Biomechanical study of screw-supported prosthesis in acetabular revision

Area of Science:

• Orthopedic Surgery
• Biomechanical Engineering
• Materials Science

Background:

• Acetabular bone defects present a significant challenge in revision total hip arthroplasty (THA).
• Screw-supported prostheses have been utilized for severe acetabular defects, yielding positive early clinical outcomes.
• A critical failure mode observed was the loosening of the screw-cup connection.

Purpose of the Study:

• To investigate the mechanical characteristics and identify weak points of a screw-supported prosthesis system.
• To analyze the failure mechanism of the screw-cup connection under physiological loading conditions.
• To propose and evaluate strategies for improving the prosthesis system's mechanical integrity.

Main Methods:

• Finite element analysis (FEA) was employed to model the prosthesis and simulate stress distribution under gait loading.
• FEA focused on identifying stress concentrations at the screw-cup interface.
• Mechanical compression tests were conducted to validate FEA findings and determine failure loads.

Main Results:

• FEA revealed the posterior iliac and pubic locking connections as critical weak points susceptible to fatigue failure.
• Mechanical testing confirmed failure of the locking connection at loads between 2,500 and 3,000 N.
• An improved sleeve connection design demonstrated enhanced strength and reduced the risk of failure.

Conclusions:

• Screw-supported prostheses offer potential for managing severe acetabular defects in revision THA.
• The screw-cup connection remains a vulnerable component requiring attention.
• Enhanced connection designs, such as sleeve connections, and adjunctive bone grafting are recommended to mitigate failure risks and improve long-term outcomes.