Download Changing Esthetic Paradigm in Hemifacial Microsomia

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Changing Esthetic Paradigm in Hemifacial
Microsomia
Amit Prakash*, Babita Raghuwanshi**, Sonali Rai***
Abstract
In hemifacial microsomia (HFM) patients the mandibular deformity is associated with
canting of the occlusal plane. It is generally believed that the mandibular hypoplasia inhibits the
normal downward growth of the maxilla. Treatment for hemifacial microsomia depends on the
child's age and how much is the severity. Mandibular distraction osteogenesis, fibula osteocutaneous
free flap for mandibular reconstruction, Composite tissue allotransplantation (CTA) is unique
methods for treatment in patients with hemifacial microsomia.
(Prakash A, Raghuwanshi B, Rai S: Changing Esthetic
www.journalofdentofacialsciences.com, 2013; 2(3): 7-11)
Paradigm
in
Hemifacial
Microsomia.
Key words: Cranio-facial, Microsomia, Distraction osteogenesis, Mandibular deformity.
Definition
Hemifacial microsomia was first described by
Arlt in 1881. Gorlin used the term hemifacial
microsomia to patient with unilateral microtia,
macrostomia and malformation of mandibular
ramus and condyle whereas; the goldenhar's
syndrome was described as a variant, with
vertebral anomalies and epibulbar dermoids. The
name, craniofacial microsomia, was proposed by
*Sr Lecturer, Department of Orthodontics and
Dentofacial Orthopedics
**Ass. Prof., Pathology, L.N. Medical College &
Research Centre, Bhopal
***Lecturer
*,***Rishiraj Dental College & Hospital, Bhopal
Address for Correspondence:
Dr Amit Prakash
e-mail: [email protected], [email protected]
Converse. Other synonyms include first arch
syndrome, first and second bronchial arch
syndrome, otomandibular dysostosis, oculoauriculovertebral dysplasia and lateral facial
dysplasia1.
All structures derived from the 1st and 2nd
Branchial arches – bones, muscles, cranial nerves,
organs and glands can be involved. The collected
group of deformities that make up this syndrome
may vary greatly in extent and degree covering a
wide
spectrum
ranging
from
mild
underdevelopment of the lower jaw to severe
deformity of the skull and face. Characteristically
this deformity, as the name implies (hemifacial),
involves one side of the face, however
involvement of both sides to some degree can be
observed in as high as 15% of all cases. The most
obvious deformity involves the lower jaw and ear,
but soft tissue deficiency, maxillary hypoplasia and
8
even orbit and skull anomalies may also be
present2-4.
Three percent of all newborns have significant
structural anomalies. Hemifacial microsomia, or
HFM, is the second most common facial anomaly,
second only to cleft lip and palate. Due to a
unilateral deficiency of the mandible and lower
face, patients who have HFM have specific dental
needs that require restorative, orthodontic and
surgical correction5. Whether the cause is genetic
or environmental, there may be a common
pathway leading to a disturbance in neural crest
cell migration in HFM patients who also have a
facial cleft. Transverse oral cleft ("macrostomia") is
known to be associated with HFM6.
Classification7
The classification system of mandibular
hypoplasia most frequently used is that of
Pruzansky:
Grade 1- mandibles are normal in configuration,
but reduced in size.
Grade 2 - mandibles demonstrate hypoplasia plus
maldevelopment of the associated condyle and
coronoid processes.
The O.M.E.N.S. classification of hemifacial
microsomia is the most accepeted classification.
Each letter of the acronym indicates one of the five
major dysmorphic manifestations of HFM.
O- Orbital asymmetry.
M- Mandibular hypoplasia.
E- Ear deformity.
N- Nerve involvement.
S- Soft tissue deficiency.
Diagnosis
While its precise etiology is not yet known, it is
likely caused by a disruption in the development of
the first two branchial arches early in embryologic
development. The resulting phenotype is one of
varying degrees of unilateral hypoplasia of the
mandible, ear deformity, and macrostomia. Early
diagnosis of hemifacial microsomia is important
not only to plan for surgical reconstruction of
affected features, but also to lead the physician in
further evaluation for associated abnormalities or
disabilities8.
