la biomécanique: passerelle entre les sciences de l...
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La Biomécanique: passerelle entre les sciences de l'ingénieur et la médecineProf. Dominique PiolettiLaboratoire de Biomécanique Orthopédique
Faites du sport, c’est bon pour vos os!
Comment nos os peuvent-ils savoir cela?
Fémur d’une souris
Normal Sans stimul. mécanique
L’activité physique va générer des stimulations mécaniques dans nos os
Cette stimulation mécanique va favoriser le maintien et la qualité de notre structure osseuse
Faites du sport, c’est bon pour vos os!
La biomécanique utilise une description multi-échelle pour faire le lien entre la biologie et la mécanique
WWW.QCTOP.COM
La biomécanique, c’est quoi?• Biomécanique: mécanique appliquée au bio -> biomécanique
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Orthopédique
www.engineering.uiowa.edu/ ~raghavan/
Cardiovasculaire
Sécurité
Plantes
Que peut-on faire avec la biomécanique
• Evaluer les performances d’un implant orthopédique
• Calculer les contraintes de cisaillement dans une artère
• Quantifier le transport de protéines dans le système lymphatique
• Analyser les performances d’un golfeur
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Le système musculo-squelettique subit des contraintes mécaniques importantes
© 2003 Primal Pictures
BR
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W
e1
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FORCE DE CONTACT DANS LA HANCHE: 2000 N ! © 2003 Primal Pictures© 2003 Primal Pictures© 2003 Primal Pictures© 2003 Primal Pictures© 2003 Primal Pictures
Développement d’implants “traditionnels”
Développement d’implants “biologiques”
Compréhension de la “mécano-transduction”
L’ingénieur mécanicien peut intervenir à 3 niveaux dans la recherche médicale (orthopédique)
Une 1ère étude numérique est effectuée afin d’évaluer le design
4000N
3 nodes
1/3 fixed
PMMA, 50MPa
PMMA, 500MPaLat. Med.
Implant traditionnel Implant biologique Mécano-transduction
Le design de l’implant est ensuite amélioré à mesure des études faites
Implant traditionnel Implant biologique Mécano-transduction
Finalement l’implant définitif est testé extensivement
Implant traditionnel Implant biologique Mécano-transduction
o°
flexiondu genou
6o°
9o°
pression de contact
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Figure 2.2: Principle of the open wedge tibial osteotomy. A) Before the surgicalintervention, the tibial axis differs from the weight bearing axis. B) In order torestore a favourable weight bearing axis, the surgeon carries out a high tibial os-teotomy, open the tibia to the desired angle (1), and introduce a wedge to maintainthe tibia in this position (2).
correction of varus lower limb deformation. It is preferred to the lateral closingwedge osteotomy as numerous complications are avoided such as neurologicalcomplication [15], compartment syndrome [44], lateral muscle detachment, proxi-mal fibula osteotomy and leg shortening [24]. In twol clinical studies [2, 21] betterscore on open wedge than on closing wedge osteotomy are observed. Moreover,the open wedge osteotomy is preferred as the difficulties encountered when per-forming a subsequent total knee arthroplasty are reduced [15].
The medial open wedge tibial osteotomy requires a supply of some matierial toact as a wedge. Such material may be of natural source such as allo and auto bonegraft and may also well be synthetical bone graft. Each of these possible solutionhas its drawbacks and advantages which are exposed in details sections 2.2.1-2.2.3.
