# US 2019/0172373 A1 · Method for creating a computer model of a joint for treatment planning

> Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt

- Number: US 2019/0172373 A1
- Document ID: US20190172373A1
- Status: Published application
- Kind: A1
- Application number: 16/266,594
- Filed: 2019-02-04
- Published: 2019-06-06
- Earliest claimed: 2015-12-07
- Assignees: Hospital for Special Surgery
- Applicants: Hospital for Special Surgery
- Inventors: Carl Imhauser; Kevin Schafer
- Web page: https://patentgrep.com/patent/US20190172373A1

## CPC

- G09B 23/30: Anatomical models {(G09B23/281 - G09B23/288 take precedence)}
- G09B: EDUCATIONAL OR DEMONSTRATION APPLIANCES; APPLIANCES FOR TEACHING, OR COMMUNICATING WITH, THE BLIND, DEAF OR MUTE; MODELS; PLANETARIA; GLOBES; MAPS; DIAGRAMS (devices for psychotechnics or for testing reaction times A61B5/16; games, sports, amusements A63; projectors, projector screens G03B)

## Abstract

The present invention provides a method for creating a computer model of a patient specific joint for treatment planning. The method includes identifying a ligament of a joint of a patient under a load at a predefined position of the joint. The method further includes constructing, with the use of a computer, a computer model of the joint of the patient having: a first bone model, a second bone model, and a ligament model connecting the first and second bone models corresponding to the identified ligament, wherein the ligament model is constructed as at least one fiber based on a predefined slack length.

## Claims

### Claim 1

A method for creating a computer model of a patient specific joint for treatment planning, comprising:
identifying a ligament of a joint of a patient under a load at a predefined position of the joint; and
constructing, with the use of a computer, a computer model of the joint of the patient having:
a first bone model,
a second bone model, and
a ligament model connecting the first and second bone models corresponding to the identified ligament, wherein the ligament model is constructed having at least one fiber based on a predefined slack length, and wherein the predefined slack length is determined based on the load at the predefined position.

### Claim 2 (depends on 1)

The method of claim 1, wherein the predefined slack length is determined by an objective function based on a predetermined force carried by the identified ligament at the predefined position and/or a force on a fiber of the at least one fiber of the ligament model at the predefined position.

### Claim 3 (depends on 2)

The method of claim 2, wherein the objective function is further based upon one or more of a number of ligament models, a number of fibers for the ligament model, the slack length of the ligament, and the force on the fiber of the at least one fiber of the ligament model at the predefined position.

### Claim 4 (depends on 3)

The method of claim 3, wherein the force of the fiber of the at least one fiber of the ligament model at the predefined position is determined based on one or more of an inter-insertional distance, a first derivative of the inter-insertional distance with respect to time, a parametric function of a ligament force-elongation response in a toe region, and a transition between the toe region and a linear region.

### Claim 5 (depends on 2)

The method of claim 2, wherein the objective function comprises:

∑
j
=
1
a

F
j
m

(
l
,
l
·
,
l
0
)

-
F
e
wherein α is a number of fibers for the ligament model, j is an identified fiber of the fibers for the ligament model, Fjm is a force on a fiber of the at least one fiber of the ligament model at the predefined position, l is an inter-insertional distance, {dot over (l)} is a first derivative of the inter-insertional distance with respect to time, l0 is the slack length of the ligament, and Fe is a predetermined force carried by the identified ligament at the predefined position.

