Three-Dimensional Approach To Analysis

and Treatment of Hemifacial Microsomia

LEONARD B. KABAN, D.M.D., M.D.

JOHN B. MULLIKEN, M.D.

JOSEPH E. MURRAY, M.D.Boston, Massachusetts 02115

Based on our experience with 40 patients with hemifacial microsomia (first and secondbranchial arch deformity), we have developed a three-dimensional analytic approach tothe skeletal deformity.

The sagittal plane x-ray views (lateral cephalogram and panorex) demonstrate theanatomy of the temporomandibular joint as well as the shape and height of themandibular rami.

The frontal plane is demonstrated by the anterio-posterior (A-P) cephalogram, whichshows the discrepancy in ramus height and the abnormal are of mandibular rotationtoward the affected side.

The transverse plane is evaluated with a submental vertex radiograph, which showsthe shape of the mandibular body and medial displacement of the temporomandibularjoint.

Three-plane radiographic analysis demonstrates the total anatomic distortion and theabnormal growth vectors We hypothesize that abnormal mandibular growth is ofprimary importance in this deformity. Application of this analysis has influenced thetiming of intervention and the design of corrective procedures.KEY WORDS: branchial arch, cephalometrics, hemifacial microsomia, mandible,

temporomandibular joint.

Introduction

Hemifacial microsomia is a variable con-

genital anomaly manifested by progressive

asymmetric growth of structures derived from

the 1st and 2nd branchial arches (Figure 1).

We have developed a three-dimensional ap-

proach to analysis and treatment of this de-

formity based on our experience with 40 pa-

This paper was presented at the Annual Meeting ofthe American Cleft Palate Association on June 1, 1980,Lancaster, Pennsylvania. The work was supported inpart by the Brigham Surgical Group Foundation, Inc.,The Harry Doehla Foundation, Inc., and the Massachu-setts Cosmetologists Association, Inc.

Dr. Kaban is Assistant Professor of Oral and Maxil-lofacial Surgery, Harvard School of Dental Medicine,Junior Associate in Surgery, Brigham & Women's Hos-pital and Associate in Surgery, Children's Hospital Med-ical Center, Boston, MA. Dr. Mulliken is Assistant Pro-fessor of Surgery, Harvard Medical School, Junior Asso-ciate in Surgery, Brigham & Women's Hospital, andAssociate in Surgery, Children's Hospital Medical Cen-ter, and Dr. Murray is Professor of Surgery, HarvardMedical School, Chief, Division of Plastic and Maxillo-facial Surgery, Brigham & Women's Hospital and theChildren's Hospital Medical Center.

90

tients with hemifacial microsomia (Murray et

al, 1979). _The mandibular anomaly is classified into

three types depending on the skeletal anatomyof the ramus and temporomandibular joint(Pruzansky, 1969; Swanson and Murray,1977). A Type I deformity consists of a mina-ture mandible and temporomandibular joint;all structures are present but are hypoplastic.A Type II deformity is characterized by asmall, abnormally shaped ramus and anunderdeveloped displaced temporomandibu-lar joint. In a Type III deformity, the ramusand glenoid fossa are both absent. The skeletaltype is not predictably related to the facialsoft tissue contour, appearance of the externalear, or cranial nerve function.

Serial observation of the growth patterns inhemifacial microsomia has stimulated the de-velopment of a three-dimensional analyticsystem. The deformed skeleton is demon-strated radiographically in the sagittal, fron-tal, and transverse planes. This facilitates ac-curate assessment of the anatomic deformity

Kaban, Mulliken and Murray, HEMIFACIAL MICROSOMIA ANALYSIS 91

FIGURE 1. Serial frontal photographs show the progressive distortion that occurs with untreated hemifacialmicrosomia. Note the short affected mandible, midline deviation toward the affected side and abnormal location ofthe affected pyriform region of the nose. Figure 1A. 10 months of age; 1B. 10 years; 1C. 16 years.

and planning for a complete skeletal correc-

tion.

