Bone biology and bone healing

1. M A X I L L O FA C I A L R E G I O N
BONE BIOLOGY &
HEALING
M O D E R A T O R –
D R . R A J A S E K H A R G .
P R E S E N T E D B Y -
D R . S H E E T A L K A P S E

2. CONTENTS
• Introduction
• Embryology and development
• Structure
• Chemical composition
• Mechanical properties
• Biomechanics of craniomaxillofacial skeleton
• Fracture and role of blood supply
• Biological reaction and healing of bone
• Complications of bone healing
• Metals, surfaces and tissue interactions

3. INTRODUCTION
• WHAT IS BONE ?
• FUNCTION ?
• NUMBERS

4. EMBRYOLOGY AND DEVELOPMENT
MEMBRANOUS
OSSIFICATION
Frontal
Parietal
Nasal bones
Maxilla
Zygoma
Mandible
ENDOCHONDRAL
OSSIFICATION
Skull base
Occipital bone
Nasal septum
Internal
components of the nose

5. STRUCTURE

6. CHEMICAL COMPOSITION
INORGANIC
1. Hydroxyapatite
[Ca10(PO4)6(OH)2]
2. Magnesium
3. Potassium
4. Chlorine
5. Iron
6. Carbonate
ORGANIC
1. 90% collagen, primarily type I
2. 10% Non-collagenous proteins
and lipids
a. 23% osteonectin
b. 15% osteocalcin
c. 9% sialoprotein,
d. 9% phosphoproteins
e. 5% α2-HS-glycoproteins
f. 4% proteoglycans
g. 3% albumin

7. MECHANICAL PROPERTIES
Collagen fibers Mineral phase
Specific
orientation
Specific length
Shear forces
Tensile forces Compressive forces
• Elongation of 2%
• Strength about 1Mpa
• Tensile strength = 2/3rd
compressive strength

8. BIOMECHANICS OF
CRANIOMAXILLOFACIAL SKELETON

11. Maximum bite forces in an average population
200 to 300 N - incisor area
300 to 500 N - premolar region
500 to 700 - molar area

12. R. C. W. Wong, H. Tideman, L. Kin, M. A. W. Merkx:
Biomechanics of mandibular reconstruction: a review. Int. J. Oral
Maxillofac. Surg. 2010; 39: 313–319.

13. FRACTURE AND ROLE OF
BLOOD SUPPLY
INJURY
INTRAVASCULAR CLOTTING CONGESTION
DECREASED BLOOD SUPPLY
NECROSIS
OSTEOBLASTIC ACTIVITY
OSTEOCLASTIC ACTIVITY
BONY BRIDGING
VASCULAR INVASION

14. BIOLOGICAL REACTION AND
HEALING OF BONE
• Dependent on the biological and biomechanical environment, three basic
scenarios can be differentiated:
1. Primary bone healing (contact or gap healing)
2. Secondary bone healing via callus formation
Sufficient blood supply
Presence of specific cells
Adequate mechanical conditions
Undisturbed
fracture healing

15. 1. PRIMARY BONE HEALING
(CONTACT OR GAP HEALING)
• In cases where inter-fragmentary motion can be completely avoided, a healing
pattern results which is characterized by an increased amount of intracortical
remodelling, inside and in between the fragment ends.
• As long as there is no destruction of bone in the contact areas, the motion in the
gap is small enough to keep inter-fragmentary strain below 2%.
• The pattern of direct healing per se is not a goal to strive for, but the absence of
this pattern, ie, the formation of periosteal callus under conditions of plate
fixation is an indicator that complete immobilization was not achieved.

16. a Functionally stable
fixation of a mandibular
fracture with excellent
repositioning as a precondition
for primary bone healing.
b Enlarged section of (a):
primary bone healing contact
area, direct bony bridging
showing osteons crossing the
fracture area.
a Stable fixation, load
sharing with contact area
superiorly and gap area
inferiorly.
b Enlarged section of (a):
primary healing gap area:
complete filling of the fracture
gap with lamellar bone in a
direction parallel to the
fracture surface.

17. 2. SECONDARY BONE HEALING
VIA CALLUS FORMATION
• In cases when no fracture fixation or just loose adaptation fixation is done,
macromotion between the fragment ends occurs.
• The strain in between the fragments exceeds what bone can tolerate, and
new bone developing between the fracture ends would be destroyed before
it is formed.
Endosteal callus
Periosteal callus

18. In between the fracture ends a tissue differentiation cascade
takes place, during which stiffness and strength increases and
strain tolerance gradually decreases.
Hematoma
Granulation tissue
Connective tissue
Fibrocartilage
Mineralized cartilage
Woven bone
Compact bone

19. Secondary bone healing,
phase 1: hematoma filling the fracture gap.

20. Secondary bone healing,
phase 2: granulation tissue and connective tissue replacing the
hematoma in the fracture gap.
• The elongation to
rupture is found to
be between 5% and
17%.
• Fibrous tissue is
found in areas where
tensile forces act,
• Cartilage is formed
in zones of
hydrostatic pressure

21. Secondary bone healing,
phase 3: fibrocartilage replacing the connective tissue in the
fracture gap.

22. Secondary bone healing,
phase 4: woven bone replaced by lamellar bone through Haversian
remodelling.

23. COMPLICATIONS OF BONE HEALING
1. Non-union
2. Delayed union
3. Malunion
FACTORS
PATIENT ASSOCIATED
OPERATOR ASSOCIATED
HARDWARE ASSOCIATED
LOCAL
SYSTEMIC

24. METALS, SURFACES AND TISSUE
INTERACTIONS
 62.5% iron
 18% chromium
 14% nickel
 2.5% molybdenum
 minor elemental
316 L iron-base alloy
Allergic reactions to nickel 3–15%
Titanium alloys
 Ti grades 1–4
 Ti-6Al-7Nb alloy
 Ti-15Mo alloy
(α & β)

25. FIXATION DEVICE BLOOD
BLOOD PROTEINS COVERING
THE FIXATION DEVICE
(matrix for platelets and other cells)
PLATELET
DEGRANULATION
INFLAMMATION
(cytokines & growth factors)
HEMATOMA
FORMATION
Proliferation
Remodelling

26. BIODEGRADABLE MATERIALS
Water and CO2
In the future, maxillofacial
fracture fixation may utilize
biodegradable bone adhesives
and composites in lieu of the
traditional titanium plate/screw
systems. The adhesives
currently under study are in the
cyanoacrylate polymer family,
namely, butyl-2-cyanoacrylate.

27. REFERENCE
1. Fonseca Raymond J, Walker Robert V, Barber H Dexter, Powers, Michael P,
Frost David E. oral and maxillofacial trauma. China: Saunders; 2013.
2. Hom, Hebda, Gosain, Friedman. Essential tissue healing of the face and neck.
India. Peoples medical publishing house.
3. AOCMF principles of internal fixations of craniomaxillofacial skeleton, trauma
& orthognathic surgery.
4. Rowe NL, William JL. Maxillofacial injuries. 1st ed. India ISBN 978-81-312-
1840—2 2009.

28. THANK YOU