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Tutorials
Golfing
Bike
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Bungee Jump
Muscle Relocation
Antagonistic Muscles
Hip Replacement
Detailed Knee
Detailed Spine
Rehabilitation Machine
Gait Analysis
Walking
Lifting Styles
Bed Settling
Fighting
Car Crash
Fall
Grasping
NeckSIM:Whiplash
Tennis

Orthopedics Application - Total Knee Replacement

The LifeMOD™ Biomechanics Modeler creates a standard kinematic joint knee by default, however, the user may create a more biofidelic representation of a force based knee joint. This example involves the addition of the geometry for a total knee replacement system. A sophisticated solid-solid contact algorithm is used to accurately calculate the tibio-femoral and patello-femoral forces of contact.

The knee is stabilized with ligament forces and driven using muscle forces. Tibio-femoral and patello-femoral contact forces are examined as well as ligament and muscle loads for a deep knee bend.

This example also walks the user through the process of changing the contribution of various muscle groups on the knee flex motion.

Features of this model include:

  • Force-based knee joint.
  • Importing total knee replacement geometry
  • Muscle driven model
  • Point-to-point ligament forces
  • Running a parametric analysis
  • Changing the contribution of various muscle groups
  • Inverse-dynamics, forward-dynamics simulations.

Sections

Generating the Body Segments

In this phase, the leg model is created for simulation. The model will consist of a single leg with a mass at the hip location to represent the mass of the upper body. Contact ellipsoids will be created to describe the tibio-femoral and patello-femoral contact elements. Muscle forces will be used for the stabilizing tissues and the quadriceps and hamstrings muscle groups.


Figure 1: Body segment create panel and full body model

Step 1: Bring up segments panel and set fields
Begin the ADAMS/View modeling session and select the LifeMOD/BodySIM™ button at the bottom left portion of the screen. Select SEGMENTS from the main-menu and CREATE BASE SET from the sub-menu. Name the model Ryan.

Step 2: Create the body
Generate a full body model using the GeBod database. Select a 70 lbs, 170 inch tall male. Select Create Body Parameter Table to create the body measurement table, then select Create Human Model from Parameter Table to create the body.

Reducing the Model

In this phase, the segments of the model are deleted to focus only on the knee joint. All segments are deleted except for the lower_torso, left_upper_leg and the left_lower_leg.


Figure 2: Segment delete panel and the resulting sub-model

Step 3: Bring up segment delete panel
Select SEGMENTS on the main-menu and DELETE on the sub-menu.

Step 4: Delete the various body segments
All segments are deleted except for the central_torso, lower_torso, left_upper_leg left_lower_leg, and left_foot.

Step 5: Increase the mass of the pelvis to compensate for the rest of body
Right click on the lower_torso segment and select modify. Adjust the mass to 119.3.

Generating the Simple Joints

In this phase, simple kinematic joints with small damping and stiffness forces are used to model the ankle and hip joints. These simple joints are part of the BASE set of joints.


Figure 3: Left leg joint matrix to create the passive hip and ankle joints. Be sure to unselect the left knee.

Step 6: Bring up the joint create panel
Select JOINTS from the main-menu and CREATE BASE SET on the sub-menu.

Step 7: Create the passive spring-damper joints
Enter 1 for the nominal stiffness and .1 for the damping. Check only the left leg and select "Modify" to bring up the left leg joint matrix panel.

Step 8: De-select the knee joint and create the hip and ankle joints.
Uncheck the "Create" box for the knee and select "Apply" to create the joints.

Importing the TKR Components

Solid models of the femoral component, tibial insert component and patella component are imported into LifeMOD/BodySIM. LifeMOD/BodySIM™ supports Parasolids, IGES, Wavefront/OBJ, general polygon and many other formats.


Figure 4: Panel to create tibial insert component by importing Parasolids solid geometry.


Figure 5: Panel to create femoral component by importing Parasolids solid geometry.


Figure 6: Location and orientation of the contact marker on the tibial plateau


Figure 7: Leg model with the tibial insert, femoral and patellar components installed.

Step 9: Bring up the create single segment panel
Select SEGMENTS in the main-menu and CREATE SINGLE in the sub-menu.

