Fractures and
Bone Healing
H Biology II
Adapted 2014-2015
Response to Mechanical Stress
 Wolff’s
law – a bone grows or remodels in
response to the forces or demands placed
upon it
 Observations supporting Wolff’s law
include
 Long
bones are thickest midway along the
shaft (where bending stress is greatest)
 Curved bones are thickest where they are
most likely to buckle
Response to Mechanical Stress
 Trabeculae
form along lines of stress
 Large, bony projections occur where
heavy, active muscles attach
Response to Mechanical Stress
Statistics
Fractures of extremities most common
 More common in men up to 45 years of age
 More common in women over 45 years of age
 Before 75 years wrist fractures (Colles’) most
common
 After 75 years hip fractures most common

Fractures
A fracture is any break in a bone.

Fracture repair involves formation of a clot called
a fracture hematoma, organization of the
fracture hematoma into granulation tissue called
a procallus (subsequently transformed into a
fibrocartilaginous [soft] callus), conversion of the
fibrocartilaginous callus into the spongy bone of
a bony (hard) callus, and, finally, remodeling of
the callus to nearly original form.
6
Bone Fractures (Breaks)
 Bone
 The
fractures are classified by:
position of the bone ends after fracture
 The completeness of the break
 The orientation of the bone to the long axis
 Whether or not the bones ends penetrate the
skin
Common Types of Fractures
 Magnitude
and direction of force are
determining factors in type of fracture.
 Closed

– Bone fragments do not pierce skin
 Open/compound

– Bone fragments pierce skin
 Displaced or undisplaced
Common Types of Fractures
– bone fragments into three
or more pieces; common in the elderly
 Spiral – ragged break when bone is
excessively twisted; common sports injury
 Depressed – broken bone portion pressed
inward; typical skull fracture
 Compression – bone is crushed; common
in porous bones
 Comminuted
Common Types of Fractures
– epiphysis separates from
diaphysis along epiphyseal line; occurs
where cartilage cells are dying
 Greenstick – incomplete fracture where
one side of the bone breaks and the other
side bends; common in children
 Epiphyseal
Common Types of Fractures
Common Types of Fractures
Common Types of Fractures
Common Types of Fractures


Named for shape or position of fracture line
Common types of fracture



Pott’s -- distal fibular fracture
Colles’s -- distal radial fracture
stress fracture -- microscopic fissures from
repeated strenuous activities
14
Transverse fracture

Usually caused by directly applied force to
fracture site
Spiral (Oblique)

Caused by violence transmitted through
limb from a distance (twisting movements)
Greenstick

Occurs in children: bones soft and bend
without fracturing completely
Compression (Crush) fractures

Fracture in cancellous bone: result of
compression (osteoporosis)
Burst fracture

Occurs in short bones, e.g. vertebra from
strong direct pressure such as impaction
of disc.
Avulsion fracture



Caused by traction, bony fragment usually torn off by a
tendon or ligament.
What muscle group attaches to this bony prominence
and what nerve also runs in close proximity?
Forearm flexors (common flexor origin) ulnar nerve
Fracture dislocation/subluxation

Fracture involves a joint: results in
malalignment of joint surfaces.
Impacted fracture

Bone fragments are impacted into each
other.
Comminuated fracture

Two or more bone pieces - high energy
trauma
Comminuated fractures can require
serious hardware to repair.
Stress Fracture

Abnormal stress on normal bone (fatigue
fracture) or normal stress on abnormal
bone (insufficiency fracture).
Functions of the X-ray
Localizes fracture and number of fragments
 Indicates degree of displacement
 Evidence of pre-existing disease in bone
 Foreign bodies or air in tissues
 May show other fractures
 MRI, CT or ultrasound to reveal soft tissue
damage

Repair/Healing of Bone
Healing is faster in bone than in cartilage due to
lack of blood vessels in cartilage
 Healing of bone is still slow process due to
vessel damage
 Clinical treatment

closed reduction = restore pieces to normal position
by manipulation
 open reduction = realignment during surgery

27
How to Handle Fractures

Reduction



Open reduction
– Allows very accurate reduction
– Risk of infection
– Usually when internal fixation is
needed
Manipulation
– Usually with anesthesia
Traction
– Fractures or dislocation requiring slow therapy
Fracture Fixation
 4-12
weeks
 External fixation
 Internal fixation

Intermedually nails, compression plates
 Frame
fixation
External fixation

Used for fractures that are too unstable for
a cast. You can shower and use the hand
gently with the external fixator in place.
Frame fixation

Allows correction of deformities by moving
the pins in relation to the frame.
Internal fixation
Repair of
a
Fracture
33
Stages in the Healing of a Bone
Fracture
 Hematoma
formation
Torn blood vessels
hemorrhage
 A mass of clotted
blood (hematoma)
forms at the
fracture site
 Site becomes
swollen, painful,
and inflamed
 3-4 hours
Hematoma

1
Hematoma formation
Stages in the Healing of a Bone
Fracture

The fibrocartilaginous callus forms when:
Osteoblasts and fibroblasts migrate to the
fracture and begin reconstructing the bone
 Fibroblasts secrete collagen fibers that
connect broken bone ends
 Osteoblasts begin forming spongy bone
 Osteoblasts furthest from capillaries secrete
an externally bulging cartilaginous matrix that
later calcifies

Stages in the Healing of a Bone
 Fibrocartilagino Fracture
us callus forms
 Granulation
tissue (soft
callus) forms a
few days after
the fracture
 Capillaries grow
into the tissue
and phagocytic
cells begin
cleaning debris
External
callus
Internal
callus
(fibrous
tissue and
cartilage)
2 Fibrocartilaginous
callus formation
New
blood
vessels
Spongy
bone
trabeculae
Stages in the Healing of a Bone
Fracture

Bony callus formation
New bone trabeculae
appear in the
fibrocartilaginous callus
 Fibrocartilaginous callus
converts into a bony
(hard) callus
 Bone callus begins 3-4
weeks after injury, and
continues until firm union
is formed 2-3 months
later

Bony
callus of
spongy
bone
3 Bony callus
formation
Stages in the Healing of a Bone
Fracture

Bone remodeling
Excess material on
the bone shaft
exterior and in the
medullary canal is
removed
 Compact bone is
laid down to
reconstruct shaft
walls

Healing
fracture
4 Bone remodeling