Acetabular strains produced by oversized press fit cups

Area of Science:

• Orthopedic surgery
• Biomechanical engineering
• Materials science

Background:

• Acetabular component fixation is crucial for total hip arthroplasty success.
• Understanding acetabular deformation during press-fit insertion is vital for implant stability and patient safety.
• Current oversizing strategies may not account for anatomical variations in acetabular size.

Purpose of the Study:

• To quantify acetabular deformation and strain during press-fit insertion of various acetabular component sizes.
• To investigate the relationship between acetabular size, component oversizing, and resulting biomechanical changes.
• To establish evidence-based oversizing guidelines to optimize press-fit stability and reduce complication risks.

Main Methods:

• Utilized an axisymmetric finite element model to simulate press-fit insertion.
• Calculated changes in acetabular volume for 1- to 3-mm oversized cups in acetabuli ranging from 40 to 80 mm.
• Analyzed maximum acetabular strain distribution, particularly at the cup periphery.

Main Results:

• Acetabular strain is highest at the cup periphery, contributing to press-fit stability.
• Using the same oversizing results in higher maximum strain in smaller acetabula compared to larger ones.
• A constant oversizing increment increases pelvic fracture risk in small acetabula and risks inadequate stability in large acetabula.

Conclusions:

• Acetabular deformation and strain are size-dependent, necessitating tailored oversizing strategies.
• Recommended oversizing: 1 mm for cups <52 mm, 2 mm for 52-76 mm, and 3 mm for cups >76 mm.
• Adjusting oversizing based on acetabular diameter can enhance implant fixation and mitigate surgical risks.