Step 10: Create the tibial insert component using geometry from library
Set the segment name to tibCMP and locate the CM at 3.0510154532, -17.5486593628, 4.65868456E-002 with a 180,90,0 orientation. Select "Calculate Mass Properties based on Material". Select polyethylene as the material. Select "Import Parasolids Geometry". Select Geometry type of "Other". Select File Type "ASCII". Select [adams_ installation]\lifemod\Demo_Files\Knee\insert.xmt_txt as the parasolids file. Select APPLY to create the insert component. LifeMOD/BodySIM™ will use the material and solid geometry to create the mass properties of the component.

Step 11: Create the femoral component using geometry from library
Set the segment name to femCMP and locate the CM at 3.0462981041, -17.4379596676, 0.3547902754 with a 179.9782358787, 105.2951776296, 359.9832371446 orientation. Select "Calculate Mass Properties based on Material". Select polyethylene as the material. Select "Import Parasolids Geometry". Select Geometry type of "Other". Select File Type "ASCII". Select [adams_ installation]\lifemod\Demo_Files\Knee\femoral.xmt_txt as the parasolids file. Select APPLY to create the insert component. LifeMOD/BodySIM™ will use the material and solid geometry to create the mass properties of the component.

Step 12: Create the patella component using geometry from library
Set the segment name to patCMP and locate the CM at 3.0492544755, -15.9492562045, 1.4243131206 with a 0,95,0 orientation. Select "Calculate Mass Properties based on Material". Select polyethylene as the material. Select "Import Parasolids Geometry". Select Geometry type of "Other". Select File Type "ASCII". Select [adams_ installation]\lifemod\Demo_Files\Knee\patella.xmt_txt as the parasolids file. Select APPLY to create the insert component. LifeMOD/BodySIM™ will use the material and solid geometry to create the mass properties of the component.

Step 13: Move and reassign the patella bone to the component
Right click on the patella bone and select .World.Ryan_Left_Lower_Leg.Skel_lpatella. When the Geometry Modify panel appears, enter .World.Ryan_patcmp.Skel_lpatella as the New Shell Name and select OK to change the ownership of the patella bone shell from the lower leg to the patcmp part.

Step 14: Create fixed joints between the femCMP and the femur
Create a fixed joint between the femCMP and the femur bone by issuing the following ADAMS/View commands:

marker create marker=.World.Ryan_femCMP.MARKER_833 location=3, -17, 0.0 orientation=0.0, 0.0, 0.0

marker create marker=.World.Ryan_Left_Upper_Leg.MARKER_834 location=3, -17, 0.0 orientation=0.0, 0.0, 0.0

constraint create joint Fixed joint_name=.World.Ryan_JOINT_1 i_marker_name=.World.Ryan_femCMP.MARKER_833 j_marker_name=.World.Ryan_Left_Upper_Leg.MARKER_834

Step 15: Create fixed joints between the tibCMP and the tibia
Create a fixed joint between the tibCMP and the tibia bone by issuing the following ADAMS/View commands:

marker create marker=.World.Ryan_tibCMP.MARKER_833 location=3, -17, 0.0 orientation=0.0, 0.0, 0.0

marker create marker=.World.Ryan_Left_Lower_Leg.MARKER_834 location=3, -17, 0.0 orientation=0.0, 0.0, 0.0

constraint create joint Fixed joint_name=.World.Ryan_JOINT_2 i_marker_name=.World.Ryan_tibCMP.MARKER_833 j_marker_name=.World.Ryan_Left_Lower_Leg.MARKER_834

Generating the Patello-Femoral and Tibio-Femoral Contact Joints

With the solid models of the TKR components implanted to the leg model, contact forces are created between the solids of each interacting component. LifeMOD/BodySIM™ uses a very robust contact algorithm to calculate the normal and frictional forces of contact between to solids. For information on selecting specific model parameters for this section see Choosing Model Parameters


Figure 8: Panel used to create tibio-femoral contact forces


Figure 9: Panel used to create the patello-femoral contact forces.

Step 16: Bring up the create contact panel
Select CONTACTS in the main-menu and CREATE SINGLE in the sub-menu.

