technique

1. Calvarial bone graft harvesting
Jameel kifayatullah

2. Calvaria
• The calvaria is the top
part of the skull. It is the
upper part of
the neurocranium and
covers the cranial
cavity containing the
brain. It forms the main
component of the skull
roof.
• The calvaria is made up of
the superior portions of
the frontal bone, occipital
bone, and parietal bones

3. Calvaria
• Most bones of the
calvaria consist of internal
and external tables or
layers of compact bone,
separated by diploë. The
diploë is cancellous bone
containing red bone
marrow during life,
through which run canals
formed by diploic vein

4. Harvesting of calvarial bone graft
• The cranial vault offers a large
stock for harvesting calvarial
bone grafts.
Depending on the type and size
of the defect to be repaired,
various harvesting techniques can
be used. A coronal incision
provides excellent access for the
harvesting of calvarial bone graft,
though other incisions can also
be used.
If the pericranium(periosteum)
has been elevated posteriorly
already, the dorsal wound edges
may be reflected posteriorly for
additional exposure of the donor
site.

5. Harvesting of calvarial bone graft
• Even the harvesting of outer table calvarial
bone grafts is associated with potential
intracranial injury. Therefore the graft should
be taken from the skull over the non-dominant
hemisphere.

6. Harvesting of calvarial bone graft
• The parietal bone is the
most appropriate source
for cranial bone grafts.
The inner and the outer
cortex is thick with a wide
diploë in between.
The harvesting area
should stay away 2.0 cm
from the cranial suture
lines, in particular from
the midline, in order to
prevent injury to the
sagittal sinus.

7. Harvesting of calvarial bone graft
Precautions when harvesting outer table bone
grafts
• Ensure sufficient bone thickness, ideally with CT
scan.
• Accidental full thickness harvesting may occur. In
this case, the integrity of the dura must be
checked and absence of bleeding must be
confirmed.
• Some surgeons prefer special observations
(neuro checks) to monitor patients for 24 hours
to rule out any intracranial complications.

8. Types of calvarial bone grafts
Various types of calvarial bone graft
There are several types of calvarial bone grafts that
may be taken:
• Shaved corticocancellous outer table graft with
attached pericranium
• Bone paste or bone dust
• Split thickness outer table grafts
• Full thickness parietal bone graft
• Inner table grafts taken from a full thickness bone flap

9. Shaved corticocancellous outer table
graft with attached pericranium
• These small grafts are
taken with a sharp
osteotome after scoring
their outlines with a side-
cutting burr or by direct
tangential cutting off a
bone convexity with a
reciprocating or
oscillating saw. The
resulting bone splinters
are held together by the
pericranium left on the
surface.

10. Harvesting of calvarial bone graft
• The thin grafts will curl
and are malleable
within certain limits

11. Harvesting of calvarial bone graft
Bone paste or bone dust
• Bone paste or bone dust may
be harvested with a hand-
powered instrument or a large
neurosurgical perforator at
very low speed passing
through the outer table into
the diploë.
• Additional cancellous bone
can be harvested from the
diploic layer using bone
curettes or bone splitters.
• Note: Do not use bone dust
that is the byproduct of high
speed drilling.

12. Harvesting of calvarial bone graft
Bone paste or bone dust
• Alternatively, a bone
scraping instrument
may be used to scrape
bone particles from the
calvarium.

13. Harvesting of calvarial bone graft
• Split thickness outer table
grafts
• For such grafts, the outer table
is split from the inner table at
the level of the diploic layer.
The grafts are taken in strip
segments either single or in a
series.
The segments are oriented
either in a sagittal or
transverse direction.
The outline of the grafts is
traced with a side-cutting burr
or a saw.

14. Harvesting of calvarial bone graft
• The initial grooves are deepened
to the level of the diploë.
The diploë must be visible, which
is indicated by cancellous bone
bleeding.
A trough is created along the side
of the bone graft by tangential
saw cuts. The outer edges are
beveled smooth to give a flat
access angle for an osteotome
and thereby permit calvarial
splitting.
The outer cortex grafts are
separated from the calvarium by
sequential advancement of thin
osteotomes through the diploic
layer.

15. Harvesting of calvarial bone graft
• Alternatively, elevation
of the outer table can
be accomplished using
a sagittal saw with a 90°
bend to elevate the
outer table.

16. Harvesting of calvarial bone graft
• Technique: partial
thickness
Separation of the graft
from the inner table is
achieved with chisels.

17. Harvesting of calvarial bone graft
• N.B.: perforation into
the cranial cavity should
be avoided. If there is a
perforation into the
cranial cavity, integrity
of the dura and absence
of bleeding must be
confirmed.

18. Harvesting of calvarial bone graft
• Depending on what is
required, the outer
table grafts are sized to
a width of up to 20 mm
and may be slightly
curved.

19. Harvesting of calvarial bone graft
• The normal contour of
the cranial bone can be
restored using bone
substitutes but it is not
necessary unless there
are aesthetic concerns.

20. Harvesting of calvarial bone graft
• Full thickness parietal bone graft
• These grafts are removed with a
formal craniotomy and are
indicated if long biparietal bone
struts across the sagittal sinus or
grafts with special curvatures are
required.
Burr holes are made with a
trephine followed by dural
dissection and craniotomies.
The harvested bicortical parietal
bone can be split into its two
laminae. The inner cortex is used
for facial reconstruction while the
outer cortex is returned to cover
the donor site.

21. Harvesting of calvarial bone graft
• Technique using a
craniotome
The donor area is
chosen. Then one burr
hole is made and.

22. Harvesting of calvarial bone graft
• the desired shaped
graft is harvested using
a craniotome

23. Harvesting of calvarial bone graft
• The bone flap is
carefully lifted making
sure that no dural
lacerations occur.

24. Harvesting of calvarial bone graft
• Dural suspension at the
edges of the craniotomy
should be performed. In
case of dural leakage,
depending on the size
of the defect, either
dural repair, dural
patches, or sealant
techniques should be
used.

25. Harvesting of calvarial graft
• If full thickness cranial bone
is harvested reconstruction
of the defect is necessary
not only to restore the
contour but to protect the
brain. Techniques are
analogous as in partial
thickness, reconstructive
options include titanium
mesh, porous polyethylene
and
polymethylmethacrylate
PMMA.