Impingement in total hip arthroplasty: A geometric model.

Area of Science:

• Orthopedic surgery
• Biomechanical engineering
• Medical device design

Background:

• Total hip arthroplasty (THA) is a highly successful surgery with excellent long-term survivorship.
• Early revision THA, particularly within the first year, is often necessitated by dislocation or subluxation.
• Identifying the causes of early THA failure, such as component impingement, is crucial for improving patient outcomes.

Purpose of the Study:

• To develop a predictive geometric model of bone and in situ total hip replacement.
• To investigate the relationship between acetabular cup positioning, component impingement, and dislocation risk during activities of daily living.
• To identify optimal acetabular cup orientations to minimize impingement and reduce early dislocation rates.

Main Methods:

• Development of a detailed geometric model of the hip bone and implanted components.
• Simulation of various acetabular cup positions (inclination and anteversion).
• Analysis of impingement occurrence and location during simulated daily activities.

Main Results:

• Anterior-superior component impingement correlates with posterior dislocation risk, reducible by increasing cup anteversion and inclination.
• Posterior-inferior impingement correlates with anterior dislocation risk, reducible by decreasing cup anteversion and inclination.
• A specific range of acetabular cup positioning (45° inclination/25° anteversion to 70° inclination/15°-20° anteversion) was identified as impingement-free.

Conclusions:

• Acetabular cup orientation significantly influences the risk of component impingement and subsequent dislocation after THA.
• Optimizing cup inclination and anteversion can mitigate impingement-related complications and reduce early revision rates.
• The identified impingement-free range provides valuable guidance for surgical planning to enhance THA stability.