Step 17: Create contact between the femoral component and the tibial component
Select solid-solid contact. Select Ryan_femCMP.solid as Contact Solid 1 and Ryan _tibCMP as Contact Solid 2. Select Ryan_tibCMP.cm as the results reference marker. Select the following contact properties:
stiffness:5.7e6
exponent:2
damping:1e4
damping depth:1e-2
dynamic friction:.1
static friction:.3
friction transition velocity:40
stiction transition velocity:3.9

Step 18: Create contact between the patella component and the femoral component
Select solid-solid contact. Select Ryan_patCMP.solid as Contact Solid 1 and Ryan_femCMP as Contact Solid 2. Select Ryan_patCMP.cm as the results reference marker. Select the following contact properties:
stiffness:8.7e6
exponent:2.1
damping:5000
damping depth:1e-3
dynamic friction:.1
static friction:.3
friction transition velocity:40
stiction transition velocity:4

Generating the Ligament Forces

With the contact forces generated between the condyles and the tibial plateau and the condyles and the patella segment, the joint must be stabilized by adding ligament forces. Forces representing the MCL and LCL ligaments are created in this phase. For information on selecting specific model parameters for this section see Choosing Model Parameters.


Figure 10: Location of the LCL (left) and MCL (right) ligaments


Figure 11: Panel used to create the MCL ligament

Step 19: Bring up the create soft tissue panel
Select SOFT TISSUES in the main-menu and CREATE SINGLE on the sub-menu. Select Ligament/Tendon Tissue

Step 20: Create the MCL ligament
Set part 1 to .World.Ryan_Left_Upper_Leg with attachment at 1.5, -17, -0.5 and part 2 to .World.Ryan_Left_Lower_Leg with attachment at 1.5, -18, -0.3. Set the ligament strain stiffness to 5000.0, the damping to 50.0 and the preload to 7 lbs. Select APPLY.

Step 21: Create the LCL ligament
Set part 1 to .World.Ryan_Left_Upper_Leg with attachment at 4.8, -16, -0.2 and part 2 to .World.Ryan_Left_Lower_Leg with attachment at 4.8, -18.6, -0.3. Set the ligament strain stiffness to 5000.0, the damping to 50.0 and the preload to 7 lbs. Select APPLY.

Generating the Tendon Forces

With the knee joint stabilized using ligament forces a patellar tendon is added between the patella and the tibia.


Figure 12: Patellar Tendon Fiber Strand Insertion Points.


Figure 13: Panel to create the lateral strand of the patellar tendon

Step 22: Create the lateral strand of the patellar tendon
Set part 1 to .World.Ryan_patCMP with attachment at 3.3, -16.7, 1.4 and part 2 to .World.Ryan_Left_Lower_Leg with attachment at 3.3, -19.3, 1.0. Set the ligament strain stiffness to 5000.0, the damping to 50.0 and the preload to 0 lbs. Select APPLY.

Step 23: Create the medial strand of the patellar tendon
Set part 1 to .World.Ryan_Patella with attachment at 2.8, -16.7, 1.4 and part 2 to .World.Ryan_left_Lower_Leg with attachment at 2.8, -19.3, 1.0. Set the ligament strain stiffness to 5000.0, the damping to 50.0 and the preload to 0 lbs. Select APPLY.

Generating the Muscle Forces

The next step in the process is to create soft tissues (muscles) on the model. LifeMOD/BodySIM™ automatically creates a set of basic muscle groups for the body. Muscles consist of training elements or trained elements. The training elements are simple data collectors which record the contraction history of the muscle during an activity when the model is moved using external drivers such as motion agents. The trained elements use the contraction data in a PD-Servo linear force actuator to induce the force on the skeleton the replicate the recorded motion. Muscle parameters such as physiological cross sectional area (pCSA) and maximum tissue stress are used to calculate the maximum force potential of the particular muscle. LifeMOD/BodySIM™ contains a database of pCSA values for each muscle and is scaled accordingly based on the input body parameters (ht, wt, gender and age). Further, the force output of the muscle may be scaled from 0% to 200% to change the contributions of each particular muscle.

