Post-operative prediction
This disclosure relates to methods and systems to assist in surgery of a joint. The system determines a mechanical property of one or more ligaments associated with the joint based on measurement data indicative of a movement of the bones relative to each other under multiple mechanical loads. The system then determines a predicted characteristic of the joint after the surgery based on a spatial parameter of the surgery and based on the mechanical property of the one or more ligaments and generates an output signal indicative of the predicted characteristic to assist the surgery. Since the predicted characteristic of the joint is determined based on the mechanical property of the ligaments, the prediction is more accurate than other methods that rely on only bone geometries to predict a surgery outcome.
1. A method for assisting surgery of a joint comprising a kinematic system of two or more bones, the method comprising:
simulating a ligament force of each of one or more ligaments associated with the joint based on pre-defined load values of multiple mechanical loads applied to the joint;
receiving measurement data indicative of an amount of movement of the bones relative to each other as a result of the multiple mechanical loads being applied to the joint;
evaluating a mathematical relationship between the simulated ligament force and the movement to determine a mechanical property, including a stiffness value and a length value, of each of the one or more ligaments based on the simulated ligament force and the measurement data indicative of the amount movement of the bones relative to each other;
determining a predicted characteristic over a range of flexion of the joint after the surgery based on a planned spatial parameter of the surgery and based on the mechanical property of the one or more ligaments; and
generating an output signal indicative of the predicted characteristic over the range of flexion of the joint to assist the surgery.
2. The method of claim 1 , wherein the kinematic system comprises three or more bones.
3. The method of claim 1 , wherein the spatial parameter of the surgery is a cutting angle for attaching an implant.
4. The method of claim 1 , wherein determining the predicted characteristic comprises determining a predicted laxity of the joint over the range of flexion of the joint.
5. The method of claim 1 , wherein generating the output signal comprises generating a display of the predicted characteristic.
6. The method of claim 1 , further comprising using the output signal to optimise the spatial parameter of the surgery.
7. The method of claim 6 , wherein optimising the spatial parameter of the surgery comprises adjusting a pre-defined value of the spatial parameter of the surgery.
8. The method of claim 1 , further comprising determining the measurement data based on multiple first images, each of the multiple first images representing a position of the bones relative to each other under the respective mechanical load.
9. The method of claim 8 , wherein each of the multiple first images is an X-ray image of the joint.
10. The method of claim 1 , further comprising determining the measurement data based on contact-based data representing a position of the bones relative to each other under the respective mechanical load.
11. The method of claim 1 , wherein determining the mechanical property comprises determining the mechanical property based on a spatial configuration of the joint.
12. The method of claim 11 , further comprising determining the spatial configuration of the joint based on a second image of the joint.
13. The method of claim 12 , wherein determining the spatial configuration of the joint comprises determining the spatial configuration of the joint based on a 3D scan of the joint.
14. The method of claim 12 , wherein determining the spatial configuration of the joint comprises determining the spatial configuration of the joint based on a CT scan or MM scan or both.
15. The method of claim 1 , further comprising receiving input data indicative of a desired characteristic of the joint, wherein generating an output signal comprises generating an output signal that is indicative of a correspondence between the desired characteristic and the predicted characteristic.
16. The method of claim 15 , further comprising determining a modification of the one or more ligaments to adjust the predicted characteristic towards the desired characteristic based on the spatial parameter of the surgery and based on the mechanical property of the one or more ligaments,
wherein generating an output signal comprises generating an output signal that is indicative of the modification of the one or more ligaments.
17. The method of claim 1 , wherein determining the mechanical property of the one or more ligaments comprises determining the mechanical property of the one or more ligaments based on measurement data indicative of the movement of the bones relative to each other under multiple angles between the two bones.
18. The method of claim 1 , wherein the joint is a knee.
19. A non-transitory computer readable medium with instructions stored thereon that, when executed by a computer, cause the computer to perform the method of claim 1 .
20. A computer system for assisting surgery of a joint comprising a kinematic system of two or more bones, the computer system comprising:
an input port to receive measurement data indicative of an amount of movement of the bones relative to each other as a result of the multiple mechanical loads applied to the joint;
a processor to:
simulate a ligament force of each of one or more ligaments associated with the joint based on pre-defined load values of multiple mechanical loads applied to the joint;
receive the measurement data,
evaluate a mathematical relationship between the simulated ligament force and the movement to determine a mechanical property, including a stiffness value and a length value, of each of the one or more ligaments based on the simulated ligament force and the measurement data indicative of the amount movement of the bones relative to each other; and
determine a predicted characteristic over a range of flexion of the joint after the surgery based on a planned spatial parameter of the surgery and based on the mechanical property of the one or more ligaments; and
an output port for an output signal indicative of the predicted characteristic over the range of flexion of the joint to assist the surgery.
21. A method for assisting surgery of a joint comprising a kinematic system of two or more bones, the method comprising:
applying multiple mechanical loads with respective pre-defined load values to the joint;
measuring an amount of movement of the bones relative to each other as a result of the multiple mechanical loads being applied to the joint to determine measurement data;
simulating a ligament force of each of one or more ligaments associated with the joint based on the load values of the multiple mechanical loads applied to the joint;
evaluating a mathematical relationship between the simulated ligament force and the movement to determine a stiffness value of each of the one or more ligaments based on the simulated ligament force and the measurement data indicative of the amount movement of the bones relative to each other;
determining a predicted characteristic over a range of flexion of the joint after the surgery based on a planned spatial parameter of the surgery and based on the mechanical property of the one or more ligaments; and
generating an output signal indicative of the predicted characteristic over the range of flexion of the joint to assist the surgery.