TOOL AND METHOD FOR DIGITAL ACQUISITION OF A TIBIAL MECHANICAL AXIS

• US 20140005673A1
• Filed: 09/03/2013
• Published: 01/02/2014
• Est. Priority Date: 08/31/2010
• Status: Active Grant

• Current Assignee: ORTHOsoft ULC. (Zimmer Biomet Holdings, Inc.)
• Original Assignee: Orthosoft Inc. (Zimmer Biomet Holdings, Inc.)
• Inventors: PELLETIER, Benoit, Duval, Karine, Nguyen, Trong Tin, Couture, Pierre, Amiot, Louis-Philippe, Boutin, Yannick, Richard, Alain, Proulx, Catherine
• Granted Patent: US 9,433,473 B2
• Time in Patent Office: Days
• US Class Current: 606/102
• CPC Class Codes: A61B 17/154 for preparing bone for knee prosthesis
• CPC Class Codes: A61B 17/157 Cutting tibia
• CPC Class Codes: A61B 2034/2048 using an accelerometer or inertia sensor
• CPC Class Codes: A61B 2034/2068 using pointers, e.g. pointers having reference marks for determining coordinates of body points
• CPC Class Codes: A61B 34/20 Surgical navigation systems; Devices for tracking or guiding surgical instruments, e.g. for frameless stereotaxis
• CPC Class Codes: A61B 5/4528 Joints A61B5/4533, A61B5/4538 take precedence
• CPC Class Codes: A61B 5/4538 Evaluating a particular part of the muscoloskeletal system or a particular medical condition
• CPC Class Codes: A61B 5/4585 Evaluating the knee
• CPC Class Codes: A61B 90/06 Measuring instruments not otherwise provided for
• CPC Class Codes: A61F 2/46 Special tools or methods for implanting or extracting artificial joints, accessories, bone grafts or substitutes, or particular adaptations therefor
• CPC Class Codes: A61F 2/4657 Measuring instruments used for implanting artificial joints for surgical instruments A61B90/06

Abstract

A tool for digitizing a mechanical axis of a tibia using a computer-assisted surgery system is described. The tool includes upper and lower mounting ends interconnected by an alignment rod extending therebetween. The upper mounting end is releasably fastenable to an upper reference point on a tibial plateau and the lower mounting end includes a self-centering malleoli engaging mechanism having opposed caliper arms displaceable in a common plane relative to each other for clamping engagement with the medial and lateral malleoli of the ankle. At least one trackable member is mounted to the alignment rod of the tool and is in communication with the computer assisted surgery system for providing at least orientation information of the alignment rod. The mechanical axis of the tibia is parallel to the alignment rod and extends between the upper and lower reference points when the tool is mounted on the tibia.

Claims

1. A digitizing tool adapted for digitizing a mechanical axis of a tibia using a computer-assisted surgery system, the tool comprising:

an upper mounting end and a lower mounting end interconnected by an alignment rod extending therebetween, the upper mounting end being releasably fastenable to an upper reference point on a tibial plateau and the lower mounting end having a self-centering malleoli engaging mechanism thereon, the self-centering malleoli engaging mechanism including opposed caliper arms each having a malleolus clamp, the caliper arms being displaceable in a common plane relative to each other for clamping engagement with the medial and lateral malleoli, such that a midpoint between the caliper arms corresponds to a lower reference point defined midway between the medial and lateral malleoli; and

at least one trackable member mounted to the alignment rod of the tool, the trackable member producing at least orientation information and being adapted for communication with the computer-assisted surgery system;

wherein the alignment rod is aligned parallel with the mechanical axis of the tibia which extends between the upper reference point and the lower reference point when the tool is mounted on the tibia.

2. The tool as defined in claim 1, wherein the trackable member includes an inertial sensor.

3. The tool as defined in claim 2, wherein the inertial sensor produces at least orientation-based data for at least two degrees of freedom in orientation of the sensor and thus of the alignment rod on which the sensor is mounted.

4. The tool as defined in claim 2, wherein the inertial sensor includes one or more micro-electro-mechanical sensors, accelerometers, gyroscopes, compasses, and electronic tilt sensors.

