Stereolithography A Method for Planning the Surgica hiprteloimo hidalgo2009

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Copyright @ 2009 Mutaz B. Habal, MD. Unauthorized reproduction of this article is prohibited.
Stereolithography: A Method for Planning the Surgical
Correction of the Hypertelorism
Hector Malagon Hidalgo, MD, Gabriela Wong Romo, DDS, and Roberto Takeo Rivera Estolano, DDS
Abstract: Hypertelorism is a deformity characterized by an increase
in interorbital distance. The treatment can be orbital mobilization, or if
the malformation goes along with occlusal alterations, the indicated
treatment is a facial bipartition with hemifacial rotation.
The intention of the present study was to describe a surgical
planning technique in locating the anatomic points and planes on a
stereolithographic model of a patient with 0Y14 fissure and its surgical
application.
Key Words: Stereolithography, surgical correction, hypertelorism,
facial bipartition
(J Craniofac Surg 2009;20: 1473Y1477)
Hypertelorism is a deformity based on the increase of the in-terorbital distance, and it appears like a manifestation of diverse
pathologic conditions. The word hypertelorism is derived from the
Greek hyper, which means much; tele, distance; and horizo, very
separated, which talks about the distance of any bilateral structure.
Orbital hypertelorism probably originates before the 28-mm
embryonic stage, when a deficient remodeling of the nasal capsule
stops the future frontonasoethmoidal complex, limiting the medial
displacement of the eyes. Another possible cause is a deficiency in
the lateromedial movements of the orbits by a premature closing of
the sphenofrontal suture.1,2
Based on anatomic and morphogenetic classifications, there
are 5 diagnostic categories of hypertelorism: frontonasal malfor-
mation, craniofrontonasal dysplasia, craniofacial fissures, encepha-
locele, and a miscellaneous group that includes syndromic or
chromosomal disorders.3
The morphologic characteristics that habitually go along with
hypertelorism include a short, wide nose that can be divided medial
or paramedially, a vertical dimension of the face that can be dimin-
ished, an increase in the horizontal dimension of the ethmoid, an
anterior open bite, and an exaggerated interorbital distance. Hyper-
telorism is considered when the distance between the lacrimal crest
is greater than 28 mm in a woman and 32 mm in a man, in such a
way that they are possible to be classified in 3 degrees4: first degree,
30 to 34 mm; second degree, 34 to 40 mm; and third degree, greater
than 40 mm.
The surgical treatment for the correction of hypertelorism
is based on its origin; generally, if the deformity includes only the
increase of the interorbital distance, this can be corrected with the
orbital medialization, and if the malformation goes along with
occlusal alterations, the indicated treatment is the facial bipartition
with rotation of hemifaces. Generally, the intracranial route is cho-
sen, but a subcranial approach also can be performed when the
deformity is less severe or when other contraindications for intra-
cranial operation exist.
Stereolithography is a technique of manufacturing with com-
puterized support that is used to make a high-precision model.
Originally developed in the aerospace industry, this technology uses
the detailed surface description to create a plastic model in layers.
An ultraviolet laser controlled by computer catalyzes the polymer-
ization of the curable plastic in a tomographic way to create a solid
model, layer by layer. Combining the scanned information of the
tomography with this manufacturing technology is possible to cre-
ate exact anatomic models of not only the external surface but also
the complete representation of the internal structures.6
A presurgical planning technique of high prediction for the
correction of hypertelorism in patients with occlusal alterations was
described in 1989 by Ortiz-Monasterio et al,5 based on the location
of anatomic points and planes on a posteroanterior x-ray to obtain
the measures and location of the osteotomies to realize.
The intention of the present study was to describe the surgical
planning of locating the anatomic points and planes previously de-
scribed, on a stereolithographic model of a patient with 0Y14 fissure.
SURGICAL PLANNING
The anatomic points are located: dacryon, the highest point of
the anterior lacrimal crest; T point (temporal), in the temporal crest
of both sides, approximately 15 mm superior to the supraorbital rim;
I point (interincisor), between the 2 upper incisors; LM point (lateral
maxilla), on the lateral union of the last molar with the alveolar
ridge; and S point (sagittal), on the center of the frontal bone be-
tween both T points (Fig. 1).
