Keywords
pediatric cranioplasty - autologous - donor graft origin - synthetic cranioplasty
material - survey
Introduction
A literature review was previously conducted to investigate the materials used in
pediatric cranioplasty.[1]
It was concluded that particulate bone grafts or exchange cranioplasty were commonly
used in infants.[1] In older children, custom-made implants using titanium or hydroxyapatite were more
frequently used.[1] However, the conclusion from the review was that there was not enough evidence to
recommend an ideal pediatric cranioplasty material for all age groups.[1] All the existing studies have very small sample sizes, which makes it difficult
to develop an age-based protocol for pediatric patients. Hence, we conducted a survey
to explore the current practice among the neurosurgeons in Australia and New Zealand.
The research questions in this study were aimed at examining the material of choice
for pediatric cranioplasty in four different age groups of children: 0 to 2, 3 to
5, 6 to 10, and 11+ years of age. The survey also explored the preferred donor site
for autologous cranioplasty.
Methods
The survey was conducted with the online survey tool Survey Monkey. The survey was
sent via email to 244 consultant members of the Neurosurgical Society of Australasia.
The survey explored preferences in different materials used for pediatric cranioplasty
surgeries as well as preferred donor site for autologous cranioplasty, based on patient
age and size of defect. The data were analyzed using the tool “Survey Monkey” and
the results are discussed below.
The survey consisted of the following questions:
-
How many pediatric neurosurgical operations do you perform per year?
-
When native bone cannot be replaced, what is your preferred material for cranioplasty
in small skull defects (< 3 cm)?
-
When native bone cannot be replaced, what is your preferred material for cranioplasty
in large skull defects (> 3 cm)?
-
If using autologous cranioplasty for small defects (< 3 cm), what is your preferred
donor origin?
-
If using autologous cranioplasty for large defects (> 3 cm), what is your preferred
donor origin?
Results
Responses were received from 22 neurosurgeons (9%) out of 244 contacted.
Question 1
How many pediatric neurosurgical operations do you perform every year?
The survey results showed that approximately 32% of the respondents perform more than
50 pediatric neurosurgical cases annually, as shown in [Table 1]. However, approximately 50% of the neurosurgeons perform less than 10 pediatric
neurosurgeries annually.
Table 1
Percentage of surgeons categorized by the number of surgeries performed annually
|
Number of operations
performed annually
|
Surgeons %,
(number of surgeons)
|
|
< 10
|
50% (11)
|
|
11–30
|
13.64% (3)
|
|
31–50
|
4.55% (1)
|
|
> 50
|
31.82% (7)
|
Question 2
When native bone cannot be used, what is your preferred material for cranioplasty
in SMALL skull defects < 3 cm?
A total of 20 respondents answered this question (two respondents chose not to answer).
The percentages of surgeons who opted for each type of cranioplasty (titanium, hydroxyapatite
[HA], methylmethacrylate [MMA], autologous and none), in treating a small skull defect
of < 3 cm in different pediatric age groups are given in [Table 2] and [Fig. 1].
Table 2
Percentage of surgeons who prefer each cranioplasty material in skull defects < 3
cm across different pediatric age groups
|
Age groups (years)
|
Autologous donor (%)
|
Titanium (%)
|
HA (%)a
|
MMA (%)b
|
None (%)
|
|
aHydroxyapatite.
bMethymethacrylate.
|
|
0–2
|
20
|
5
|
10
|
0
|
65
|
|
3–5
|
35
|
10
|
20
|
5
|
30
|
|
6–10
|
40
|
10
|
35
|
10
|
5
|
|
11+
|
16.67
|
27.78
|
38.89
|
16.67
|
0
|
Fig. 1 Percentage of surgeons who prefer each cranioplasty material in skull defects < 3
cm across different pediatric age groups.
The results indicate that with small skull defects (< 3 cm) in patient’s aged 0 to
2 years, conservative management with observation alone is the preferred option (65%),
as shown in [Table 2]. In patients aged 3 to 5 years and 6 to 10 years, autologous donor was the most
popular option (35% and 40%, respectively), whereas for 11+ years, HA was the material
of choice (38.89%), followed by titanium (27.78%) ([Fig. 1]).