5. The tool as defined in claim 1, wherein the self-centering malleoli engaging mechanism includes at least a second trackable member thereon, the second trackable member produces orientation-based data of the self-centering malleoli engaging mechanism.

6. The tool as defined in claim 1, wherein the self-centering malleoli engaging mechanism includes a mechanism permitting the caliper arms to be displaced in an inward direction towards each other without restriction such as to clamp onto the malleoli but at least restricting movement of the caliper arms in an opposed outward direction unless a locking feature of the mechanism is released.

7. The tool as defined in claim 6, wherein the mechanism includes one of a ratchet mechanism and a spring-loaded mechanism.

8. The tool as defined in claim 1, wherein the alignment rod defines a longitudinal axis extending therethrough, the alignment rod being adjustable in length relative to the longitudinal axis such as to vary a distance between the upper and lower mounting ends.

9. The tool as defined in claim 8, wherein the alignment rod telescopes such as to adjust the length thereof.

10. The tool as defined in claim 1, wherein the alignment rod is pivotally mounted to both the upper and lower mounting ends, such as to permit an orientation of the alignment rod to be adjustable in at least a varus-valgus plane once the upper and lower mounting ends are fastened in place to the tibia.

11. The tool as defined in claim 1, wherein the alignment rod includes a visual guide thereon, the visual guide being disposed on the alignment rod in a proximal-distal position corresponding to a location of an anatomical landmark on the tibia used to align the alignment rod.

12. The tool as defined in claim 11, wherein the visual guide includes an opening extending through the alignment rod within which the anatomical landmark is visually centered to align the alignment rod with the mechanical axis of the tibia.

34. The tool as defined in claim 5, wherein the second trackable member is mounted on one of the caliper arms of the self-centering malleoli engagement mechanism.

13. A method for determining a mechanical axis of a tibia using an inertial-based computer assisted surgery system and a tibial digitizer having an upper mounting end, a lower mounting end and an alignment rod extending therebetween, the tibial digitizer including at least one inertial sensor in communication with the computer assisted surgery system, the method comprising:

determining an upper reference point on a tibial plateau of the tibia, the upper reference point being an entry point of the mechanical axis;

fastening the upper mounting end of the tibial digitizer to the tibial plateau at the upper reference point;

fastening the lower mounting end of the tibial digitizer to medial and lateral malleoli of the ankle;

determining a lower reference point located at a midpoint between the medial and lateral malleoli by identifying a corresponding midpoint on the lower mounting end of the tibial digitizer;

adjusting an orientation of the alignment rod such that the alignment rod is aligned with an anatomical landmark on the tibia; and

using the computer assisted surgery system to determine the mechanical axis of the tibia extending between the upper and lower reference points by providing at least orientation data of the tibial digitizer to the computer assisted surgery system using the inertial sensor.

14. The method as defined in claim 13, wherein determining the mechanical axis further comprises determining at least orientation of the tibial digitizer using the computer assisted surgery system such as to digitally acquire the mechanical axis of the tibia based on the determined orientation of the alignment rod of the tibial digitizer and a known distance between the inertial sensor on the tibial digitizer and the mechanical axis.

15. The method as defined in claim 13, wherein adjusting the orientation of the alignment rod further comprises orienting the alignment rod to be parallel with the mechanical axis of the tibia extending between the determined upper and lower reference points.

16. The method as defined in claim 13, wherein locating the upper reference point further comprises locating a mechanical axis entry point on the tibial plateau.

17. The method as defined in claim 16, wherein locating the mechanical axis entry point includes identifying an intersection point between a first axis centered medial-laterally on the tibial plateau and a second axis located one-third anterior and two-thirds posterior, the first and second axis lying in a common plane transverse to the mechanical axis.

18. The method as defined in claim 13, wherein the lower mounting end of the tibial digitizer includes a self-centering clamp mechanism, the step of fastening the lower mounting end further comprising inwardly displacing opposed caliper arms of the self-centering clamp mechanism towards each other until the caliper arms abut the medial and lateral malleoli of the ankle.

