Bone-grafts are able to stimulate new bone growth and provide a scaffold for osteogenesis. There are several types of bone grafts including autografts which are transferred from one site to another in the same individual, allografts which are transferred between individuals of the same species, and artificial grafts made of materials like hydroxyapatite. Limb lengthening and reconstruction can be achieved through distraction osteogenesis which involves gradually distracting a bone callus to stimulate new bone formation.

1. BONE-GRAFTS
Bone-grafts are both osteoinductive and osteoconductive,
i.e. they are able to stimulate osteogenesis, and they also
provide linkage across defects and a scaffold upon which new
bone can form. Osteogenesis is brought about partly by the
activity of cells surviving on the surface of the graft, but mainly
by the stimulation of osteoprogenitor cells in the host bed - an
effect that is due to the presence of bone morphogenetic
protein in the graft matrix. Cancellous grafts are more rapidly
incorporated into host bone than cortical grafts, but
sometimes the greater strength of cortical bone is needed to
provide structural integrity.

2.  TYPES:
 1- Autografts (autogenous grafts)
 In these, bone is transferred from one place to another in the same
individual. This is the most commonly used form of bone-grafting, but it
depends on there being sufficient donor bone of the sort required and a
recipient site with a clean vascular bed. Most of the transplanted bone
dies, but it continues to act as a scaffold, which is gradually replaced by a
process of creeping substitution. Cancellous Autografts can be obtained
from the thicker portions of the ilium, the greater trochanter, the
proximal metaphysis of the tibia, the lower radius, the olecranon, or from
an excised femoral head. Cortical grafts can harvested from any
convenient long bone or from the iliac crest; they usually need to be fixed
with screws, sometimes reinforced by a plate, and can be placed on the
host bone, or inlaid, or slid along the long axis of the bone.
 The ideal vascularised autograft is one with an intact blood supply.
Bone is transferred complete with its blood vessels, which are
anastomosed to vessels at the recipient site. The technique is difficult and
time consuming, requiring microsurgical skill. Available donor sites
include the iliac crest (complete with one of the circumflex arteries), the
fibula (with the peroneal artery) and the radial shaft. Vascularized grafts
remain completely viable and become incorporated by a process
analogous to fracture healing.

3. 2- Allografts (homografts)
With these, bone is transferred from one individual (alive
or dead) to another of the same species. The bone is
harvested and stored until needed. The method is
particularly useful when large defects have to be filled.
 Fresh allografts, though dead, are not immunologically
inert. They induce an inflammatory response in the host
and this may lead to rejection. However, the antigenicity
can be reduced by freezing or freeze-drying, or by ionizing
radiation. The process of incorporation (when it occurs) is
similar to that with auto grafts but slower and less
-complete. Demineralization is another way of reducing
antigenicity and it may also enhance the osteoinductive
properties of the graft.

4. Allografts are plentiful and can be stored for long periods.
However, sterility must be ensured. This can be done by
exposure to ethylene oxide or by ionizing radiation, but
their physical properties and potential for osteoinduction
may be altered by doses that are high graft must then be
harvested under sterile conditions and the donor must be
cleared for (A)malignancy, (B)venereal disease,
(C)hepatitis and (D)human immunodeficiency virus
(HIV).

5. Other types of graft
3- Xenografts
are obtained from another mammalian species, such as
pigs or cows. After treatment for antigenicity, they should,
theoretically, behave like allografts, but in practice they
are much less effective unless host marrow is added to the
graft.
4- 'Artificial bone‘
 made of hydroxyapatite composites can be used in the
same way to fill a cavity or bridge a small gap. Bioactive
bone cements (injectable calcium phosphate preparations)
offer a simple alternative, e.g. for replacing bone loss in
metaphyseal fractures.

6. Applications
Cancellous grafts are used for filling cavities,
augmenting healing and promoting arthrodesis.
Cortical or corticocancellous grafts are needed where
bone has been lost as a result of trauma or has been
removed because it contained a tumour. When
reinforced by metallic implants, large gaps can be
filled. Vascularized grafts tend to be used only in
exceptional circumstances, such as treating large
bone defects.

7. DISTRACTION HISTOGENESIS AND LIMB
RECONSTRUCTION
Present-day limb reconstruction is founded on the
principle that new-bone formation is stimulated in
response to gradual increases in tension. This was
originally discovered by Gavril Ilizarov in Russia and the
application of this principle to bone reconstruction is
widely referred to as the Ilizarov method.

8. Distraction histogenesis
Callotasis

Callus distraction, or callotasis, is perhaps the single most
important application of the tension-stress principle. It is used
for limb lengthening or the filling of large defects in bone,
through either bone transport or other strategies. The basis of
the technique is to produce a careful fracture through the bone,
followed by a short wait (5-10 days) before the young callus is
gradually distracted by traction on the bone via a circular or
unilateral external fixator" Distraction proceeds at 1 mm a day,
with small (usually 0.25 mm) increments spaced out evenly. New
callus can be seen on the x-ray after 3 weeks; in optimum
conditions, it forms an even column in the gap between the bone
fragments (this is called the regenerate) . If the distraction rate is
too fast, or the osteotomy performed poorly, the regenerate may
be thin with an hourglass appearance; conversely,

9. if distraction is too slow, it may appear bulbous or, worse
still, may consolidate prematurely, thereby preventing any
further lengthening. When the desired length is reached, a
second waiting period follows which allows the regenerate
callus to consolidate and harden. Weight-bearing is
permitted throughout this period. When cortices of even
thickness appear in the regenerate, the fixator can be
removed. Throughout treatment, physiotherapy is
important to preserve joint movement and avoid
contractures. Patients should be warned that bone
lengthening takes months rather than weeks and carries a
risk of complications, such as pin-track infection,
angulatory deformity, re-fracture and non-union. Ilizarov
techniques should be employed only by surgeons who
have undergone training in this method.

