5.b BASIC FRACTURE HEALING
Definition of fracture:
Fracture is defined as a break in continuity of the bone.
Healing
of fractures in long bones
Fracture healing in a
long bone can be divided conveniently into 3 phases.
1.Inflammatory
phase
2.Reparative
phase
3.Remodelling
phase
1.Inflammatory phase:
After the fracture the bone itself is damaged along with the surrounding soft tissues including periosteum & surrounding muscles. There is accumulation of haematoma between fracture ends. Blood vessels crossing the fracture site are ruptured resulting in death of osteocytes due to lack of nutrition as far as the junction of collateral channels. So the immediate ends of the bone become dead. This dead bone along with damaged periosteum and soft tissues elicits an immediate and intense acute inflammatory reaction. There are widespread vasodilation and plasma exudation. Acute inflammatory cells like polymorphonuclear leucocytes migrate to the region, followed by macrophages. As a result of this acute inflammatory reaction acute edema is seen in the region of a fresh fracture.
2.Reparative phase:
The initial stimulus
that results in cellular activity aimed at fracture repair includes
A. Alteration in PH of microenvironment
B. Chemotactic factors
C. Bioelectrical stimuli
Cells
involved in reparative process:
Cells involved are of
mesenchymal origin and are pleuripotential. These cells form collagen,
cartilage and bone. Majority of the cells involved in fracture healing enter
the fracture site with the granulation tissue. The repair is indivisibly linked
with ingress of capillary buds. It appears that, under ordinary circumstances
the periosteal vessels contribute to capillary buds early in the normal bone
healing, with the nutrient medullary artery becoming more important later in
the process. But when the surgeon interferes with this
natural process, either by stripping the periosteum excessively while plating
or destroying the intramedullary system through the use of the medullary nails
repair must proceed with vessels derived from the surviving system.
These
cells invade the haematoma and form a tissue known as callus which contains
fibrous tissue, cartilage and young immature bone. This quickly envelops bone
ends and leads to gradual stability of fracture ends.
In
addition to bone formation, bone resorption also takes place by osteoclasts
which are derived from circulating monocytes from the blood.
In
this way bony ends gradually become enveloped in a mass of fusiform tissue
(callus) and eventually clinical union is said to have occurred.
3.Remodelling phase:-
In
this phase Osteoclastic resorption of superfluous or poorly placed
trabeculae occurs and new struts of bone are laid down that corresponds to
lines of force. The control mechanism that modulates this cell behavior is now
believed to be electrical.
In
1892, Wolff postulated his law. When a bone is subjected to stress,
electropositivity occurs on the convex surface and electronegativity appears on
the concave side, this current having been produced by a piezoelectric like
effect. Circumstantial evidence indicates that region of electropositivity are
associated with osteoclastic activity and regions of electronegativity are
associated with osteoblastic activity.
The
cellular module that controls remodeling is the resorption unit, consisting of
osteoclasts which first resorb the bone and followed by osteoblasts which lay
down new haversian systems. The end result of remodeling is that even if the
bone has not returned to its original form, it has been altered so it may best
perform the function demanded of it.
Healing
of fractures in cancellous bone
Charnley & Becker studied the healing process in
humans.
The
first difference lies in the differing vascular arrangements which ensure that
terminal bone death does not occur.
Under
conditions of close opposition healing proceeds by intramembranaous
ossification which becomes laid down upon and attached to, the original
trabaculae thus creating a bond between the two fragments .
Once union is established, then the now thickened trabaculae at the junctional
region are remodelled by the simple surface process.
1.
Healing
of long bones in special situations –depending upon treatment modality
By this is meant those methods in which fracture is
not deliberately exposed & immobilization is produced by splints, casts or
traction.
Under these conditions fracture should heal by the
“natural healing process” providing external callus formation.
Causes
of failure of union by closed methods
Healing
of bone as influenced by fixation with plates and screws (Traditional
devices)
Many
of traditional devices merely maintain the position of the fragments. Given
that their introduction does not lead to infection normal healing process need
not necessarily be affected. External callus is still the medium by which the
fragments are first bridged although it is often reduced in quantity when
compared with fixation by external means alone.
(AO plates/ compression plates etc)
The
work of Schnek and Willinegger established the reality of the healing process
histologically. They found that all of the dead bone became revitalized by new
harvesian systems & where there was perfect contact between the fragments
of this now revarcularised bone the new harvesian systems were able to cross
directly from one fragment to the other . Where small
gaps existed these were first filled with new owen
bone, so called “gap healing” & and thus in turn acted as a conducting
medium for the new osteones. It will be perceived that this process represents
nothing more than the remodeling process already described except for the
conditions are rather ideal with a minute fracture gap & perfect alignment
so that the amount of remodelling required is minimum.
The main disadvantage of this method being the damage
it inflicts on the medullary blood supply.
If
relatively narrow implants such as rush nails and the like are used there is no
damage / minimum damage to the medullary blood supply. In such instances
healing process is probably little different from that which occurs using
external fixation alone.