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Prakash et al.
A team approach is necessary for the diagnosis
of each patient and it must establish the extent of
the anatomical deformity and the associated
degree of functional impairment. A panoramic
radiograph provides an excellent overview of the
osseous structures of the mandible and
maxillofacial complex. The occlusal radiograph is
needed to depict the osseous integrity of the
palatal vault. The relationship of the mandible and
maxilla to the cranial base can be established
initially with a lateral cephalometric radiograph. A
posterior-anterior view can be used to depict the
degree of osseous asymmetry of the face9.
Variations expressed clinically and radiographically
in hemifacial microsomia preclude classifying all
the abnormalities as coming from the first and
second branchial arches. Anatomic structures
arising from the branchial arches are directly
involved but the final expression results from the
combined impact of the primary anatomic defect
and the secondary effects on contiguous
structures10.
Dental considerations
The primary and permanent molars in
hemifacial microsomia were significantly smaller in
the mesiodistal dimensions. The most posterior
tooth in each arch being the most severely affected
and no effect on the canines and the incisors.
These findings suggest that the dental lamina in
hemifacial microsomia is affected, and support the
view that its pathogenesis involves an abnormality
of the neural crest11.
Treatment
From an orthodontic point of view,
asymmetries can be gathered in three great clinical
entities: mandibular lateral deviations, dental
asymmetries without skeletal involvement, skeletal
asymmetries. Vertical non-surgical asymmetry may
have an obvious local origin. Frequently the
occlusal slippage of a severe sagittal or a vertical
malformation, which may evolve as a borderline
surgery case, is suspected to be the real cause. The
treatment needs peculiar strong asymmetric
mechanics and, sometimes, unilateral mixed
extractions. The post-treatment occlusion can be
unstable; for this reason, the finishing steps must
be carefully conducted12.
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Prakash et al.
The effect of Herbst appliance treatment on
facial growth in terms of displacement of the
mandible was studied by Sarnäs. During treatment
facial growth was redirected and the jaws were
displaced anteriorly and to the unaffected side,
decreasing the degree of retrognathia and
asymmetry. At the same time, however, the tilt of
the mandible to the affected side was increased,
possibly because of the morphologic and
functional conditions of the jaws in hemifacial
microsomia. The dental malocclusion was
corrected partly through displacement of the jaws
and partly through dentoalveolar adaptation13.
Functional appliance therapy with hemifacial
microsomia promotes masticatory muscle function
on the affected side, thereby stimulating bone
growth in the affected condyle over and above
what would occur without any treatment
intervention. Removable functional appliance
therapy, and later, unilateral Herbst appliance
therapy, produced a dramatic change in the
condylar growth on the affected side. Herbst
therapy has the advantage over a removable
functional appliance in that patient acceptance is
much greater. Lack of patient compliance may be
the primary cause of the variable results obtained
with
functional
appliances
in
hemifacial
microsomia cases 14.
Leonardi had treated a case of mandibular
asymmetry with a modified activator appliance.
The patient was given a Haupl-Andresen activator,
which had been modified to reposition the right
mandible downward and forward. The functional
appliance therapy lasted for approximately 4
years. The affected side showed remarkable
condylar growth compared with the normal side.
Seven years later, the correction of the mandibular
asymmetry was stable and no relapse had
occurred15.
A new appliance with samarium cobalt
magnets (The propellant unilateral magnetic
appliance, PUMA) embedded in unilateral blocks
of acrylic is a way of stimulating an autogenous
costochondral graft, in hemifacial microsomia
patients16.
Distraction
osteogenesis
is
increasingly
advocated in treating patients with HM as it is
considered as a good alternative for the classical
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9
surgical interventions (like osteotomies and bone
grafts) and its presumed positive effect on the soft
tissue. From an overall dentofacial point of view,
good final results were achieved with the
combined orthodontic and maxillo-facial treatment
of this patient with HM. Craniofacial problems like
HM should be treated in craniofacial teams with
enough clinical experience in treating these
dentofacial malformations. This definitely will lead
to more predictable and better results, fewer
complications and a smaller number of surgical reinterventions17. The use of a semiburied curvilinear
distraction device, with 3D treatment planning, is a
potentially powerful tool to correct complex
mandibular deformities18.
