Methods for generating intraoperative surgical guidance during joint arthroplasty based on dynamic ligament tension

1. A method for generating intraoperative surgical guidance, the method comprising:

by a computer system at a first time preceding resection of a first bone and a second bone in a knee of a patient:

accessing a first set of lengths of a first ligament recorded by a measurement device during articulation of the knee during a first test period;

accessing a first set of forces on the first ligament recorded by the measurement device during articulation of the knee during the first test period; and

generating a first tension function for the first ligament based on the first set of forces on the first ligament and the first set of lengths of the first ligament; and

by the computer system at a second time succeeding resection of the first bone and succeeding placement of a first test implant on the first bone:

accessing a first interoperative set of lengths of the first ligament recorded by the measurement device during articulation of the knee during an interoperative test period;

accessing a first interoperative set of forces on the first ligament recorded by the measurement device during articulation of the knee during the interoperative test period; and

generating a second ligament tension function representing an interoperative relationship between tensions on the first ligament and lengths of the first ligament over the first set of angular positions of the knee resulting from placement of the first test implant on the first bone;

retrieving a first target tension function, representing a first target postoperative relationship between tensions on the first ligament and lengths of the first ligament over a first set of angular positions of the knee, based on the first tension function; and

characterizing a first phase difference between the first target tension function and the second ligament tension function; and

in response to the first phase difference exceeding a threshold negative phase difference, rendering a first prompt, on a display, to further resect the first bone, by a first resection difference, the first resection difference based on the first phase difference.

2. The method of claim 1 :

wherein accessing the first set of lengths of the first ligament recorded during articulation of the knee during the first test period comprises:

recording, via an angular position sensor, a first set of angular positions of the knee, during articulation of the knee through a range of motion during the first test period; and

generating the first set of lengths of the first ligament corresponding to the articulation of the knee through the range of motion during the first test period based on the first set of angular positions of the knee;

wherein accessing the first set of forces on the first ligament recorded during articulation of the knee during the first test period comprises:

recording, via a force sensor, a set of forces on the first ligament during articulation of the knee through the range of motion during the first test period; and

wherein generating the first tension function for the first ligament comprises

generating the first tension function for the first ligament based on the first set of forces on the first ligament and the first set of lengths of the first ligament.

3. The method of claim 1 :

further comprising:

by the computer system at the first time preceding resection of the first bone and the second bone in a knee of a patient:

characterizing a first set of geometries descriptive of the first bone;

characterizing a second set of geometries descriptive of the second bone; and

computing a first set of resection parameters for the first bone based on the first target tension function and the first set of geometries; and

by the computer system at the second time succeeding resection of the first bone and succeeding placement of the first test implant on the first bone:

rendering a second prompt, on the display, to further resect the first bone according to the first set of resection parameters for the first bone.

4. The method of claim 3 :

wherein computing the first set of resection parameters for the first bone comprises computing the first set of resection parameters for a tibia bone based on the first target tension function and the first set of geometries of the tibia bone; and

further comprising, computing a second set of resection parameters for a femur bone based on the first target tension function and the second set of geometries of the femur bone.

5. The method of claim 1 , further comprising:

accessing a first implant geometry characteristic of the first test implant;

predicting a postoperative tension function for the first ligament based on the first implant geometry of the first test implant; and

in response to the postoperative tension function approximating the first target tension function, rendering a recommendation on the display for the first test implant.

6. The method of claim 1 , further comprising, in response to the first phase difference falling below the threshold negative phase difference:

computing a target spacer geometry of a spacer based on current surgical parameters; and

rendering a second prompt, on the display, to insert the spacer, defining the target spacer geometry, between the first test implant and the second bone.

7. The method of claim 6 , further comprising:

calculating a first amplitude difference between the third ligament tension function and the first target tension function; and

in response to the first amplitude difference exceeding a threshold amplitude difference:

accessing a set of implant geometries characteristic of implants in a kit of implants;

selecting a first spacer geometry characteristic of a first spacer height from the kit of spacer geometries based on the first amplitude difference; and

rendering a fourth prompt, on the display, to insert a spacer of the first spacer geometry between the first test implant and the second bone.

