Modularity of a new cementless acetabular revision cup system based on research of the anatomic variability of the pelvis

There is a growing need for specific revision implants to meet the increasing occurrence of failed total hip arthroplasties displaying massive deficiencies in acetabular bone stock. The developed acetabular revision cup presented in this study is aimed at individual patient solutions using a multi-axial and angular stable fixation peg as well as a modular adaptable lateral flap. To obtain an optimum implant design, a database of computed tomography scans of 69 patients' pelves was collected and computational reconstruction of the pelvic bone morphology was conducted. Based on the anatomic measurements, the direction of the fixation peg of the revision cup was evaluated using custom software and the geometry of the lateral flaps was evaluated using rapid prototyping models of the pelvis. Furthermore, we conducted preclinical examinations of the acetabular revision system with regard to the safety of the angular stable locking mechanism of the fixation pegs and the mechanical stability of the lateral flap. The dynamic tests showed no mechanical failure of the fixation peg and its angular stable connection using a cyclic maximum torque of 24.5 Nm for one million cycles. The lateral flap and its fixation showed no mechanical failure using a cyclic maximum torque of 28.4 Nm for two million cycles. In conclusion, a promising solution to satisfy the requirements for adequate anatomical fit in a wide range of acetabular defects is presented.