Abstract

Excessive unilateral condylar growth is a well-known phenomenon that has been previously described [1]. Condylar hyperplasia (CH) can be defined as the excessive growth of one condyle over the contralateral, causing an increase in bone mass of varying degree in instances where the subject’s growth has decreased or ceased [2].

Norman & Painter [1] conducted a historical review of CH and in 1980 published a series of cases that were previously described by Robert Adams in 1836, George Humphry in 1856 and others that demonstrate knowledge of the disease, emphasizing the facial deformity and chin displacement as the main characteristics.

The diagnosis of this pathology is initially made with facial analysis and imaging; the patient frequently consults for dental alterations, motivated by the use of corrective orthodontic devices [3]. Asymmetric facial deformities (AFD) and malocclusion are a clear consequence of CH. Generally, there is no pain associated with the affected joint, although joint noises linked to CH and deviation of the mouth opening towards the contralateral side have been described [2].

From the point of view of facial analysis, the patient with CH and AFD are initially evaluated by means of a central line drawn up from the tip of the glabella, passing through the pronasal point to the end of the chin, where both hemifacial areas are identified in order to ascertain the difference in size and position between them [4]. There is generally a deviation of the chin towards the contralateral side of the condyle with CH [5].  The Management of Condylar Hyperplasia Essay.From the dental point of view, the difference between interincisive midlines and the unilateral posterior inverted occlusion or the unilateral posterior open bite also enable the presence of the disease to be established [6].

Etiology and diagnosis of CH

TMJ and specifically the condyle are responsible for most postnatal facial asymmetries; the pathologies are known as osteochondromas, condylar resorptions, infection-related growth deficiencies, trauma or CH [3]. One way to recognize facial asymmetries caused by condylar growth alterations in prenatal or postnatal origin is that the latter cranial asymmetries are not observed [7]; cranial asymmetry deformity is caused by alterations before 5 years of age, when he cranial base takes to form completely [8], placing CH in the postnatal category.

CH has an unknown etiology and is characterized by a progressive and independent growth, causing greater bone volume of one condyle over the other side. It generally appears in subjects in the growth phase, mainly in adolescence [3]. A systematic review by Raijmakers [9] assessed 10 articles published with a total of 275 patients diagnosed with CH; in the sample a statistically significant tendency was observed that women present with CH more frequently with 0.64% more than men.

In terms of age and given that etiology is definitively unknown, it has not been possible to define an absolute age of presentation [2,3,9]. It is estimated that subjects in adolescence or young adults can present with the active pathology, although it has also been seen that subjects over 50 can also exhibit CH in progress [3]. With the current information in the literature, it is not possible to define the date at which CH begins or ends. The Management of Condylar Hyperplasia Essay.

Nitzan [3] and Raijmakers [9] indicated that the severity of the asymmetry was also statistically associated with age and gender; the type of condylar deformity (morphological characteristics of the condyle) was not related to the type of asymmetry [6], presenting horizontal in 53%, vertical in 31% and combined in 16%. In the group of 36 patients of Villanueva-Alcojol [2] 66.7% presented cross-sectional pathology, 22.2% vertical and 11.1% was a combination of the two; as a result, the highest incidence of the cross-sectional pathologies is observed.

Bone scintigram and diagnostic methods

Although the diagnosis of CH is essentially clinical, there are supporting studies that determine the activity and morphology of the condyle affected. Without a doubt, computerized tomography (CT) has contributed to establishing the pathology and condylar morphology (comparing both condyles), making it possible to recognize and classify the different degrees of the disease [10] (Table 1); in the tomographic images of condyles with CH, limited cortical areas are observable in the upper pole, characteristic of zones with active bone metabolism [11] (Figure 1). Before CT, radiographs were protocoled how serial image in follow-up, which enabled the size and shape of the condyle to be compared at 6-month intervals to determine whether the CH was growing or if this growth had stopped [12].

Figure 1

Cone beam CT image comparing different serial sections at a thickness of 1 mm of the condyle from right to left. The right condyle exhibits active growth and a greater volume than its contrateral.