Horizontal lines are drawn: intercristal, between the lacrimal
crests (D-D), and temporal, between the temporal crests (T-T). The
temporal line predicts the inferior osteotomy of the frontal bar that
is created when the frontal cover is removed for the intracranial
approach and another line from the LM to the I points bilaterally that
represents the occlusal plane. A vertical line goes from the S to the
I points (middle line).
The surgical planning resembles the measuring of the desired
distance between the lacrimal crest and the middle line on the inter-
cristal line, and a line is drawn from the I point to the point of ideal
intercristal distance and continued to exceed the temporal line. This
line would represent the middle line when both hemifaces rotate
medially.
Finally, a parallel line to the occlusal plane is drawn. This will
link the T point with the line that passes through the ideal intercris-
tal distance; the distance between this line and the temporal line
CLINICAL NOTE
The Journal of Craniofacial Surgery & Volume 20, Number 5, September 2009 1473
From the Plastic and Reconstructive Surgery Department of Centro Me´dico,
ISSEMYM, Metepec, Mexico.
Received February 24, 2009.
Accepted for publication March 22, 2009.
Address correspondence and reprint requests to Hector Malagon Hidalgo,
MD, Plastic and Reconstructive Surgery Department Centro Me´dico,
ISSEMYM, Metepec, Mexico; E-mail: hectormalagon@hotmail.com
Copyright * 2009 by Mutaz B. Habal, MD
ISSN: 1049-2275
DOI: 10.1097/SCS.0b013e3181b09a70
Copyright @ 2009 Mutaz B. Habal, MD. Unauthorized reproduction of this article is prohibited.
represents the distance in millimeters that the maxilla’s vertical
dimension will increase and the bony gap that will be needed to be
grafted subsequent to the bipartition (Fig. 2).
Once the planning is realized, the osteotomies are performed to
remove the triangle of the central resection to determine the location
and size of bony grafts and osteosynthesis material (Figs. 3 and 4).
RESULTS
The surgical technique is based on the hypertelorism correc-
tion described by Ortiz-Monasterio and Molina.6
A coronal approach is performed to design the osteotomies
previously established in stereolithography (Fig. 5). It is necessary
to remove the frontal cover to realize the intracranial approach of
the orbit ceilings.
A central triangle is removed; this includes the frontal, eth-
moidal, nasal, maxillary bones, and septum; the size is established
by the millimeters necessary for the resection to manage the suitable
interorbital distance after realizing hemifacial medialization (Fig. 6).
The positioning of the bony grafts is necessary to cover the
setout areas that were planned with the stereolithography (Fig. 7).
At the same surgical event, a costal graft for nasal reconstruction
is placed.
The results reached with the surgical technique, besides the
reduction of the hypertelorism, include lateral cantus directional
vector correction, facial half third enlargement, depth palate reduc-
tion, and maxillary occlusal plane levelling (Fig. 7).
Stereolithography becomes a precise and functional method
for the planning of the hypertelorism correction, offeringthe oppor-
tunity to predict the findings that could be found during the surgical
FIGURE 1. A, Frontal view of stereolithographic model with
dacryon (D) and interincisal point (I) markings. B, Lateral
view with dacryon (D), temporal (T), and lateral maxillary
(LM) markings.
FIGURE 2. A, Frontal view of surgical planning. The central
black lines after the mobilization will be in the middle line.
B, Three-fourths view. LM-I line runs parallel until it joins the
T-T line with the future middle line. The lateral osteotomy
will be made at level of the zygomatic arc.
Hidalgo et al The Journal of Craniofacial Surgery & Volume 20, Number 5, September 2009
1474 * 2009 Mutaz B. Habal, MD
Copyright @ 2009 Mutaz B. Habal, MD. Unauthorized reproduction of this article is prohibited.
procedure and establish the size of the bony defect, thus planning
the location of the grafts and the osteosynthesis material (Fig. 8).
DISCUSSION
The stereolithographic model provides the possibility to
observe a disorder from an infinite way of angles. The space realism
and the tactile capacities of these models offer a type of virtual
reality for the surgeon to have a multisensorial approach (visual and
tactile) about the surgery without touching or knowing the patient.7
Stereolithography is a widely known technique in the creation
of prototypes; like the preoperative model to simulate a surgical
procedure, this technique has been used in the craniofacial surgery
field on different pathologic conditions.
In surgical pathology, stereolithography, combined with
selective staining of some structures, provides a very precise
direction because the stain delimits the injury and its relation with
adjacent structures such as the paranasal sinus, orbit, or infra-
temporal grave.
