CRANIOMAXILLOFACIAL DEFORMITIES/SLEEP DISORDERS/COSMETIC SURGERY

Crouzon Syndrome: A Case Series of

Craniomaxillofacial Distraction
Osteogenesis for Functional
Rehabilitation
Firdaus Hariri, MBBS, BDS, MDS(OMFS),* Zainal Ariff Abdul Rahman, BDS, MSc,y
Nor Faizal Ahmad Bahuri, MBBS, MSurg, DPhil,z Mohd Nazri Azmi, BDS,
MClinDent(OMFS),x Norli Anida Abdullah, BSc, MSc, PhD,k
and Dharmendra Ganesan, MBBS, MSurg{

Crouzon syndrome (CS) is the most common craniosynostosis syndrome and requires a comprehen-
sive management strategy for the optimization of care and functional rehabilitation. This report pre-
sents a case series of 6 pediatric patients diagnosed with CS who were treated with distraction
osteogenesis (DO) to treat serious functional issues involving severe orbital proptosis, an obstructed
nasopharyngeal airway, and increased intracranial pressure (ICP). Three boy and 3 girls were 8 months
to 6 years old at the time of the operation. The mean skeletal advancement was 16.1 mm (range, 10
to 27 mm) with a mean follow-up of 31.7 months (range, 13 to 48 months). Reasonable and success-
ful outcomes were achieved in most patients as evidenced by adequate eye protection, absence of
signs and symptoms of increased ICP, and tracheostomy tube decannulation except in 1 patient. Com-
plications were difficult fixation of external stabilizing pins in the distraction device (n = 1) and
related to surgery (n = 4). Although DO can be considered very technical and can have potentially
serious complications, the technique produces favorable functional and clinical outcomes in treating
severe CS.
Ó 2017 American Association of Oral and Maxillofacial Surgeons
J Oral Maxillofac Surg -:1.e1-1.e12, 2017

More than 100 craniosynostosis syndromes have been nostoses related to multiple fibroblast growth factor
described, with an estimated birth prevalence of 1 in receptor 2 (FGFR2) mutations and was first reported
2,000 to 2,500.1 Syndromic craniosynostoses are esti- by Louis Edouard Octave Crouzon in 1912 who
mated to constitute 15% of all craniosynostoses and described craniofacial dysostosis with the triad of
more than 180 craniosynostosis syndromes have calvarial deformities, facial anomalies, and exoph-
been identified to date, of which approximately 8% thalmos in a woman and her son.2,3
of cases are inherited or familial.2 Crouzon syndrome Over the years, conventional craniofacial surgical
(CS) is one of the most common syndromic craniosy- techniques, such as strip craniectomy, fronto-orbital

Received from the University of Malaya, Kuala Lumpur, Malaysia. Conflict of Interest Disclosures: None of the authors have a rele-
*Associate Professor and Consultant, Oro-Craniomaxillofacial vant financial relationship(s) with a commercial interest.
Research and Surgical Group, Faculty of Dentistry. Address correspondence and reprint requests to Dr Hariri: Oro-
yProfessor and Senior Consultant, Oro-Craniomaxillofacial Craniomaxillofacial Research and Surgical Group, Faculty of
Research and Surgical Group, Faculty of Dentistry. Dentistry, University of Malaya, 50603 Kuala Lumpur, Malaysia;
zConsultant Neurosurgeon, Division of Neurosurgery, e-mail: firdaushariri@um.edu.my
Department of Surgery, Faculty of Medicine. Received August 1 2017
xClinical Specialist, Oro-Craniomaxillofacial Research and Accepted November 17 2017
Surgical Group, Faculty of Dentistry. Ó 2017 American Association of Oral and Maxillofacial Surgeons
kSenior Lecturer, Mathematics Division, Centre for Foundation 0278-2391/17/31449-0
Studies in Science. https://doi.org/10.1016/j.joms.2017.11.029
{Professor and Senior Consultant, Division of Neurosurgery,
Department of Surgery, Faculty of Medicine.

