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Influence of modified muscle morphology and activity pattern on the results of musculoskeletal system modelling in cerebral palsy patient

Ogrodnik J., Piszczatowski Sz.

Acta of Bioengineering and Biomechanics

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2017

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Vol. 19, no. 3

63--75

EN

Purpose: The aim of the present study was to evaluate the influence of modified morphological parameters of the muscle model and excitation pattern on the results of musculoskeletal system numerical simulation in a cerebral palsy patient. Methods: The modelling of the musculoskeletal system was performed in the AnyBody Modelling System. The standard model (MoCap) was subjected to modifications consisting of changes in morphological parameters and excitation patterns of selected muscles. The research was conducted with the use of data of a 14-year-old cerebral palsy patient. Results: A reduction of morphological parameters (variant MI) caused a decrease in the value of active force generated by the muscle with changed geometry, and as a consequence the changes in active force generated by other muscles. A simulation of the abnormal excitation pattern (MII variant) resulted in the muscle’s additional activity during its lengthening. The simultaneous modification of the muscle morphology and excitation pattern (MIII variant) points to the interdependence of both types of muscle model changes. A significant increase in the value of the reaction force in the hip joint was observed as a consequence of modification of the hip abductor activity. Conclusions: The morphological parameters and the excitation pattern of modelled muscles have a significant influence on the results of numerical simulation of the musculoskeletal system functioning.

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Biomechanical evaluation of a novel Limb Prosthesis Osseointegrated Fixation System designed to combine the advantages of interference-fit and threaded solutions

Prochor P., Piszczatowski Sz., Sajewicz E.

Acta of Bioengineering and Biomechanics

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2016

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Vol. 18, no. 4

21--31

EN

Purpose: The study was aimed at biomechanical evaluation of a novel Limb Prosthesis Osseointegrated Fixation System (LPOFS) designed to combine the advantages of interference-fit and threaded solutions. Methods: Three cases, the LPOFS (designed), the OPRA (threaded) and the ITAP (interference-fit) implants were studied. Von-Mises stresses in bone patterns and maximal values generated while axial loading on an implant placed in bone and the force reaction values in contact elements while extracting an implant were analysed. Primary and fully osteointegrated connections were considered. Results: The results obtained for primary connection indicate more effective anchoring of the OPRA, however the LPOFS provides more appropriate stress distribution (lower stress-shielding, no overloading) in bone. In the case of fully osteointegrated connection the LPOFSs kept the most favourable stress distribution in cortical bone which is the most important long-term feature of the implant usage and bone remodelling. Moreover, in fully bound connection its anchoring elements resist extracting attempts more than the ITAP and the OPRA. Conclusions: The results obtained allow us to conclude that in the case of features under study the LPOFS is a more functional solution to direct skeletal attachment of limb prosthesis than the referential implants during short and long-term use.

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Geometrical aspects of growth plate modelling using Carter's and Stokes's approaches

Piszczatowski Sz.

Acta of Bioengineering and Biomechanics

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2012

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Vol. 14, no. 1

93-106

EN

Development of the skeleton is a complex mechanobiological process. Shape and size of the majority of bone elements are the result of endochondral growth and ossification occurring during childhood and adolescent period. The influence of mechanical loading acting in the skeletal system on bone development is known since the 19th century, but understanding of such phenomenon seems to be still insufficient. Traditionally accepted Hueter-Volkmann law claims that increased pressure acting on a growth plate retards bone growth and, conversely, reduced pressure or even tension accelerates it. Stokes's approach is directly based on this theory. Carter's model seems to be slightly more complex because takes into account three-dimensional stress state. The subject of the research was to evaluate the mechanobiological condition of endochondral bone growth occurring within the growth cartilage where different geometrical structures (8 models) of the growth plate and various loading conditions (5 variants) were considered. Simulations were made using the finite element method and both Stokes's and Carter's models were used to estimate mechanical stimulation of bone growth. Results indicate non-uniformity of the growth conditions occurring within the growth cartilage when its layer is located between two bone blocks. Non-axial loadings result in dissymmetry of mechanical stimulation of bone growth. In general, its minimum is located in the regions of the cartilage to which maximal loadings were directed. Carter's approach is, however, more sensitive to interrelation between growth plate geometrical structure and loading direction, compared to Stokes's model. Obtained results indicate the necessity of realistic modelling of the growing bone geometrical structure, including the elaboration of custom-made models. Further research is necessary to elaborate the new formula describing mechanical influences on bone growth, taking into account the cyclic loading of a constant direction. In this way it will be possible to overcome the still existing problems with the explanation of numerous clinical phenomena.

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Analysis of the stress and strain in hip joint of the children with adductors spasticity due to cerebral palsy

Piszczatowski Sz.

Acta of Bioengineering and Biomechanics

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2008

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Vol. 10, nr 2

51-56

EN

Mechanical factors have a strong influence on the development of the musculoskeletal system. Muscle forces are one of the most important sources of the loadings acting on the bone elements and any disturbances in their activity can lead to severe pathology. Cerebral palsy is an example of such a situation and hip joint deformity, leading to its dislocation, is one of the most serious complications accompanied with muscle spasticity. The aim of the study is to perform an analysis of the stress and strain in hip joint of the children with the imbalance in muscle forces due to adductors spasticity (overactivity). Finite element model has been developed based on anatomical data obtained from computer tomography. The results of numerical simulations show an increase in stress and strain occurring in the femoral head and acetabulum as well as some relocation of its concentration zone in the medial direction.