It is useful in facial trauma surgery to facilitate anatomic
reduction, minimize surgical approaches, and save operation time.
Thanks to surgical simulation, now, it is possible to preform the
miniplates or microplates. During reconstruction procedures, it is
used to determine the osteotomies, grafts, or implant’s dimension;
location and form; and the preform fixation plates.8
The goals of the encephaloceles correction include urgent
closing to prevent infection and loss of a viable cerebral tissue,
removal of nonfunctional extracranial cerebral tissue with a dura
mater hermetic seal, and total craniofacial reconstruction. In 1999,
Holmes9 describes a technique to realize definitive surgical correc-
tion of the craniofacial malformation, based on the separation of the
supraorbital rimYmedial wall complex including a part of the ante-
rior cranial grave located next to the encephalocele egress foramen,
with presurgical support on stereolithographic models.
The use of computed tomography and three-dimensional re-
constructions on the preoperative evaluation and the optimization of
the surgical technique for the hypertelorism correction have been
described. The Analyze/AVW version 3.1 (Biomedical Imaging
Resource Company, Mayo Foundation of Rochester, MN) allowed
for the simulation of the surgical planning of the osteotomies and
changed the original image according to normal measures corre-
sponding to age of each patient, surgeon’s opinion, and visualization
result after the simulation. When the results of the computerized
simulation were compared with the postsurgery reconstructions,
they found a great similarity between both images.10
Different degrees of hypertelorism recurrence have been
reported. For that reason, it is necessary to overcorrect when a
surgical treatment is planned. In addition, it is known that only the
60% of the bony correction can be appreciated when the soft tissues
return to their original position.11,12
The ideal age to perform a face bipartition is still on debate. It
is important to evaluate the development of the frontal sinus that
FIGURE 4. Stereolithographic simulation once the
mobilization of the orbits is performed; this shows how the
occlusal plane is aligned.
FIGURE 3. A, Frontal view of the surgical planning. The
numbers indicate the distance in millimeters of the medial
bone that will be removed at intertemporal and interdacryon
level. B, The planning of the osteotomy is viewed, the frontal
cover is removed to approach the orbital ceilings, and the
bony fragment of the medial portion is removed and will be
used at the sites that require the graft.
The Journal of Craniofacial Surgery & Volume 20, Number 5, September 2009 Surgical Correction of Hypertelorism
* 2009 Mutaz B. Habal, MD 1475
Copyright @ 2009 Mutaz B. Habal, MD. Unauthorized reproduction of this article is prohibited.
FIGURE 5. Osteotomies’ design,
regarding the measurements
previously established in the
three-dimensional model.
FIGURE 6. A, Operative photograph
during resection of interorbital
medial triangle. B, Resection of
interorbital triangle makes possible
to mobilize hemifaces, leaving a
lateral area that requires grafts.
The measurement of this area is
proportional to the descended
occlusal plane.
FIGURE 7. Operative view after
placement and fixation of bone
grafts with resorbable material and
repositioning of frontal cover.
FIGURE 8. A, Preoperative frontal
view. B, Postsurgical frontal view.
Hidalgo et al The Journal of Craniofacial Surgery & Volume 20, Number 5, September 2009
1476 * 2009 Mutaz B. Habal, MD
Copyright @ 2009 Mutaz B. Habal, MD. Unauthorized reproduction of this article is prohibited.
begins to occupy a space at 7 years of age; therefore, any bipartition
realized after this age would need the obliteration of the nasofrontal
duct and the removal of the frontal sinus posterior wall.9
CONCLUSIONS
The use of a stereolithographic model for the surgical planning
of severe craniofacial deformities as is the case of hypertelorism turns
out to bevery useful and reduces surgical time on a significant way. It is
possible to establish the measurement and location of the osteotomies
avoiding unexpected findings, the use of autologous bone grafts, and
the previous quantification of the osteosynthesis material required for
the fixation of the mobilized bony segments.
This article settles the location of the points to realize the
planning of the orbit’s medialization based on the described technique
of a posteroanterior x-ray but with its own variations to realize it on a
three-dimensional model, in this way obtaining the exact identification
of the eventualities that can appear during the surgery and the previous
resolution of them.
Stereolithography allows one to show to the patient’s relatives
the malformation’s dimension and the desired postsurgical results.
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* 2009 Mutaz B. Habal, MD 1477