The BASE muscle set will be used to create the musculature at the knee. Since a new patella segment was created, the attachments of the muscles will have to be repositioned to the new patella segment.


Figure 14: Muscle groups created on the model. Note that the color of the muscles is "rust" indicating passive training elements.


Figure 15: Panel set up to create the left leg muscle groups.

Step 24: Bring up muscle-tendon panel
Select SOFT TISSUES on the main-menu and CREATE BASE SET on the sub-menu.

Step 25: Set the parameters for the muscle set
Set the tendon stiffness to be 1e6 and the damping to be 1e4. Set the tendon preload to be 3 lbs. Check the force vectors and check the left Leg box. Select "Modify" to bring up the tissue matrix.

Step 26:Create the left leg muscles
Uncheck the "Create" box for the Psoas Muscle so as to not create it with the other muscles in the group. This is done since, this muscle spans to the central torso segment which was deleted in a prior phase.

 

 

Generating the Quadriceps Tendon

By default LifeMOD/BodySIM™ automatically generates a set of base muscles for a standard configuration of the body. In some cases, such as this tutorial, muscles must be adjusted to include necessary effects for the analysis. Since the patella component part is a non-standard part in the model, the attachments of several muscles must be changed from other bones (the lower leg in this example). For this tutorial the quadriceps muscles are attached to a dummy part which is in turn connected via a tendon to the patella component.


Figure 16: Creating of the quadriceps tendon. Medial and lateral strands of the patellar tendon are connected between the patellar componen part and the tendon dummy part. The quadriceps muscle attachments are reassigned to the tendon dummy part.


Figure 17: Panel set up to move the quad muscle attachment points.

 

 

Step 27: Zoom in and create a muscle-tendon interface part
Use the Adams/View tools to zoom into the patella location. Create a dummy part using the following commands.

part create rigid_body name part=.World.Tendon

marker create makrer=.World.Tenodn.cm location=3.1,-13.6,1 rel=world

part modify rigid mass_properties &
part_name=.World.Tendon &
mass = .01 &
center_of_mass_marker = .World.tendon.cm &
ixx = .01 &
iyy = .01 &
izz = .01


Step 28: Bring up the soft tissues edit panel
Select SOFT TISSUES in the main-menu and EDIT PROPERTIES in the sub-menu. Click on the light bulb next to Edit Tissue Attachment Points to bring up the attachment point editing panel.

Step 29: Move the Vastus Lateralis attachment
In the panel in figure 17 enter .World.Ryan_Left_Lower_Leg.LVasLat_mell as the attachment (or right click in the field and cursor select the attachment on the model). Enter 3.3, -13.6, 1 as the location and select Modify to move the attachment.

Step 30: Reassign the Vastus Lateralis muscle
In the panel in figure 17 enter .World.Tendon in the Reassign to Segment field and select Apply to change the part the muscle is attached to from the lower leg to the tendon dummy part.

Step 31: Move the Rectus Femoris attachment
In the panel in figure 17 enter .World.Ryan_Left_Lower_Leg.LRecFem_mell as the attachment (or right click in the field and cursor select the attachment on the model). Enter 3.05, -13.6, 1 as the location and select Modify to move the attachment.

Step 32: Reassign the Rectus Femoris muscle
In the panel in figure 17 enter .World.Tendon in the Reassign to Segment field and select Apply to change the part the muscle is attached to from the lower leg to the tendon dummy part.

Step 33: Move the Vastus Medialis attachment
In the panel in figure 17 enter .World.Ryan_Left_Lower_Leg.LVasMed_mell as the attachment (or right click in the field and cursor select the attachment on the model). Enter 2.8, -13.6, 1 as the location and select Modify to move the attachment.

Step 34: Reassign the Vastus Medialis muscle
In the panel in figure 17 enter .World.Tendon in the Reassign to Segment field and select Apply to change the part the muscle is attached to from the lower leg to the tendon dummy part.

Step 35: Bring up the create soft tissues panel
Select SOFT TISSUES in the main-menu and CREATE SINGLE in the sub-menu. Select Ligament/Tendon Tissue.