The latency, rate and rhythm of distraction
influence the quality of the regeneration. Most
maxillofacial surgeons recommend 4-7 days
waiting following corticotomy before initiating
distraction. In younger children, the high rate of
bone metabolism favour a shorter waiting period.
Waiting too long increases the risk of premature
bone union. The rate and frequency of distraction
are also important. If widening occurs too rapidly,
a fibrous non-union results, whereas if the rate is
too slow, premature bony union prevents
lengthening. The ideal rhythm is a continuous
form of distraction. The length of consolidation
ranged from 4-6 weeks19.
Since the initial application of distraction
osteogenesis to the human mandible by McCarthy,
distraction osteogenesis has been used for gradual
lengthening of the midface in hemifacial
microsomia. Both external and internal devices are
available that permit midface distraction. The
background of midface distraction and the
development of a Modular Internal Distraction
(MID) system that permits widespread use of easily
customized, buried distraction devices throughout
the craniofacial region are available20.
The reconstruction of severe mandibular
deformities in patients with hemifacial microsomia
(HFM) is difficult. The multiple requirements
include temporomandibular joint construction,
mandibular ramus and body reconstructions with
autogenous bone grafts, and soft tissue facial
augmentation. These reconstructions include
staged procedures, generally performed at the time
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10
of skeletal maturity. Mandibular distraction
osteogenesis has gained popularity as a technique
for
managing
patients
with
mandibular
hypoplasia.However, the use of distraction
osteogenesis in HFM patients with severe grade III
mandibular deformities. Mandibular distraction
osteogenesis has unique advantages for these
patients in that it can be performed early in
childhood with minimal morbidity21.
Wolff’s law and the functional matrix theory of
Moss established the relationship between bone
morphology and the functional and soft tissue
forces. A direct relationship between the
mandibular deformity and the status of the
muscles of mastication has been reported with
HFM. The pathogenesis of HFM used as a guide
to reconstructing patients, Poswillo reported a
direct relationship between the success of a
surgical treatment and the ability to reconstruct the
components of the functional matrix. Early
reconstruction of the facial skeleton is fated to
failure because of the impossibility of
reconstructing the muscle-periosteal component of
the growth force22.
The use of the fibula osteocutaneous free flap
for mandibular reconstruction in severe hemifacial
microsomia patients have been reported in
literature. The free flap is safe and effective, and
should be considered as a first choice in
mandibular reconstruction in severe cases of
hemifacial
microsomia
where
distraction
osteogenesis is not possible23.
Composite tissue allotransplantation (CTA) in
children could offer a unique reconstructive
opportunity. Treatment of hemifacial microsomia
can yield unsatisfactory results, even after multiple
surgeries. CTA provides the advantage of intact
vascularized bone that would not need to be
reshaped to fit the defect, with the correct donor
match. CTA also provides reconstruction with
similar tissue type in regions of the central midface
such as the nose, lips, and eyelids. With advances
in transplant immunology to devise mechanisms to
decrease immunosuppression and induce donor
antigen-specific tolerance, CTA may be a future
reality in the pediatric population24.
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Prakash et al.
Conclusion
Treatment of craniofacial microsomia is
individualized. Principles basic to all cases include
treating bony tissue deficits first, followed by soft
tissue augmentation. The mandible is addressed
initially
since
correction
of
mandibular
malformations often stimulates maxillary growth.
Maxillary growth is further enhanced with the use
of maxillary activators. Costochondral grafts must
be used in TMJ reconstructions. Soft tissue deficits
are corrected with local and microvascular free
flaps. Facial nerve defects usually are permanent
and hearing must be assessed early to allow for
hearing augmentation. Reconstruction of middle
ear structures is often delayed until craniofacial
reconstruction is complete.
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