Condylar Hyperplasia of the Mandible: Diagnosis and Treatment

Diagnosis and treatment

Background: Condylar hyperplasia of the mandible is characterized by abnormal size and configuration of the condylar process. In Germany, the administrative prevalence of diagnosed and/or treated condylar hyperplasia is 2.4–9.6 cases per 100 000 persons. Misdiagnosis is common and can lead to severe esthetic and functional complications, including facial deformity that can progress into the patient’s twenties, as well as dysfunctional speech and mastication.

Methods: We conducted a systematic review of the literature and a structured consensus-finding process with the Delphi method.

Results: The experts recommend timely diagnosis of condylar hyperplasia so that its progression can be prevented by appropriate treatment. The basic diagnostic evaluation consists of history taking, physical examination, and imaging with orthopantomography. If condylar hyperplasia is confirmed, three-dimensional imaging is performed, usually with SPECT. The treatment is mainly surgical: partial condylectomy techniques and orthognathic surgery are the most common methods. If left untreated, the disorder causes severe dysfunction of mastication as well as disfigurement. Most studies of treatments for condylar hyperplasia have been based on low case numbers and have yielded only level 4 or level 5 evidence.

Conclusion: Condylar hyperplasia is a common, but not widely known problem. Its early diagnosis and treatment can prevent severe jaw asymmetry and further complications such as craniomandibular dysfunction and arthrosis of the temporomandibular joints.

Cite this as:

Riechmann M, Gellrich NC, Kress B, Schmidt C, Schröder C, Neff A: Clinical practice guideline: Condylar hyperplasia of the mandible—diagnosis and treatment. Dtsch Arztebl Int 2024; 121: 816–23. DOI: 10.3238/arztebl.m2024.0210

Condylar hyperplasia of the mandible most commonly affects young adults (1, 2). It involves an as yet unexplained autonomous activation of the condylar growth area in the region of the condylar process.

Since the cause of the excessive growth is still unknown, it is not possible to predict when growth will cease. Left untreated, it leads to progressive facial asymmetry, malocclusion, temporomandibular joint (TMJ) pain, and disturbance of TMJ function when speaking and chewing (3). During the growth phase, asymmetric mandibular growth can be compensated for on the whole by alveolar growth of the maxilla, resulting in greater or lesser degrees of asymmetry. However, if condylar growth has not stopped by the end of puberty, abnormalities of occlusion will develop and require subsequent mandatory treatment. Ultimately, all cases run a self-limiting course, although their timing is not predictable. The untreated course has not yet been scientifically followed-up and published over the long term.

Early diagnosis and treatment are crucial in order to avoid progressive facial deformities and more complex surgery to achieve a good esthetic outcome (4). This is all the more important given that prognostic factors based on available data to date are still unknown. Late surgery requires greater surgical time and effort and is therefore associated with significantly higher risks. An early operation avoids the problem of asymmetry from developing in the first place and can sometimes even be compensated for spontaneously (this applies to its development during puberty). If craniomandibular dysfunction develops as a result of the asymmetry, then prognosis will worsen; unfortunately, comparative data on this are not available to date.

Early detection forms the basis of patient care and is achieved in a general medical or pediatric setting. The patients are then managed in multidisciplinary centers for TMJ surgery with the involvement of orthodontics/dentistry, oral and maxillofacial surgery, radiology, and physiotherapy.

Data on the prevalence of condylar hyperplasia are sparsely available in the literature and can only be derived indirectly. According to the German Federal Statistics Office and the Central Research Institute of Ambulatory Health Care in Germany, around 36 800 cases were recorded annually during the period 2019 to 2022 under the ICD code K10.8, which, apart from condylar hyperplasia, also includes patients with condylar hypoplasia, cherubism (an autosomal dominant condition with enlargement of the mandible and maxilla), oral exostoses, and fibrous dysplasia. Since the prevalence of condylar hyperplasia in patients with facial asymmetry (Q67.0, around 7850 each year) is reported in the literature (5, 6) to be 30 to 50%, this is equivalent to a calculated theoretical (eTable 1) case number of between 2000 and 4000 patients each year (6, 7).

