Accuracy and reliability of different methods to evaluate the acetabular cup version from plain radiographs

Area of Science:

• Orthopedic surgery
• Radiology
• Medical imaging analysis

Background:

• Accurate assessment of acetabular cup version is crucial for successful hip arthroplasty.
• Plain radiographs are commonly used but their reliability in determining cup version can vary.
• Established methods for radiographic evaluation may have limitations in accuracy and reproducibility.

Purpose of the Study:

• To compare the accuracy and reliability of different radiographic methods for evaluating metallic acetabular cup version.
• To identify the most reliable technique for determining acetabular cup anteversion and retroversion from plain radiographs.
• To assess inter- and intra-observer variability associated with different evaluation methods.

Main Methods:

• A phantom model with a metallic acetabular cup was used, with defined ante- and retroversion angles.
• Conventional anterior-posterior radiographs were obtained.
• Five independent examiners applied four different established methods to derive cup version angles from the radiographs.

Main Results:

• A modified technique of Pettersson et al. demonstrated the highest accuracy in determining radiographic cup version.
• The modified Pettersson technique also yielded the highest intra- and inter-observer reliability.
• This modified method enhances the applicability of radiographic evaluation for metal-backed acetabular cups.

Conclusions:

• The modified Pettersson technique offers a more reliable radiographic method for assessing acetabular cup version compared to the original method.
• While valuable, radiographic evaluation of cup position should not be overemphasized in clinical practice.
• Computed tomography (CT) remains essential for critical cases requiring precise determination of acetabular cup positioning.