Bone anatomy and fracture healing

1. ANATOMY OF BONE AND
FRACTURE HEALING

2. ANATOMY OF BONE
• INTRODUCTION
• GENERAL FEATURES OF BONE
• CLASSIFICATION OF BONE
• MACROSCOPIC ANATOMY OF BONE
• MICROSCOPIC STRUCTURE OF BONE
• COMPOSITION OF BONE
• HISTIOGENESIS OF BONE

3. INTRODUCTION
• The basic unit of human skeleton is BONE.
• Human body contains 206 bones.
• It is remarkable for its hardeness, resilience &
regenerative tissue.
• Bone matrix composed of organic materials,
mainly collagen fibres & inorganic salts rich in
calcium & phosphate.

4. GENERAL FEATURES OF BONE
• Typical long bone has
• DIAPHYSIS
• EPIPHYSIS
• METAPHYSIS

5. PARTS OF BONE

6. CLASSIFICATION OF BONE:
• A)According to Positon:
Axial: Bones forming axis of body
Ex:skull,ribs,sternum,vertebrae.
Appendicular Bones: forming skeleton of limbs
Ex: Femur, Humerus, Radius etc
• B)According to Size& Shape:
Long bones:Present in upper & lower limbs.
Ex.Femur,radius
Act as levers for movements & locomoIon.

7. • Short bones:Polyhedral & cuboidal in shape.
Ex:Carpal & tarsal bone.
• Flat bones:Exapanded & plate like.
Ex:scapula,sternum,ribs.
• Irregular bones:Ex:vertebrae
• Pneumatic bones:Flat or irregular bones
possessing a hollow space within their body
containing air. Ex:ethmoid,mastoid bones....
• Sesamoid bones:They are nodules of bones
which develop in certain tendons.
Do not possess periosteum & haversian system.
Ossify after birth Ex:pisiform,patella.

9. According to Gross structure:
• Compact(Lamellar)bone: Outer cortical part of
long bones, which is hard & homogeneous
appearence
• Spongy(Cancellous) bone:The inner part of long
bones,less hard & presents a spongy appearance.
• Diploic bone:Consists of inner & outer tables of
compact bone & in between a porous layer. Ex:
cranial bones
According to Development:
• Membranous bones.
• Cartilaginous bones.

11. MICROSCOPIC STRUCTURE OF BONE:
•The basic structural unit of compact bone
is Haversian system or Osteon,named
after Clopton Havers(1691).
•It contains following structures:
•Haversian canal
•Lamellae
•Lacunae
•Canaliculi
•Volkamann's canal

13. Organic matrix
bone cells
4%
Intercellular matrix
20%
•Collagens
•Protein peptides
•Proteoglycans
•Lipids
• Osteoprogenator stromal cells
• Osteocyte
• Osteoblast Bone lining cells
• Osteoclast
Mesenchymal
precursor cells

16. Blood Supply:
•One or two main diaphyseal nutrient arteries
enter shaft obliquely through nutrient foramina
leading into nutrient canals.
•Entry is directed away from dominant growing
epiphysis.
•Nutrient arteries divided into ascending and
descending branches in medullary cavity.

17. • Near epiphysis these vessels joined by
terminals of numerous metaphyseal and
epiphyseal arteries.
• Medullary arteries of shaft give of:
• Centripetal branches
• Cortical branches
• Large irregular bones recieve a periosteal
supply and large nutrient arteries penetrating
directly into cancellous bone.

19. Nerve Supply:
•These are most numerous in articular extremities
of long bones,vertebrae and larger flat bones
•Nerves occur widely in periosteum, fine
myelinated and non-‐myelinated fibres
accompany nutrient vessels into bone marrow
and lie in perivascular spaces of Haversian canals

20. HISTIOGENESIS OF BONE:
• Bone first appears after 7th embryonic week.
• They develop from embyonic mesenchymal
tissue.
• The process of gradual bone formation is
called Ossification.
• These are of two types:
1)Endochondral Ossification
2)Membranous Ossification

21. • 1)Endochondral Ossification:
• In embryonic life most of skeleton is
composed of carIlage, which is absorbed &
replaced by bone.
• This process known as Endochondral
Ossification.
• It begins prenatally & continous throughout
postnatal period until growth is complete.

22. • 2)Membranous Ossification:
When bone is formed directly from a loose
form of connective tissue without intervening
stages of cartilage formation, calcification and
resorption and process is known as
Membranous Ossification

23. FRACTURE HEALING
• HISTORY
• INTRODUCTION
• STAGES OF FRACTURE HEALING
• VARIABLES INFLUENCE IN # HEALING

24. HISTORY:
•Bones have broken since begining of humanity
and have been recognised as long as recorded
history.
•John Hunter,a pupil of Haller described
morphologic sequence of fracture healing.
•In 1917,Bier reported stimulation factor for
new bone formation was present in organized
blood clot of the fracture haematoma.

