1. Bone fracture healing occurs in three phases - inflammatory, reparative, and remodeling. 2. During the inflammatory phase, granulation tissue forms between fracture fragments from fibroblasts and new blood vessels. This produces a soft tissue callus. 3. The reparative phase involves formation of woven bone and cartilage that are later replaced by stronger lamellar bone through endochondral ossification. This results in a bony callus. 3. Finally, remodeling reshapes the bone to its original contour by resorbing excess callus, replacing trabecular bone with compact bone over 6-8 weeks.

1. BONE HEALING DR N MANJULA

2. INTRODUCTION
The skeletal system consists of the bones, their associated
cartilages, and the joints.
Bone is a specialized connective tissue which has structural,
protective, metabolic and hematopoietic functions (produces
blood cells).

3. CELLS OF THE BONE
TISSUE
Osteoblasts: produce osteoid -
bone forming cells.
Osteoclasts: These are mature
multinucleated cells - responsible
for bone resorption.

4. FRACTURE
A fracture is a broken bone.
It can range from a thin crack to a complete
break in the bone.
Phases of Fracture Healing:
1. Inflammatory Phase
2. Reparative Phase
3. Remodeling Phase

5. FRACTURE AND
HEMORRHAGE
Soon after fracture, blood vessels rupture which leads to
extensive hemorrhage (hematoma) at the fracture site and
surrounding tissue.
Necrosis of bone also occurs at the fracture site.

6. INFLAMMATORY PHASE

7. INFLAMMATORY CELLS
Fibrin meshwork in the clotted blood helps to seal the
fracture site.
Influx of inflammatory cells (neutrophils and macrophages)
to the area.
In growth of fibroblasts and new capillary vessels to the site,
producing granulation tissue between the fracture
fragments.

9. Activation of osteoprogenitor cells:
The inflammatory cells and platelets release
cytokines → activate the osteoprogenitor cells in:
 Periosteum
 Medullary cavity
 Surrounding soft tissues.

10. FORMATION OF
GRANULATION TISSUE
It consists of proliferating capillaries
and fibroblasts and are formed at the
site of fractures.
Simultaneously, degranulated platelets
and migrating inflammatory cells
release PDGF, TGF-β, FGF.

11. CALLUS
Osteoprogenitor cells → activate both osteoblastic and
osteoclastic activities at the fracture site.
Osteoblasts derived from activated osteoprogenitor cells
migrate into the granulation tissue and differentiate into
osteoid synthesizing units.
They deposit large quantities of osteoid collagen in a
haphazard pattern producing woven bone (unmineralized
bone is called osteoid).

12. STAGES OF BONE HEALING

13. Granulation tissue containing (mineralized or unmineralized)
bone or cartilage is termed a callus.
At this stage, callus is predominantly uncalcified and is
called soft-tissue callus or pro callus, which provides a
type of temporary connection between the ends of the
fractured bones.
However, pro callus does not have any structural rigidity for
any weight-bearing.
The callus depending on its site and appearance can be
divided into external and internal callus.
The repair tissue attains maximal thickness at the end of the
second or third week and consists of hyaline cartilage and
woven bone.

14. Internal callus
It is derived from osteoprogenitor
cells of medullary cavity and
grows outward towards the
fracture site.
This bridges the fracture in the
region of medullary cavity.
External callus
It is formed from the
osteoprogenitor cells of
periosteum and is found on the
surface of the bone.
It bridges the fracture site outside
the bone and continues to grow
inwards toward the fracture site.
In this region, the osteoprogenitor
cells may differentiate into
cartilage around the fracture site.

15. REPARATIVE PHASE

16. Lamellar Bone Formation
As the healing advances, the hyaline cartilage and woven
bone of the original fracture callus are replaced by lamellar
bone.
This is stronger and consists of parallel collagen fibers.
Endochondral Ossification
The replacement process is known as endochondral
ossification with respect to the hyaline cartilage and bony
substitution with respect to the woven bone.

17. Bony Callus
Mineralized (calcified) callus - Bony (osseous) callus. As the
mineralization proceeds, the stiffness and strength
increases.
By the second or third week, controlled weightbearing can
be tolerated.

18. REMODELING PHASE

19. Several weeks after a callus has sealed the bone ends, the
remodeling phase begins.
During healing, excess of bony callus is formed around the
fracture site which is resorbed.
As the callus is subjected to weight-bearing forces, the portions of
bony callus that are not physically stressed by this weight are
slowly resorbed by osteoclasts.
Thus, the osteoclasts act to remodel bone and decrease the size
of callus.

20. The remodeling phase substitutes the trabecular bone with
compact bone.
Remodeling phase continues till the original bone shape
(contour), outline and strength of the fractured bone is re-
established.
The whole process of healing of a bone fracture usually
takes about 6–8 weeks.

22. Fracture healing: Three phases
1. Inflammatory - Fracture and inflammatory cells & Granulation tissue
formation.
Callus: Granulation tissue containing (mineralized or unmineralized) bone or
cartilage.
Fracture healing: First forms woven bone followed by lamellar bone.
2. Reparative
3. Remodeling - Remodeling to original bone contour.
Mineralized callus is called bony/osseous callus.
Complications of fracture healing:
• Delayed union / nonunion
• Pseudoarthrosis
• Large callus with deformity

23. CAUSES OF DELAYED
HEALING

24. COMPLICATIONS OF HEALING
Delayed union and nonunion of fracture.
Pseudoarthrosis.
Large callus with deformity.

25. THANK YOU!!!