Cranioplasty is a surgical procedure to reconstruct and repair a defect in the skull. Some key points:
- The first documented cranioplasty used a piece of dog cranium to repair a defect in a Russian nobleman in the 17th century.
- Autologous bone is still considered the best graft material due to its biocompatibility and ability to integrate with native bone. Other common materials include methyl methacrylate, titanium, and hydroxyapatite.
- Indications for cranioplasty include protecting the brain, restoring cosmetic appearance, relieving headaches, and preventing brain herniation. Early repair may help alleviate symptoms of the "syndrome of the
7. ⢠The first reported cranioplasty was probably that
of a Russian nobleman who, after receiving a
sword blow to the head, had the resultant defect
(and his health) restored with a piece of dogâs
cranium (Van Meekeren, 1668).
⢠Subsequently, after he had been
excommunicated from the Russian church (which
could not accept the presence of animal bone on
a human skull), removal of the graft was
impossible due to bony union.
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9. Definition
The restoration of a defect in the cranial bone
or correction of a deformity of the bone that
may happen after trauma as in depressed
fracture
10. Bone graft integration
⢠The dynamic nature of living bone was first
realised in 19th century.
⢠In 1893 the histological sequence of bone
replacement, âcreeping substitutionâ
⢠Survival of a bone implantation graft depends
on the reaction of the surrounding tissue and
on functional contact between cancellous
bone and adjacent resident bone.
11. ⢠1st week â Capillaries from surrounding bone
diploe, dura and scalp infiltrate the transplant
bed.
⢠2nd week â fibrous granulation tissue
proliferates and osteoplastic activity occurs.
⢠Osteoinduction â
â Primitive mesenchymal cells â Osteoprogenitor cells
â Osteoblasts that are capable of forming newbone
to replace the necrotic bone which is gradually
absorbed
12. ⢠Osteoconduction â Osteoprogenitor cells from
the surrounding tissue migrate into the 3-D
structure of bony and protein matrix.
⢠Auto- and allo-grafts have relied on
osteoconduction as the main principle of
cranioplasty.
⢠In osteoinduction, cells do not have to migrate
from the surrounding tissues but, probably with
the help of bone morphogenetic proteins, can be
produced in situ.
13. ⢠Osteoactivity â Ability of the biomaterial to be
replaced with bone formation either through
osteoinduction / osteoconduction
⢠Osteoproductivity â The process whereby a
bioactive surface is colonised by osteogenic
stem cells from the defective environment as
a result of surgical intervention
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15. AETIOLOGY OF THE CRANIAL DEFECT
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Trauma
Decompressive craniectomy
Infection
Neoplasms
Congenital: Encephalocele,
meningoencephalocele, large parietal
foramina, aplasia cutis congenita, cranium
bifida, sphenoid wing defect
16. INDICATIONS
⢠Aesthetic / protective / discomfort
⢠Those prone for trauma - seizure disorder,
sports, military
⢠? Local tenderness
⢠? Post traumatic seizure
⢠Hemispheric collapse
⢠Childrenâasymmetric growth and cerebral
hernia
17. INDICATIONS
⢠GRANT AND NORCROSS (1939)
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Severe headache and syndrome of trephined
Epilepsy assumed to be due to defect
Danger of trauma
Unsightly defect
Pulsate unduly and painful
18. When to do it?
⢠3-6 months after compound wounds
⢠1 year after wound infection / if frontal sinus
is opened
⢠3 months with autograft
⢠Wait for 1 year after craniectomy in a child
19. SYNDROME OF THE TREPHINED
⢠Yamura and Makino (1977) coined the term
âsyndrome of the sunken skin flapâ to describe
the neurological symptoms due to a
craniectomy defect
⢠Progressive contralateral hemiparesis, local
pain and postural headache with cognitive
and functional decline due to a skull defect
⢠Not affected by size or location of defect
⢠Early cranioplasty may improve the symptoms
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21. SYNDROME OF THE TREPHINED
⢠Pathophysiology
â Stretching of the dura and underlying cortex due
to the atmospheric pressure
â Cicatrical changes occurring between the
cortex, dura and the skin exerting pressure on the
skull contents
â Impairment of the venous return due to the
atmospheric pressure acting on the region of skull
defect with a resultant increase in the local
external pressure
22. SYNDROME OF THE TREPHINED
⢠How does cranioplasty work?
â Increase in cerebrospinal fluid (CSF) and superior
sagittal sinus pressure, cerebral expansion,
increase in CSF motion after cranioplasty due to
an increase in cerebral arterial pulsations and
improvement in cerebral blood flow, cerebral
metabolism and cerebral vascular reserve capacity
have been demonstrated after cranioplasty.
26. Preservation of autografts
⢠In the interim - âhockey helmetâ
⢠Boiling (Westermann â 1916)
⢠Alcohol / formalin / autoclaving ď Bone resorption &
infection
⢠Bone flap in abominal wall (Kreider â 1920) ď Another
operation, unsightly scar, no osteogenic potential
⢠The bone flap remains sterile in a â70°C freezer for
many months.