### Claim 6 (depends on 2)

The method of claim 2, wherein the objective function comprises
min


∑
i
=
1
y

(

∑
j
=
1
a
i

F
i
,
j
m

(
l
,
l
·
,
l
0
)

-
F
i
e
)
4
wherein y is a number of ligament models, i is an identified ligament of the number of ligaments, αi is a number of fibers for the ligament model, j is an identified fiber of the fibers for the ligament model, Fie is a predetermined force carried by the identified ligament at the predefined position, l is the inter-insertional distance, {dot over (l)} is the first derivative of the inter-insertional distance with respect to time, l0 is a slack length of the ligament, and Fi,jm is a force of a fiber of the at least one fiber of the ligament model at the predefined position determined by the following Equation 1:
F

(
l
,
l
·
,
l
0
)
=
1
n

{
[
f
*

(
l
)
+
c
d

l

·

B
1
]

B
2
+
[
K

(
l
-
(
l
0
+
Δ
t
)
)
+
f
*

(
l
0
+
Δ
t
)
+
c
d

l

·

B
1
]

B
3
}



B
1
=
step

(
l
·
,
0
,
0
,
l
·
+
0.1
,
1
)


B
2
=
step

(
l
,
l
0
,
0
,
l
0
+
0.1
,
1
)
×
step

(
l
,
(
l
0
+
Δ
t
)
,
1
,
(
l
0
+
Δ
t
)
+
0.001
,
0
)



B
3
=
step

(
l
,
(
l
0
+
Δ
t
)
,
0
,
(
l
0
+
Δ
t
)
+
0.001
,
1
)
(
1
)
wherein n is the number of fibers, f*(l) is a cubic spline of a ligament force-elongation response in a toe region, K represents a linear portion of a force-elongation response, Δt is a transition between the toe region and the linear region, B1,2,3 are step functions, and cd is a damping term constant.

### Claim 7 (depends on 1)

The method of claim 1, further comprising determining a length of the at least one fiber at the predefined position wherein the predefined slack length is based on the determined length of the at least one fiber at the predefined position, or determining a target load for the identified ligament wherein the predefined slack length is based on the determined target load.

### Claim 8 (depends on 1)

The method of claim 1, further comprising outputting on a display operatively connected to the computer forces or kinematic motion predicted by the computer model of the joint as it simulates a range of motion.

### Claim 9 (depends on 8)

The method of claim 8, wherein the forces predicted by the computer model of the joint is a ligament load on the ligament model, a contact force between the first and second bone models, or a directional force of movement of one of the first and second bone models relative to the other of the first and second bone models, or wherein the computer model further includes a menisci, and the forces predicted by the computer model of the joint is a contact force on the menisci or between the menisci and at least one of the first and second bone models.

### Claim 10 (depends on 1)

The method of claim 1, wherein the computer model of the joint is a model of a knee joint, an ankle joint, a hip joint, an elbow joint, a wrist joint, a finger joint, a toe joint, patellofemoral joint or a shoulder joint, or wherein the computer model of the joint is a model of a knee joint and the ligament model is a model of an anterior cruciate ligament, a posterior cruciate ligament, a superficial medial collateral ligament, a posterior oblique ligament, a medial posterior capsule, a lateral posterior capsule ligament, a lateral collateral ligament, an anterolateral ligament, a fabellofibular ligament, a coronary ligament, or a lateral coronary ligament.

### Claim 11 (depends on 1)

The method of claim 1, wherein the ligament model includes a predetermined linear or non-linear stiffness, or wherein the predefined position is at full extension of the joint.

### Claim 12 (depends on 1)

The method of claim 1, further comprising acquiring at least one of image data and geometric data of the joint of the patient, and wherein constructing the computer model of the joint is based on the acquired at least one of image data and geometric data.

### Claim 13

A method of developing a treatment plan for treating a joint of a patient comprising:
identifying at least one ligament of a joint of a patient carrying a load at a predefined position of the joint;
constructing, with the use of a computer, a computer model of the joint of the patient having ligament models corresponding to the identified at least one ligament, wherein each of the ligament models is constructed having at least one fiber based on a predefined slack length, and wherein the predefined slack length is determined based on the load at the predefined position;
outputting on a display operatively connected to the computer at least one of forces and motions predicted by the computer model of the joint as it simulates a range of motion; and
developing a treatment plan for surgically treating the joint based on the at least one of forces and motions predicted by the computer model.

