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Multiscale Modelling of Proximal Femur Growth: Importance of Geometry and Influence of Load
KTH, School of Engineering Sciences (SCI), Mechanics, Structural Mechanics. KTH, School of Engineering Sciences (SCI), Centres, BioMEx.ORCID iD: 0000-0002-4701-8860
2017 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Longitudinal growth of long bone occurs at growth plates by a process called endochondral ossification. Endochondral ossification is affected by both biological and mechanical factors. This thesis focuses on the mechanical modulation of femoral bone growth occurring at the proximal growth plate, using mechanobiological theories reported in the literature. Finite element analysis was used to simulate bone growth.

The first study analyzed the effect of subject-specific growth plate geometry over simplified growth plate geometry in numerical prediction of bone growth tendency. Subject-specific femur finite element model was constructed from magnetic resonance images of one able- bodied child. Gait kinematics and kinetics were acquired from motion analysis and analyzed further in musculoskeletal modelling to determine muscle and joint contact forces. These were used to determine loading on the femur in finite element analysis. The growth rate was computed based on a mechanobiological theory proposed by Carter and Wong, and a growth model in the principal stress direction was introduced. Our findings support the use of subject- specific geometry and of the principal stress growth direction in prediction of bone growth.

The second study aimed to illustrate how different muscle groups’ activation during gait affects proximal femoral growth tendency in able-bodied children. Subject-specific femur models were used. Gait kinematics and kinetics were acquired for 3 able-bodied children, and muscle and joint contact forces were determined, similar to the first study. The contribution of different muscle groups to hip contact force was also determined. Finite element analysis was performed to compute the specific growth rate and growth direction due to individual muscle groups. The simulated growth model indicated that gait loading tends to reduce neck shaft angle and femoral anteversion during growth. The muscle groups that contributes most and least to growth rate were hip abductors and hip adductors, respectively. All muscle groups’ activation tended to reduce the neck shaft and femoral anteversion angles, except hip extensors and adductors which showed a tendency to increase the femoral anteversion.

The third study’s aim was to understand the influence of different physical activities on proximal femoral growth tendency. Hip contact force orientation was varied to represent reported forces from a number of physical activities. The findings of this study showed that all studied physical activities tend to reduce the neck shaft angle and anteversion, which corresponds to the femur’s natural course during normal growth.

The aim of the fourth study was to study the hypothesis that loading in the absence of physical activity, i.e. static loading, can have an adverse effect on bone growth. A subject-specific model was used and growth plate was modeled as a poroelastic material in finite element analysis. Prendergast’s indicators for bone growth was used to analyse the bone growth behavior. The results showed that tendency of bone growth rate decreases over a long duration of static loading. The study also showed that static sitting is less detrimental than static standing for predicted cartilage-to-bone differentiation likelihood, due to the lower magnitude of hip contact force.

The prediction of growth using finite element analysis on experimental gait data and person- specific femur geometry, based on mechanobiological theories of bone growth, offers a biomechanical foundation for better understanding and prediction of bone growth-related deformity problems in growing children. It can ultimately help in treatment planning or physical activity guidelines in children at risk at developing a femur or hip deformity. 

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2017. , 38 p.
Series
TRITA-MEK, ISSN 0348-467X ; 2017:08
Keyword [en]
bone tissue modeling, deformity, biomechanics, osteogenic index, poroelastic material, octahedral shear stress, hydrostatic stress, fluid velocity, octahedral shear strain, MRI, walking, jumping, sedentation
National Category
Other Mechanical Engineering
Research subject
Engineering Mechanics
Identifiers
URN: urn:nbn:se:kth:diva-209149ISBN: 978-91-7729-455-9 (print)OAI: oai:DiVA.org:kth-209149DiVA: diva2:1110288
Public defence
2017-06-12, E3, Osquars backe 14, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

QC 20170616

Available from: 2017-06-16 Created: 2017-06-15 Last updated: 2017-06-29Bibliographically approved
List of papers
1. Effect of growth plate geometry and growth direction on prediction of proximal femoral morphology
Open this publication in new window or tab >>Effect of growth plate geometry and growth direction on prediction of proximal femoral morphology
2016 (English)In: Journal of Biomechanics, ISSN 0021-9290, E-ISSN 1873-2380, Vol. 49, no 9, 1613-1619 p.Article in journal (Refereed) Published
Abstract [en]

Mechanical stimuli play a significant role in the process of endochondral growth. Thus far, approaches to understand the endochondral mechanical growth rate have been limited to the use of approximated location and geometry of the growth plate. Furthermore, growth has been simulated based on the average deflection of the growth plate or of the femoral neck. It has also been reported in the literature that the growth plate lies parallel to one of the principal stresses acting on it, to reduce the shear between epiphysis and diaphysis. Hence the current study objectives were (1) to evaluate the significance of a subject-specific finite element model of the femur and growth plate compared to a simplified growth plate model and (2) to explore the different growth direction models to better understand proximal femoral growth mechanisms. A subject-specific finite element model of an able-bodied 7-year old child was developed. The muscle forces and hip contact force were computed for one gait cycle and applied to a finite element model to determine the specific growth rate. Proximal femoral growth was simulated for two different growth direction models: femoral neck deflection direction and principal stress direction. The principal stress direction model captured the expected tendency for decreasing the neck shaft angle and femoral anteversion for both growth plate models. The results of this study suggest that the subject-specific geometry and consideration of the principal stress direction as growth direction may be a more realistic approach for correct prediction of proximal femoral growth morphology.

Place, publisher, year, edition, pages
Elsevier, 2016
Keyword
Deformity development, Specific growth rate, Octahedral shear stress, Hydrostatic stress, MRI
National Category
Biophysics
Identifiers
urn:nbn:se:kth:diva-189665 (URN)10.1016/j.jbiomech.2016.03.039 (DOI)000377731200028 ()27063249 (PubMedID)2-s2.0-84973468416 (Scopus ID)
Note

QC 20160715

Available from: 2016-07-15 Created: 2016-07-11 Last updated: 2017-06-16Bibliographically approved
2. Influence of muscle groups’ activation on proximal femoral growth tendency
Open this publication in new window or tab >>Influence of muscle groups’ activation on proximal femoral growth tendency
(English)Manuscript (preprint) (Other academic)
Identifiers
urn:nbn:se:kth:diva-177928 (URN)
Note

QS 2015

Available from: 2015-11-30 Created: 2015-11-30 Last updated: 2017-06-16Bibliographically approved
3. How can the load directions due to different physical activities affect proximal femoral growth tendency?
Open this publication in new window or tab >>How can the load directions due to different physical activities affect proximal femoral growth tendency?
(English)Manuscript (preprint) (Other academic)
National Category
Engineering and Technology
Research subject
Engineering Mechanics
Identifiers
urn:nbn:se:kth:diva-209194 (URN)
Note

QC 20170616

Available from: 2017-06-16 Created: 2017-06-16 Last updated: 2017-06-16Bibliographically approved
4. Modelling the effects of static load on proximal femoral growth behavior
Open this publication in new window or tab >>Modelling the effects of static load on proximal femoral growth behavior
(English)Manuscript (preprint) (Other academic)
National Category
Engineering and Technology
Research subject
Engineering Mechanics
Identifiers
urn:nbn:se:kth:diva-209196 (URN)
Note

QC 20170616

Available from: 2017-06-16 Created: 2017-06-16 Last updated: 2017-06-16Bibliographically approved

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