Biomechanical study of screw-supported prosthesis in acetabular revision

Acetabular bone defects pose a common challenge in revision total hip arthroplasty (THA). Our team has applied screw-supported prostheses to the revision of severe acetabular defects and achieved good early clinical results. However, in one of our cases, loosening of the screw-cup connection occurred five months after surgery. Therefore, we investigated the mechanical characteristics and weak points of this prosthesis system through finite element analysis (FEA) and mechanical testing, and proposed improvement strategies.

A screw-supported prosthesis used in clinical practice was modelled, and FEA was performed to obtain its displacement and von Mises stress distribution under gait loading. Emphasis was placed on the stresses at the screw-cup connection to analyze the failure mechanism. Mechanical compression tests were subsequently performed on the prosthesis, and the failure mode of the prosthesis verified the results of the FEA.

FEA identified the posterior iliac and pubic locking connections as weak points prone to fatigue failure. Mechanical tests confirmed that the locking connection failed under 2,500 to 3,000 N loads. The improved sleeve connection enhanced connection strength and reduced failure risk.

The screw-supported prosthesis shows potential for severe acetabular defects, but the screw-cup connection remains a vulnerable site. Enhanced connection designs (e.g. sleeve connection) and bone grafting effectively mitigate failure risk.