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Research Papers

Evaluating the Effects of Ankle-Foot Orthosis Mechanical Property Assumptions on Gait Simulation Muscle Force Results

[+] Author and Article Information
Amy K. Hegarty, Anthony J. Petrella

Department of Mechanical Engineering,
Colorado School of Mines,
Golden, CO 80401

Max J. Kurz

Department of Physical Therapy,
Munroe-Meyer Institute for Genetics
and Rehabilitation,
University of Nebraska Medical Center,
Omaha, NE 68198

Anne K. Silverman

Department of Mechanical Engineering,
Colorado School of Mines,
1500 Illinois Street,
Golden, CO 80401
e-mail: asilverm@mines.edu

1Corresponding author.

Manuscript received July 21, 2016; final manuscript received November 21, 2016; published online January 23, 2017. Assoc. Editor: Tammy L. Haut Donahue.

J Biomech Eng 139(3), 031009 (Jan 23, 2017) (8 pages) Paper No: BIO-16-1308; doi: 10.1115/1.4035472 History: Received July 21, 2016; Revised November 21, 2016

Musculoskeletal modeling and simulation techniques have been used to gain insights into movement disabilities for many populations, such as ambulatory children with cerebral palsy (CP). The individuals who can benefit from these techniques are often limited to those who can walk without assistive devices, due to challenges in accurately modeling these devices. Specifically, many children with CP require the use of ankle-foot orthoses (AFOs) to improve their walking ability, and modeling these devices is important to understand their role in walking mechanics. The purpose of this study was to quantify the effects of AFO mechanical property assumptions, including rotational stiffness, damping, and equilibrium angle of the ankle and subtalar joints, on the estimation of lower-limb muscle forces during stance for children with CP. We analyzed two walking gait cycles for two children with CP while they were wearing their own prescribed AFOs. We generated 1000-trial Monte Carlo simulations for each of the walking gait cycles, resulting in a total of 4000 walking simulations. We found that AFO mechanical property assumptions influenced the force estimates for all the muscles in the model, with the ankle muscles having the largest resulting variability. Muscle forces were most sensitive to assumptions of AFO ankle and subtalar stiffness, which should therefore be measured when possible. Muscle force estimates were less sensitive to estimates of damping and equilibrium angle. When stiffness measurements are not available, limitations on the accuracy of muscle force estimates for all the muscles in the model, especially the ankle muscles, should be acknowledged.