1.e1
1.e2 DISTRACTION OSTEOGENESIS IN CROUZON SYNDROME

advancement, and Le Fort III procedures, have and comprehensive assessment from neurosurgeons,
proved reliable to treat symptomatic syndromic cra- maxillofacial surgeons, pediatric ophthalmologists,
niosynostosis. However, in severe conditions, large pediatric otolaryngologists, pediatric respiratory
segmental advancement requires the gap to be grafted, therapists, anesthetists, and clinical genetics. As part
stabilized, and closed primarily because inadequate of the presurgical workup, the baseplates for the mid-
stability secondary to soft tissue restriction and unsta- face internal devices were pre-bent and fixed on a 3D
ble bone segment fixation can cause graft resorption, skull bio-model for each patient to allow surgical
thus causing relapse and creating less than an ideal simulation and vector determination and minimize
long-term outcome. operating time.
The introduction of distraction osteogenesis (DO) Based on specific functional indications, 5 patients
to craniofacial surgery has provided a reliable surgical underwent monobloc DO to achieve intracranial
alternative in achieving superior segmental advance- decompression, orbital protection, and nasopharyn-
ment compared with conventional techniques in treat- geal airway relief and 1 patient underwent posterior
ing functional issues in syndromic craniosynostosis. cranial vault DO to address the isolated increase in ICP.
Apart from obviating an additional bone grafting To treat the 3 functional issues optimally, 4 patients
procedure, the natural process of bone regeneration (patients 1 to 4) with severe structural deficiency
through gradual traction simultaneously produces received a combination of bilateral internal midface
new histogenesis, which overcomes the soft tissue devices and a rigid external device (Synthes, Oberdorf,
limitation. Switzerland) and 1 patient (patient 5) with moderate
In cases of severe CS, patients can present with functional discrepancies received only bilateral inter-
major functional disturbances, namely increased intra- nal midface distractors (Synthes). Because patient 6
cranial pressure (ICP), severe exorbitism with the presented only with signs of a potential progressive
inability to achieve eyelid closure for orbital protec- increase in ICP, posterior cranial vault expansion was
tion, and serious upper airway obstruction with indicated using internal distractors (Synthes).
progressive obstructive sleep apnea (OSA) secondary All procedures were performed through the coronal
to a severely hypoplastic maxilla, which eventually approach. Before the osteotomy, the internal devices
might require a tracheostomy to bypass the obstructed were placed to mark the planned placement site. In
airway. As such, the indication for each major surgery patients who underwent monobloc DO, the osteot-
in pediatric patients with this condition should be omy was performed at the fronto-orbital region before
agreed to by the craniofacial team members because completion of the Le Fort III osteotomy and completed
the procedure carries substantial mortality and through the maxillary tuberosity cut intraorally. Once
morbidity risks.4 the midface was separated, the internal devices were
This report presents a case series of pediatric fixed and trial activation was performed to ensure
patients with CS who underwent craniomaxillofacial correct vector trajectory. For patients receiving an
DO to manage functional deficiencies, with the focus external device, bilateral protective titanium temporal
on surgical indications, choice of device, and the plates were fabricated and placed subperiosteally to
distraction protocol and its associated complications. prevent temporal bone perforation before the external
frame was placed at the end of surgery. Patient 6, who
underwent posterior cranial vault expansion, had a
Report of Cases
similar presurgical workup of the distractor applica-
This study was approved by the medical ethics com- tion on his skull bio-model for surgical simulation
mittee of the Faculty of Dentistry of the University of and vector determination.
Malaya (Kuala Lumpur, Malaysia; institutional review All patients were admitted to the pediatric intensive
board reference number DF OS1516/0053[P]) and all care unit for 3 to 5 days for close monitoring before
participants signed an informed consent agreement. being transferred to the pediatric ward. The mean
This report describes 6 pediatric patients with CS latency period was 2.5 days (range, 1 to 3 days). The
(3 boys and 3 girls; age range, 8 months to 6 years). activation rate was 1 mm per day and the mean skeletal
Five patients (patients 1 to 5) presented with advancement was 16.1 mm (distraction range, 10 to
increased ICP, severe exorbitism with an inability to 27 mm), with a mean consolidation period of 24 weeks
achieve eyelid closure, and OSA secondary to a narrow (12 to 48 weeks). Mean follow-up was 31.7 months
nasopharyngeal space, and 1 patient (patient 6) pre- (range, 13 to 48 months). Reasonable and successful
sented with increased ICP only. All patients underwent functional rehabilitation outcomes were documented
a standard craniofacial protocol as routinely practiced in most patients as evidenced by the absence of
in the authors’ multidisciplinary craniofacial clinic, signs and symptoms of increased ICP, ability for eyelid
which involved computed tomographic (CT) analysis, closure to achieve adequate eye protection, tracheos-
fabrication of a 3-dimensional (3D) skull bio-model, tomy tube decannulation, resolved OSA, and an
HARIRI ET AL 1.e3

