Keywords cone-beam computed tomography - facial asymmetry - mandibular condyle - panoramic
radiography
Introduction
Unilateral mandibular condylar hyperplasia is a rare developmental disorder. Mandibular
condylar hyperplasia was first described in 1836 by Robert Adams.[1 ] The etiology and pathogenesis are poorly understood. It is self-limiting and tends
to stabilize or stop with aging. It may progress slowly or rapidly, producing mandibular
asymmetry, chin deviation, limited mouth opening, posterior open bite on the affected
side, and cross-bite on the contralateral side.[2 ]
[3 ] Since the growth vector of the mandible is the condyle, condylar hyperplasia is
often accompanied by an increase in height of ramus or body or alveolar process of
the affected side of the mandible. Imaging plays a vital role in accurate measurement
of the condyle, thereby helping the treatment plan. This case report deals with the
role of cone-beam computed tomography (CBCT), a recent imaging modality in diagnosis
and treatment plan in a patient with condylar hyperplasia.
Case Report
A 35-year-old female patient reported to the department with the chief complaint of
deviation of lower jaw toward the right side from the age of 15 years. She also noticed
a swelling in her left preauricular region that was insidious in onset, small initially,
and gradually attained the present size. No history of pain or clicking was found
in that region. There was no history of trauma and a similar type of swelling in other
parts of the body. The patient had difficulty in chewing initially; later she got
adapted. The patient had a history of gastritis for 3 months and was under medication.
Her dental history revealed uneventful extraction before 2 months. The patient was
well oriented to time, place, and person. All her vitals were within the normal range.
On extraoral examination, facial asymmetry was noted. Chin has been deviated toward
the right side. On mouth opening, facial midlines coincide and get deviated to the
right side during closing of the mouth ([Fig. 1 ]). Mouth opening was 35 mm. Lateral and protrusive movements were restricted. A single
right submandibular lymph node measuring ∼1 × 0.5 cm was palpable, soft in consistency,
tender, freely movable.
Fig. 1 (A ) Deviation of mandible toward right side. (B ) Swelling in the left preauricular region. Yellow line indicates midline and red
line indicates the deviation of mandible towards right side.
On temporomandibular joint (TMJ) examination, a well-defined solitary swelling measuring
∼1.5 × 2 cm was present in the left preauricular region, the skin over the swelling
was stretched, and the color of the skin appears similar to adjacent skin. Secondary
changes such as ulcer and sinus opening were not present. All inspectory findings
regarding site, size, and shape were confirmed by palpation. The swelling was bony
hard in consistency (prominent condyle) and nontender. No warmth felt. No clicking
sound, crepitus heard. The swelling was found to move during mandibular movements.
Muscles of mastication were nontender ([Fig. 1 ]).
On intraoral examination, dental midline did not coincide. Generalized gingival recession
and attrition were present. Mesial tilting of 41, 42, 43 and distal tilting of 31,
32 were present. The posterior's mandibular teeth were lingually tilted (44, 45, 34,
37) ([Fig. 2 ]).
Fig. 2 Tilting of lower anteriors toward left side.
The provisional diagnosis was made as unilateral condylar hyperplasia of the mandible
(left). The differential diagnosis was osteochondroma and osteoma.
Panoramic tomography (PLANMECA Proline XC) revealed enlarged condyle on the left side
with altered shape ([Fig. 3 ]). The cortical border was intact and the trabecular pattern was homogenous. An increase
in height of the left-side ramus of the mandible was also noted. Mesial tilting of
41, 42, 43 and distal tilting of 31, 32 were present.
Fig. 3 (A ) Vertical condylar asymmetry index described by Habets. (B ) The highest point of the condyle; (02) the most lateral point of the condyle; (01)
the most lateral points of the mandibular ramus; (RH) the mandibular ramus height
and (CH) condylar height.
Asymmetry Index Calculation
In panoramic radiographs, 18 to 21% magnification in vertical height is seen according
to Larheim and Svanaes (1986). In 1988, Habets et al proposed a Habets asymmetry index
for determining the asymmetry using panoramic radiographs.[4 ]
[5 ]
[6 ]
Habets asymmetry index (AI) was calculated from the formula, AI = [(R-L)/(R + L)] × 100%.
A difference of ∼3% is considered as asymmetrical. AI can be calculated for both condyle
and ramus. In the present case, AI for condyle was 12.69% and for ramus was 8.42%,
showing that condyle and ramus of both right and left side were asymmetric ([Fig. 3 ]).
In this case, unilateral enlargement of the condyle with the asymmetry of the mandible
was clearly made out in posteroanterior view of skull and reverse Towne's projection
([Fig. 4 ]).