25. INTRODUCTION:
•A fracture is defined as a break in continuity of
bone.
•Fracture in man heal and unite by two main
ways:
1)Primary/Osteonal/Direct Healing:
•Bone formation occurs directly without any
callus formation.
•This occurs parIcularly in stable,aligned,closely
apposed fracture.

26. 2)Secondary/Indirect Healing:
•It is usual type consisIng of formation of callus
either of cartilaginous or fibrous.
•This callus is later converted into lamellar bone.
•When fracture is not rigidly fixed and
movements occur,in such cases callus is
replaced by bone healing.
•On x ray charecterised by abundant callus
formation, temporary widening of fracture gap
and slow disappearance of radiolucent fracture
line due to fibrocarIlage mineralisaIon.

27. STAGES OF FRACTURE HEALING:
•Osteoinduction is a first step in bone healing.
•It causes mesenchymal cells to differentiate into
various cells which then proliferate & produce
messenger substances which further stimulate
mesenchymal cells to differentiate.
•Osteconduction a scaffold of collagenous
network has developed upon which reparative
cells produce callus & bone.

28. The various stages of # Healing includes:
•Stage of Haematoma Formation.
•Stage of Granulation Issue.
•Stage of Repair/Callus.
•Stage of Consolidation
•Stage of Remodelling

29. Stage of Haematoma Formation:
•Begins immediately following injury and
followed rapidly by repair.
•The Haematoma provides 3 imp. factors:
 It immobilizes # and swellings
hydrostatically splints the # and thus
provides small amount of mechanically
stability of # site.

30.  It provides a fibrin scaffold that facilitates
migration of repair cells.
 Haematoma brings the osteclast &
chondrocyte precursors to # site in large
numbers that begin to differentiate into
osteoblasts and chondrocytes to begin
producing matrix.
The loss of haematoma will impair the # healing.

32. Stage of Granulation Tssue:
•Granulation tissue replaces initial haematoma &
differentiates into connective tissue & fibrocarIlage
Injured tissue & platelets
Vasoactive meditors
New vessels,fibroblasts, intercellular matrix
Granulation tissue

33. Stage of Repair/Callus:
Osteogenesis
Cartilage cells lay in osteoid tissue
Matrix with type 1 collagen fibrils
Deposition of calcium Hydroxyappetite
Callus / Woven/Immature bone

34. Stage of Consolidation:
•By the acIvity of osteoblasts woven bone
transformed into mature bone.
Stage of Remodelling:
•The process occurs along with deposition-‐
resorption phenomenon
•osteoclast has important role in this phase

35. Remodelling does four things:
•It replaces mineralised cartilage with woven
bone.
•Packets of new lamellar bone.
•New secondary Osteons made of Lamellar
bone
•It tends to remove any callus plugging marrow
cavity

37. FRACTURE HEALING IN CANCELLOUS BONE:
•The extent of bone & marrow necrosis
following cancellous bone # is much less than
in compact bone,because of good circulaIon.
•Primary healing takes place in this,secondary
healing is rare and endochondral bone
formation exceptional.

38. VARIABLES INFLUENCE IN # HEALING:
•Cruses and Buck Walter have divided variables
into four groups
1)INJURY VARIABLES:
Open Fractures: Delays repair by soft
tissue disruption & disturbed blood supply to #
site.
severity of injury: Extensive soft tissue &
bone damage leads to delayed # healing.

39. Intraarticular fracture: It requires
reconstruction of joint surface,stable fixation
& early mobilisaIon.
Segmental fracture: It leads to delayed
union/ non union due to disrupted
intramedullary blood supply of middle
fragments.
Soft Tissue interposition: Open reducIon to
extricate interposed tissue will enhance #
healing process.
Damage to blood supply:Delay # healing

40. 2)PATIENT VARIABLES:
Age:Extremes of age have influenes on
# healing.
Nutrition:Poor nutritional status affects
# healing & can lead to mortality & surgical
complications.
Systemic Hormones:
Steroids,anIcoagulants,antiinflammatory
drugs inhibit whereas GH,insulin thyroid
hormone enhance # healing.
Nicotine

41. 3)TISSUE VARIABLES:
Form of bone:Cancellous bone healing is
rapid due to larger surface,rich in cells & blood
supply.
Bone Necrosis
Bone diseases:Osteoporosis,Primary
malignant bone tumours,metastasis,bone cysts
etc... all cause pathological bone # and delay
bone healing.
Infection:It slows down/prevents healing.

42. 4)TREATMENT VARIABLES:
Apposition of # Fragments:Decreasing # gap
decreases volume of repair Issue needed to
heal #.
Loading & Micrimotion:Loading a # site &
induced micrimotion along bone # sites
promotes healing but too much motion lead to
non union.
Fracture Stabilisation:It will prevents
repeated disruption of repair & enhances #
callus.

43. Rigid Fixation:Stable fixation allows early
mobilisaIon of joints & hence prevents
stiffness.
Bone Grafting:It is osteoinductive &
osteoconductive.
Demineralised Bone marrow:The factors in
bone marrow stimulate bone formation,by
migration of undifferentied mesenchymal cells
to implanted matrix & differentiation into
mesenchymal cells.

44. Thank you