acceptable facial appearance (Figs 1-6), except in the test was that there would be no difference in the
patient 3 who had restricted maxillary movement. median of the pre- and postsurgical phases, which
The objective outcomes of 5 patients (patients 1 to can be expressed as H0:v(j)pre = v(j)post. The results
5) who underwent monobloc DO were measured presented in Table 1 show non-rejection of the H0
using various parameters from the pre- and postopera- and indicate successful functional rehabilita-
tive CT scans compared with the respective distrac- tion outcomes.
tion amount of each case to support favorable Complications were difficult fixation of external sta-
functional and clinical outcomes. For patient 6, who bilizing pins in the distraction device (n = 1) and
underwent posterior vault DO, a marked increase of related to surgery (n = 4), namely lateral rectus muscle
the intracranial perimeter was found when the pre- impingement and cerebrospinal fluid (CSF) leak in
and postoperative values were compared (Fig 7). For patient 2, restricted maxillary movement in patient
the assessment of patients 1 to 5, the distance from 3, and localized wound infection in patient 6. The
the sella turcica to the nasion, the distance from the management of these complications is comprehen-
sella turcica to the deepest concavity of the maxilla, sively described in the Discussion section. All data
and the point between the borders of the orbital floor for the DO protocol, complications, and management
and the lateral orbital border were measured at the are presented in Table 2.
presurgical and post-distraction phases (Fig 8). They
were labeled v(j) = (vj1, vj2, . vjN), where j = 1, 2, 3
indicates the variables described earlier and N = 5 is
Discussion
the total number of patients considered. The variable
for the pre- and postsurgical phase were denoted as CS is usually diagnosed at birth or during infancy
v(j)pre and v(j)post, respectively, and the statistical com- based on a thorough clinical evaluation, the identifica-
parison of these variables was performed using the tion of characteristic physical findings, and results
Wilcoxon signed rank test (IBM SPSS Statistics 24; from different specialized tests. Nevertheless, an expe-
IBM Corp, Armonk, NY). The null hypothesis (H0) of rienced ultrasonographer or obstetrician also can

FIGURE 1. A, Preoperative and B, latest postoperative photos of patient 1 (Crouzon syndrome).

Hariri et al. Distraction Osteogenesis in Crouzon Syndrome. J Oral Maxillofac Surg 2017.
1.e4 DISTRACTION OSTEOGENESIS IN CROUZON SYNDROME

FIGURE 2. A, Preoperative and B, latest postoperative photos of patient 2 (Crouzon syndrome).

Hariri et al. Distraction Osteogenesis in Crouzon Syndrome. J Oral Maxillofac Surg 2017.

FIGURE 3. A, Preoperative and B, latest postoperative photos of patient 3 (Crouzon syndrome).

Hariri et al. Distraction Osteogenesis in Crouzon Syndrome. J Oral Maxillofac Surg 2017.
HARIRI ET AL 1.e5

FIGURE 4. A, Preoperative and B, latest postoperative photos of patient 4 (Crouzon syndrome).

Hariri et al. Distraction Osteogenesis in Crouzon Syndrome. J Oral Maxillofac Surg 2017.

FIGURE 5. A, Preoperative and B, latest postoperative photos of patient 5 (Crouzon syndrome).

Hariri et al. Distraction Osteogenesis in Crouzon Syndrome. J Oral Maxillofac Surg 2017.
1.e6 DISTRACTION OSTEOGENESIS IN CROUZON SYNDROME

FIGURE 6. A, Preoperative and B, latest postoperative photos of patient 6 (Crouzon syndrome).