### Claim 14 (depends on 12)

The method of claim 12, wherein the predefined slack length is determined by an objective function based on a predetermined force carried by the identified ligament at the predefined position and/or a force on a fiber of the at least one fiber of the ligament model at the predefined position.

### Claim 15 (depends on 14)

The method of claim 14, wherein the objective function is further based on one or more of a number of ligament models, a number of fibers for the ligament model, the slack length of the ligament, and the force on the fiber of the at least one fiber of the ligament model at the predefined position.

### Claim 16 (depends on 15)

The method of claim 15, wherein the force on the fiber of the at least one fiber of the ligament model at the predefined position is determined based on one or more of an inter-insertional distance, a first derivative of the inter-insertional distance with respect to time, a parametric function of a ligament force-elongation response in a toe region, and a transition between the toe region and a linear region.

### Claim 17 (depends on 14)

The method of claim 14, wherein the objective function comprises

∑
j
=
1
a

F
j
m

(
l
,
l
·
,
l
0
)

-
F
e
wherein α is a number of fibers for the ligament model, j is an identified fiber of the fibers for the ligament model, Fjm is a force on a fiber of the at least one fiber of the ligament model at the predefined position, l is an inter-insertional distance, {dot over (l)} is a first derivative of the inter-insertional distance with respect to time, l0 is the slack length of the ligament, and Fe is a predetermined force carried by the identified ligament at the predefined position.

### Claim 18 (depends on 14)

The method of claim 14, wherein the objective function comprises
min


∑
i
=
1
y

(

∑
j
=
1
a
i

F
i
,
j
m

(
l
,
l
·
,
l
0
)

-
F
i
e
)
4
wherein y is a number of ligament models, i is an identified ligament of the number of ligaments, αi is a number of fibers for the ligament model, j is an identified fiber of the fibers for the ligament model, Fie is a predetermined force carried by the identified ligament at the predefined position, l is the inter-insertional distance, {dot over (l)} is the first derivative of the inter-insertional distance with respect to time, l0 is a slack length of the ligament, and Fi,jm is a force of a fiber of the at least one fiber of the ligament model at the predefined position determined by the following Equation 1:
F

(
l
,
l
·
,
l
0
)
=
1
n

{
[
f
*

(
l
)
+
c
d

l

·

B
1
]

B
2
+
[
K

(
l
-
(
l
0
+
Δ
t
)
)
+
f
*

(
l
0
+
Δ
t
)
+
c
d

l

·

B
1
]

B
3
}



B
1
=
step

(
l
·
,
0
,
0
,
l
·
+
0.1
,
1
)


B
2
=
step

(
l
,
l
0
,
0
,
l
0
+
0.1
,
1
)
×
step

(
l
,
(
l
0
+
Δ
t
)
,
1
,
(
l
0
+
Δ
t
)
+
0.001
,
0
)



B
3
=
step

(
l
,
(
l
0
+
Δ
t
)
,
0
,
(
l
0
+
Δ
t
)
+
0.001
,
1
)
(
1
)
wherein n is the number of fibers, f*(l) is a cubic spline of a ligament force-elongation response in a toe region, K represents a linear portion of a force-elongation response, Δt is a transition between the toe region and the linear region, B1,2,3 are step functions, and cd is a damping term constant.

### Claim 19 (depends on 13)

The method of claim 13, further comprising determining loads carried by the identified at least one ligament, determining target loads for the identified at least one ligament, and determining lengths of the at least one fiber, and wherein the predefined slack length is based on the determined load, the determined target load of the at least one ligament, and the determined length of the at least one fiber.