Question 3
When native bone cannot be used, what is your preferred material for cranioplasty
in large skull defects > 3 cm?
A total of 20 respondents answered this question. The percentages of surgeons who
opted for each material (titanium, hydroxyapatite [HA], methylmethacrylate [MMA],
autologous and none) in treating large skull defects of > 3 cm in different pediatric
age groups are given in [Table 3] and [Fig. 2].
Table 3
Percentage of surgeons who prefer each cranioplasty material across different age
groups with respect to skull defects of (> 3 cm)
|
Age groups (years)
|
Autologous
donor (%)
|
Titanium (%)
|
HA (%)a
|
MMA (%)b
|
None (%)
|
|
aHydroxyapatite.
bMethymethacrylate.
|
|
0–2
|
36.84
|
10.53
|
15.79
|
0
|
36.84
|
|
3–5
|
47.37
|
21.05
|
26.32
|
0
|
5.26
|
|
6–10
|
31.58
|
26.32
|
31.58
|
10.53
|
0
|
|
11+
|
6.67
|
46.67
|
20
|
26.67
|
0
|
Fig. 2 Percentage of surgeons who prefer each cranioplasty material in skull defects > 3
cm across different pediatric age groups.
In cases with a defect more than 3 cm, autologous donor was the preferred option in
patients aged 3 to 10 years. In patients above 11 years of age, titanium was the preferred
choice in 46.67% of respondents ([Table 3]). In the age group 0 to 2 years, the majority of respondents preferred a conservative
approach (37%) or autologous cranioplasty (37%) ([Table 3]).
MMA was commonly preferred for patients above 6 years of age. About 10% of respondents
chose MMA in those between 6 to 10 year of age and approximately 27% chose MMA for
11+ years ([Fig. 2]).
Question 4
If using autologous cranioplasty for small skull defects < 3 cm, what is your preferred
donor origin?
A total of 20 respondents answered this question. The donor origin preferred by surgeons
for < 3 cm skull defects in different age groups is shown in [Fig. 3].
Fig. 3 Percentage of surgeons who opted for each donor origin across different age groups
for < 3 cm skull defects.
When using autologous cranioplasty for small skull defects (< 3 cm), the preferred
donor origin was split calvarial grafts for all age groups, except in patients aged
0 to 2 years ([Fig. 3]). In patients aged 0 to 2 years, a conservative “watch and wait” approach was preferred
by 68.42% of respondents, compared with split calvarial graft, which was preferred
by 31.58% of respondents ([Fig. 3]).
Question 5
If using autologous cranioplasty for large defects > 3 cm, what is your preferred
donor origin?
A total of 20 respondents answered this question. The donor origin preferred by surgeons
in different age groups for > 3 cm skull defects is shown in [Fig. 4].
Fig. 4 Percentage of surgeons who opted for each donor origin across different age groups
for > 3 cm skull defects.
For autologous cranioplasty in large skull defects (> 3 cm), the preferred donor origin
was split calvarial graft for ages 3 to 5 years, 6 to 10 years and 11+ years (50%,
50% and 45%, respectively). In patients aged 0 to 2 years, a conservative “watch and
wait” approach was again the preferred option (47.37% of respondents), followed by
exchange cranioplasty (31.58%) as seen in [Fig. 4].
Other materials have also been reported by the respondents for treatment of > 3 cm
defects in children of more than 2 years of age. These include custom acrylic cranioplasty
made using CT models and floating bone. Porous polyethylene was used by one neurosurgeon
in all age groups and in all size defects.
Discussion
The present study aimed to evaluate the current practice of neurosurgeons in Australia
and New Zealand with regard to pediatric cranioplasty material. The reason for conducting
this study was a lack of strong evidence as to the optimum material to use for cranioplasty
in pediatric patients. All the existing studies have very small sample sizes, making
it difficult to develop an age-based protocol for choosing optimal material.