Hariri et al. Distraction Osteogenesis in Crouzon Syndrome. J Oral Maxillofac Surg 2017.

detect the early evidence of cranial suture fusion dur- ophthalmologic assessment and funduscopy are para-
ing ultrasound or detailed 3D scanning procedures. mount to detect any potential pathologic process of
The molecular genetic protocol for the diagnosis of orbital proptosis, and a tonometer can be used to
CS includes first-line tests of FGFR2 exons IgIIIa and check intraocular pressure. Respiratory issues require
IgIIIc followed by second-line tests of FGFR2 exons nasoendoscopy for the assessment of the nasopharyn-
3, 5, 11, and 14 to 17 and FGFR3 Pro250Arg and geal airway and, if indicated, polysomnography for the
Ala391Glu as proposed by Wilkie et al.5 Clinically, cra- diagnosis of OSA.
nial malformation with shallow orbits and ocular prop- Increased ICP with hydrocephalus would necessi-
tosis are diagnostic features of CS. tate ventriculoperitoneal shunting, severe orbital
Plain radiographs and CT scans also can assist in the proptosis might indicate temporary tarsorrhaphy,
diagnosis and assessment of CS.6 A copper beaten and respiratory difficulty would necessitate a contin-
appearance, enlarged hypophyseal cavity, maxillary uous airway pressure device, a nasal stent, or a trache-
hypoplasia, and mandibular prognathism can be visu- ostomy depending on the severity and the specific
alized on a lateral skull plain radiograph. Brain CT anatomic obstruction.
scan can provide a detailed image of diffuse indenta- Extent of surgical treatment of the deformities of CS
tion of the inner table of the skull and the degree of hy- depends on how functionally and severely the patients
drocephalus. CT scan also can be used for the are affected according to their age. Surgical interven-
fabrication of a 3D bio-model for the actual structural tion can be performed as staged or combined to
evaluation and surgical simulation. address these functional issues. For example,
Intracranial evaluation can be performed using plain increased ICP alone can be treated by posterior cranial
radiography, CT scanning, or magnetic resonance im- vault expansion,7,8 increased ICP with orbital
aging. Cranial bone thinning or a copper beaten proptosis might require fronto-orbital advancement
appearance strongly suggests increased ICP. Clinical with or without cranioplasty,9 and increased ICP in
HARIRI ET AL 1.e7

FIGURE 7. Comparison of the cranial perimeter of patient 6 who underwent posterior vault distraction osteogenesis. A, Preoperative.
B, Postoperative.
Hariri et al. Distraction Osteogenesis in Crouzon Syndrome. J Oral Maxillofac Surg 2017.

the presence of orbital proptosis and hypoplastic new histogenesis compared with conventional
maxilla might require a monobloc as practiced in the surgical procedures.14 All patients in the present study
authors’ center. Surgery can be performed convention- had their 3D skull bio-model fabricated to allow surgi-
ally or combined with a DO technique, which is indi- cal simulation and vector determination to optimize
cated for superior structural expansion. Patients with the outcome of surgery. The pre-bending of the dis-
asymptomatic CS can undergo orthodontic treatment tractor footplates for the internal device and presurgi-
with or without orthognathic surgery to correct dental cal simulation proved critical because it contributed to
and jaw discrepancies at growth maturation. the precision of device fixation and correct segmental
The application of DO in treating craniofacial defor- movement to ensure a favorable final outcome and
mity was first reported in 1992.10 Since then, the ben- decrease operating time.
efits of this technique in treating syndromic The selection of devices in the present patients was
craniosynostosis as reported in the literature are based on device suitability and functional indications.
similar to those in the present study, which include Increased ICP was assessed by history, presence of
marked improvements in functional parameters signs or symptoms, imaging analysis, and ophthalmo-
involving eye protection, preventing the increase of logic assessment. For the eye, the patients’ ability to
ICP, and treating airway deficiency.11-14 The achieve eyelid closure was assessed and documented
technique has major advantages, which include and supplemented with eye examinations that
producing superior advancement, obviating included optic disc condition and cup-to-disc ratio
additional bone grafting, and achieving simultaneous through funduscopy. Airway function was assessed
1.e8 DISTRACTION OSTEOGENESIS IN CROUZON SYNDROME

FIGURE 8. Variables measured from computed tomograms of each patient. A, Anatomic points of the computed tomographic midsagittal view.
B, Anatomic points at the most lateral point of the orbit from the computed tomographic sagittal slice.
Hariri et al. Distraction Osteogenesis in Crouzon Syndrome. J Oral Maxillofac Surg 2017.