But
when the aim is secure fixation in lower limbs sufficient to allow weight
bearing and free joint movement large diameter nails are used which usually
requires extensive reaming causing damage to medullary blood supply
. So in these conditions if the periosteal blood supply is also damaged
by extensive soft tissue injury whole diaphysis may be devascularised & may
be sequestrated.
The method on the other hand
offers certain advantages. Union is usually rapid as external callus is seldom
completely suppressed. This is mainly due to the fact that a nail can never
offer complete rigidity as with a plate. In this situation the phenomena of “stress protection
osteopenia ” is also avoided.
2.Healing of cancellous bone as
influenced by treatment
Many of these injuries involve joints so that
accurate reconstruction is essential in order accurately to restore the
congruity of the articular surface. This usually demands operative reduction
& fixation often with screws. While fixing these fractures surgeon should
be careful about avoidance of gaps & not to devatalize the fragments. If
there are gaps, they should be filled with cancellous bone grafts which will
prevent entry of fibrous tissue into the gaps and get revascularized and
incorporated into the cancellous bone
FAILURE OF
Failure
of union embraces both terms delayed union and non union.
Delayed union: Delayed union indicates that it takes
longer than the average time for a given fracture to heal.
Non-union: Non union refers to an arrest of healing
process and the formation of a pseudoarthosis or a fibrous union in which the
bone ends are either osteoporotic and atrophied or sclerotic.
Slow union: Watson Jones refers to another condition
called slow union. Here the fracture line is still clearly visible, but there
is no undue seperation of the fragments, no cavitation, no calcification and no
sclerosis. Union has not been necessarily delayed and it is not an
ununited fracture. This is a well recognized phenomenon in fracture treatment
and only a variation from normal.
Bone grafts may be used in the treatment of delayed or
non union. The objectives in grafting are to stimulate bony union, to replace
lost tissues and to assist in the revascularization of
avascular segments of bone.
There are four
types of bone grafts.
FACTORS AFFECTING BONE HEALING:
Healing of fractures in living
organism is modified by local and systemic factors.
Local factors:
Systemic Factors:
Other hormones like Thyroid
hormone, Calcitonin, Insulin, vitamins like A and D in physiological doses
enhance the rate of bone healing.
Diabetes,
castration, hypervitaminosis D and A as well as rachitic states retard bone
healing.
PRESENTATION
History:- -There is usually a history of trauma in
fractures.
Presenting complaints
-Pain,
swelling, deformity & loss of function of the affected limb following a
history of trauma.
Mechanism of injury
Mechanism of injury is important as it gives
a clue to which bone may be fractured.
Ex:-Fall on outstretched hand usually causes fracture of
clavicle, fractures around the elbow and colles fracture.
-Fall on paint of the elbow causes fracture dislocation of elbow.
PHYSICAL EXAMINATION
Proper exposure of the body part is
crucial to an accurate examination
1) Inspection:-Localized swelling ,
echymosis & deformity may be seen on
inspection while examining a case of bone injury.
2)Palpation: -
Tenderness is almost always
associated with a fracture.
-
Crepitus, this clinical sign
is due to grating of fragments on each other.
-
Abnormal mobility.
-
Bony irregularity.
-
Absence of transmitted
movements.
ANY ASSOCIATED COMPLICATION?
Complications such as injuries to the nerves
and vessels etc. may be associated with the fracture. These have to be
carefully looked for.
INVESTIGATIONS
Labs:-Scintigraphy may be useful in detecting subtle acute
fractures when radiographs are normal(eg: in the
carpal bones) or in excluding fractures in the presence of significant clinical
findings..
X-rays:- It must be recognized that a radiograph is no more
than a shadow & that shadows often distort & conceal. Even when a bone
is angulated in one direction to 90 degrees, there is a plane where the film
shows an appearance of perfect alignment. It is almost better to have no
radiograph at all than a single film in one projection.
At least two radiographic projections at right angles are
always necessary. Two films should always be examined side-by-side, surgeon
always thinking in terms of three dimensions. He should also remember that no
displacements may be revealed in this there two films of a fracture of a long
bone because displacement may be in “the third dimension” that is in a
rotational direction. This rotational deformity is of course revealed by
careful clinical examination.
CLASSIFICATION OF
FRACTURES:
Fractures can be classified on the basis of
etiology, on the basis of the displacement, on the basis of relationship with
external environment & on the basis of pattern.
ON THE BASIS OF ETIOLOGY:
ON THE BASIS OF
DISPLACEMENTS:
ON THE BASIS OF RELATIONSHIP WITH EXTERNAL
ENVIRONMENT
ON
THE BASIS OF PATTERN
DIFFERENTIAL
DIAGNOSIS:
Traumatic
fractures: In this type of fracture there is a clear cut history of trauma
followed by signs & symptoms of fracture.
Pathological
fractures: In this type of fractures there is no significant history of trauma
or history of very trivial trauma. But there will be sudden history of
swelling, deformity or abnormal mobility.
