Related Experiment Video
Updated: Aug 18, 2026
In Vivo Quantification of Hip Arthrokinematics during Dynamic Weight-bearing Activities using Dual Fluoroscopy
Published on: July 2, 2021
Standard orientation of the pelvis: validation on a model and ten patients
L Olivecrona1, P Aspelin, L Weidenhielm
1Department of Radiology, Karolinska University Hospital Solna, Stockholm, Sweden. charlotta.olivecrona@karolinska.se
Purpose:
To validate an image post-processing method for re-orienting the pelvis in CT volumes to a standardized orientation in a model and in 10 patients.
Material And Methods:
Twenty-four CT volumes of a pelvic model and 10 pairs of postoperative total hip arthroplasty (THA) patient CT scans were rotated to a defined pelvic standard orientation and the rotation was recorded. For precision, a test-retest procedure was used. For accuracy, three exactly represented coordinate points were used. For clinical application, the standard orientation was used for calculating the direction of acetabular cup migration from a previous model study.
Results:
Precision of pelvic standard orientation, calculated as maximal directional error, was better than 1 degrees in the model study and better than 1.5 degrees in the patient study. Accuracy, expressed as angle between ideal and measured coordinate axes, was 0.1 degrees for x, y, z axes. No measurable systematic errors were found. When applied to acetabular cup migration in the model, standardization of pelvic orientation had no significant effect on the measurements.
Conclusion:
Reorienting the pelvis during image post-processing was shown to be accurate. It enables measurements relative to the pelvis and minimizes the dependency of patient positioning.
