Weight-bearing radiography in total hip replacement

Area of Science:

• Orthopedic Surgery
• Radiology
• Biomedical Engineering

Background:

• Accurate assessment of total hip replacement (THR) outcomes is crucial for patient recovery.
• Standard radiographic techniques can suffer from variations in patient positioning, affecting measurements.
• Quantifying leg length inequality (LLI) and component angles is essential for evaluating THR success.

Purpose of the Study:

• To present a standardized and reproducible radiographic technique for serial anteroposterior (AP) pelvic and hip imaging in THR patients.
• To establish the reliability of pelvic tilt and rotation measurements using a novel positioning aid.
• To demonstrate the utility of this method for assessing LLI, acetabular cup angle (AA), and prosthetic implant status.

Main Methods:

• Serial AP radiographs of the weight-bearing pelvis and hips were obtained from 29 THR patients.
• A specific positioning protocol included straight knees, a block between heels, and a U-shaped mercury level for horizontal reference.
• Pelvic tilt and rotation variations were analyzed across serial films to assess reproducibility.

Main Results:

• Average individual variation in pelvic tilt was 1 degree, and pelvic rotation was 3.5 degrees, indicating high reproducibility.
• The mercury level provided a reliable horizontal reference line on radiographs.
• The technique facilitates accurate pre- and postoperative estimation of LLI and AA.

Conclusions:

• This reproducible radiographic method enhances the reliability of pelvic and hip imaging in THR follow-up.
• The technique allows for precise assessment of component positioning and quantitative evaluation of radiolucency and bone resorption.
• This standardized approach improves the monitoring of THR outcomes and implant longevity.