Phantom validation of a novel RSA-based impingement metric to assess component-on-component impingement risk

Area of Science:

• Orthopedic Surgery
• Biomedical Engineering
• Radiology

Background:

• Component-on-component impingement is a risk in total hip arthroplasty (THA), potentially causing dislocation.
• Current assessment methods (radiography, FEA, cadaver studies) lack precision for in vivo impingement measurement.
• A need exists for more accurate research tools to quantify impingement in THA.

Purpose of the Study:

• To validate a novel Roentgen Stereophotogrammetric Analysis (RSA)-based metric for measuring component-on-component impingement in vivo.
• To establish a precise and repeatable method for assessing impingement risk in THA patients.

Main Methods:

• A phantom model of a metal-on-polyethylene THA system was used for validation.
• Standard weight-bearing RSA examinations were performed on the phantom.
• The phantom was positioned in 10 impinged and 1 neutral position, with double exposure radiographs taken for repeatability assessment.
• The closest distance between the femoral head skirt and acetabular cup liner was measured.

Main Results:

• Distances in impinged positions ranged from 0.05 to 1.03 mm (average 0.67 mm); the neutral position measured 11.02 mm.
• Excellent repeatability was demonstrated with a standard deviation of 0.03 mm.
• A validated RSA-based metric for in vivo hip impingement was established.

Conclusions:

• The novel RSA-based metric provides precise in vivo measurement of component-on-component impingement in THA.
• A 1 mm threshold may indicate increased impingement risk, guiding clinical assessment.
• This metric shows promise for future clinical studies on THA impingement and dislocation prevention.