Dislocation after total hip arthroplasty: implant design and orientation

Area of Science:

• Orthopedic surgery
• Biomedical engineering
• Implant design

Background:

• Total hip arthroplasty (THA) relies on implant design and positioning for stability and dislocation prevention.
• Modular implants offer versatility but can lead to intra-articular prosthetic impingement, causing limited motion, wear, osteolysis, and instability.
• Understanding impingement mechanisms is key to improving THA outcomes.

Purpose of the Study:

• To identify key factors in implant design and positioning that minimize intra-articular impingement after total hip arthroplasty.
• To provide evidence-based recommendations for optimizing implant selection and surgical placement to reduce complications.

Main Methods:

• Review of implant design features contributing to impingement.
• Analysis of biomechanical principles governing prosthetic joint motion.
• Computer modeling to determine optimal acetabular cup positioning (abduction and anteversion).

Main Results:

• Avoiding skirted heads and matching 22-mm heads with appropriate acetabular components are recommended.
• Maximizing the head-to-neck ratio and utilizing chamfered liners and trapezoidal neck cross-sections can reduce impingement.
• Optimal cup position is 45-55 degrees abduction, with 10-20 degrees anteversion for both stem and cup when abduction is <55 degrees.

Conclusions:

• Specific implant design choices (e.g., head size, neck geometry, liner type) significantly impact impingement risk.
• Precise control of acetabular cup positioning (abduction and anteversion) is critical for minimizing impingement and dislocation.
• These findings offer guidance for surgeons to enhance stability and function in total hip arthroplasty patients.