by history from the guardians, symptoms of OSA, but might not be suitable for a very young infant and
airway endoscopic evaluation, overnight pulse oxime- carries the risk of stabilizing pin perforation of a very
try, and, when indicated, polysomnography. thin temporal bone surface.15 The internal device is
The combination of internal and external devices compact and more suitable for small patients but pro-
provides stable advancement at the central and lateral vides only a single vector, thus requiring bilateral fixa-
midface components and the internal device can act as tion, and has been reported to have the disadvantage
a temporary rigid fixation during the consolidation of central component relapse because it provides
period after the external frame is removed at the end only lateral retention.15
of the activation phase. Nevertheless, it is vital to The amounts of advancement achieved in the pre-
comprehensively assess each case before the selection sent patients (range, 10 to 28 mm) can be considered
of a device because different distractors can differ in substantially superior to the conventional surgical
suitability, vector control, and limitations. The technique and comparable to those of another larger
external device focuses more on the central compo- craniofacial DO study.14 The distracted bone space
nent and can be considered to have multiple vectors was noted to be filled with new bone (Fig 9). All

Table 1. PRE- AND POSTSURGICAL VARIABLES MEASURED FROM COMPUTED TOMOGRAM

Variable Patient 1 Patient 2 Patient 3 Patient 4 Patient 5 P Value*

j = 1 (S-N) v(1)pre 46.50 53.87 42.50 40.50 58.00 .043

v(1)post 64.50 65.00 44.50 48.00 59.00
j = 2 (S-A) v(2)pre 57.00 58.25 50.00 46.00 56.00 .043
v(2)post 76.50 69.50 53.50 58.00 56.5
j = 3 (Co-O) v(3)pre 31.00 32.50 33.00 30.00 41.50 .043
v(3)post 46.50 42.50 42.50 35.00 44.00
Abbreviations: Co-O, point between the borders of the orbital floor and lateral orbital border; S-A, distance from sella turcica to
deepest concavity of the maxilla; S-N, distance from sella turcica to nasion; post, postsurgical; pre, presurgical.
* By Wilcoxon signed rank test (2-tailed).
Hariri et al. Distraction Osteogenesis in Crouzon Syndrome. J Oral Maxillofac Surg 2017.
HARIRI ET AL 1.e9

patients achieved a stable clinical outcome (Figs 1-6),

Customized headgear for fixation

pterygomaxillary disjunction
Management of Complication
with resolved functional discrepancies indicated by

and antibiotic prescription

of external stabilizing pins

osteotomy, conservative
the absence of signs and symptoms of increased ICP,

Secondary osteotomy for

antibiotic prescription
Lateral orbital wall box
the ability to achieve eyelid closure with stable

Wound dressing and

funduscopic findings, and the absence of OSA
symptoms after tracheostomy decannulation,
indicating adequate nasopharyngeal airway opening,
except in 1 patient because of restricted maxillary
movement. Findings from the statistical analysis of
the pre- and postsurgical data support the clinical
outcome in which the desirable segmental
advancement is evident (Table 2). Note that the results
Loose stabilizing
impingement,
Complications

of the study at this stage are confined to a relatively

Lateral rectus

movement

Local wound
of maxilla

infection
CSF leak

small sample. Nevertheless, the statistical inference

Restricted

can be considered reliable because of the rare cases

pins

of severe CS that require the complex surgical proced-

ure at the authors’ craniofacial center. The authors’
management strategy for functional rehabilitation of
Follow-Up

patients with CS is presented in Figure 10.

(mo)

48
48

33

29

19
13

Serious complications arising from craniofacial sur-

gery include mortality, severe blood loss, dural tear,
CSF leak, acquired hypernasality, infection, and frontal
Consolidation

bone necrosis.4,14,16,17 One patient developed

(wk)

postoperative CSF rhinorrhea for 2 weeks and was

21
16

48

16

31
12

conservatively treated with a decreased activation

Abbreviations: CSF, cerebrospinal fluid; DO, distraction osteogenesis; Ext, external; Int, internal.

rate, antibiotics, and neurologic monitoring. The

same patient also developed an unusual exodeviation
Advancement

of the right eye with associated abduction during the

(mm)

activation phase secondary to direct impingement of

23
27

10

11

15
11

the lateral orbital wall on the lateral rectus muscle.

Hariri et al. Distraction Osteogenesis in Crouzon Syndrome. J Oral Maxillofac Surg 2017.