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References

Zajac, F. E. , Neptune, R. R. , and Kautz, S. A. , 2003, “ Biomechanics and Muscle Coordination of Human Walking—Part II: Lessons From Dynamical Simulations and Clinical Implications,” Gait Posture, 17(1), pp. 1–17. [CrossRef] [PubMed]
Pandy, M. G. , Lin, Y.-C. , and Kim, H. J. , 2010, “ Muscle Coordination of Mediolateral Balance in Normal Walking,” J. Biomech., 43(11), pp. 2055–2064. [CrossRef] [PubMed]
Silverman, A. K. , and Neptune, R. R. , 2012, “ Muscle and Prosthesis Contributions to Amputee Walking Mechanics: A Modeling Study,” J. Biomech., 45(13), pp. 2271–2278. [CrossRef] [PubMed]
Knarr, B. A. , Reisman, D. S. , Binder-Macleod, S. A. , and Higginson, J. S. , 2014, “ Changes in Predicted Muscle Coordination With Subject-Specific Muscle Parameters for Individuals After Stroke,” Stroke Res. Treat., 2014, pp. 1–7. [CrossRef]
Peterson, C. L. , Hall, A. L. , Kautz, S. A. , and Neptune, R. R. , 2010, “ Pre-Swing Deficits in Forward Propulsion, Swing Initiation and Power Generation by Individual Muscles During Hemiparetic Walking,” J. Biomech., 43(12), pp. 2348–2355. [CrossRef] [PubMed]
Chambers, H. G. , 2001, “ Treatment of Functional Limitations at the Knee in Ambulatory Children With Cerebral Palsy,” Eur. J. Neurol., 8(5), pp. 59–74. [CrossRef] [PubMed]
Steele, K. M. , Van der Krogt, M. M. , Schwartz, M. H. , and Delp, S. L. , 2012, “ How Much Muscle Strength Is Required to Walk in a Crouch Gait?,” J. Biomech., 45(15), pp. 2564–2569. [CrossRef] [PubMed]
Knutson, L. M. , and Clark, D. E. , 1991, “ Orthotic Devices for Ambulation in Children With Cerebral Palsy and Myelomeningocele,” Phys. Ther., 71(12), pp. 947–960. [PubMed]
Sumiya, T. , Suzuki, Y. , and Kasahara, T. , 1996, “ Stiffness Control in Posterior-Type Plastic Ankle-Foot Orthoses: Effect of Ankle Trimline—Part 2: Orthosis Characteristics and Orthosis/Patient Matching,” Prosthet. Orthotics Int., 20(2), pp. 132–137. http://www.oandplibrary.org/poi/1996_02_132.asp
Yamamoto, S. , Ebina, M. , Iwasaki, M. , Kubo, S. , Kawai, H. , and Kayashi, T. , 1993, “ Comparative Study of Mechanical Characteristics of Plastic AFOs,” J. Prosthet. Orthotics, 5(2), pp. 59–70. http://www.oandp.org/jpo/library/1993_02_059.asp
Yamamoto, S. , Miyazaki, S. , and Kubota, T. , 1993, “ Quantification of the Effect of the Mechanical Property of Ankle-Foot Orthoses on Hemiplegic Gait,” Gait Posture, 1(1), pp. 27–34. [CrossRef]
Bregman, D. J. J. , Rozumalski, A. , Koops, D. , de Groot, V. , Schwartz, M. H. , and Harlaar, J. , 2009, “ A New Method for Evaluating Ankle Foot Orthosis Characteristics: BRUCE,” Gait Posture, 30(2), pp. 144–149. [CrossRef] [PubMed]
Kobayashi, T. , Leung, A. K. L. , and Hutchins, S. W. , 2011, “ Techniques to Measure Rigidity of Ankle-Foot Orthosis: A Review,” J. Rehabil. Res. Dev., 48(5), pp. 565–576. [CrossRef] [PubMed]
Schwartz, M. H. , Rozumalski, A. , Truong, W. , and Novacheck, T. F. , 2013, “ Predicting the Outcome of Intramuscular Psoas Lengthening in Children With Cerebral Palsy Using Preoperative Gait Data and the Random Forest Algorithm,” Gait Posture, 37(4), pp. 473–479. [CrossRef] [PubMed]
Dreher, T. , Vegvári, D. , Wolf, S. L. , Klotz, M. , Müller, S. , Metaxiotis, D. , Wenz, W. , Döderlein, L. , and Braatz, F. , 2013, “ Long-Term Effects After Conversion of Biarticular to Monoarticular Muscles Compared With Musculotendinous Lengthening in Children With Spastic Diplegia,” Gait Posture, 37(3), pp. 430–435. [CrossRef] [PubMed]
Delp, S. L. , Loan, P. J. , Hoy, M. G. , Zajac, F. E. , Topp, E. L. , and Rosen, J. M. , 1990, “ An Interactive Graphics-Based Model of the Lower Extremity to Study Orthopaedic Surgical Procedures,” IEEE Trans. Biomed. Eng., 37(8), pp. 757–767. [CrossRef] [PubMed]