Fig. 4 (A ) Posteroanterior view of skull shows deviation of mandible toward right side. (B ) Reverse Towne's projection shows left condylar enlargement.
CBCT of right and left TMJs was advised for more accurate measurements of the condylar
dimensions.
After studying the various views, the left-side condyle and neck were found to be
enlarged in all the three planes ([Figs. 5 ] and [6 ]). The shape of the condyle and the articular tubercle was altered. The shape of
the left condyle resembles a heart in the coronal section with a bony projection extending
anteriorly that was seen in the sagittal section. The cortical border was intact.
The trabecular pattern of the condyle was homogenous except for an area of radiopacity
measuring 0.3 cm in diameter. The articular tubercle was flattened with an increased
dimension anteroposterior dimension.
Fig. 5 Various section in cone-beam computed tomography showing comparison between both
condyles with measurements.
Fig. 6 Three-dimensional reconstructed view of right and left condyle compared in different
views.
Measurements were made in all three planes using the software (Horos v3.3.6) ([Table 1 ]). The maximum difference in dimension was observed in the sagittal section that
suggests that the condyle was more enlarged anteroposteriorly. The Hounsfield unit
of both the condyles was indicated as calculated by the software ([Fig. 7 ]).
Fig. 7 Hounsfield units (HU) calculated using gray values. (A –C ) Hounsfield unit values of affected left condyle. (D and E ) Hounsfield unit values of unaffected right condyle.
Table 1
Measurements of both condyle in all planes using CBCT
Right condyle (mm)
Left condyle (mm)
Axial section (mediolateral dimension)
18.3
26.7
Coronal section (mediolateral dimension)
18.7
22.9
Sagittal section (anteroposterior dimension)
9.6
23.2
Abbreviation: CBCT, cone-beam computed tomography.
According to Obwegeser and Makek classification, the present case is type III condylar
hyperplasia (chin deviation toward the contralateral side with a sloping rima oris,
midline shift, possible open bite and/or cross-bite) and according to Wolford classification,
the present case is CH type I B (unilateral mandibular elongation chin deviation toward
contralateral side, midline shift to contralateral side, lingual deviation of contralateral
mandibular molars, possible posterior cross-bite, ipsilateral Class III occlusion).[1 ]
Following the diagnosis, the surgical correction procedure was advised for the patient.
However, the patient refused the treatment procedure.
Discussion
TMJ condylar hyperplasia is a reactive hyperplastic growth of the condyle, in which
there are an impressive adaptive capacity and compensatory mechanisms of the human
body. It is illustrated as a rare unilateral growth of the mandibular condyle, characterized
by excessive bone growth resulting in facial asymmetry.[1 ]
[7 ]
The condylar cartilage is a secondary cartilage that is highly responsible to mechanical
stimuli and responds differently to various hormonal and chemical agents. Growth at
the condyle is pressure adapted. The cap of the condyle undergoes endochondral ossification,
whereas the rest of the condyle and the neck undergoes intramembranous ossification.
The zone of growth in the condyle contains proliferative cells like skeletoblasts
and prechondroblasts, that are exposed to the environment and are moldable to external
stimuli. It has a multidirectional proliferative capacity.[8 ]
Condylar hyperplasia may be due to overactive cartilage or persistent cartilaginous
rests, increasing the thickness of the entire cartilaginous and precartilaginous layers.
Condylar hyperplasia is more common in the females before the age of 20 years. It
is usually unilateral, self-limiting, and gets arrested with the termination of skeletal
growth.
Facial asymmetry involving the TMJ can be TMJ pathology, unilateral condylar hyperplasia,
unilateral mandibular condylar osteoma or osteoblastoma, and condylar resorption,
among which unilateral condylar hyperplasia has the features of progressively worsening
Class III occlusal relationship with a contralateral cross-bite, mandibular, and chin
deviation to the opposite side. These characteristic features of condylar hyperplasia
are seen in the present case.[9 ]
The most common benign tumor of condyle is osteochondroma followed by osteoma. In
the present case, the patient was asymptomatic, whereas in the case of osteochondroma
and osteoma, the patient may experience pain, clicking sound on the affected side,
and is rarely asymptomatic.[2 ] Radiographic features of this case were a well-defined altered condyle, altered
articular eminence, thickened condylar neck, and increased ramus height on the affected
side. The cortical border was well defined and the trabecular pattern was homogenous
except for a 0.3 cm area of radiopacity. In case of osteochondroma and osteoma, the
condyle is irregular in shape and the trabecular pattern is heterogeneous. The articular
eminence may be altered to compensate the altered condyle changes. The alteration
in the condylar neck and ramus may be secondary to degenerative changes due to altered
forces on the joint. Hence, the history of onset of the lesion (observed at her age
of 15 years) and from the above features, it is an indication of developmental disorder
of the mandibular condyle probably mandibular condylar hyperplasia. Since osteochondroma
and osteoma are benign tumors, there will be no such secondary degenerative changes
as noted in condylar hyperplasia.