The bony impingement was successfully relieved by

a lateral bony osteotomy, resulting in resolution of
Activation
(mm/day)

the residual proptosis and free lateral ocular

movement.18 The authors also fabricated a customized
1
1

1
1

headgear in a very young patient (patient 4) to allow

Table 2. SUMMARY OF DO PROTOCOL AND COMPLICATIONS

stable positioning of the temporal stabilizing pins of

Latency

the external device and prevent potential temporal

(days)

bone perforations.19
2
3

3
3

Postoperative long-term stability remains a major

concern in the management of syndromic craniosy-
Ext + Int
Ext + Int

Ext + Int

Ext + Int
Device

nostosis because minimizing the number of sur-

geries will benefit patients’ growth and
Int
Int

development. Three of 4 patients in the present

Posterior cranial

study after more than 2 years of postoperative

Monobloc DO
Monobloc DO

Monobloc DO

Monobloc DO

Monobloc DO
Procedure

follow-up have remained healthy and asymptomatic

vault DO

and do not require any additional procedure after

the monobloc DO procedure. There were no long-
term side effects reported during the follow-up
period. The parents of 5 patients (patients 1, 2, 4,
Operation

5, and 6) expressed satisfaction with the functional

Age at

(yr)

outcomes. The parent of patient 3 was not satisfied

8 mo

because his daughter remained on the tracheostomy

4
3

6
2

owing to an unsatisfactory nasopharyngeal opening

and is currently undergoing further surgical plan-
Patient

ning at a later stage. Although residual functional

1
2

5
6

issues should be anticipated, especially in those

1.e10 DISTRACTION OSTEOGENESIS IN CROUZON SYNDROME

FIGURE 9. Posterior cranial vault distraction osteogenesis in patient 6. A, Distractor before activation. B, Trial activation of bilateral distractors
showing an increased gap with favorable segmental movement. C, Gap filled with new bone after 3-month consolidation phase.
Hariri et al. Distraction Osteogenesis in Crouzon Syndrome. J Oral Maxillofac Surg 2017.

who undergo surgery at a young age, a long-term In conclusion, the introduction of the DO technique
study by Gwanmesia et al20 showed that the distrac- provides a reliable surgical alternative and a predict-
tion procedure produced long-term stable advance- able outcome in the functional rehabilitation of severe
ment and functional gains. CS. However, its application requires comprehensive
HARIRI ET AL 1.e11

DIAGNOSIS
Antenatal At birth
Ultrasound suspicion Clinical features
3D detailed scan Genec study

ASSESSMENT

Intracranial Pressure (ICP) Eye and visual Airway

CT scan Clinical Endoscopy
MRI Eyelid closure funcon CT scan
Plain radiograph Fundoscopy Overnight pulse oximetry
ICP probe Tonometer Polysomnography
Airway analysis soware

+ Fabricaon of 3D skull biomodel

TEMPORARY INTERVENTION

Raised ICP with hydrocephalus Orbital proptosis* OSA**

VP shunt Tarsorrhaphy Nasal stent
Eyelid taping Posive airway pressure device
Tracheostomy

SURGICAL INTERVENTION

Raised ICP Orbital proptosis* OSA** Raised ICP Raised ICP Orbital Proptosis
+ + +
Orbital proptosis* Orbital proptosis* OSA**
+
OSA**

Post cranial Frontofacial Le Fort I Monobloc DO Fronto-orbital Le Fort III osteotomy

vault expansion osteotomy osteotomy advancement (+/- DO)
(+/- DO) (+/- DO) (+/- DO) (+/- DO)
Cranioplasty Box osteotomy So ssue (+/- cranioplasty)
ENT procedure

ICP = Intracranial pressure VP = Venculo-peritoneal DO = Distracon osteogenesis

OSA = Obstrucve sleep apnea +/- = with or without ENT = Ear nose throat/otorhinolaryngolog
Orbital proptosis* with inability for full eyelid closure 3D = 3-dimensional
OSA** secondary to severe maxillary hypoplasia in anterior posterior dimension

FIGURE 10. Craniofacial intervention protocol for functional rehabilitation.

Hariri et al. Distraction Osteogenesis in Crouzon Syndrome. J Oral Maxillofac Surg 2017.

presurgical planning and carries considerable 8. Salokorpi N, Vuollo V, Sinikumpu JJ, et al: Increases in cranial vol-
ume with posterior cranial vault distraction in 31 consecutive
morbidity risks.
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