There are four characteristics that an ideal bone graft material should exhibitwhich include: [25], (i) osteointegration, the ability to chemically bond to the sur-face of bone without an intervening layer of fibrous tissue; (ii) osteoconduction, theability to provide a support on which bone cells can attach, migrate, grow and di-vide; (iii) osteoinduction, the capacity to stimulate primitive stem cells or immaturebone cells to differentiate into mature, bone forming cells; and (iv) osteogenesis,the formation of new bone by osteoblastic cells present within the graft material.In addition, bone graft material should be mechanically resistant and offer a panelof different stiffness characteristics depending on the location it is planed to be im-plented. Finally, the ideal bone graft substitute shall be remodelled in a way thatsufficent mechanical resistance and stiffness is ensured until complet substitute
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Figure 2.2: Principle of the open wedge tibial osteotomy. A) Before the surgicalintervention, the tibial axis differs from the weight bearing axis. B) In order torestore a favourable weight bearing axis, the surgeon carries out a high tibial os-teotomy, open the tibia to the desired angle (1), and introduce a wedge to maintainthe tibia in this position (2).
correction of varus lower limb deformation. It is preferred to the lateral closingwedge osteotomy as numerous complications are avoided such as neurologicalcomplication [15], compartment syndrome [44], lateral muscle detachment, proxi-mal fibula osteotomy and leg shortening [24]. In twol clinical studies [2, 21] betterscore on open wedge than on closing wedge osteotomy are observed. Moreover,the open wedge osteotomy is preferred as the difficulties encountered when per-forming a subsequent total knee arthroplasty are reduced [15].
The medial open wedge tibial osteotomy requires a supply of some matierial toact as a wedge. Such material may be of natural source such as allo and auto bonegraft and may also well be synthetical bone graft. Each of these possible solutionhas its drawbacks and advantages which are exposed in details sections 2.2.1-2.2.3.
There are four characteristics that an ideal bone graft material should exhibitwhich include: [25], (i) osteointegration, the ability to chemically bond to the sur-face of bone without an intervening layer of fibrous tissue; (ii) osteoconduction, theability to provide a support on which bone cells can attach, migrate, grow and di-vide; (iii) osteoinduction, the capacity to stimulate primitive stem cells or immaturebone cells to differentiate into mature, bone forming cells; and (iv) osteogenesis,the formation of new bone by osteoblastic cells present within the graft material.In addition, bone graft material should be mechanically resistant and offer a panelof different stiffness characteristics depending on the location it is planed to be im-plented. Finally, the ideal bone graft substitute shall be remodelled in a way thatsufficent mechanical resistance and stiffness is ensured until complet substitute
Implant traditionnel Implant biologique Mécano-transduction
Certaines situations requièrent un implant ayant des propriétés biologiques
Implant: flexible (E ≈ 500 MPa)mais résistant (s > 50 MPa)
Optimisation des propriétés mécaniques de l’implant
Evaluation de l’effet mécanique de la position de la plaque
Tests numériques des differentes formes de l’implant
Des informations mécaniques sont obtenues afin de proposer des solutions
Implant traditionnel Implant biologique Mécano-transduction
La stimulation mécanique est impliquée dans la structre et la forme des tissus biologiques
Implant traditionnel Implant biologique Mécano-transduction
Fémur d’une sourisNormal Sans stimul.
mécanique
Implant de hanche
Post-op 2 ans 7 ans
L’OS SE “REMODELLE” EN FONCTION DE LA STIMULATION MÉCANIQUE
Il est possible d’anticiper la repousse osseuse autour des implants
Implant traditionnel Implant biologique Mécano-transduction
ψ
dφdt
ψr ψd
vr
vd
equilibrium densificationresorption
0< 0dφ
dt
= 0dφdt
> 0dφdt
FEM Distribution des contraintes
Densité osseuse
La biomécanique permet aussi de comprendre la cause de problèmes médicaux (ex: mal de dos)
enfant Jeune adulte
Nordin, 2001
moins jeune …
L’activité musculaire et la gravité induisent des charges mécaniques importantes dans le disque
LG
G
Afin de limiter la dégénérescence du disque, les charges devraient être « raisonnables »
http://www.healtheast.org
Pression dans L4
Développement d’implants “traditionnels”
Développement d’implants “biologiques”
Compréhension de la “mécano-transduction”
En conclusion, les activités de l’ingénieur mécanicien sont également importantes dans la recherche médicale: