Bone biology and bone healing

M A X I L LO FAC I A L R E G I O N

BONE BIOLOGY & HEALING

MODERATOR – DR . RA JASEKHAR G .

PRESENTED BY-DR . SHEETAL KAPSE

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

INTRODUCTION

• WHAT IS BONE ?• FUNCTION ?• NUMBERS

EMBRYOLOGY AND DEVELOPMENT

MEMBRANOUS OSSIFICATION

Frontal Parietal

Nasal bones Maxilla Zygoma Mandible

ENDOCHONDRAL OSSIFICATION

Skull base Occipital bone Nasal septum

Internalcomponents of the nose

Skeletal_System__3A_Bone_Formation__28_Intramembranous_Ossification__26_Endochondral_Ossification_29_22.mp4

STRUCTURE

Microscopic_Bone_Structure.mp4

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

MECHANICAL PROPERTIESCollagen 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

BIOMECHANICS OF CRANIOMAXILLOFACIAL SKELETON

Maximum bite forces in an average population

200 to 300 N - incisor area

300 to 500 N - premolar region

500 to 700 - molar area

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.

FRACTURE AND ROLE OF BLOOD SUPPLY

INJURY

INTRAVASCULAR CLOTTING CONGESTION

DECREASED BLOOD SUPPLY

NECROSIS

OSTEOBLASTIC ACTIVITY

OSTEOCLASTIC ACTIVITY

BONY BRIDGING

VASCULAR INVASION

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

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.

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.

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

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

Secondary bone healing,

phase 1: hematoma filling the fracture gap.

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

Secondary bone healing,

phase 3: fibrocartilage replacing the connective tissue in the

fracture gap.

Secondary bone healing,

phase 4: woven bone replaced by lamellar bone through Haversian

remodelling.

COMPLICATIONS OF BONE HEALING

1. Non-union2. Delayed union3. Malunion

FACTORSPATIENT ASSOCIATED

OPERATOR ASSOCIATED

HARDWARE ASSOCIATED

LOCAL

SYSTEMIC

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)

Cell-to-Cell_Communication_-_Osseointegration.mp4

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

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.

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.

THANK YOU