Stress
fracture: Here again no significant history of trauma could be elicited. But
history of strenuous activity could be elicited followed by subtle signs and
symptoms of fracture.
Compound
fracture: In this type of fracture laceration in the overlying skin and soft
tissues can be seen.
TREATMENT:
Treatment of a fracture can be considered
in three phases:
Phase 1: Emergency care
Phase 2: Definitive care
Phase 3: Rehabilitation
PHASE 1:
EMERGENCY CARE
At the site of accident:
Emergency care of a fracture begins
at the site of the
accident. In principle, it consists of “splint them where they lie”
PHASE 2: DEFINITIVE
CARE
The three fundamental
principles in fracture treatment are: 1.reduction; 2.immobilization; and 3.
preservation of functions. Reduction is the technique of setting a displaced
fracture in proper alignment. Immobilazation is done to maintain the reduction.
To preserve the functions of the limb, physiotheraphy during
and after immobilization is necessary.
REDUCTION OF FRACTURES:
Indications: Not all
fractures require reduction, either because there is no displacement or because
the displacement is immaterial to the final outcome. For example, a child’s
clavicle fracture does not need reduction because normal function and
appearance will be restored without any intervention. In general imperfect
apposition of fragments can be accepted more readily than imperfect alignment
or rotational mal-alignment. Anotomical reduction is desirable in some
fractures even if it requires an operative procedure (e.g., intra-anticular
fractures).
Methods: Reduction of a fracture
can be carried out by one of the following methods:
a) Closed manipulations
b) Continuous traction.
c) Open reduction:
IMMOBILIZATION OF FRACTURES
Indications: Not all fractures require immobilization. The
reasons for immobilizing a fracture may be:
a) To prevent displacement or angulation of the fracture
b) To relieve pain
c) To prevent movement
METHODS: immobilization of a
fracture can be done by conservative or operative methods.
CONSERVATIVE METHODS
Most
fractures can be immobilized by one of the following conservative methods:
STRAPPING
SLING
CAST IMMOBILIZATION
FUNCTIONAL BRACING
SPLINTS & TRACTION
OPERATIVE
METHODS
Wherever open reduction is performed, fixation(internal or external) should also be used. External
fixation is usually indicated in cases where internal fixation cannot be done.
INTERNAL FIXATION: In this method, the fracture, once
reduced, is fixed internally with the help of some metallic or non metallic
device such as steel wire, screw, plate, Kirschner wire, intramedullary nail
etc.
INDICATIONS: Internal fixation of
fractures may be indicated under the following circumstances:
EXTERNAL FIXATION: It is a device by which
the fracture is held in a frame outside the limb. For this, steel pins are passed percutaneously to hold the bone, and are connected outside
to a bar with the help of clamps. This method is useful in the treatment of
open fractures where internal fixation cannot be carried out due to risk of
infection, and plaster application makes dressing the wound difficult.
COMPLICATIONS OF
FRACTURES.
CLASSIFICATION:
a. Immediate complications: Complications occurring at
the time of the
fracture.
b. Early
complications: Complications occurring in the initial few days of the fracture.
c. Late complications: Complications occurring a long
time after the fracture.
IMMEDIATE
COMPLICATIONS:
SYSTEMIC
·
Hypovolaemic
shock
LOCAL
·
Injury to major
vessels,nerves,joints etc.
·
Injury to
muscles and tendons
EARLY
COMPLICATIONS
SYSTEMIC
*Hypovolaemic
shock*ARDS*Fat embolism syndrome*DVT & Pulmonary embolism*Aseptic traumatic
fever*Septicaemia
LOCAL
*Infection
*Compartment
syndrome
LATE
COMPLICATIONS
*Imperfect union of the fracture*Delayed union*Non
union*Cross union
Others*Shortening*Joint stiffness*Sudecks’
dystrophy
REHABILITATION
Rehabilitation may be in the form of social service, physical treatment or occupational therapy.
THE
FUTURE
EFFECTS OF PROSTAGLANDINS ON SKELETON:
Prostaglandins particularly those of the E
series, have potent effects on bone resorption in vitro and on the bone
formation and bone remodelling in vivo.
GROWTH FACTORS AND ELECTROMAGNETIC FIELDS IN BONE:
Stimulation of bone by low-energy
electromagnetic fields (EMF s) may prove to be an efficient therapy for
skeletal disorders
ANORGANIC BOVINE BONE AND CERAMIC ANALOGS OF BONE MINERAL
AS IMPLANTS TO FACILITATE BONE REGENERATION
The
natural bone mineral of anorganic bovine bone has been used
as a
substitute for allogenic bone for grafting procedures. Synthetic calcium
phosphate ceramic materials also have been developed for this application.
REFERENCES
Charles
A. Rockwood, Jr. and
David
P. Green
Fractures in adults Second Ed.
Maheswari
J. Essential
Orthopaedics.
Resnick and
Niwayama Diagnosis of
Bone and Joint Disorders, 1981.
Watson Jones, R: Fractures and
Joint Injuries, Vol. 2, 4 th Ed.
Clinics in Plastic Surgery