Growth patterns in hemifacial microsomia

Although hemifacial microsomia is classi-

cally described as a unilateral anomaly, 20 to

30% of patients have bilateral abnormalities

(Ross, 1975; Murray et al, 1979). The deform-

ity, however, is always asymmetric with more

severe skeletal and soft tissue involvement on

one side of the face. The less severely affected

side exhibits a mild external ear abnormality

or a preauricular skin tag. The mildly affected

side usually has a normal underlying skeleton

and, therefore, will be referred to as "normal,"

in contrast to the "affected" side of the face.

Although the maxilla, nose, orbit, and zyg-

oma may all be involved in hemifacial micro-

somia, the mandibular deformity is assumed

to be the abnormal keystone. Asymmetric

mandibular growth is the earliest skeletal

manifestation and seems to play a pivotal role

in the progressive distortion of both ipsilateral

and contralateral skeletal structures.

The total deformity is not restricted to the

skeleton. The ear defect, soft tissue and muscle

deficiency, and facial nerve palsy must also

be considered. This paper analyzes the skele-

tal deformity and its correction in a three-

dimensional approach. Other aspects of cor-

rection are the subject of another paper (Mur-

ray et al, 1979).

For clarification, we use the terms superior,

inferior, anterior, and posterior throughout

this paper to describe directions of movement.

Manomurar GrowtH. Normal mandibu-

lar growth involves programmed bone depo-

sition and resorption on periosteal and endos-

teal surfaces (Enlow, 1975). This process de-

termines the ultimate mandibular size and

shape as well as its location with respect to

the maxilla and base of the skull. The in-

crease in vertical height of the ramus and its

movement in a posterior direction is a result

of bone deposition on the posterio-inferior

surface and resorption on the anterior. Re-

sorption along the anterior border of the ra-

mus also contributes to the length of the

mandibular body. With unilateral growth im-

pairment, the mandibular skeletal midline

deviates to the affected side (Figure 2a). An

axis drawn through the mandibular dental

midline and symphysis is rotated toward the

affected side inferiorly and toward the normal

side superiorly (Figure 2B). The occlusal

plane thus tilts superiorly on the affected side.

The same process, resorption on the medial

surface and deposition on the lateral, accounts

for the shape and width of the mandibular

body and arch. Failure of remodeling in the

92 _Cleft Palate Journal, April 1981, Vol. 18 No. 2

A

B

FIGURE 2. 2A; A-P cephalogram shows typical rotational distortion of the mandible and maxilla in hemifacialmicrosomia. The affected ramus is short and medially displaced. 2B: The tracing shows tilting of the pyriformaperture and occlusal plane relative to the vertical reference plane drawn through glabella and anterior nasal spine(¥ - Y"). A line through the mandibular dental and skeletal midlines demonstrates deviation of the skeletal midlinetoward the normal side. Arrows indicate correction of the mandible by elongation of the affected ramus, rotation ofthe mandibule to the vertical reference line, and telescoping of the "normal" ramus. Note that the ramus heightdiscrepancy equals the amount of deviation of the mandibular skeletal midline from Y - Y".

transverse plane results in a narrow body and

a medially displaced ramus.

Maxitrary Growtn. The maxilla grows

inferiorly and anteriorly, the result of bone

resorption on the superior (nasal) and anterior

surfaces with concomitant deposition on the

inferior (palatal) surface (Enlow, 1975). As

the naso-maxillary region is displaced down-

ward and forward (away from the cranium),

there is expansive growth of the overlying soft

tissues. In turn, soft tissue mass and muscle

function affect skeletal growth (Moss, 1972).

On the abnormal side, downward growth of

the maxilla is restricted by the short mandi-

ble. This restriction of vertical maxillary

growth prevents the usual progressive sepa-

ration of the orbit from the maxillary alveolar

ridge and pyriform region of the nose. The

distance between the orbital floor and maxil-

lary alveolus is decreased. In some patients,

the orbit is inferiorly displaced. In addition,

the zygoma may be hypoplastic.

Method

In the past, hemifacial microsomia was an-

alyzed in one dimension using lateral cephal-

ometric and panoramic radiographs. More

recently, Converse (1979) and Edgerton and

Marsh (1977) have emphasized the need for

a more complete skeletal analysis. Currently,

we analyze the deformity in all three planes:

sagittal, frontal, and transverse (Figures 3a

and 3B). Although this simplified analysis

does not assess the influence of abnormal

growth on the base of the skull, the method is

presented as a useful concept to aid clinical

planning.