8. The method of claim 1 , further comprising, at a third time succeeding the second time and succeeding further resection of the first bone:

generating a third ligament tension function for the first ligament representing an interoperative relationship between tensions on the first ligament and lengths of the first ligament over the first set of angular positions of the knee resulting from further resection of the first bone;

calculating a first slope difference between the third ligament tension function and the first target tension function; and

in response to the first slope difference exceeding a threshold slope difference:

accessing a set of implant geometries characteristic of implants in a kit of implants;

selecting a second implant geometry, from the set of implant geometries, based on the first slope difference; and

rendering a third prompt, on the display, to exchange the first test implant for a second test implant characteristic of the second implant geometry.

9. The method of claim 7 , further comprising defining the threshold amplitude difference based on a first set of geometries of the tibia bone, a second set of geometries of the femur bone, and the set of implant geometries.

10. The method of claim 1 , further comprising:

predicting a target interoperative event, based on a current surgical step, to yield the target tension function;

prioritizing executing of the target interoperative event by the surgeon; and

rendering a second prompt, on the display, directed to the surgeon, to perform the target interoperative event immediately succeeding the current surgical step.

11. A method for generating intraoperative surgical guidance during a knee arthroplasty, comprising:

by a computer system at a first time preceding resection of a first bone and a second bone in a knee of a patient:

accessing a first set of lengths of a first ligament recorded by a measurement device during articulation of the knee within the first test period;

accessing a first set of forces on the first ligament recorded by the measurement device during articulation of the knee within the first test period; and

generating a first tension function for the first ligament based on the first set of forces on the first ligament and the first set of lengths of the first ligament; and

by the computer system at a second time succeeding resection of the first bone and succeeding placement of a first test implant on the first bone:

accessing a first interoperative set of lengths of the first ligament recorded by the measurement device during articulation of the knee within an interoperative test period;

accessing a first interoperative set of forces on the first ligament recorded by the measurement device during articulation of the knee within the interoperative test period;

generating a second ligament tension function representing an interoperative relationship between tensions on the first ligament and lengths of the first ligament over the first set of angular positions of the knee resulting from placement of the first test implant on the first bone;

retrieving a first target tension function, representing a first target postoperative relationship between tensions on the first ligament and lengths of the first ligament over a first set of angular positions of the knee, based on the first tension function; and

characterizing a first phase difference between the first target tension function and the second ligament tension function; and

in response to the first phase difference exceeding a threshold negative phase difference:

calculating a set of resection parameters for the first bone based on the first phase difference; and

rendering a first prompt, on a display, to resect the first bone according to the set of resection parameters.

12. The method of claim 11 , further comprising, at a third time succeeding the second time and succeeding further resection of the first bone:

generating a third ligament tension function for the first ligament representing an interoperative relationship between tensions on the first ligament and lengths of the first ligament over the first set of angular positions of the knee resulting from further resection of the first bone;

calculating a first slope difference between the third ligament tension function and the first target tension function; and

in response to the first slope difference exceeding a threshold slope difference:

selecting a second implant geometry from the kit of implant geometries based on the first slope difference, a first implant geometry of the first test implant, and the set of resection parameters; and

rendering a third prompt, on the display, directed to the surgeon, to exchange the first test implant for a second test implant defining the second implant geometry.

13. The method of Claim 12 , further comprising, at a third time succeeding the second time and succeeding further resection of the first bone:

in response to calculating a negative amplitude difference between the third ligament tension function and the first target tension function:

selecting a first shim geometry characteristic of a first shim height from a set of shim geometries based on the first amplitude difference, and the set of resection parameters; and

rendering a fourth prompt, on the display, directed to the surgeon, to insert a shim of the first shim geometry between the first test implant and the second bone.