Step 36: Create the lateral strand of the quad tendon.
Set part 1 to .World.Tendon with attachment at 3.3, -13.6, 1.0 and part 2 to .World.Ryan_patCMP with attachment at 3.3, -15.4, 1.3. Set the ligament strain stiffness to 5e4, the damping to 500.0 and the preload to 0 lbs. Select APPLY.

Step 37: Create the medial strand of the quad tendon.
Set part 1 to .World.Tendon with attachment at 2.8, -13.6, 1.0 and part 2 to .World.Ryan_patCMP with attachment at 2.8, -15.4, 1.3. Set the ligament strain stiffness to 5e4, the damping to 500.0 and the preload to 0 lbs. Select APPLY.

 

Generating the Tissue Contact-Based Wrapping Elements

With the quadriceps tendon complex created, contact-based wrapping elements may be created between the quad tendon and the femoral component and the patellar tendon and the tibial insert component.

 


Figure 18: Quadriceps tendon and patellar tendon are discretized into contact element to wrap about the femoral componen and the tibial insert component respectively.

 


Figure 19: Panel used to create the contact-based tissue wrapping elements.

Step 38: Bring up the soft tissues edit panel
Select SOFT TISSUES in the main-menu and EDIT PROPERTIES in the sub-menu. Select the light bulb at Contact Surface Based Tissue Wrapping Tool to bring up the panel in figure

Step 39: Generate wrap elements between medial patellar tendon and insert
In the panel displayed in figure 19, enter .World.Ryan_Out_NStiss_4P as the tissue, .World.Ryan_Left_Lower_Leg.NStiss_4_Mell as the Tissue Attachment, .World.Ryan_tibCMP.solid as the Wrap Geometry, .8 as the Segmentation length, and 3 as the Number of Segments. Select Apply to discretize the tissue and create the contact forces.

Step 40: Generate wrap elements between lateral patellar tendon and insert
In the panel displayed in figure 19, enter .World.Ryan_Out_NStiss_3P as the tissue, .World.Ryan_Left_Lower_Leg.NStiss_3_Mell as the Tissue Attachment, .World.Ryan_tibCMP.solid as the Wrap Geometry, .8 as the Segmentation length, and 3 as the Number of Segments. Select Apply to discretize the tissue and create the contact forces.

Step 41: Generate wrap elements between medial quad tendon and femoral component
In the panel displayed in figure 19, enter .World.Ryan_Out_NStiss_6P as the tissue, .World.Ryan_patcmp.NStiss_6_Mell as the Tissue Attachment, .World.Ryan_femCMP.solid as the Wrap Geometry, 1.4 as the Segmentation length, and 5 as the Number of Segments. Select Apply to discretize the tissue and create the contact forces.

Step 42: Generate wrap elements between lateral quad tendon and femoral component
In the panel displayed in figure 19, enter .World.Ryan_Out_NStiss_5P as the tissue, .World.Ryan_patcmp.NStiss_5_Mell as the Tissue Attachment, .World.Ryan_femCMP.solid as the Wrap Geometry, 1.4 as the Segmentation length, and 5 as the Number of Segments. Select Apply to discretize the tissue and create the contact forces.

Adding Motion Agents to the Model

A motion agent is added to stabilize the knee model for an equilibrium analysis. The agent basically adds a fixed constraint along the z-axis (anterior to posterior) of the knee and is free in the other 5 dof's. This motion agent will be removed for the inverse-dynamics simulation which follows the equilibrium simulation.


Figure 20: Motion agent creation panel and knee model with motion agent


Figure 21: Spline Data for Motion Agent.


Figure 22: Location of the Motion Agent.

Step 43: Bring up the create motion agent panel
Select MOTION on the main-menu and CREATE SINGLE AGENT sub-menu.

Step 44: Create a spline using data from Figure 21
Create the data spline to flex the knee with the following ADAMS/View command:

data_element create spline &
spline=.World.Ryan_SPLINE_1 &
x=0.0, .5, 1, 1.5, 2, 2.5, 3, 3.5, 4 &
y=0.0, 4, 7, 9, 9.3, 9, 7, 4, 0.0 &
linear_extrapolate=no &
units=no_units

Step 45: Create motion agent on the lower leg
Select .World.Ryan_left_Lower_Leg as the body segment and select Manually Select Location for the agent positioning method using a location of 2.8, -15, 1.2. Set the stiffness to be 1e7 and the damping to be 1e5. Specify all dof's to be free except for the z-dof which is driven using the spline created in the previous step.