A panoramic radiograph is generally a quick and convenient radiographic technique
that is used for assessing mandibular lesions. It has a low radiation dose and covers
broad coverage of facial bones and teeth[2 ]
[4 ] Since panoramic radiography involves distortion and elongation, CBCT was used to
get more accurate measurements.
With CBCT, high-resolution images can be obtained with reduced radiation exposure
to the patient when compared with multislice CT.[10 ] It also can produce images resembling panoramic images with which the dentists are
familiar (pseudopanoramic). Alveolar buccolingual cross-sectional images can also
be produced by routine CBCT software that is also an advantage. Surface rendering
can be done and the image analysis can also be done by the end-users. Carestream9300
S 3D extraoral imaging system (Carestream Health, Inc., Rochester, New York, United
States) was used for obtaining CBCT images. Radiation exposure to the patient in CBCT
was: 90 kVP, 5 mAs, and scan time 8.01s. Radiation exposure to the patient was 568 mGycm2 . Field of view for single TMJ was 180 × 180 × 180 μm.
Direct measurements of mandible were done in panoramic software (Romexis) and the
asymmetry index was determined by Habets method. This method revealed both the condyle
and ramus of the mandible of the present case were asymmetric. The altered articular
tubercle and condylar neck were better appreciated on CBCT than a panoramic radiograph.
In a panoramic radiograph, the shape of the condyle was noted to be enlarged, whereas
in CBCT the sagittal section showed a bony projection extending anteriorly. Pinpoint
radiopacity in the condylar trabecular pattern was appreciated only in CBCT, where
a homogenous trabecular pattern was seen in a panoramic radiograph. In the present
case, bone density in Hounsfield units was also calculated for both the condyles using
CBCT.
Obwegeser and Makek divided unilateral condylar hyperplasia into three types. Type
I is hemimandibular elongation, type II is hemimandibular hyperplasia, and type III
is a combination of type I and type II. The present case is type III condylar hyperplasia
(chin deviation toward contralateral side with a sloping rima oris, midline shift,
possible open bite and/or cross-bite). According to Wolford classification, unilateral
condylar hyperplasia is divided into four types, among which type I and II have subtypes
A and B. The present case is CH type IB (unilateral mandibular elongation chin deviation
toward the contralateral side, midline shift to contralateral side, lingual deviation
of contralateral mandibular molars, possible posterior cross-bite, ipsilateral Class
III occlusion).[1 ]
Nuclear imaging like bone scintigraphy, positron emission tomography, and single-photon
emission computed tomography can be advised before surgery that helps to determine
the growth phase of the condyle.[11 ]
[12 ] This nuclear medicine examination uses technetium-99 along with methylene diphosphonate
as phosphated radiotracer.[13 ] The principle behind nuclear imaging is hydroxyapatite crystals and calcium from
the bone tissue will be absorbed by the radioisotopes, so that the fixation intensity
is proportional to the degree of osteoblast activity.
The primary treatment protocol for unilateral condylar hyperplasia is surgery followed
by orthodontic teeth correction. The various surgical methods for unilateral condylar
hyperplasia include unliteral sagittal split, bilateral sagittal split ramus osteotomies,
unilateral or bilateral maxillary osteotomies with or without Le Fort I leveling osteotomy,
and condylectomy. Surgical correction is indicated only after the completion of growth.[1 ]
[14 ] Following surgery, joint functional exercises can be advised to recover mandible
lateral and vertical movements and also to minimize the occurrence of intra-articular
adhesions and capsular retractions. The various joint functional exercises include
massage, masticatory, and cervical muscle relaxation, joint distraction, joint kinesiotherapy,
joint mobilization exercises, mandibular mobilization exercises with hyperboloid and
against resistance for muscular reinforcement.[15 ] However, in the present case, the patient refused the treatment.
Conclusion
Condylar hyperplasia is a rare unilateral (rarely bilateral) growth of the mandibular
condyle, characterized by excessive bone growth resulting in facial asymmetry. CBCT,
an advanced imaging, can be used in diagnosis, assessment, and treatment planning
of unilateral condylar hyperplasia of the mandible. The role of CBCT in the measurements
for the assessment of condylar hyperplasia and vertical height of ramus is emphasized.
