Bone-on-bone versus hardware impingement in total hips: a biomechanical study.

Area of Science:

• Orthopedic Surgery
• Biomechanical Engineering
• Materials Science

Background:

• Dislocation is a significant complication in total hip arthroplasty (THA).
• Component impingement, particularly between the femoral neck and acetabular cup, is a primary cause of dislocation.
• Advancements in bearing technology have led to larger femoral head diameters, potentially altering impingement mechanisms.

Purpose of the Study:

• To biomechanically compare bone-on-bone versus component-on-component impingement in THA.
• To investigate the influence of femoral head diameter on impingement-related stress and dislocation resistance.
• To evaluate the impact of impingement type on implant damage and stability.

Main Methods:

• Finite element (FE) analysis was employed to simulate impingement scenarios.
• Parametric investigation of head diameter effects on local biomechanics.
• Analysis of various dislocation-prone patient motion challenges, including squatting.

Main Results:

• Squatting consistently induced bone-on-bone impingement, unlike other motions.
• Hardware impingement generated greater implant stress concentrations than bony impingement across all head sizes.
• Bony impingement demonstrated significantly higher dislocation resistance compared to hardware impingement.

Conclusions:

• Component impingement remains a risk even with larger heads, especially with suboptimal cup positioning.
• Hardware impingement is more prone to dislocation and implant damage than bony impingement.
• Understanding impingement modes is crucial for improving THA safety and longevity.