10. Chondrodiatasis
In children, bone lengthening can be achieved by
distracting the physis (growth plate). No osteotomy is
needed and the distraction rate is slower, usually 0.25 mm
twice daily. Although a wide, even column of regenerate is
usually seen, the fate of the physis is sealed: it frequently
closes after the process, and for this reason the technique
is best reserved for children close to the end of growth.

11. Bone transport
The principle of callotasis is used not only for limb
lengthening bur also as a means of treating non-union
and filling defects in bone. Bone transport allows a
defect (or gap) to be filled in gradually creating a
'floating' segment of bone through corticotomy either
proximal or distal to the defect, and slowly moving
the isolated segment of bone across the gap. As the
segment is transported from the corticotomy site to
the new docking site, leaves a trail of regenerate new
bone behind it. An external fixator provides stability
during this process.

12. DEFORMITIES OF THE FOOT
The normal position of the foot is plantigrade - i.e.
when the patient stands, the sole is at right angles to
the leg. Equinus (like a horse's foot) means .that the
hindfoot is fixed in plantarflexion (pointing
downwards), Plantaris looks similar, but the ankle is
neutral and only the forefoot is plantarflexed.
Calcaneus is fixed dorsiflexion at the ankle. A
dorsiflexion deformity in the mid-foot produces a
rocker-bottom foot.

13. Normally the medial border of the foot, even when
weight-bearing, forms a longitudinal arch. The
arrangement of the metatarsals also produces an
anterior or transverse arch in the forefoot. Flattening
of the longitudinal arch is referred to as a planus
deformity or flat-foot; and a dropped metatarsal arch
as anterior flat-foot. An excessively high arch
produces a cavus deformity.

Common deformities of the toes are lateral deviation
of the big toe (hallux valgus), proximal
interphalangeal flexion of one of the lesser toes
(hammer-toe) and flexion of both interphalangeal
joints of several toes (claw-toes).

14. CONGENITAL TALIPES EQUINOVARUS (IDIOPATHIC
CLUB-FOOT)

In this deformity the heel is in equinus (pointing
downwards), the entire hindfoot in varus (tilted towards
the midline) and the mid-foot and forefoot adducted and
supinated (twisted medially and the sole turned upwards).
It is relatively common; the incidence is 1 or 2 per 1000
birth and boys are affected twice as often as girls. The
condition is bilateral in one-third of cases. Similar
deformities are seen in neurological disorders e.g.,
myelomeningocele, and in arthrogryposis.
 The skin and soft tissues of the calf and the medial side
of the foot are short and underdeveloped. If the condition
is not corrected early, secondary growth changes occur in
the bones and these are permanent. Even with treatment,
the foot is liable to be short and the calf may remain thin.

16. Clinical features

The deformity is usually obvious at birth; the foot is both
turned and twisted inwards so that the sole faces
posteromedially. The heel is usually small and high, and
deep creases appear posteriorly and medially. In a normal
baby the foot can be dorsiflexed and everted until the toes
almost touch the front of the leg. In club-foot this
manoeuvre meets with varying degrees of resistance and
in severe cases the deformity is fixed.
 The infant must always be examined for associated
disorders such as congenital hip dislocation and spina
bifida.

X-rays
The tarsal bones are incompletely ossified at this age and
the anatomy is therefore difficult to define. However, the
shape and position of the tarsal ossific centres are helpful
in assessing progress after treatment.

20. Treatment

The aim of treatment is to produce and maintain a
plantigrade, supple foot that will function well. There are
several methods of treatment, but relapse is common,
especially in babies with associated neuromuscular
disorders.

Conservative treatment

Treatment should begin early, preferably within a day or two
of birth. This consists of repeated manipulation and adhesive
strapping or application of plaster-of-Paris casts, which will
maintain the correction. If adhesive strapping is used,
parent, are taught how to do the manipulation and they can
then carry out gentle stretches on a regular basis with the
strapping still in place. Treatment is supervised by a
physiotherapist, who alters the strapping as correction is
gradually obtained. Plaster-of-Paris casting requires serial
changes and manipulations in a clinic setting. Sometimes
surgical release of the Achilles tendon is needed to complete
the correction.

21. Operative treatment
Resistant cases will need surgery. The objectives are
(a) the complete release of joint tethers (capsular
and ligamentous contractures and fibrotic bands)
and (b) lengthening of tendons so that the foot can
be positioned normally without undue tension. A
detailed knowledge of the pathological anatomy is a
sine qua non. After operative correction, the foot is
immobilized in its corrected position in a plaster
cast. Kirschner wires are sometimes inserted across
the intertarsal and ankle joints to augment the hold.
The wires and cast are removed at 6-8 weeks, after
which hobble boots (Dennis Browne) or a
customized orthosis are used to maintain the

22. LATE OR RELAPSED CLUB-FOOT

Late presenters often have severe deformities with
secondary bony changes, and the relapsed club-foot
is complicated by scarring from previous surgery. A
revision .of the soft-tissue releases may be
considered; this can be combined with shortening
of the lateral side of the foot by calcaneocuboid
fusion or cuboid enucleation (Dilwyn Evans).
Alternatively, gradual correction by means of a
circular external fixator (the Ilizarov method) has
proved effective in treating difficult relapsed cases
and severe deformities; the early results are
encouraging.
