Postmortem Analysis of Osseointegration in Cementless Acetabular Components After Total Hip Arthroplasty: A Multimodal Study.

Abstract

Press-fit acetabular components achieve long-term fixation through osseointegration, yet the extent of bone ingrowth necessary for durable stability in well-functioning implants remains unclear. Postmortem retrievals provide a unique opportunity to directly assess the bone-cup interface in clinically successful total hip arthroplasties. This study evaluated osseointegration and biomechanical fixation strength in deceased-donor acetabular components to better define the characteristics of stable long-term fixation. Cadaver pelvis specimens containing uncemented total hip arthroplasties from a single institution were evaluated. There were 29 acetabular components that underwent axial pull-out testing using a universal testing machine. A total of seven of these were additionally processed for histologic evaluation, including dehydration, acrylic embedding, thin-sectioning, staining, and digital imaging. Osseointegration was quantified by bone area fraction occupancy (%BAFO), representing the proportion of bone occupying the porous thread spaces of the cup. All 29 specimens failed through fracture of the ilium rather than at the bone-cup interface, indicating that the mechanical integrity of the osseointegrated construct exceeded that of the surrounding bone under axial tension. Among the seven histologically analyzed components, %BAFO ranged from 4.2 to 27.0% (mean 15.1%), despite all implants being clinically stable at the time of death. There were no significant linear correlations observed between %BAFO and time implanted, fracture load, or body mass index. A significant quadratic relationship between %BAFO and age was identified, peaking near 81 years CONCLUSIONS: Cementless acetabular components exhibited strong fixation despite modest osseointegration, with failure occurring through host bone on axial testing. Durable biological fixation appears achievable with limited, but mechanically favorable bone ingrowth.