Table 1

Characteristics of some relevant studies performed on patients with condylar hyperplasia (CH)

Authors	Aim	n	Age (years)	Female/Male	Diagnosis	Treatment	Follow-up (years)
Hampf, 1985 [39]	Analysis of treatment of patients with CH	35 (in active CH in 9 cases)	15.6 (7-30 years)	24/11	-Clinical	Condylar surgery (34 cases) with other osteotomies (mandibula. maxilla) and/or extractions	0.5 (0.1-3)
			5 patients under 15 years		-Radiography
					-Scintigram (23 cases)
Slootweg and Müller 1986 [20]	Clinical and pathological analysis of patients with CH	22	24.5 (14-59 years)	16/6	-Clinical	Condylectomy and maxillary and mandibular osteotomies	–
					-Radiography
					-Scintigram (12 cases)
Iannetti, 1989 [34]	Analysis of treatment of patients with CH	12	23.5	–	-Clinical	Orthognatic surgery	4.6 (3-8)
					-Radiography
Gray, 1990 [19]	Study relation between histology and scintigram	20	25.8 (15-55 years)	15/5	-Clinical	Condylectomy	–
					-Radiography
					-Scintigram
Mutoh, 1991 [10]	Analysis of condylar morphology with CT	6	15-20	1/5	-Clinical	–	–
					-Radiography
					-CT
Motamedi, 1996 [31]	Analysis of treatment of patients with CH	13	25.8 (19-37 years)	1/12	-Clinical	Orthognatic surgery with unilateral (6 cases) or bilateral (7 cases) mandibular osteotomy	4.5 (0.7-10)
					-Radiography
					-Scintigram in some cases
Wolford, 2002 [33]	Comparison of treatments in patients with CH	25	16.7 (13-24 years)	12/13	-Clinical	High condylectomy with disc reposition and simultaneous orthognatic surgery	5.3 (2.8-16.9)
		-13 unilateral			-Serialized radiographs with superposition
		-12 bilateral
Eslami, 2003 [21]	Comparison of normal and hyperplastic condyles through histological methods	9	20.4	–	-Scintigram	High condylectomy	–
Pripatnanont, 2005 [14]	Evaluation of SPECT in CH diagnosis.	21	12-46	7/14	-Clinical	–	–
					-Radiography
					-Dental models
					-Scintigram
Saridin, 2007 [15]	Analysis of scintigram evaluation methods	20	21.5	12/8	-Clinical	–	–
					-Radiography
					-Scintigram
Lippold, 2007 [23]	Analysis of treatment of patients with CH	6	27±3	4/2	-Clinical	Condylectomy together with orthognatic surgery	3.1±1.2
					-Radiographic
					-Scintigram
Nitzan, 2008 [3]	Analysis of condylar morphology and characteristics of patients with CH	61	27.8 (11-80 años)	46/15	-Clinical	–	–
					-Panoramic and lateral radiography
					-Scintigram at presentation and at 6 months
Saridin, 2010 [13]	Analysis of mandibular function after condylectomy	32	26.7 (19-48 años)	18/15	-Scintigram	High condylectomy	4.3
Villanueva-Alcojol, 2010 [2]	Evaluation of diagnosis and treatment of patients with CH	36	22.7 años (11-42 años)	11/25	-Clinical	High condylectomy and orthognatic surgery in 6 cases	4.3
					-Radiographic
					SPECT (24 cases)
Brusati, 2010 [38]	Evaluation of the functional TMJ results before and after high condylectomy	15	22 (12-42 años)	–	-Clinical	High condylectomy with simultaneous orthognatic surgery in some cases (does not indicate how many)	4.5 (1-8)
					-Dental models
					-Panoramic, posteroanterior and lateral radiography
					-Scintigram
Jones and Tier 2011 [25]	Evaluation of surgical treatment of patients with CH	16	–	15/1	-Clinical	High condylectomy and simultaneous orthognatic surgery	–
					-Dental models
					-Panoramic, lateral and posteroanterior radiography
					-Scintigram

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Research obtained from database in english and spanish literature between january, 1980 and january, 2012.