Running the Equilibrium Simulation

To produce smooth simulations for both the inverse-dynamics and forward-dynamics simulations, it is strongly recommended that an equilibrium simulation be performed to equilibrate the forces in the model. These forces occur due to misplacement of the contact ellipsoids, balancing the preloaded soft tissues, etc. Before the simulation may be performed the model must be constrained to the environment. This is done using a joint combination, which will allow the knee to flex in 6 degrees-of-freedom. Following this, an inverse-dynamics simulation is performed to capture the muscle elongation data for a subsequent forward-dynamics simulation.


Figure 23: Joints Constraining Model to the Environment.


Figure 24: Panel set up for equilibrium simulation. Be sure to check "Freeze Motion Agents for Equilibrium" to make sure the motion agent does not move and only acts as a stabilizer.

Step 46: Create a fixed joint between the foot and ground
Use the following ADAMS/View commands to create a fixed joint between the foot and ground:

marker create marker=.World.Ryan_Left_Foot.ground location=6, -36, -0.3 rel=.world

marker create marker=.World.ground.foot location=6, -36, -0.3 rel=.world

constraint create joint Fixed joint_name=.World.Foot_Ground i_marker_name=.World.Ryan_Left_Foot.ground j_marker_name=.World.ground.foot

Step 47: Constrain the motion of the body by creating a translational joint between pelvis and ground
Use the following ADAMS/View commands to create a universal joint between the femur and the pelvis:

marker create marker=.World.Ryan_Lower_Torso.MARKER_860_2 loc=0, 0.6, -0.8 ori=0,-90,0 rel=(none)

marker create marker=.World.ground.MARKER_861_2 loc=0, 0.6, -0.8 ori=0,-90,0 rel=(none)

constraint create joint Translational joint_name=.World.Ryan_JOINT_5 i_marker=.World.Ryan_Lower_Torso.MARKER_860_2 j_marker=.World.ground.MARKER_861_2

Step 48: Bring up the analyze panel
Select ANALYZE on the main-menu and DYNAMICS on the sub-menu.

Step 49: Run the dynamics simulation, freeze the motion agent
Select "Freeze Motion Agents for Equilibrium Simulation" Set gravity at -386.0885826772 in the y direction and run the simulation for 1 second and 100 time steps using the default integrator settings and freeze the motion agent. By freezing the motion agent, it will provide a force to stabilize the knee into an equilibrium position

Step 50: View the equilibrium simulation results
Use the ADAMS/View toolbox to animate the equilibrium results

Step 51: Update the model configuration with static results
Select UPDATE MODEL POSTURE WITH EQUILIBRIUM RESULTS button on the analyze panel.

Running the Inverse-Dynamics Simulation

With the updated model configuration, the model is ready for the inverse-dynamics simulation. The motion agent will be used to manipulate the model into a deep knee bend activity. During this analysis the muscle contractions in the muscle training elements will be recorded.


Figure 25: Animation from the Inverse-Dynamics Simulation.

Step 52: Uncheck Freeze Motion Agent and run the simulation
Uncheck Freeze Motion Agent in the panel displayed in figure 24. Set gravity at -386.0885826772 in the y direction and run the simulation for 4 seconds and 200 time steps using the "Contacts Optimized " integrator settings.

Step 53: Display animation
Use the ADAMS/View toolbox to animate the equilibrium results

Running the forward-Dynamics Simulation

With the muscle contraction histories recorded from the inverse-dynamics simulation, the data may now be used in an active muscle formulation to produce a force to recreate the motion history. The process entails removing the Motion Agents and updating the muscles. Also the passive stiffness in the hip and ankle joints are reduced from the higher values used in the inverse-dynamics simulation for stabilization.


Figure 26: Three successive frames of the forward-dynamics simulation. Note the color of the muscle is now deep red indicating active muscle forces. Also note the scaling muscle graphics indicating force magnitudes thorough the muscles, tendons and ligaments.