⢠Autoclaving of the bone (e.g., if contaminated by a
compound scalp wound before cranioplasty) ď
reduce the viability of the graft.
⢠ETO sterilisation
27. Critical size of defect
⢠Bone defects > 2 cm on the cerebral convexity
and bone defects of glabrous frontal region
⢠No need for repair in
â Defects below the temporal & occipital muscles
â Very elderly
â Children < 6 yrs in whom dura is not damaged
â Parietal area defect < 5 cm2
29. Preparation of the cranial defect
⢠The surgical bed must be clean and free of debris
⢠Both surgical bed and overlying surgical flap must be
well-vascularised
⢠Incorporate the previous scar into repair
⢠Scars in hair-bearing areas, avoiding parallel ones
⢠Cranialise the sinus
⢠Pericranium brought up as second layer with pedicle
intact
⢠Bone edges freshened
⢠Meticulous hemostasis & gentle handling of soft
tissues
⢠Any foreign material that is used should be perforated
30. AUTO BONE GRAFT
⢠Wrap in blood soaked sponge for 4-6 hrs
⢠More than 6 hrs â 10 % serum / 90 % salt
solution at 3 C.
⢠Donât expose to air for more than 30 min.
⢠Normal saline is toxic
⢠Avoid antibiotic soak
⢠Split bone graft â Outer & inner tables split
31. ⢠RIB
â 3-4 times more resorption
â Contour deformity
â Difficult to stabilize
⢠ILIUM
â Post op pain
â Second operation site
â Difficult to contour
⢠TIBIA
â Small segments
â Difficult to contour
â # Tibia
⢠VASCULAR FLAP â IRRADIATED TISSUE
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33. Cranioplasty after left decompressive hemicraniectomy for intractable
intracranial hypertension.
A. Preoperative CT scan demonstrating Lt skull defect
B. autologous bone flap secured to native skull with plating system
C. Postoperative computed tomographic scan
demonstrating cranioplasty
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35. POLYMETHYL METHACRYLATE
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Inert
Minimum reaction
Tight adherence
Not thermoconductive
MRI compatible
Prepare intra-operatively
Powder polymerised ester of acrylic acid + benzoyl
peroxide liquid monomer (2:1)
⢠A paste-like substance into a translucent material with
strength comparable to that of native bone
38. Cranioplasty after resection of right frontal meningioma with growth through the skull.
⢠A skull defect
⢠B methyl methacrylate sheet over skull defect
⢠C methyl methacrylate plated into skull defect.
⢠D Postoperative CT scan
40. Nova Bone (Porex Surgical)
⢠Synthetic bio-active glass particulate
⢠45% silica dioxide + 45% sodium oxide + 5%
calcium + 5% phosphate
⢠Osteoproductive and osteoconductive
41. POROUS POLYETHYLENE
⢠For facial augmentation and to restore continuity
to craniofacial skeletal defects
⢠Straight chain aliphatic hydrocarbons
⢠Non toxic, inert and stable
⢠Ingrowth of bone and soft tissue rapid.
⢠Small and medium defects
⢠Pattern transferred to smooth surface.
⢠Cut with knife
⢠Soak in sterile saline at 180°F - to modify shape
⢠Secure using titanium screws.
49. OSTEOINDUCTIVE AGENTS
⢠Bone morphogenic protein
â Group of proteins extracted from the bone matrix
that stimulate bone growth
â Some are well-characterized biochemically and
produced by recombinant DNA techniques
â Wozney et al defined 7 BMPs
â BMP 2 to 7 are related by amino acid homology
and are members of TGF-β superfamily
51. PAEDIATRIC PLASTY
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Not in less than 3 yrs
Wait for 1 yr
Auto bone preferred
No alloplasty less than 8 yrs
No split graft in infants
Alloplasty â dislodges, retards growth
52. Methyl methacrylate
⢠At least 5mm thick except over temporal
region or in child.
⢠Antibiotics
⢠Scalp incision outside defect, never parallel to
previous scar.
⢠Avoid incising dura
⢠Reflect temporalis
53. Split skull
⢠Autograft of choice.
⢠Either totally removed and then split or only outer
table removed.
⢠Along margin of defect outer table removed to create
5mm shelf.
⢠Transfer to paper, avoid bone wax.
⢠Donor---full thickness skull excised.
54. Rib and ilium
⢠Sub periosteal excision of rib
⢠Alternate ribs (never take >2 adjacent ribs)
⢠Total length = A/W à 2
A - area of defect
W - width of rib
⢠Cut 4 mm longer than defect
57. Dead space morbidity
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Following planned plasty
Childrenâobliterate spontaneously
Adults - uncertain
Microvascular free flap under plasty
Mass effect, prolonged surgery
Does not alter either external contour or protective
function
⢠Causes late infection