19. The method as defined in claim 13, wherein adjusting an orientation of the alignment rod further comprises aligning the anatomical landmark on the tibia with a visual guide defined on the alignment rod.

20. The method as defined in claim 19, wherein the anatomical landmark is a tibial tuberosity and the visual guide is an opening defined in the alignment rod, the step of adjusting further comprising displacing the alignment rod until the tibial tuberosity is centered within the opening of the visual guide.

21. The method as defined in claim 20, wherein displacing the alignment rod includes at least one of a translation in a medial-lateral direction and a rotation in a varus-valgus plane.

22. The method as defined in claim 13, wherein the method is performed on a bone model or cadaver.

23. A digitizing tool adapted for acquiring a mechanical axis of a tibia using a computer assisted surgery system, the digitizing tool comprising:

spaced apart upper and lower mounting ends each having at least one mounting point respectively adapted to be secured to a tibial plateau and malleoli of the tibia, the mounting point of the upper mounting end being fasteneable to the tibial plateau at a mechanical axis entry point defining an upper reference point;

an alignment rod extending between and interconnecting the upper and lower mounting ends, the alignment rod defining a longitudinal axis and being disposed a common distance from the mounting points on the upper and lower mounting ends, at least one trackable member mounted to the alignment rod, the trackable member producing at least orientation-based data for at least two degrees of freedom in orientation of the trackable member and thus of the alignment rod;

the lower mounting end including a self-centering malleoli engagement mechanism having a base portion pivotally connected to the alignment rod and opposed caliper arms slideably mounted on the base portion for displacement relative to each other in a plane transverse to the longitudinal axis of the alignment rod, wherein the caliper arms, when displaced towards each other, are adapted to abut the most medial and lateral points on the malleoli to clamp the self-centering malleoli engagement mechanism in place thereto; and

wherein a midpoint between the caliper arms of the self-centering malleoli engagement mechanism corresponds to a lower reference point located at a midpoint between the most medial and lateral points on the malleoli, and the mechanical axis extends between the lower reference point and the upper reference point at said common distance from the alignment rod which is aligned parallel thereto.

24. The digitizing tool as defined in claim 23, wherein the trackable member includes an inertial sensor.

25. The digitizing tool as defined in claim 24, wherein the inertial sensor includes one or more micro-electro-mechanical sensors, accelerometers, gyroscopes, compasses, and electronic tilt sensors.

26. The digitizing tool as defined in claim 23, wherein the self-centering malleoli engaging mechanism includes at least a second trackable member thereon having a second inertial sensor, the second inertial sensor producing at least orientation-based data of the self-centering malleoli engaging mechanism for one or more degrees of freedom in orientation of the second inertial sensor independently of the first inertial sensor.

27. The digitizing tool as defined in claim 26, wherein the second inertial sensor is mounted on one of the caliper arms of the self-centering malleoli engagement mechanism.

28. The digitizing tool as defined in claim 23, wherein the self-centering malleoli engaging mechanism includes a mechanism which permits the caliper arms to be displaced in an inward direction towards each other without restriction for clamping onto the malleoli but at least restricting movement of the caliper arms in an opposed outward direction unless a locking feature of the mechanism is released.

29. The digitizing tool as defined in claim 28, wherein the mechanism includes one of a ratchet mechanism and a spring-loaded mechanism.

30. The digitizing tool as defined in claim 23, wherein the alignment rod is longitudinally adjustable such as to vary a length thereof.

31. The digitizing tool as defined in claim 30, wherein the alignment rod telescopes to provide longitudinal adjustment between the upper and lower ends along the longitudinal axis.

32. The digitizing tool as defined in claim 23, wherein at least an orientation of the alignment rod is adjustable in at least a varus-valgus plane once the upper and lower ends are fastened in place to the tibia.

33. The digitizing tool as defined in claim 23, wherein the alignment rod is pivotally mounted to both the upper and lower mounting ends, permitting orientation of the alignment rod to be adjustable once the upper and lower mounting ends are fastened in place to the tibia.