Figure 27: Panel to update muscle formulation with ACTIVE (Trained) contraction elements based on data from inverse-dynamics analysis

 

Step 54: Bring up the tissue training panel
Select SOFT TISSUES on the main-menu and TRAINING on the sub-menu.

Step 55: Install ACTIVE contractile element
Select the light bulb to bring up the INSTALL TRAINED DRIVER ELEMENTS panel.

Step 56: Set fields and update joints
Specify 1e6 as the proportional gain and 1e4 as the derivative gain. These values control how well the PD-servo actuators will track the desired contraction at each time step in the analysis. Note that the individual muscle will not produce a force greater than the physiological cross

Step 57: Bring up the analyze panel
Select ANALYZE on the main-menu and DYNAMICS on the sub-menu.

Step 58: Disable motion agents and run the forward-dynamics simulation
Set gravity at -386.0885826772 in the y direction and run the simulation for 2 seconds and 200 time steps using the default integrator settings. Be sure to disable the motion agents and set the integrator to "contacts optimized".

Running the Parametric Analysis

LifeMOD/BodySIM™ manages the redundant muscle problem in human mechanics by allowing for equal contribution for each muscle involved in the motion across the joint. This contribution is effected by the maximum force output of each muscle and can further be effected by the user. This section the user will reduce the contributions of three muscles to examine the effects load redistribution effects on the other muscles.


Figure 28: Panel used to reduce the contributions by 50% of the gluteus maximus 1, 2 and the Soleus muscles.

Step 59: Display animation
Use the ADAMS/View toolbox to animate the results

Step 60: Bring up the results panel.
Select RESULTS on the main-menu and DATA DISPLAY on the sub-menu.

Step 61: Display muscle strip charts
Enter Soft Tissues as the Data Type. Select the soft tissue Ryan_VasLat_Ltiss_1, Tension as the Characteristic and Creat Strip Chart Measure to creat the strip chart for the muscle. Select the soft tissue Ryan_GlutMax1_Ltiss_1, Tension as the Characteristic and Creat Strip Chart Measure to creat the strip chart for the muscle. Two data strip charts will be displayed with the muscle forces for this activity.

Step 62: Turn on muscle graphics scaling
Select ANIMATION on the sub-menu. Select Scale Joint/Tissue Graphics, Tissues, Scale Globally and the light bulb to scale the muscle graphics.

Step 63: Display animation
Use the ADAMS/View toolbox to animate the results. Observe the scaling muscle forces.

Step 64: Save the muscle force curves
On each strip chart, right click on the curve and select "save".

Step 65: Bring up soft tissue edit panel
Select SOFT TISSUES on the sub-menu and EDIT PROPERTIES on the panel.

Step 66: Bring up the left leg tissue panel
Select the "Edit Individual Tissue Properties" light bulb. Check left leg to bring up the muscle panel.

Step 67: Reduce the contribution of the Gluteus Maximus 1, 2 and the Soleus Muscles
Move the slider to read 25% of the normal value for each muscle and select APPLY.

Step 68: Bring up the analyze panel
Select ANALYZE on the main-menu and DYNAMICS on the sub-menu.

Step 69: Disable motion agents and run the forward-dynamics simulation
Set gravity at -386.0885826772 in the y direction and run the simulation for 2 seconds and 200 time steps using the default integrator settings. Be sure to disable the motion agents and set the integrator to "contacts optimized".

Interrogating the Results

When the simulation is complete the model may be animated. Figure 26 displays the model animation. The appearance of the animations may differ from the figure, depending on the placement of the muscle attachment points.

Various data may be presented from the forward-dynamics simulation including:

  • Tibia-femoral and patello-femoral contact forces
  • Ligament tensions
  • Muscle Forces
  • Relative Displacements


Figure 29: Animation Sequence and Data Display from comparing case 1 (before muscle contribution adjustment) to case 2 (after reducing the GM and Soleus muscles.


Figure 30: Plot of the PF and TF contact forces

Step 70: Bring up the results panel.
Select RESULTS on the main-menu and ANIMATION on the sub-menu.

