Method and system for aligning a prosthesis during surgery

1. A system to guide surgery comprising:

a first sensor unit comprising an optical sensor configured to attach to a first bone of a patient, the optical sensor configured to receive light and determine a direction of the light;

a second sensor unit to couple to an object, the second sensor unit comprising at least three markers configured to emit and/or reflect light to provide a signal representing a six degrees of freedom position to the first sensor unit and, in response to the signal, the first sensor unit generating and communicating sensor information with which to determine a relative position in six degrees of freedom of the object with respect to the first bone;

a coupler to attach the second sensor unit to the object in a known or measurable orientation such that a relative position of the second sensor unit with respect to the object is known when attached and wherein the object comprises a surgical tool or a second bone of the patient;

a processor; and

a non-transitory computer readable storage device storing instructions, which when executed by the processor, configure the processor to:

receive the relative position of the second sensor unit with respect to the object;

receive the sensor information from the first sensor unit;

determine the relative position in six degrees of freedom of the object with respect to the first bone in accordance with the sensor information and the relative position of the second sensor unit with respect to the object;

determine display information in accordance with the relative position in six degrees of freedom of the object with respect to the first bone; and,

provide the display information for a presentation.

2. The system in accordance with claim 1 wherein the relative position in six degrees of freedom of the object with respect to the first bone defines a first relative position and wherein the processor is configured to:

determine a second relative position in six degrees of freedom of the object with respect to the first bone in accordance with second sensor information received from the first sensor unit and the relative position of the second sensor unit with respect to the object;

determine new display information in accordance with the second relative position; and

provide the new display information for display.

3. The system in accordance with claim 1 wherein the relative position in six degrees of freedom of the object with respect to the first bone defines a first relative position and wherein the processor is configured to:

determine a second relative position in six degrees of freedom in accordance with second sensor information received from the first sensor unit and the relative position of the second sensor unit with respect to the object;

determine new display information in accordance with a comparison of the first relative position and the second relative position; and

provide the new display information for display.

4. The system in accordance with claim 1 comprising at least one human interface sensor configured to receive user input and configured to provide an input signal to the processor to invoke an operation, wherein either the first sensor unit or the second sensor unit comprises the at least one human interface sensor.

5. The system in accordance with claim 4 wherein the processor is configured to receive the input signal from the at least one human interface sensor to invoke the processor to save the relative position in six degrees of freedom of the object with respect to the first bone.

6. The system in accordance with claim 1 comprising a display unit to receive and present the display information.

7. The system in accordance with claim 1 wherein the display information is determined in accordance with a registration between the first sensor unit and the first bone thereby to present the relative position of the object relative to an anatomy of the patient.

8. The system in accordance with claim 7 wherein the registration determines a positional relationship of the first sensor unit to a pre-determined geometry of the first bone.

9. The system in accordance with claim 1 wherein the first bone is a pelvis.

10. The system in accordance with claim 9 wherein the object is the second bone and the second bone is a femur.

11. The system in accordance with claim 10 wherein the second sensor unit is attached to the femur such that the processor determines the relative position of the femur and the pelvis and provides the display information based on the relative position in six degrees of freedom of the femur and the pelvis.

12. The system in accordance with claim 1 wherein the surgical tool is one of a tool for joint replacement surgery, a tool for joint resurfacing surgery and a tool for joint revision surgery.

13. The system in accordance with claim 1 wherein the optical sensor comprises a camera and is configured to determine the sensor information from the signal.

14. The system in accordance with claim 1 wherein the first sensor unit, when in use, is attached to the bone and has a field of view aligned with a surgical site; and wherein the second sensor unit, when in use, provides the signal representing the six degree of freedom position to the first sensor unit when in the field of view.

15. A method to guide surgery comprising:

receiving, at a processor, sensor information from a first sensor unit comprising an optical sensor configured to attach to a first bone of a patient, the optical sensor configured to receive light and determine a direction of the light;

receiving, at the processor, a relative position of a second sensor unit with respect to an object comprising a surgical tool or a second bone of the patient, wherein the second sensor unit is attached via a coupler to the object in a known or measurable orientation such that the relative position of the second sensor unit with respect to the object is known when attached and wherein the second sensor unit comprises at least three markers configured to one of emit, reflect, and both emit and reflect light to provide a signal representing a six degrees of freedom position of the second sensor unit to the first sensor unit and, in response to the signal, the first sensor unit generating and communicating the sensor information with which to determine the relative position in six degrees of freedom of the object with respect to the first bone;

determining, by the processor, the relative position in six degrees of freedom of the object with respect to the first bone in accordance with the sensor information and the relative position of the second sensor unit with respect to the object;

determining, by the processor, display information in accordance with the relative position in six degrees of freedom of the object with respect to the first bone; and,

providing, by the processor, the display information for a presentation.

16. The method in accordance with claim 15 wherein the relative position in six degrees of freedom of the object with respect to the first bone defines a first relative position and wherein the method comprises:

determining by the processor a second relative position in six degrees of freedom of the object with respect to the first bone in accordance with second sensor information received from the first sensor unit and the relative position of the second sensor unit with respect to the object;

determining by the processor new display information in accordance with the second relative position; and

providing by the processor the new display information for the presentation.

17. The method in accordance with claim 15 wherein the relative position in six degrees of freedom of the object with respect to the first bone defines a first relative position and wherein the method comprises:

determining by the processor a second relative position in six degrees of freedom in accordance with second sensor information received from the first sensor unit and the relative position of the second sensor unit with respect to the object;

determining by the processor new display information in accordance with a comparison of the first relative position and the second relative position; and

providing by the processor the new display information for the presentation.

18. The method in accordance with claim 15 wherein the display information is determined by the processor in accordance with a registration between the first sensor unit and the first bone thereby to present the relative position of the object relative to an anatomy of the patient.

19. The method in accordance with claim 18 wherein the registration determines a positional relationship of the first sensor unit to a pre-determined geometry of the first bone.

20. The method in accordance with claim 15 wherein the first bone is a pelvis; wherein the object is the second bone and the second bone is a femur; and wherein the second sensor unit is attached to the femur such that the method determines the relative position of the femur and the pelvis and provides display information based on the relative position in six degrees of freedom of the femur and the pelvis.

21. The method in accordance with claim 15 comprising receiving input via a human interface sensor to save the relative position in six degrees of freedom of the object with respect to the first bone.

22. A system for intra-operative surgical measurement and display of a relative position of a surgical tool with respect to a pelvis of a patient in total hip arthroplasty (THA) surgery, the system comprising:

an optical sensor comprising a camera, the optical sensor which, when in use, is attached to the pelvis to position a field of view of the optical sensor in alignment with a surgical site for the THA;

a sensor unit and a coupler which, when in use, the sensor unit is attached to the surgical tool via the coupler, the sensor unit comprising at least three markers configured to emit or reflect light to provide a signal representing a six degrees of freedom position for receiving by the optical sensor, the optical sensor generating and communicating sensor information in response to the signal with which to determine position in six degrees of freedom; and wherein the coupler attaches the sensor unit to the surgical tool in a known or measurable orientation such that a relative position of the sensor unit with respect to the surgical tool is known when attached; and

a processor configured to:

receive the sensor information from the optical sensor;

receive the relative position of the second sensor unit with respect to the surgical tool;

determine the relative position in six degrees of freedom of the surgical tool with respect to the pelvis in accordance with the sensor information and the relative position of the sensor unit with respect to the surgical tool;

determine display information in accordance the relative position in six degrees of freedom of the surgical tool with respect to the pelvis; and,

provide the display information for presentation by a display unit.