Yamaguchi, G. T. , and Zajac, F. E. , 1989, “ A Planar Model of the Knee Joint to Characterize the Knee Externsor Mechanism,” J. Biomech., 22(1), pp. 1–10. [CrossRef] [PubMed]
Anderson, F. C. , and Pandy, M. G. , 1999, “ A Dynamic Optimization Solution for Vertical Jumping in Three Dimensions,” Comput. Methods Biomech. Biomed. Eng., 2(3), pp. 201–231. [CrossRef]
Anderson, F. C. , and Pandy, M. G. , 2001, “ Dynamic Optimization of Human Walking,” ASME J. Biomech. Eng., 123(5), pp. 381–390. [CrossRef]
Lu, T.-W. , and O'Connor, J. J. , 1999, “ Bone Position Estimation From Skin Marker Co-Ordinates Using Global Optimisation With Joint Constraints,” J. Biomech., 32(2), pp. 129–134. [CrossRef] [PubMed]
Thelen, D. G. , and Anderson, F. C. , 2006, “ Using Computed Muscle Control to Generate Forward Dynamic Simulations of Human Walking From Experimental Data,” J. Biomech., 39(6), pp. 1107–1115. [CrossRef] [PubMed]
Bregman, D. J. J. , De Groot, V. , Van Diggele, P. , Meulman, H. , Houdijk, H. , and Harlaar, J. , 2010, “ Polypropylene Ankle Foot Orthoses to Overcome Drop-Foot Gait in Central Neurological Patients: A Mechanical and Functional Evaluation,” Prosthet. Orthotics Int., 34(3), pp. 293–304. [CrossRef]
Condie, D. N. , and Meadows, C. B. , 1977, “ Some Biomechanical Considerations in the Design of Ankle-Foot Orthoses,” Orthotics Prosthet., 31(3), pp. 45–52. http://www.oandplibrary.org/op/1977_03_045.asp
Crabtree, C. A. , and Higginson, J. S. , 2009, “ Modeling Neuromuscular Effects of Ankle Foot Orthoses (AFOs) in Computer Simulations of Gait,” Gait Posture, 29(1), pp. 65–70. [CrossRef] [PubMed]
Klasson, B. , Convery, P. , and Raschke, S. , 1998, “ Test Apparatus for the Measurement of the Flexibility of Ankle-Foot Orthoses in Planes Other Than the Loaded Plane,” Prosthet. Orthotics Int., 22(1), pp. 45–53. http://www.oandplibrary.org/poi/1998_01_045.asp
Major, R. E. , Hewart, P. J. , and Macdonald, A. M. , 2004, “ A New Structural Concept in Moulded Fixed Ankle Foot Orthoses and Comparison of the Bending Stiffness of Four Constructions,” Prosthet. Orthotics Int., 28(1), pp. 44–48. http://www.tandfonline.com/doi/abs/10.3109/03093640409167924?journalCode=ipoi20
Sumiya, T. , Suzuki, Y. , and Kasahara, T. , 1996, “ Stiffness Control in Posterior-Type Plastic Ankle-Foot Orthoses: Effect of Ankle Trimline—Part 1: A Device for Measuring Ankle Moment,” Prosthet. Orthotics Int., 20(2), pp. 129–131. http://www.oandplibrary.org/poi/1996_02_129.asp
Kobayashi, T. , Leung, A. K. L. , Akazawa, Y. , Naito, H. , Tanaka, M. , and Hutchins, S. W. , 2010, “ Design of an Automated Device to Measure Sagittal Plane Stiffness of an Articulated Ankle-Foot Orthosis,” Prosthet. Orthotics Int., 34(4), pp. 439–448. [CrossRef]
Easley, S. K. , Pal, S. , Tomaszewski, P. R. , Petrella, A. J. , Rullkoetter, P. J. , and Laz, P. J. , 2007, “ Finite Element-Based Probabilistic Analysis Tool for Orthopaedic Applications,” Comput. Methods Programs Biomed., 85(1), pp. 32–40. [CrossRef] [PubMed]
Middleton, E. A. , Hurley, G. R. B. , and McIlwain, J. S. , 1988, “ The Role of Rigid and Hinged Polypropylene Ankle-Foot-Orthoses in the Management of Cerebral Palsy: A Case Study,” Prosthet. Orthotics Int., 12(3), pp. 129–135. http://www.oandplibrary.org/poi/1988_03_129.asp
Gage, J. R. , 1990, “ Surgical Treatment of Knee Dysfunction in Cerebral Palsy,” Clin. Orthop. Relat. Res., 253, pp. 45–54.
Kamp, F. A. , Lennon, N. , Holmes, L. , Dallmeijer, A. J. , Henley, J. , and Miller, F. , 2014, “ Energy Cost of Walking in Children With Spastic Cerebral Palsy: Relationship With Age, Body Composition and Mobility Capacity,” Gait Posture, 40(1), pp. 209–214. [CrossRef] [PubMed]