Step 71: Turn muscle graphics scaling on
Select ANIMATION on the sub-menu. Select Scale Joint/Tissue Graphics, Tissues, Scale Globally and the light bulb to scale the muscle graphics.

Step 72: Display animation
Select Fix Camera to Marker and select .World.Ryan_tibCMP.cm. Select right view and the Play arrow in the panel to animate. Note the change in force distribution between the two cases.

Step 73: Display animation without muscles
Use the BodySIM Display Toolbox to turn off the muscles, tendons and ligamments. Then animate the model to examine the interaction of the components.

Step 74: Display animation without bones
Use the BodySIM Display Toolbox to turn off the bones to get a better view of the motion of the components. Set the view to wireframe by selecting Render on the Adams/View toolbox panel. Select Fix Camera to Marker and select .World.Ryan_tibCMP.cm. Select play in the animation panel to display the animation.

Step 75: Animate the front view
Select front view animate animate.

Step 76: Animate the top view
Select top view animate animate.

Step 77: Bring up results panel
Select DATA DISPLAY on the sub-menu. Select "Results Window" button to bring up the results processor. Select Soft Tissues as the Data Type.

Step 78: Plot the LCL ligament forces
Select Ryan_NStiss_1P for the soft tissue and tension characteristic. Select a low pass butterworth data filter with a cutoff frequency of 5.0 and an order of 1. Select Create Full Plot to create the curve.

Step 79:Plot the MCL ligament forces
Select Ryan_NStiss_2P for the soft tissue and tension characteristic. Select a low pass butterworth data filter with a cutoff frequency of 5.0 and an order of 1. Select Create Full Plot to create the curve.

Step 80: Animate right view
Select right view, divide window and select PLAY.

Step 81: Animate the view close up.
Check zoom on the results panel and enter -0.5378289278, -17.502685398, 3.1299660314 for the zoom center and 2.75 for the zoom scale. select PLAY.

Step 82: Bring up contact panel
Select Data Display in the sub-menu. Select Contacts as the Data Type.

Step 83: Plot the AP-Shear component of the TF contact force
Select Ryan_NScon_1 as the contact force and the Z component Select a low pass butterworth data filter with a cutoff frequency of 5.0 and an order of 1. Select Create Full Plot to create the curve.

Step 84: Plot the Normal component of the TF contact force
Select Ryan_NScon_1 as the contact force and the Y component Select a low pass butterworth data filter with a cutoff frequency of 5.0 and an order of 1. Select Create Full Plot to create the curve.

Step 85: Plot the normal component of the PF contact force
Select Ryan_NScon_2 as the contact force and the Y component Select a low pass butterworth data filter with a cutoff frequency of 5.0 and an order of 1. Select Create Full Plot to create the curve.

Step 86: Turn off bones/muscles and animate right view
Turn off the bones and muscles using the BodySIM Display Toolbox. Select Fix Camera to Marker and .World.Ryan_tibCMP.cm as the marker. Set view to right, select divide window and animate.

Step 87: Animate the right view in wire frame.
Set the model rendering to wireframe and run the animation.

Step 88: Animate the top view
Set the model rendering to shaded, set view to top and run the animation.

Step 89: Animate the top view, wire frame.
Set the model rendering to wireframe, set view to top and run the animation.

Step 90: Animate the front view.
Set the model rendering to shaded, set view to front and run the animation.

Step 91: Animate the front view, wire frame.
Set the model rendering to wireframe and run the animation.

Step 83: DEMO COMPLETE

Further

This model was put forth to demonstrate the creation of a human joint with a relatively high degree of biofidelity. Obviously the model can be further refined and improved, from the point developed in this example. The intention with this example was to touch of the various modeling functions of both the LifeMOD/BodySIM™ Biomechanics Modeler and ADAMS/View necessary to create a joint of this nature.

This model may be refined in many areas including:

  • Performing a sensitivity analysis by examining the effects of repositioning the ligament attachment points
  • Adding more ligament, muscle and tendon strands to better represent the nature of these soft tissue forces
 
COPYRIGHT© 2007 Biomechanics Research Group, Inc.