BONE TRACKING WITH A GYROSCOPE SENSOR IN COMPUTER-ASSISTED SURGERY

• US 20120029389A1
• Filed: 07/30/2010
• Published: 02/02/2012
• Est. Priority Date: 07/30/2010
• Status: Active Grant

• Current Assignee: ORTHOsoft ULC. (Zimmer Biomet Holdings, Inc.)
• Original Assignee: ORTHOsoft ULC. (Zimmer Biomet Holdings, Inc.)
• Inventors: Amiot, Louis-Philippe, Zuhars, Joel, Proulx, Catherine, Pelletier, Benoit, Richard, Alain, Boutin, Yannick, Valin, Mynam, Nguyen, Tin, Duval, Karine Duval, Kiblawi, Rula
• Granted Patent: US 9,597,156 B2
• Time in Patent Office: Days
• US Class Current: 600/595
• CPC Class Codes: A61B 2034/2048 using an accelerometer or inertia sensor
• CPC Class Codes: A61B 2090/3983 Reference marker arrangements for use with image guided surgery
• CPC Class Codes: A61B 34/20 Surgical navigation systems; Devices for tracking or guiding surgical instruments, e.g. for frameless stereotaxis

Abstract

A system tracks an object in computer-assisted surgery. The system comprises a sensor unit secured to the femur. Gyroscopes on the sensor unit produce readings related to orientation data about three axes of rotation. A tracking unit receives the gyroscope readings. An axis calibrator on the tracking unit comprises a calculator for adding at least part of the gyroscope readings for specific movements of the object about a desired axis. An axis normalizer on the tracking unit determines an orientation of the desired axis with respect to the sensor unit from the added gyroscope readings. A tracking processor tracks the desired axis from the gyroscope readings. An interface displays orientation data for the object from a tracking of the desired axis. A method for tracking an object with a gyroscope sensor unit is also provided.

Claims

1. A system for tracking an object in computer-assisted surgery, comprising:

a sensor unit adapted to be secured to the femur, the sensor unit comprising a gyroscope producing gyroscope readings related to orientation data about three axes of rotation;

a tracking unit for receiving the gyroscope readings and comprising;

an axis calibrator comprising a gyroscope reading calculator for adding at least a part of the gyroscope readings for specific movements of the object about a desired axis, and an axis normalizer for determining an orientation of the desired axis with respect to the sensor unit from the added gyroscope readings; and

a tracking processor for subsequently tracking the desired axis from the gyroscope readings; and

an interface for displaying the orientation data for the object from a tracking of the desired axis.

2. The system according to claim 1, wherein the object is a femur, and wherein the system further comprises support tools to support the femur to generally restrict motion of the femur to rotations about an axis of the femur.

3. The system according to claim 2, wherein the support tools comprise a femoral fixation and an external holder concurrently forming a joint at a knee end of the femur, with the femur restricted to rotations by the joint at the knee end, and a hip joint of the femur at an opposite end.

4. The system according to claim 3, further comprising a motion sensor unit on the external holder to provide readings for unstable gyroscope readings, and wherein the axis calibrator comprises a filtering unit for discarding the unstable gyroscope readings for the gyroscope reading calculator.

5. The system according to claim 1, wherein the axis calibrator comprises a filtering unit for discarding outlier gyroscope readings for the gyroscope reading calculator.

6. The system according to claim 1, wherein the axis calibrator comprises a three-axis setter for setting two additional axes to the desired axis to define a three-axis coordinate system.

7. A method for tracking an object with a gyroscope sensor unit secured to the object, comprising:

obtaining gyroscope readings for three axes of rotation during specific movements of the object about a desired axis;

summing at least part of the gyroscope readings;

determining an orientation of the desired axis with respect to the gyroscope sensor unit by normalizing the summed gyroscope readings;

tracking the orientation of the desired axis of the object from the gyroscope readings; and

displaying tracking data from the tracked orientation of the desired axis.

8. The method according to claim 7, wherein obtaining gyroscope readings for specific movements comprises obtaining gyroscope readings for reciprocating movements about the desired axis.

9. The method according to claim 8, wherein summing at least part of the gyroscope readings comprises changing a direction of the gyroscope readings for all reciprocating movements in a first direction prior to summing.

10. The method according to claim 7, further comprising identifying any unstable gyroscope readings, and discarding the unstable gyroscope readings prior to determining the orientation of the desired axis.

11. The method according to claim 10, wherein identifying any unstable gyroscope readings comprises obtaining a motion sensor signal associated with at least some of the gyroscope readings.

12. The method according to claim 7, further comprising identifying and discarding outlier values from the gyroscope readings prior to determining the orientation of the desired axis.

13. The method according to claim 7, further comprising setting a second and a third axis to the desired axis to form a three-axis coordinate system.

14. The method according to claim 13, wherein setting a second axis comprises identifying a given axis of the sensor unit as the second axis.

15. The method according to claim 7, wherein the method is performed for a femur, and the desired axis is a mechanical axis of the femur.

16. The method according to claim 15, wherein the specific movements are rotations about the mechanical axis from the femur being constrained by a joint at a knee end, and by a hip joint at an opposite end.

17. The method according to claim 7, wherein the method is performed on a bone model or cadaver.