetic cup in the bipolar hip prosthesis

By calculating the tension and distortion of the elements composing the bipolar prosthesis under extreme conditions encountered in real life using a special post-processing program, we established the variation curves of the contact pressure at the hip bone-cup, armor-cup and cup-femoral head interface. By comparing the data obtained from all the examined cases, important conclusions were drawn regarding the influence of tension and pressure distribution on the structural integrity and biomechanics of the prosthesis, as well as the acetabular wear and tear, in order to assess its reliability. The experimentally determined tension and distortion status at the acetabular bone-metal armour interface, lead to the wear and tear phenomenon, which can be explained by three mechanisms and theories incompletely reflecting the overall process. The histopathologic study of the acetabular bone tissue using FEM (finite elements method) on surgically removed specimens will probably lead to the identification of a series of factors that could reduce the rate of the wear and tear process.