Acetabular Inclination as a Function of Hip Center of Rotation While Obtaining Inferior Screw Fixation: A Simulation Model

Abstract

AbstractClinical success of cementless total hip arthroplasty is predicated on proper component position, restoration of biomechanics, and implantation of a mechanically stable construct. In the setting of acetabular bone loss, this target is more difficult to achieve, and elevation of the center of hip rotation may compromise the ability to obtain inferior screw fixation. We used the LifeMOD virtual human modeling simulation software (Smith & Nephew, San Clemente, CA) to determine the relationship between cup inclination and center of rotation position while maintaining the ability to obtain screw fixation within the superior pubic ramus. This simulation demonstrated that for every 5 mm of hip center elevation, cup inclination increased by 5.67 degrees. Based on this data, we recommend the use of a porous acetabular component when the hip center is elevated. This acetabular reconstruction allows for cementation of a liner to address the vertical nature of the cup needed to obtain inferior screw fixation within the superior pubic ramus.