Sagittal rotation determination

A system for determining a sagittal rotation of a patient's pelvis, comprising:

• a computer configured to:
• acquire image data describing a two-dimensional X-ray-image of the patient's pelvis made in an anterior-posterior direction;
• determine, based on the image data, position data describing the position of a plurality of pelvic landmarks reproduced in or derivable from the two-dimensional X-ray-image;
• acquire calibration data describing the position of a calibration plane with respect to the patient's pelvis, the calibration plane being perpendicular to the anterior-posterior direction;
• determine, based on the position data and the calibration data, calibrated projection data describing a two-dimensional projection representing the plurality of pelvic landmarks of the actual patient's pelvis being projected into the calibration plane in the anterior-posterior direction;
• acquire distance data describing at least one of a medial-lateral distance and a cranial-caudal distance between at least one first pelvic landmark and at least one second pelvic landmark in the calibrated two-dimensional projection;
• acquire, from a database, regression data describing a linear correspondence between at least one of said medial-lateral distances and cranial-caudal distances, and a pelvic sagittal rotation;
• and
• determine, based on the distance data and the regression data, the sagittal rotation of the patient's pelvis.

A non-transitory computer readable storage medium storing a computer program for determining a sagittal rotation of a patient's pelvis which, when running on a computer or loaded onto the computer, causes the computer to:

• acquire image data describing a two-dimensional X-ray-image of the patient's pelvis made in an anterior-posterior direction;
• determine, based on the image data, position data describing the position of a plurality of pelvic landmarks reproduced in or derivable from the two-dimensional X-ray-image;
• acquire calibration data describing the position of a calibration plane with respect to the patient's pelvis, the calibration plane being perpendicular to the anterior-posterior direction;
• determine, based on the position data and the calibration data, calibrated projection data describing a two-dimensional projection representing the plurality of pelvic landmarks of the patient's pelvis being projected into the calibration plane in the anterior-posterior direction;
• acquire distance data describing at least one of a medial-lateral distance and a cranial-caudal distance between at least one first pelvic landmark and at least one second pelvic landmark in the calibrated two-dimensional projection;
• acquire, from a database, regression data describing a linear correspondence between at least one of said medial-lateral distances and cranial-caudal distances, and a pelvic sagittal rotation;
• and
• determine, based on the distance data and the regression data, the sagittal rotation of the patient's pelvis.