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Overview and Authors
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The Gait2392 and Gait2354 models are three-dimensional, 23-degree-of-freedom computer models of the human musculoskeletal system. The models were created by Darryl Thelen (University of Wisconsin-Madison) and Ajay Seth, Frank C. Anderson, and Scott L. Delp (Stanford University). The models feature lower extremity joint definitions adopted from Delp et al. (1990), low back joint and anthropometry adopted from Anderson and Pandy (1999), and a planar knee model adopted from Yamaguchi and Zajac (1989). The Gait2392 model features 92 musculotendon actuators to represent 76 muscles in the lower extremities and torso. For the Gait2354 model, the number of muscles was reduced by Anderson to improve simulation speed for demonstrations and educational purposes. Seth removed the patella to avoid kinematic constraints; insertions of the quadriceps are handled with moving points in the tibia frame. The default, unscaled version of these models represents a subject that is about 1.8 m tall and has a mass of 75.16 kg. |
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The experimental data included with the model files in the OpenSim distribution was collected as part of the study cited below. Please note that the data distributed with OpenSim is from a different subject than the one described in the paper. Data collection protocols were the same for both subjects.
Chand T. John, Frank C. Anderson, Jill S. Higginson & Scott L. Delp (2012): Stabilisation of walking by intrinsic muscle properties revealed in a three-dimensional muscle-driven simulation, Computer Methods in Biomechanics and Biomedical Engineering, DOI:10.1080/10255842.2011.627560. Download here
Accessing the Models
The musculoskeletal file (.osim), the setting files (.xml), and associated result files (.mot, .sto) for this model are provided free of charge with the OpenSim software for researchers interest in reproducing the result of the simulation. These files can be accessed via the Models/Gait2392_Simbody or Models/Gait2354_Simbody folder in the OpenSim 3.0 installation directory, and the example/Gait2392_Simbody or Models/Gait2392_Simbody folder in the OpenSim 2.4.0 installation directory.
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The lower extremity has seven right-body segments: pelvis, femur, patella, tibia/fibula, talus, foot (which includes the calcaneus, navicular, cuboid, cuneiforms, metatarsals), and toes. Reference frames are fixed in each segment.
Figure 1 Location of the body-segmental reference frames (Delp et al., 1990).
- Pelvis: The pelvic reference frame is fixed at the midpoint of the line connecting the two anterior superior iliac spines
- Femur: The femoral frame is fixed at the center of the femoral head
- Tibia: The tibial frame is located at the midpoint of the line between the medial and lateral femoral epicondyles
- Patella: The patellar frame is located at the most distal point of the patella
- Talus: The talar frame is located at the midpoint of the line between the apices of the medical and lateral malleoli
- Calcanus: The calcaneal frame is located at the most interior, lateral point on the posterior surface of the calcanus
- Toe: The toe frame is located at the base of the second metatarsal
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Pelvic Tilt and Hip Flexion Angle (Gait2354 vs. Clinical Measurements)
The pelvic frame is located midway between the two ASIS. In the neutral position, the model has zero pelvic tilt with respect to ground (or lab). In other words, the pelvic frame and ground frame are aligned at neutral (pelvic tilt = 0 degrees). In many clinical papers, neutral corresponds to 12-13 degrees of pelvic tilt. This will lead to an offset when comparing pelvic tilt and hip flexion angles from the gait2354 model to some data from clinical papers or gait analysis lab data.
To compare angles from the gait2354 model to clinical data, you can subtract the angle formed between the horizontal plane and a line between the ASIS and PSIS markers from the clinical pelvic tilt measurements. You should also add this value to the clinical hip flexion measurement. If angle formed between the horizontal plane and a line between the ASIS and PSIS markers is not known, a value of 12-13 degrees is typical.
Hip Joint
The hip is characterized as a ball-and-socket joint. The transformation between the pelvic and femoral reference frame is thus determined by successive rotations of the femoral frame about three orthogonal axes fixed in the femoral head.
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The ankle, subtalar, and metatarsophalangeal joints are modeled as frictionless revolute joints (as seen in Figure 3).
Figure 3. The ankle, subtalar, and metatarphalangeal joints are modeled as revolute joints with axes oriented as shown. (Delp et al., 1990)
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Table 2: Inertial parameters for the body segments included in the model
Body segment | Mass (kg) | Moments of inertia | ||
xx | yy | zz
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Torso | 34.2366 | 1.4745 | 0.7555 | 1.4314 |
Pelvis | 11.777 | 0.1028 | 0.0871 | 0.0579 |
Right femur | 9.3014 | 0.1339 | 0.0351 | 0.1412 |
Right tibia | 3.7075 | 0.0504 | 0.0051 | 0.0511 |
Right patella | 0.0862 | 0.00000287 | 0.00001311 | 0.00001311 |
Right talus | 0.1000 | 0.0010 | 0.0010 | 0.0010 |
Right calcaneus | 1.250 | 0.0014 | 0.0039 | 0.0041 |
Right toe | 0.2166 | 0.0001 | 0.0002 | 0.0010 |
Left femur | 9.3014 | 0.1339 | 0.0351 | 0.1412 |
Left tibia | 3.7075 | 0.0504 | 0.0051 | 0.0511 |
Left patella | 0.0862 | 0.00000287 | 0.00001311 | 0.00001311 |
Left talus | 0.1000 | 0.0010 | 0.0010 | 0.0010 |
Left calcaneus | 1.250 | 0.0014 | 0.0039 | 0.0041 |
Left toe | 0.2166 | 0.0001 | 0.0002 | 0.0010 |
Actuators and Other Force-Generating Elements
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Hoy, M. G., Zajac, F. E., and Gordon, M. E., "A musculoskeletal model of the human lower extremity: the effect of muscle, tendon, and moment ann on the moment-angle relationship of musculotendon actuators at the hip, knee, and ankle," J. Biomech., vol. 23, pp. 157-169, 1990.