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K. Veerkamp

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3 records found

Interacting effects of AFO stiffness, neutral angle and footplate stiffness on gait in case of plantarflexor weakness

A predictive simulation study

Journal article - Niels F.J. Waterval, Niels F.J. Waterval, M. A. Brehm, M. A. Brehm, K. Veerkamp, K. Veerkamp, K. Veerkamp, T. Geijtenbeek, J. Harlaar, J. Harlaar, F. Nollet, F. Nollet, Marjolein M. van der Krogt, Marjolein M. van der Krogt

To maximize effects of dorsal leaf ankle foot orthoses (AFOs) on gait in people with bilateral plantarflexor weakness, the AFO properties should be matched to the individual. However, how AFO properties interact regarding their effect on gait function is unknown. We studied the i ...

The interaction between muscle pathophysiology, body mass, walking speed and ankle foot orthosis stiffness on walking energy cost

A predictive simulation study

Journal article - Niels F.J. Waterval, Niels F.J. Waterval, Marjolein M. van der Krogt, Marjolein M. van der Krogt, Marjolein M. van der Krogt, K. Veerkamp, K. Veerkamp, K. Veerkamp, T. Geijtenbeek, J. Harlaar, J. Harlaar, F. Nollet, F. Nollet, M. A. Brehm, M. A. Brehm

Background: The stiffness of a dorsal leaf AFO that minimizes walking energy cost in people with plantarflexor weakness varies between individuals. Using predictive simulations, we studied the effects of plantarflexor weakness, passive plantarflexor stiffness, body mass, and walking speed on the optimal AFO stiffness for energy cost reduction. Methods: We employed a planar, nine degrees-of-freedom musculoskeletal model, in which for validation maximal strength of the plantar flexors was reduced by 80%. Walking simulations, driven by minimizing a comprehensive cost function of which energy cost was the main contributor, were generated using a reflex-based controller. Simulations of walking without and with an AFO with stiffnesses between 0.9 and 8.7 Nm/degree were generated. After validation against experimental data of 11 people with plantarflexor weakness using the Root-mean-square error (RMSE), we systematically changed plantarflexor weakness (range 40–90% weakness), passive plantarflexor stiffness (range: 20–200% of normal), body mass (+ 30%) and walking speed (range: 0.8–1.2 m/s) in our baseline model to evaluate their effect on the optimal AFO stiffness for energy cost minimization. Results: Our simulations had a RMSE < 2 for all lower limb joint kinetics and kinematics except the knee and hip power for walking without AFO. When systematically varying model parameters, more severe plantarflexor weakness, lower passive plantarflexor stiffness, higher body mass and walking speed increased the optimal AFO stiffness for energy cost minimization, with the largest effects for severity of plantarflexor weakness. Conclusions: Our forward simulations demonstrate that in individuals with bilateral plantarflexor the necessary AFO stiffness for walking energy cost minimization is largely affected by severity of plantarflexor weakness, while variation in walking speed, passive muscle stiffness and body mass influence the optimal stiffness to a lesser extent. That gait deviations without AFO are overestimated may have exaggerated the required support of the AFO to minimize walking energy cost. Future research should focus on improving predictive simulations in order to implement personalized predictions in usual care. Trial Registration Nederlands Trial Register 5170. Registration date: May 7th 2015. http://www.trialregister.nl/trialreg/admin/rctview.asp?TC=5170.@en

O 037 – Estimating musculotendon forces in children with cerebral palsy

The importance of the use of electromyography in neuromusculoskeletal modelling

Abstract - K. Veerkamp, K. Veerkamp, K. Veerkamp, Wouter Schallig, J. Harlaar, J. Harlaar, C. Pizzolato, Christopher P. Carty, D. G. Lloyd, M. van der Krogt

Computational modelling of the neuromusculoskeletal system (NMSS) can potentially provide detailed insight into muscle function to optimize treatment planning and evaluation in cerebral palsy (CP). Commonly, static optimization is used to solve the redundancy problem in estimatin ...

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Eccentric contraction during gait is associated with muscle fat replacement in Duchenne Muscular Dystrophy

Master thesis - R.D. Boon, J. Harlaar, J. De Groot, A. Seth, K. Veerkamp, L. Marchal Crespo, T.T.J. Veeger

Duchenne Muscular Dystrophy (DMD) is a neuromuscular disorder characterized by progressive muscle weakness as well as progressive muscle fat replacement. Absence of functional dystrophin in muscles is believed to cause membrane instability, making the sarcolemma susceptible to damage when subjected to mechanical stress. However, the process leading from dystrophin-absence to muscle degeneration, and ultimately fat replacement, is still not well understood. Therefore, several hypotheses currently co-exist. Interestingly, muscles of DMD patients are not equally affected, and a more or less consistent successive pattern of muscle fat replacement exists in the lower extremities. The aim of this study was to investigate a possible mechanical role in explaining differential muscle fat replacement in the legs of DMD patients. Based on a published preliminary study, it was hypothesized that eccentric contraction, during which a muscle generates force while lengthening, is associated to muscle fat replacement during gait. 3D gait analysis data of a small cross-sectional sample of typically developing children was used to predict muscle contributions during gait in OpenSim. In one analysis, negative work, the time-integral of force multiplied by lengthening velocity, was normalized to account for differences in physiological cross-sectional area (PCSA) and fiber length, and was subsequently tested for a relation with muscle fat replacement. Furthermore, since muscle architecture parameters PCSA and fiber length are associated to muscle fat replacement, separate effects of total negative work and muscle volume (PCSA*fiber length) on muscle fat replacement were also analyzed. Normalized negative work was significantly associated with muscle fat replacement, where upper leg muscles generally showed higher fat fractions than lower leg muscles. Furthermore, both the effect of total negative work as well as muscle volume on muscle fat replacement were significant. The effect of total negative work on muscle fat replacement was stronger if muscle volume was smaller. In contrast, normalized and total positive work (i.e., concentric contraction) was not significantly associated with muscle fat replacement. Eccentric contraction during gait helps explain the differential progression of muscle fat replacement seen among leg muscles of DMD patients. The results of this study generate more insight regarding a mechanical role in the pathophysiology of DMD, and may potentially help in generating or improving therapies that focus on prolonged muscle function preservation.