Nevertheless, it is the nuclear medicine studies that are most associated with the diagnosis of CH; these consist of an exploration of the bone structure that can detect the bone metabolism and its activity. To do this, Technetium-99m is administered with methylene diphosphonate, which is absorbed by hydroxyapatite crystals and calcium from the bone tissue so that the fixation intensity is proportional to the degree of osteoblast activity; the examination that obtains the scanned bone is called “single photon emission computed tomography” (SPECT) and it determines the percentage of absorption by the condyle quantitatively, by comparing it with the contralateral side [13]. The Management of Condylar Hyperplasia Essay. 0 to 5% differences in capture are observed between the condyles in healthy subjects; differences greater than 10% (pixel count) between the two condyles have been considered as active unilateral growth, establishing the presence of CH on the affected side; these are related positively to increases in the patient’s dental and facial asymmetry [14] (Figure 2A and ​and2B2B).

Figure 2

A: Image obtained by SPECT where a greater capture of the isotope is observed in the left condyle, represented by a more intense red. B: Cone beam CT image showing differences in condylar volume in acoording to the SPECT image.

No other quantitative method has shown the same efficiency as the results of the comparison between condyles using SPECT [15,16]. Other fluids have also been studied to determine the active growth of a condyle [17], which, using the same technique, are showing good results.

Histological characteristics of CH

Histologically 4 layers have been characterized as being present in condylar morphology: 1) connective tissue (fibrous joint layer), 2) undifferentiated mesenchymal layer (proliferative), 3) transitional layer and 4) hypertrophic cartilage layer [18].

In 20 condyles of patients with positive SPECT for CH, Gray [19] demonstrated the presence of a fibrous layer approximately 0.31 mm, a layer of undifferentiated mesenchymal cells with an average of 0.29 mm; the layer of hypertrophic cartilage was on average 0.52 mm. In addition, cartilaginous islands were observed inside the bone tissue, which was related to the level of capture that the affected condyle displayed in the SPECT, a situation already identified by Slootweg & Müller [20]. They also described a probable link between the origin of the pathology and the age group of the patient; thus, according to Sllotweg & Müller [20], in adolescence there is an idiopathic form and in adulthood a reactive consequence to some previous pathology or trauma. What is certain is that no matter the patient’s age, CH does not have a described cause and is possibly linked to situations such as trauma, infection or other localized alteration.

Another contribution by Slootweg & Müller [20] was the creation of a histological classification where they described 4 types of CH, with type I being the slightest and type IV being the most serious in terms of condylar size and tissue invasion. The classification is based on the amount of condylar bone structure involved and cartilaginous growth.The Management of Condylar Hyperplasia Essay.  Villanueva-Alcojol [2] described 36 patients, of which 44.4% presented with type I, 16.7% type II and 38.9% type III. Nevertheless, it was not possible to find any link between histological finding, SPECT finding and the patient’s age [2].

Eslami [21] indicated that significant differences were observed in the layer of hyperplastic cartilage in hyperplastic condyles (located in the upper pole of the condyle), whereas no differences were observed between the other layers studied in healthy condyles.

Analysis performed with AgNOR (Argyrophilic Nuclear Organizer Region) has endeavored to quantify CH; Fariña [22] reported an absence of correlation between the AgNOR results and the presence of CH, whereas Eslami [21] indicated that AgNOR was associated with the classification of the type of hyperplasia proposed by Slootweg & Müller [20], demonstrating a significant correlation. Lippold [23], in an interesting investigation, found a direct link between the histological findings with signs of arthritis and the greatest SPECT capture, which would set the basis for a condylar osteotomy of the upper segment of the condyle to limit its anomalous growth.

Facial asymmetry as a result of CH

CH determines the existence of a facial asymmetry [3]. Obwegeser & Makek [6] classified AFD in three groups: 1) vertical asymmetries, where there is no occlusal alteration of the midline but a vertical growth of the mandibular ramus is observed with a posterior open bite on the affected side, 2) horizontal asymmetries, where there is an alteration between the interincisive midlines and a cross-sectional displacement of one side of the jaw towards the contralateral side and 3) a combination of the two. Elsewhere, Hwang [24] defined 5 groups of patients with AFD with different degrees of alteration; of 8 different characteristics proposed to separate each group, only 3 criteria established clear differences in each group: 1) deviation of the chin, 2) discrepancy between dental apical midlines and 3) the vertical difference between the right and left gonion point (position of the angle of the mandible). These points are clearly linked to the initial proposal by Obwegeser & Makek [6] vertically and horizontally (Figure 3Aand ​and3B3B).