Sactrrar Prange. The Panoramic x-ray

view reveals the shape of the mandibular

Kaban, Mulliken and Murray, HEMIFACIAL MICROSOMIA ANALYSIS 93

FIGURE 3. 3A: A patient with hemifacial microsomia should be conceptualized in three planes-sagittal, frontal

and transverse. 3B: The underlying mandibular ramus is short in the sagittal plane, rotated toward the affected side,

and medially displaced in the frontal plane; and the mandibular body is narrow in the transverse plane.

A

FIGURE 4A. Sagittal plane-Tracingof a panorex radiograph illustrates a Type II deformity. The distance from

the horizontal reference line to gonion is the ramus height.

ramus and temporomandibular joint as well

as any height discrepancy in the ramus. Lines

tangent to the horizontal and ascending rami

of the mandible are drawn. The intersection

of these lines determines the lowest point on

the ascending ramus (gonion). A horizontal

line is drawn tangentially to the highest point

on the head of the condyle. The perpendicular

distance from this horizontal reference to gon-

ion is the ramus height (Figure 4A).

The lateral cephalometric x-ray view also

shows the discrepancy in ramus height as a

superimposed contour asymmetry and the re-

lationship of the maxilla and the mandible to

each other and to the base of the skull (Figure

4B). Standard orthodontic measurements are

used to determine the need for orthodontic

treatment and/or advancement of the man-

dible.

Frontar Pranr. The frontal plane is most

FIGURE

4(continued).

4B:The

lateralcephalometricstudy

also

demo

nstr

ates

thede

form

ityof

the

sagi

ttal

plan

ewith

supe

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osed

contours

ofthetw

osides

ofthemandible.4C

:FrontalPlane-A-Pcephalometricra

diog

raph

illu

stra

tesareof

mand

ibul

arro

tati

ontoward

theaffected

side

andramus

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disc

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4D:

Tran

sverse

Plan

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isvi

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exx-ray.

94 Cleft Palate Journal, April 1981, Vol. 18 No. 2

Kaban, Mulliken and Murray, uEmIFACIAL MICROSOMIA ANALYSIS 95

useful for evaluation and is best seen with an

A-P cephalometric radiograph. The anterior

nasal spine and glabella or sella turcica are

used to create a vertical reference plane (Y -

Y"). Gonion, pyriform apertures, and orbits

are located on both sides, and the planes

through these landmarks are related to the

true horizontal (X - X"). The discrepancy in

ramus height and abnormal position of the

affected pyriform aperture and orbit (Figures

2B and 4C) become clear. The A-P cephalo-

gram also demonstrates the deviation of the

mandibular dental midline toward the nor-

mal side, reverse deviation of the mandibular

skeletal midline toward the affected side, me-

dial displacement of the ramus and glenoid

fossa, and obliquity of the occlusal plane. One

can imagine that the displaced mandible

must have rotated along an arc determined

by its abnormal growth vectors.

Transverse Pane. The transverse plane is

evaluated with a sub-mental vertex x-ray

view. This demonstrates the shape and width

of the mandibular body. It also shows any

asymmetry in the zygomatic arches and any

medial and anterior displacement of the tem-

poromandibular joint (Figure 4D).

Application of three-dimensional analysis to

treatment

Type I hemifacial microsomia is illustrated

by the adult in Figure 5A. She has the char-

acteristic mild skeletal deformity and a facial

nerve deficit. The non-occluding, narrow, pos-

terior mandibular segment did not restrict

vertical maxillary growth. Therefore, the

maxillary occlusal plane remained level (Fig-

ure 5B). Sagittal plane x-ray analysis docu-

mented the difference in ramus height. A-P

x-ray revealed mild tilting of the pyriform

aperture on the left and deviation of the

mandibular skeletal midline. Transverse (sub-

mental) x-ray documented the decreased

mandibular width.

Based on this three-dimensional analysis,

the left ramus was surgically elongated, and

a compensatory osteotomy was performed on

FIGURE 5. 5A: A female with Type I, left hemifacial microsomia has a mild skeletal deformity and ViIth nervepalsy. 5B: Occlusal photograph shows narrow, non-occluding left posterior mandibular segment and horizontalocclusal plane of maxilla. 5C: Three years after surgery. Skeletal correction and occlusal plane have remained stable.

