Prevalence of impingement in explanted Charnley acetabular components

Area of Science:

• Orthopedic surgery
• Biomedical engineering
• Materials science

Background:

• Acetabular loosening is a major complication in total hip arthroplasty.
• Femoral neck impingement against the acetabular rim is a suspected contributor to loosening.
• Limited data exists on the clinical prevalence and impact of wear and neck diameter on impingement.

Purpose of the Study:

• To investigate the clinical prevalence of femoral neck impingement in explanted Charnley prostheses.
• To assess the relationship between linear wear, femoral neck diameter, and impingement.
• To evaluate the effect of reduced diameter femoral necks on impingement probability.

Main Methods:

• Analysis of 74 explanted Charnley hip prostheses.
• Examination of sockets for evidence of impingement.
• Logistic regression analysis to assess the association between penetration depth, neck diameter, and impingement.
• Comparison of impingement probability between standard and reduced diameter femoral necks.

Main Results:

• A significant positive association was found between penetration depth and impingement (P = 0.0004).
• Femoral neck diameter did not influence the association between penetration depth and impingement.
• Reduced diameter femoral necks shifted the 50% impingement probability to approximately 2 mm of penetration, compared to 0 mm for standard necks.

Conclusions:

• Femoral neck impingement is strongly associated with wear penetration.
• Reduced diameter femoral necks appear to be an effective solution for mitigating impingement.
• Further long-term survival analysis is needed to confirm the clinical significance of reduced impingement in preventing loosening.