Bone Healing in Fracture

7/30/2019 Bone Healing in Fracture

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INTRODU

Fracture healing can occur in two way :

1) Primary bone healing

2) Secondary bone healing

1. Primary bone healing also known as Haversian remodelling

occurs with absolute stability constructs


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2. Secondary bone healing

A. Involves responses in the periosteum and external soft tissues. There are two types :Enchondral healing ;

occurs with non-rigid fixation, as fracture braces, external fixation, bridge plintramedullary nailing, etc

Intramembranous healing ;occurs with semi-rigid fixation, such as locked plating (in a non-absolute staconstruct)

B. Secondary bone healing can occur as either enchondral or intramembranous alone, combination of the two.


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Most fractures are splinted, not to ensure union but to:

(1) alleviate pain

(2) ensure that union takes place in good position

(3) permit early movement of the limb and a return of function.

The process of fracture repair varies according to the type of bone involved and the

amount of movement at the fracture site.


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This is the natural form of healing in tubular bones, in the absence of rigid fixation, i

proceeds in 5 stages:

Tissue destruction and haematoma formation

Inflammation and cellular proliferation

Callus formation

Consolidation

Remodelling


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TISSUE DESTRUCTIOHAEMATOMA FORMA

A disruption of the endosteal and periosteal blood

supply following an injury causes haematoma formation

in the vicinity of the fracture.

This haematoma may occur as a localized collection of

blood bounded by aperiosteal envelope.

Provides source of hemopoieitic cells capable of

secreting growth factors.


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INFLAMMATION AND CELPROLIFER

Within 8 hours of the fracture acute inflammatory reaction

migration of inflammatory cells (cytokines and various growth factors)

initiation of proliferation and differentiation of mesenchymal stem cells

periosteum, the breached medullary canal and the surrounding muscle.

The clotted haematoma is slowly absorbed and fine new capillaries grow into the

area.


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CALLUS FORM The differentiating stem cells provide chrondrogenic and osteogenic cell

populations

the local biological and biomechanical environment start forming bone

also includes osteoclasts mop up dead bone.

The thick cellular mass, with its islands of immature bone and cartilage, forms the

callus or splint on the periosteal and endosteal surfaces.

the immature fibre bone (or woven bone) becomes more densely mine

movement at the fracture site decreases progressively and at about

injury the fracture unites .


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The formation of new bone is facilitated by avariety of osteoinductive factors;

platelet-derived growth factor ( PDGF )

transforming growth factor ( TGF )

insulin-like growth factor ( IGF)

basic fibroblast growth factor ( BFGF)

bone morphogenetic protein ( BMP).


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CONSOLIDA

Continuing osteoclastic and osteoblastic activity the woven bone lam

The system is now rigid enough to allow osteoclasts to burrow through the debris at

the fracture line, and close behind them.

Osteoblasts fill in the remaining gaps between the fragments with new bone.

This is a slow process and it may be several months before the bone is strong

to carry normal loads


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REMODE

The fracture has been bridged by a cuff of solid bone.

Over a period of months, or even years , this crude weld is resh

continuous process of alternating bone resorption and formation.

Eventually, and especially in children, the bone reassumes something like its normal

shape.


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VARIABLES THAT INFFRACTURE H

1. Internal variables blood supply (most important)

head injury may increase osteogenic response

2. External variables

Nicotine Diet

Low intensity pulsed ultrasound (LIPUS)

Bone stimulators

COX-2


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Non-union

Sometimes the normal process of fracture repair is thwarted and the bone fails to

unite. Causes of non-union are:

(1) distraction and separation of the fragments, sometimes the result of interposition of

soft tissues between the fragments(2) excessive movement at the fracture line

(3) a severe injury that renders the local tissues nonviable or nearly so

(4) a poor local blood supply


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Hypertrophic nonunion

caused by inadequate immobilization with adequate blood supply

typically heal once mechanical stability is improved

Atrophic non-union

caused by inadequate immobilization and inadequate blood supply


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THANK Y

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Bone Healing in Fracture