The limitations of this study include the small cohort of respondents (22) with 9%
response rate. However, this was the expected response, given the lower number of
surgeons who specialize in pediatric neurosurgery. To ensure maximum response, multiple
reminders were sent to all the participants. Another limitation is the low number
(< 10) of pediatric cases performed by 50% of participating surgeons. Furthermore,
this study is not a review of cases performed. It is indicative of the preference
of individual surgeons, and may not be representative of what actually occurs in practice.
Individual practice could vary based on the experience of the surgeon in using a particular
material, availability and cost of the material. Other patient factors may also determine
the specific management, such as the indication for non-native cranioplasty.
The cranial vault grows rapidly in the first 2 years and is stimulated by the growth
of the brain, which reaches approximately 67% of its adult size within the first 2
years of life.[2] The calvarium then continues to grow in a linear fashion to the brain, reaching
adult size between 6 to 10 years of age.[2] This pattern of growth determined the age groups used in our survey and served as
a rationale in considering 11+ age group as similar to adults.
The majority (65%) of participating neurosurgeons preferred conservative management
for defects less than 3 cm and did not offer cranioplasty in those under 2 years of
age. Some of these respondents indicated that they monitor patients in this group
for bone growth into the defect. This may mean that no cranioplasty is required or,
if a small defect persists, autologous cranioplasty can be considered when the patient
is older. This is consistent with evidence in the literature regarding bone formation
in this age group. According to Opperman, new bone formation occurs at the sutural
edges of the bone fronts in response to signals from growing neurocranium and continually
undergo remodeling to accommodate, protect, and keep pace with the growing brain.[2]
[3] Hence, conservative treatment is a safe and well-recognized management option for
this young age group. Smaller skull defects have a greater chance of closing without
any intervention.
Split calvarial grafts or exchange cranioplasty were the most preferred techniques
for defects greater than 3 cm in all age groups up to 10 years. There are various
studies supporting the use of split calvarial graft, particulate graft and exchange
cranioplasty.[1] They show good success rates and minimal complications for patients up to 22 years
of age. In large skull defects of more than 3 cm in the 11+ age group, titanium is
the most commonly preferred material, followed by MMA and HA. The literature supports
safe use of custom-made HA and titanium in children above 7 years of age.[1] Stefani et al conducted a study of custom-made porous HA implants for cranioplasty
in 114 pediatric patients aged 7 to 14 years.[4] There was no report of early fracture or infection and only 5% late, posttraumatic
fracture was reported.[4]
One of the respondents indicated a preference for the use of floating bone cranioplasty
in > 3 cm defects in children of more than 2 years of age. The “floating” technique
is thought to facilitate controlled volume expansion while reducing stretching and
secondary damage to the edematous brain.[5] As per Gutman et al, floating anchored craniotomy could be offered instead of decompressive
craniectomy in certain cases of traumatic brain injury. However, there is only data
available of this technique performed in 57 adults with an average age of 37.2 years.[5] Further prospective trials are warranted to further assess the safety and utility
of this procedure in the pediatric population.[5]
Conclusion
The survey results indicate that current practice in Australia and New Zealand for
cranioplasty in relation to patient age and size of defect is consistent with the
currently available best evidence, which was discussed in detail in the previously
published literature review[1]
The preferred material for cranioplasty is autologous bone with split calvarial graft
or exchange cranioplasty for defects less than 3 cm in in children aged 3 to 11 years.
In children less than 2 years, a conservative approach is preferred. In children older
than 11 years, HA and titanium are the materials of choice.
In autologous cranioplasty, the preferred donor origin for patients above 3 years
of age is split calvarial graft, irrespective of the size of skull defect. For children
under 2 years of age, when opting for surgical management, split calvarial graft for
small defects and exchange cranioplasty for large skull defects were the preferred
donor origins.
A larger study comparing different cranioplasty materials in the pediatric population
with long-term follow up would be useful to ascertain safety and efficacy before developing
a universally accepted protocol.
Note
The Tasmanian Health and Medical Human Research Ethics Committee have approved this
study. The abstract was published in the AANSIM conference abstract book in December
2019.
