In vitro evaluation of acetabular host bone coverage and cemented cup stability in total hip arthroplasty

The percentage of coverage by host bone required to achieve adequate initial cement cup fixation has not yet been determined. Therefore, in this study, we evaluated the relationship between the acetabular bone coverage and the initial cup fixation strength.

Three different defect models were used as minimum fixation models in this study along with two reconstructed models (a cup center-edge angles -10°, -5°, 0°, the bulk cement model, and the bulk bone model). Five each of models were prepared for testing. A cyclic loading test was performed to assess the initial stability of the cup based on the vertical displacement of the femoral head. All models were subjected to cyclic load testing for one million cycles.

Under cyclic loading conditions, vertical displacement of the femoral head gradually increased as the cup center-edge angle changed from 0° to -10°, with vertical displacement at the end of the test for each model being greatest at the cup center-edge angle of -10° and least at the cup center-edge angle 0°. A statistical significance was observed in all comparisons among the individual models. (P < 0.05).

This study provides valuable insights into the significance of acetabular host bone coverage on the initial stability of cemented cups. It supports the clinical practice of aiming for host bone coverage with a cup center-edge angle >0° to ensure long-term stability in case of primary total hip arthroplasty cases.