14. A method for generating intraoperative surgical guidance during a knee arthroplasty, comprising:

by a computer system at a first time preceding resection of a first bone and a second bone in a knee of a patient:

accessing a first set of lengths of a first ligament recorded by a measurement device during articulation of the knee within the first test period;

recording a first set of forces on the first ligament recorded by the measurement device during articulation of the knee within the first test period; and

generating a first tension function for the first ligament based on the first set of forces on the first ligament and the first set of lengths of the first ligament; and

by the computer system at a second time succeeding resection of the first bone and succeeding placement of a first test implant on the first bone:

accessing a first interoperative set of angular positions of the knee recorded by the measurement device during articulation of the knee within an interoperative test period;

generating a first interoperative set of lengths of the first ligament based on the first interoperative set of angular positions;

recording a first interoperative set of forces on the first ligament recorded by the measurement device during articulation of the knee within the interoperative test period;

generating a second ligament tension function representing an interoperative relationship between tensions on the first ligament and lengths of the first ligament over the first set of angular positions of the knee resulting from placement of the first test implant on the first bone;

retrieving a first target tension function, representing a first target postoperative relationship between tensions on the first ligament and lengths of the first ligament over a first set of angular positions of the knee, based on the first tension function; and

in response to characterizing a first phase difference between the first target tension function and the second ligament tension function exceeding a threshold negative phase difference:

rendering a first prompt, on a display, directed to a surgeon, to further resect the first bone, by a first resection difference, the first resection difference based on the first phase difference.

15. The method of claim 14 , wherein generating the first ligament tension function comprises:

recording a first timeseries of angular positions of the knee during articulation of the knee within the first test period;

transforming the first timeseries of angular positions into a first timeseries of lengths of the first ligament during articulation of the knee during the first test period;

recording a first timeseries of forces on the first ligament during articulation of the knee within the first test period; and

generating the first tension function for the first ligament based on the first timeseries of lengths of the first ligament and the first timeseries of forces on the first ligament.

16. The method of claim 14 , further comprising:

accessing models of a kit of implant geometries;

accessing models of a kit of spacer geometries; and

calculating the threshold negative phase difference based on the kit of implant geometries and the kit of spacer geometries.

17. The method of claim 16 :

wherein accessing the models of the kit of implant geometries comprises accessing models of the kit of implant geometries available to the surgeon during the knee arthroplasty;

wherein accessing the models of the kit of spacer geometries comprises accessing models of the kit of spacer geometries available to the surgeon during the knee arthroplasty;

further comprising predicting postoperative tension functions for the first ligament based on the kit of implant geometries available to the surgeon during the knee arthroplasty to identify a first target implant;

further comprising, in response to identifying the first target implant predicted to yield the first target tension function for the first ligament, selecting the first target implant from the kit of implant geometries; and

further comprising rendering a second prompt, on the display, directed to the surgeon, to exchange the first test implant with the first target implant.

18. The method of claim 17 , further comprising, at a third time succeeding the second time and succeeding further resection of the first bone:

generating a third ligament tension function for the first ligament representing an interoperative relationship between tensions on the first ligament and lengths of the first ligament over the first set of angular positions of the knee resulting from further resection of the first bone;

calculating a first slope difference between the third ligament tension function and the first target tension function;

in response to the first slope difference exceeding a threshold slope difference:

selecting a second implant geometry from the kit of implant geometries based on the first slope difference, a first implant geometry of the first test implant, and a current set of bone resection parameters; and

rendering a third prompt, on the display, directed to the surgeon, to exchange the first test implant for a second test implant defining the second implant geometry;

calculating a first amplitude difference between the third ligament tension function and the first target tension function; and

in response to the first amplitude difference exceeding a threshold amplitude difference:

selecting a first shim geometry characteristic of a first shim height from a set of shim geometries based on the first amplitude difference; and

rendering a fourth prompt, on the display, directed to the surgeon, to insert a shim of the first shim geometry between the first test implant and the second bone.

19. The method of claim 18 , further comprising calculating the threshold amplitude difference based on the set of shim geometries, the kit of implant geometries, and a set of current surgical parameters.

20. The method of claim 14 , further comprising:

predicting a set of target interoperative events, based on a current surgical step, to yield the target tension function;

ranking the set of target interoperative events based on a criterion for execution by the surgeon;

selecting an event from the set of target interoperative events as the target interoperative event based on a threshold rank; and

rendering a second prompt, on the display, directed to the surgeon, to perform the target interoperative event succeeding the current surgical step.