Figures

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Fig. 1

AFO model generated within the generic musculoskeletal model used for each child within the simulation framework. AFO torque development for motion at the ankle is shown for both plantarflexion torque (left) and dorsiflexion torque (right). Unidirectional stiffness terms dependent on the ankle position are shown as dorsiflexion stiffness (left) and plantarflexion stiffness (right).

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Fig. 2

Methodological diagram for the generation of each Monte Carlo simulation. Eight input parameters including ankle/subtalar joint unidirectional stiffness, damping, and equilibrium angle, defined as random variables, were described by predetermined distributions (a). Values generated from these distributions were used as inputs into the ankle-foot orthosis model to generate an equation for the external torque applied at the ankle and subtalar joints (b). The AFO torque model, perturbed by the random inputs, was applied within a standard musculoskeletal walking simulation for a single gait cycle (c). Muscle force estimates for the simulated gait cycle were recorded, and the average muscle force during stance was calculated (d). This process was repeated 1000 times to generate a distribution of possible muscle force values ((e) and (f)). The cumulative distribution function for each lower-limb muscle was used to calculate the muscles' coefficients of variation and probabilistic sensitivity factors (f).

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Fig. 3

Average coefficient of variation for muscle force estimates developed from the Monte Carlo simulations. The coefficient of variation was averaged across both legs, both trials, and both subjects, generated by individual Monte Carlo simulations.

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Fig. 4

Average (absolute value) sensitivity factor for AFO model input parameters across all the muscles for each walking trial. High sensitivity factors indicate greater influence on output metrics for an individual input parameter. Average sensitivity factors were averaged across the range of possible output values for each muscle force estimate, across both legs within each walking trial, and across walking trials for both subjects.

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Fig. 5

Ankle dorsiflexion stiffness sensitivity factors for simulation muscle force estimates. A summary of the response of each muscle, for each child and trial, is shown. Sensitivity factors are averaged across both legs for each trial. The sensitivity value for 5% of the outcome distribution (left arrow), 50% of the outcome distribution (median, square), and 95% of the outcome distribution (right arrow) is indicated.

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Fig. 6

Subtalar inversion stiffness sensitivity factors for simulation muscle force estimates. The response of each muscle, for each child and trial, is shown. Sensitivity factors are averaged across both legs for each trial. The sensitivity value for 5% of the outcome distribution (left arrow), 50% of the outcome distribution (median, square), and 95% of the outcome distribution (right arrow) is indicated.

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Fig. 7

Subtalar eversion stiffness sensitivity factors for simulation muscle force estimates. The response of each muscle, for each child and trial, is shown. Sensitivity factors are averaged across both legs for each trial. The sensitivity value for 5% of the outcome distribution (left arrow), 50% of the outcome distribution (median, square), and 95% of the outcome distribution (right arrow) is indicated.

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Fig. 8

Ankle equilibrium angle sensitivity factors for simulation muscle force estimates. The response of each muscle, for each child and trial, is shown. Sensitivity factors are averaged across both legs for each trial. The sensitivity value for 5% of the outcome distribution (left arrow), 50% of the outcome distribution (median, square), and 95% of the outcome distribution (right arrow) is indicated.

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