Tracking system and method

• US 9,115,998 B2
• Filed: 01/19/2010
• Issued: 08/25/2015
• Est. Priority Date: 01/19/2010
• Status: Active Grant

• Current Assignee: ORTHOsoft ULC. (Zimmer Biomet Holdings, Inc.)
• Original Assignee: Orthosoft Inc. (Zimmer Biomet Holdings, Inc.)
• Inventors: Proulx, Catherine, Falardeau, Bruno, Valin, Myriam, Deslongchamps, Julie
• Primary Examiner(s): DOUGHERTY, SEAN PATRICK
• Application Number:
  US13/056,132
• Publication Number:
  US 20120277634A1
• Time in Patent Office: 2,044 Days
• Field of Search: 600/424, 600/426, 600/587, 600/595, 702 92- 95
• US Class Current: 1/1
• CPC Class Codes: A61B 2017/00725 Calibration or performance testing
• CPC Class Codes: A61B 2034/2048 using an accelerometer or inertia sensor
• CPC Class Codes: A61B 34/20 Surgical navigation systems; Devices for tracking or guiding surgical instruments, e.g. for frameless stereotaxis
• CPC Class Codes: G01C 25/005 initial alignment, calibration or starting-up of inertial devices

Abstract

A tracking system is provided for tracking objects. A first and a second trackable member each have an inertial sensor unit producing at least orientation-based data. A processing unit receives the orientation-based data from the trackable members. The processing unit has an orientation calculator calculating an orientation of the second trackable member with respect to the first trackable member from the orientation-based data of the trackable members, whereby the processing unit calculates an orientation of the objects. A method for tracking objects is also provided.

Claims

1. A computer-assisted surgery system for tracking an instrument and a bone during surgery, comprising:

a first trackable member having a first inertial sensor unit producing at least orientation-based data, the first inertial sensor unit being an accelerometer-based unit adapted to be affixed to the bone, to produce orientation data for two degrees of freedom of orientation; and

a second trackable member having a second inertial sensor unit producing at least orientation-based data, the second inertial sensor unit being an accelerometer-based unit adapted to be affixed to the bone, to produce orientation data for two degrees of freedom of orientation; and

a processing unit for receiving the orientation-based data from the trackable members, the processing unit comprising;

an orientation calculator calculating an orientation of the second trackable member with respect to the first trackable member from the orientation-based data of the trackable members, the orientation calculator determining angular rates of change of the first inertial sensor unit and the second inertial sensor unit while the bone is moved in space in at least two degrees of freedom, and

a calibration calculator for calibrating an orientation of the bone with reference to the first inertial sensor unit by using the determined angular rates of change to determine a third degree of freedom of orientation of the first inertial sensor unit,

whereby the bone is trackable in three degrees of freedom of orientation.

2. The computer-assisted surgery system according to claim 1, wherein the first trackable member and the second trackable member produce position-based data, and the processing unit stores geometrical data relating at least one of the trackable members to the bone and another of the trackable members to the instrument, whereby the orientation calculator calculates a position and orientation of the instrument with respect to the bone.

3. The computer-assisted surgery system according to claim 1, wherein the processing unit is physically part of the second trackable member.

4. The computer-assisted surgery system according to claim 3, wherein the second trackable member has a user interface to display the orientation of the second trackable member with respect to the first trackable member.

5. The computer-assisted surgery system according to claim 1, wherein at least one of the trackable members has a confirmation indicator receiving signals from the processing unit to visually display a confirmation of command from the at least one trackable member.

6. The computer-assisted surgery system according to claim 1, wherein the first trackable member and the second trackable member are arbitrarily placed on the bone, and the processing unit determines a preferred virtual orientation from the orientation of the second trackable member with respect to the first trackable member, the orientation calculator determining the angular rates of change from the preferred virtual orientation.

19. The computer-assisted surgery system according to claim 1, wherein the orientation calculator determines angular rates of change of the first inertial sensor unit and the second inertial sensor unit while the bone is moved in space unconstrained to a single degree of freedom.

7. A method for tracking three degrees of freedom of orientation of an object, the method comprising:

receiving orientation data for two degrees of freedom of orientation from an accelerometer-based reference tracking member affixed to the object;

receiving orientation data for two degrees of freedom of orientation from an accelerometer-based calibration tracking member affixed to the object;

determining angular rates of change of the reference tracking member and of the calibration tracking member while the object is moved in space in at least two degrees of freedom; and

calibrating an orientation of the object with reference to the reference tracking member by using the determined angular rates of change to determine a third degree of freedom of orientation of the reference tracking member;

whereby the object is trackable in three degrees of freedom of orientation.

8. The method according to claim 7, wherein receiving orientation data comprises receiving orientation data from the reference and calibration tracking members affixed to a bone.

9. The method according to claim 7, wherein determining angular rates of change of the reference tracking member and of the calibration tracking member comprises displaying data associated to an angular rate of change, for guiding an operator in moving the object.

10. The method according to claim 7, further comprising performing the method with a bone model or a cadaver.

11. The method according to claim 7, further comprising displaying a tracking of the object in three degrees of freedom of orientation on an interface after the calibrating.

12. The method according to claim 7, wherein receiving orientation data from the reference tracking member comprises first placing the reference tracking member in alignment with object axes.

13. The method according to claim 7, wherein receiving orientation data from the reference tracking member comprises randomly placing the reference tracking member on the object, and determining a preferred orientation of the reference tracking member with respect to the object, and further wherein determining angular rates of change comprises determining angular rates of change relative to the preferred orientation of the reference tracking member.

20. The method according to claim 7, wherein determining angular rates of change of the reference tracking member and of the calibration tracking member determining angular rates of change of the reference tracking member and of the calibration tracking member while the object is moved in space unconstrained to a single degree of freedom.

14. A system for tracking three degrees of freedom of an orientation of an object, the system comprising:

an accelerometer-based reference tracking member adapted to be affixed to the object, the reference tracking member producing orientation data for two degrees of freedom of orientation;

an accelerometer-based calibration tracking member adapted to be affixed to the object, the calibration tracking member producing orientation data for two degrees of freedom of orientation;

a processing unit for receiving the orientation data from the reference tracking member and the calibration tracking member, the processing unit comprising;

an orientation calculator for determining angular rates of change of the reference tracking member and the calibration tracking member while the object is moved in space in at least two degrees of freedom; and

a calibration calculator for calibrating an orientation of the object with reference to the reference tracking member by using the determined angular rates of change to determine a third degree of freedom of orientation of the reference tracking member;

whereby the object is trackable in three degrees of freedom of orientation.

15. The system according to claim 14, wherein the system is a computer-assisted surgery system, the object is a bone and the reference tracking member and the calibration tracking member are affixed to the bone.

16. The system according to claim 14, further comprising a user interface for displaying data associated with an angular rate of change about the axis of one of the two degrees of freedom of orientation of the reference tracking member, for guiding an operator in moving the object.

17. The system according to claim 16, wherein the user interfaces displays a tracking of the object in three degrees of freedom of orientation on an interface after the calibrating.

18. The system according to claim 14, wherein the reference tracking member and the calibration tracking member are randomly placed on the object, and the processing unit determines a preferred orientation of the reference tracking member with respect to the object, the orientation calculator further determining the angular rates of change from the preferred orientation.

21. The system according to claim 14, wherein the orientation calculator determines angular rates of change of the first inertial sensor unit and the second inertial sensor unit while the bone is moved in space unconstrained to a single degree of freedom.