96 Cleft Palate Journal, April 1981, Vol. 18 No. 2

the right ramus. The mandible was rotated to

correct the skeletal but not the dental midline.

A posterior segmental osteotomy (premolar

region) widened the arch and provided sta-

bility and contact for the increased vertical

length created in the left ramus (Figure 5C).

A Type II patient is analyzed in Figures 4A

through D. Panoramic and lateral cephalo-

metric radiographs demonstrate the discrep-

ancy in ramus height and the underdeveloped

temporomandibularjoint. The relationshipof

the maxilla and mandible to one another and

to the base of the skull is also shown. The A-

P cephalogramreveals the discrepancy in ra-

mus length, the convexity of the "normal"

side of the mandible, and the mandibular and

dental midline deviation. The sub-mental

view shows the medial displacement of the

ramus as well as the medial and anterior

displacement of the temporomandibular

joint.

Treatment for this Type II deformity re-

quired correction of the discrepancy in ramus

height in the sagittal plane, the rotational

defect in the frontal plane, and the narrow

mandibular arch in the transverse plane. Bi-

lateral ramus osteotomies were done. On the

affected side, an interposition bone graft was

used to elongate the ramus and augment the

lateral contour at the angle. The "normal"

side was elongated with a sliding oblique

osteotomy. The mandible was rotated to cor-

rect the midline. An open bite, greater on the

affected side, was created in the premolar-

molar areas bilaterally to permit orthodontic

widening of the arch. The open bite was

maintained with an acrylic interocclusal ap-

pliance. 7The postoperative lateral cephalometric x-

ray shows equalization of ramus height (Fig-ure 6A). The A-P film shows midline sym-

_ metry and improved lateral contour of themandible (Figure 6B) two years postopera-tively.A second example of a Type II deformity

shows severe medial displacement of a shortramus and temporomandibular joint (Figure7A). Deviation of the mandibular midlinetoward the affected side is also demonstrated.The mandibular arch is narrow and non-oc-cluding on the affected side. Hence, the occlu-sal plane remains level.

Correction in this patient required excision

of the abnormal ramus and construction of atemporomandibular joint with the glenoidfossa and a new ramus placed in a morelateral position (Figure 7B). Compensatoryosteotomy of the normal side was required toallow rotation without placing abnormalforces on the temporomandibular joint. Pos-terior segmental osteotomy or orthodontictreatment could widen the arch in the pre-molar-molar area and help maintain the in-creased ramus length.

Type III hemifacial microsomia is illustratedin Figure 8. The A-P cephalogram of this two-year-old patient shows early malrotation andmedial displacement of the mandible. Thelateral mandibular film displays absence of aramus and temporomandibular joint. Notealso the anterior-inferior position of the tem-poral lobe (Figures 8A and B).To treat this deformity, a temporomandi-

bular joint construction is required. The newglenoid fossa and ramus should be placed asfar lateral as possible and a zygomatic archshould be constructed. Rib with costochon-dral junction is used for the ramus. The op-posite temporomandibular joint in these veryyoung patients is flexible so that a compen-satory osteotomy is not usually required. Theelongation and rotation create an open biteon the affected side and correct the midline.

Discussion

Hemifacial microsomia is a progressive de-formity. The affected side becomes increas-ingly distorted as the normal side grows. Thetypical pattern is illustrated by the Type IIpatients presented in this paper. The childshown in Figures 4 and 6 had a short affectedmandible and midline deviation. The medialdisplacement of the ramus and the temporo-mandibular joint had not progressed to itsend stage. Construction of a new ramus andtemporomandibular joint was, therefore, notrequired. The adult (Figure 7) with severemedial displacement required ramus excisionand construction of a new ramus and glenoidfossa in a more normal lateral position.The mandibular defect is the earliest skel-

etal manifestation and seems to be a key factorin later distortion of the maxilla, nose, andorbits. The pivotal role of the mandible isillustrated by the patient who has a narrow,

Kaban, Mulliken and Murray, uEmiracIAL micROSoMIA ANALYSIS 97

FIGURE 6. 6A and 6B: Postoperative lateral (A) and A-P cephalograms (B) documenting symmetry of the rami,

the mandibular midline, and level occlusal plane two years later. 6C and 6D: Pre-operative (C) and two-year post-operative (D) photographs of the patient analyzed in Figure 4.