CH involves unilateral condylar growth, which determines not only the growth of the bone structure of the affected side, but also a large part of the soft tissues of the sector including ligaments, muscles and the bone structures related to this mandibular position, which determines the presence of total facial asymmetry together to the technical difficulty for surgical correcting of residual AFD [25].

The dental and occlusal analyses also makes it possible to define facial asymmetries; maxillary cant (deviation of the occlusal plane being higher or lower on one side than the other) is also associated with facial asymmetries [26]; in the detection of this alteration, the degree of the cant is more important than the experience of the observer, who not being a trained clinician, may perceive facial asymmetries associated with the maxillary cant; 4° of occlusal cants are detected by 90% of the observers, whereas 3° of cants are detected by almost 50% of the observers [27].

For other hand, Hwang [26] indicated that the position of the chin and the cant of the occlusal plane influence the position of the lip significantly, showing it to be asymmetrical when the indicated points differ from the midline. Kwon [28] also reported that in patients with asymmetries, differences in the muscular architecture have been identified in relation to the medial pterygoid muscle due to the decrease or increase of the distance from the origin and insertion of this muscle.The Management of Condylar Hyperplasia Essay.  Relatively vertical muscles like the masseter did not present greater differences in the origin and insertion of the different sides of the asymmetrical patient. The angulation of the muscle from the axial axis is one of the reasons that explain this difference in the medial pterygoid muscle.

Tratment oportunity

Based on the existing information, two different but related clinical situations can be defined as cause – effect: on the one hand CH and its progressive growth and on the other hand AFD as a consequence of CH; the two elements can be approached jointly or separately, depending essentially on the patient’s age and the activity or inactivity of the CH [2]. Thus, the proposed treatment options range from the simplest to the most complex surgical and non-surgical procedures [29] (Table 1).

Interestingly, the study by Naini [30] concluded that as the degree of asymmetry increases, the subjects determine a greater need for surgery that repairs esthetics and function, indicating that when the chin asymmetry deviates 10 mm from the midline, there is a high demand to correct it surgically; this demand decreases in proportion to the increase in the patient’s age and to the decrease in the perception of facial esthetics. It was also concluded that with just 5 mm deviation of the chin from the midline, there is already a perception by any observer that there is facial asymmetry.

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In 1996, was presented a series of patients with CH diagnosed using clinical and radiographic studies (without SPECT or CT analysis) [31]; the patients were treated with unilateral mandibular osteotomy (the affected side), performing a mandibular rotation at the expense of the healthy condyle.  The Management of Condylar Hyperplasia Essay.This technique was complemented in some cases with a LeFort I osteotomy. In the event of inadequate follow-up, the main doubt in these patients lies in the stability of the condyle with CH and in the fact that the rotation towards the medial side of the “healthy” condyle can be altered and involved in its movement, since the disc and muscular insertions might present a change in its orientation, which could generate functional deficiencies in the TMJ and limited postoperative stability of the executed movement.

Another treatment option was presented by Choung & Nam [32], who reported a series of 4 patients with CH, where a vertical and sagittal intraoral osteotomy of the ramus was performed, enabling the complete extraction of the condylar segment and the remodeling of condyle with drills. This was then re-installed in the articular fossa and stabilized with osteosynthesis plates. According to the authors, in a follow-up of 3 years, no accentuated resorption of the condyle or any type of necrosis was observed, with total functionality.

The group of patients of Villanueva-Alcojol [2] presented a mean age of 22.7 years with a range between 11 and 42. In all the patients a high condylectomy was performed (4 mm to 5 mm from the upper pole of the condyle) (Figure 4) and in only 6 of these was performed a second procedure with orthognatic surgery to correct the resulting facial defect. The 5 mm resection of the upper pole of the condyle limits the progressive growth that CH presents [23,33]. The Management of Condylar Hyperplasia Essay.