Sagittal rotation determination
Inventors
Beck, Steffen • Schubert, Mario • Brack, Christian • POITZSCH, Luise
Assignees
Smith and Nephew Orthopaedics AG • Smith and Nephew Asia Pacific Pte Ltd • Smith and Nephew Inc
Publication Number
US-12310667-B2
Publication Date
2025-05-27
Expiration Date
2038-03-01
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Abstract
The invention relates to a method of determining the sagittal rotation of a patient's pelvis based on a standard anterior posterior X-ray-image with known image parameters and a calibration of the image, for example by using at least one King-Mark calibration object. The angle of the pelvic rotation is determined between a pelvic plane which is orthogonal to the midsagittal plane of the pelvis, and the image plane of the X-ray-image. Assuming the patient's position shown on the X-ray-image represents a standard neutral position, the X-ray-image plane can be used as a functional reference plane for further calculations, for example during hip-replacement surgery. The present invention further relates to a corresponding computer program and system.
Core Innovation
The invention provides a computer-implemented method for determining the sagittal rotation of a patient's pelvis based on a standard anterior-posterior X-ray image with known image parameters and a calibration of the image, for example by using at least one King-Mark calibration object. The angle of pelvic rotation is determined between a pelvic plane which is orthogonal to the midsagittal plane of the pelvis, and the image plane of the X-ray image. This enables the X-ray image plane to serve as a functional reference for further calculations, such as those needed during hip-replacement surgery.
A problem addressed by the invention is that prior art approaches for determining the pelvic tilt angle using only anterior-posterior X-ray images result in rough estimations, necessitating additional imaging procedures like lateral X-ray images or CT scans, which increase unwanted radiation exposure for the patient. The present invention allows for precisely determining the sagittal rotation of a patient's pelvis without imposing additional radiation exposure.
The invention acquires an anterior-posterior X-ray image of the pelvis and identifies at least two pelvic landmarks, either manually or automatically. A calibration plane is defined with respect to the pelvis so that landmarks can be projected into this plane, correcting distortion from the conical X-ray projection by determining a quasi-parallel projection. Distance measurements between the landmarks in both cranial-caudal and medial-lateral directions are taken within the calibration plane. A database containing corresponding statistical data from reference patients provides a correlation between these distances and sagittal rotation angle, allowing for the derivation of the patient’s specific sagittal rotation from a single image.
Claims Coverage
There are two independent claims describing the main inventive features of the invention: one for a computer-implemented method and one for a computer system.
Computer-implemented method for determining pelvic sagittal rotation using calibration and statistical correspondence
This feature comprises: - Determining, from a radiation distorted anterior-posterior image, the positions of a plurality of pelvic landmarks. - Determining a calibration plane with respect to the pelvis, perpendicular to the anterior-posterior direction. - Projecting the pelvic landmarks in parallel onto the calibration plane to generate a calibrated two-dimensional projection. - Determining a distance between two or more of the pelvic landmarks in the calibrated projection, in a direction perpendicular to the anterior-posterior direction. - Determining pelvic sagittal rotation based on a predetermined correspondence, where the correspondence comprises statistical data based on distances between pelvic landmarks within the calibration plane and sagittal rotation of reference patients.
Computer system for determining pelvic sagittal rotation using landmark calibration and reference data
This feature comprises: - A computer system configured to determine, from a radiation distorted anterior-posterior image, the position of each of a plurality of pelvic landmarks. - Determination of a calibration plane perpendicular to the anterior-posterior direction. - Parallel projection of pelvic landmarks onto the calibration plane to generate a calibrated projection. - Determining a distance between two or more of the landmarks in the calibrated projection, in a direction perpendicular to the anterior-posterior direction. - Determining the pelvic sagittal rotation based on predetermined correspondence that uses statistical data correlating landmark distances within the calibration plane and sagittal rotation of reference patients.
The inventive features focus on a method and system for determining pelvic sagittal rotation from a standard anterior-posterior image, using calibration, statistical correspondence from reference patient data, and projection of pelvic landmarks into a standardized calibration plane.
Stated Advantages
Precisely determines the sagittal rotation of a patient’s pelvis without imposing additional radiation exposure on the patient.
Documented Applications
Navigation software for hip surgery, including calculation of pelvic sagittal rotation for use as a reference basis in procedures such as hip replacement surgery.
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