Method for aligning an acetabular cup

A method for aligning an acetabular cup insertion instrument comprising:

• taking a pre-operative anterior/posterior view digital x-ray image and a lateral view pre-operative digital x-ray image of the pelvis of a patient;
• determining a desired acetabular cup abduction and anteversion angle;
• identifying at least three anatomic points on the digital anterior/posterior digital x-ray image and at least two points on the pre-operative lateral digital x-ray image;
• calculating the lengths and angles between each of the points on both the anterior/posterior pre-operative digital x-ray image and the pre-operative lateral digital x-ray image;
• positioning a patient on an operating table in an operating room, the operating table having a reference element thereon, the operating room having a navigation system therein, the operating table having a navigation tracker mounted in a known position with respect to the operating table;
• taking at least one pelvic digital x-ray image of the patient positioned on the operating table, the x-ray including the reference element;
• identifying at least three points on the intra-operative x-ray image, the points corresponding to the points on the pre-operative x-ray image;
• calculating the lengths and angles between each of the at least three points on the intra-operative digital x-ray image;
• calculating the intra-operative pelvic tilt, obliquity and rotation based on the changes of the lengths and angles between the points on the pre and intra-operative digital x-rays;
• calculating an intra-operative angular position of the acetabular cup insertion instrument to produce the desired abduction and anteversion angle by comparing the pre-operative tilt, obliquity and rotation to the intra-operative tilt, obliquity and rotation;
• and
• aligning the insertion instrument to the calculated angular position using the navigation camera and a navigation tracker mounted on the insertion instrument.

A method for aligning an acetabular cup insertion instrument comprising:

• taking a standing anterior/posterior view digital x-ray image and a lateral view standing digital x-ray image of the pelvis of a patient;
• determining a desired acetabular cup abduction and anteversion, angle based on a two standing x-ray images;
• identifying at least three points on the standing digital anterior/posterior digital x-ray image and at least two points on the lateral digital x-ray image;
• calculating the lengths and angles between each of the points on both the anterior/posterior standing digital x-ray image and the lateral standing digital x-ray image;
• positioning a patient on an operating table in an operating room, the operating table having a reference element thereon;
• the operating room having a navigation system therein, the operating table having a navigation tracker mounted in a known position with respect to the operating table.
• taking at least one pelvic digital x-ray image of the patient positioned on the operating table, the x-ray including the reference element;
• identifying at least three points on the intra-operative x-ray image, the points corresponding to the points on the pre-operative x-ray image;
• positioning a patient on an operating table in an operating room, the operating table having a reference element thereon, the operating room having a navigation system therein, the operating table having a navigation tracker mounted in a known position with respect to the operating table;
• taking at least one pelvic digital x-ray image of the patient positioned on the operating table, the x-ray including the reference element;
• identifying at least three points in the intra-operative x-ray image, the points corresponding to the points on the pre-operative x-ray image;
• calculating the lengths and angles between each of the at least three points on the intra-operative digital x-ray image;
• calculating an intra-operative angular deviation of the acetabular cup insertion instrument from the desired acetabular cup abduction and anteversion angle by comparing the dimensional differences between the points on the pre-operative standing x-ray images and the at least one intra-operative x-ray image;
• and
• intra-operatively aligning the acetabular cup insertion instrument to the calculated angular position, based on the intra-operative angular deviation from the desired abduction and anteversion angles, using the navigation camera and a navigation tracker mounted on the insertion instrument.