98 Cleft Palate Journal, April 1981, Vol. 18 No. 2

lio B

FIGURE 7. 7A: A-P cephalogram illustrating the typical distortion of a patient with end-stage Type II hemifacialmicrosomia. 7B: Postoperative A-P cephalogram shows the lateral position of the newly constructed temporomandi-bular joint and ramus, the corrected ramus length, and mandibular skeletal midline.

FIGURE 8. 8A: A-P cephalogram of Type III patient shows characteristic early medial displacement of affectedmandible. 8B: Lateral x-ray view shows the absence of ramus and temporomandibular joint.

non-occluding premolar-molar segment on

the affected side. Vertical maxillary growth is

not restricted and the occlusal plane remains

horizontal. There is less distortion of the pyr-

iform region, and the distance from the orbital

floor to the maxillary alveolus is closer to

normal. The orbit on the affected side is,

therefore, not inferiorly displaced. Under-

standing this progression of deformity with

growth, we have shifted our emphasis from

one-dimensional treatment of fixed end-stage

skeletal defects to earlier three-dimensional

Kaban, Mulliken and Murray, HEMIFACIAL MICROSOMIA ANALYSIS 99

analysis and intervention. This approach may

unlock growth on the affected side and dimin-

ish secondary distortion.

Three-dimensional analysis has led to a

change in the operative approach. Earlier

corrections consisted only of a ramus

lengthening procedure. Rotation of the man-

dible and correction of the midline were un-

intentional results of the ramus elongation.

Patients treated in this manner continued to

function abnormally, with deviation on open-

ing, because the ramus and the temporoman-

dibular joint were not in the proper location

in the frontal plane. With this abnormal func-

tion, the long-term prognosis for maintenance

of skeletal symmetry was poor. Placement of

the ramus and the temporomandibular joint

in the correct three-dimensional position pro-

vides better facial contour by filling out the

preauricular depression so commonly seen in

these patients. In addition, jaw function is

more symmetrical and physiological.

Summary

A method of three-dimensional analysis of

hemifacial microsomia using sagittal, anterio-

posterior, and sub-mental x-ray views has

been designed. It demonstrates the clinical

deformity more clearly than the previously

used single dimension lateral radiograph. This

method of evaluation has resulted in a treat-

ment protocol more closely related to anat-

omy and physiology.

Reprints: Leonard B. Kaban, D.M.D., M.D.

Children's Hospital Medical Center

Division of Plastic & Maxillofacial Surgery

300 Longwood Avenue

Boston, MA 02115

References

Converse, J. M., Horowitz, S. L., Coccaro, P. J. andWoodsmith, D., The corrective treatment of the skele-tal asymmetry in hemifacial microsomia, Plast. Reconstr.Surg., 52, 221-231, 1973.

Edgerton, M. T. and Marsh, J. L., Surgical treatment ofhemifacial microsomia, Plast. Reconstr. Surg., 59, 653-666, 1977.

Enlow, D. H., Handbook of Facial Growth, Philadelphia:W. B. Saunders, Co., pg. 140-141, 1975.

Moss, M. L., Twenty years of functional cranial analysis,Am. ]. Orthod., 61, 479-485, 1972.

Murray, J. E., Kaban, L. B., Mulliken, J. B., Belfer, M.L. and Swanson, L. T., Twenty year experience intreatment of hemifacial microsomia, presented at the58th Annual Meeting of the American Association ofPlastic Surgeons, Palm Beach, Florida, May 2, 1979.

Pruzansky, S., Not all dwarfed mandibles are alike. BirthDefects, Original article series, Vol. 1, No. 2, 120, 1969.

Ross, R. B., Lateral facial dysplasia, Birth Defects, Orig-- inal article series, Vol. 11, No. 7, 51-59, 1975.Swanson, L. T. and Murray, J. E., Asymmetries of the

lower part of the face, In Symposium on Reconstruc-tion ofJaw Deformity, Whitaker, L. A., and Randall,P. (Eds). St. Louis: The C.V. Mosby Co., Vol. 16, 171-196, 1978.