### Claim 20

An apparatus comprising a processor, a display, and a non-transitory computer-readable medium that includes computer instructions executable by the processor to:
receive an identification of at least one ligament of a joint of a patient carrying a load at a predefined position;
create a computer model of a patient specific joint that includes:
a first bone model,
a second bone model, and
a ligament assembly model constraining the first and second bone models, wherein the ligament assembly model includes ligaments corresponding to the identification of at least one ligament each constructed having at least one fiber having a predefined slack length, and wherein the predefined slack length is determined based on the load at the predefined position;
simulate a range of motion of the computer model to determine at least one of forces and motions predicted as the joint travels through the range of motion; and
output on the display the computer model of the joint and the predicted at least one of forces and motions of the joint generated by the computer model.

### Claim 21 (depends on 20)

The apparatus of claim 20, further comprising computer instructions executable by the processor to determine the predefined slack length by an objective function based on a predetermined force carried by the identified ligament at the predefined position and/or a force on a fiber of the at least one fiber of the ligament model at the predefined position.

### Claim 22 (depends on 21)

The apparatus of claim 21, wherein the objective function is further based upon one or more of a number of ligament models, a number of fibers for the ligament model, a slack length of the ligament, and the force on the fiber of the at least one fiber of the ligament model at the predefined position.

### Claim 23 (depends on 22)

The apparatus of claim 22, wherein the force on the fiber of the at least one fiber of the ligament model at the predefined position is determined based on one or more of an inter-insertional distance, a first derivative of the inter-insertional distance with respect to time, a parametric function of a ligament force-elongation response in a toe region, and a transition between the toe region and a linear region.

### Claim 24 (depends on 21)

The apparatus of claim 21, wherein the objective function comprises

∑
j
=
1
a

F
j
m

(
l
,
l
·
,
l
0
)

-
F
e
wherein α is a number of fibers for the ligament model, j is an identified fiber of the fibers for the ligament model, Fjm is a force on a fiber of the at least one fiber of the ligament model at the predefined position, l is an inter-insertional distance, {dot over (l)} is a first derivative of the inter-insertional distance with respect to time, l0 is the slack length of the ligament, and Fe is a predetermined force carried by the identified ligament at the predefined position.

### Claim 25 (depends on 21)

The apparatus of claim 21, wherein the objective function comprises
min


∑
i
=
1
y

(

∑
j
=
1
a
i

F
i
,
j
m

(
l
,
l
·
,
l
0
)

-
F
i
e
)
4
wherein y is a number of ligaments of the ligament assembly model, i is an identified ligament of the number of ligaments, αi is a number of fibers for each ligament of the ligament assembly model, j is an identified fiber of the fibers for the ligament model, Fie is a predetermined force carried by each identified ligament at the predefined position, l is the inter-insertional distance, {dot over (l)} is the first derivative of the inter-insertional distance with respect to time, l0 is a slack length of the ligament, and Fi,jm is a force carried by a fiber of the at least one fiber at the predefined position determined by the following Equation 1:
F

(
l
,
l
·
,
l
0
)
=
1
n

{
[
f
*

(
l
)
+
c
d

l

·

B
1
]

B
2
+
[
K

(
l
-
(
l
0
+
Δ
t
)
)
+
f
*

(
l
0
+
Δ
t
)
+
c
d

l

·

B
1
]

B
3
}



B
1
=
step

(
l
·
,
0
,
0
,
l
·
+
0.1
,
1
)


B
2
=
step

(
l
,
l
0
,
0
,
l
0
+
0.1
,
1
)
×
step

(
l
,
(
l
0
+
Δ
t
)
,
1
,
(
l
0
+
Δ
t
)
+
0.001
,
0
)



B
3
=
step

(
l
,
(
l
0
+
Δ
t
)
,
0
,
(
l
0
+
Δ
t
)
+
0.001
,
1
)
(
1
)
wherein n is the number of fibers, f*(l) is a cubic spline of a ligament force-elongation response in a toe region, K represents a linear portion of a force-elongation response, Δt is a transition between the toe region and the linear region, B1,2,3are step functions, and cd is a damping term constant.