eTable 1

Synoptic table of ICD-10 coding for the specific codes “Other specified diseases of jaws” (incl. condylar hyperplasia) (K10.8) and “Facial asymmetry” (Q67.0) and the subsuming codes “Major anomalies of jaw size” (K07.0), “Temporomandibular joint disorders” (K07.6), and “Other congenital deformities of skull, face and jaw” (Q67.4)

Based on the coding applied to outpatient and inpatient cases, a rough estimate of 2000 to 8000 patients per 83 000 000 population per year can be made. In summary, therefore, the administrative prevalence of at least diagnostically and/or therapeutically relevant condylar hyperplasia or its sequelae can be estimated at 2.4 to 9.6 cases per 100 000 population. We must assume an unknown number of cases going unreported since, in addition to undiagnosed cases, symptomatic condylar hyperplasia is also subsumed under the ICD codes K07.0 (Major anomalies of jaw size, including hyperplasia and hypoplasia of the jaw), K07.6 (Temporomandibular joint disorders), and Q67.4 (Other congenital deformities of the skull, face, and jaw) (eTable 1).

Although recent studies are available on the pathogenesis of condylar hyperplasia, the exact cause leading to the disturbance of condylar growth remains unknown to the present day (7, 8, 9, 10, 11, 12). Over the past few years, there has been increasing interest in research in the field of condylar hyperplasia, for example, with regard to diagnostic procedures using low-dose radiation (13). However, there is no consensus in the current literature with regard to classification, diagnosis, and the time and choice of treatment. Furthermore, the limited number of study results are based on publications with a predominantly low level of evidence and therefore carry a high risk of systematic bias (2, 14). This underlines the importance of presenting a standardized literature-based approach to condylar hyperplasia as part of the guideline update.

Methods

We conducted a systematic search of the literature, including updates, in four international databases for all types of studies on condylar hyperplasia (eBox 1). A total of 257 sources were identified (Figure 1).

Figure 1

Overview of systematic literature search for the search period 05/2015 to 09/2023; at this time, there were already 88 sources available from the previous guideline.

eBox 1

Methods

The evaluation of literature evidence was oriented on the Oxford criteria of 2011 (eTable 2, Figure 3). The methodological quality up to evidence level 3 was assessed using the SIGN check lists (SIGN, Scottish Intercollegiate Guidelines Network) (eTable 3). In order to assess evidence levels 4 and 5, an additional examination of clinical relevance was conducted (eTable 3).

• Level of evidence: 1–5
• SIGN check list: ++, +, -
• Clinical relevance: k++, k+, k-

Figure 3

Imaging studies of the patient in Figure 2: A total of four surgical procedures were performed to correct the condition

See eBox 1 for details of consensus building. The levels of recommendation and consensus strengths (eTable 4) are classified as follows:

• Level of recommendation: A: strong recommendation, B: recommendation, C: open recommendation
• Consensus strength: strong consensus (↑↑), consensus (↑)

After approval by the governing boards of the participating professional societies (eTable 5), the S3 guideline update was published by the Association of the Scientific Medical Societies (AWMF) on November 10, 2023 with its 28 recommendations and five statements.

eTable 5

Participating professional societies and organizations as of 2023

The most important results are presented below. Level of recommendation, consensus strength, and level of evidence are stated for the respective recommendations and consensus strength and levels of evidence for the statements.

See the guideline report of the AWMF S3 Guideline “Condylar hypoplasia and hyperplasia” as well as eBox 1 for further details on methodology.

Clinical presentation and indications for treatment

Condylar hyperplasia of the mandible is characterized by abnormal size and configuration of the condylar process, which develops spontaneously and progressively during puberty or adulthood (usually up to the age of 27 years) and is caused by an autonomic activation of the growth area. Condylar hyperplasia is usually a unilateral (2, 15, 16) and self-limiting (1, 3, 15, 17, 18) process. It presents clinically with (progressive) facial deformity, (progressive) abnormalities of occlusion, functional impairment of TMJ function (speaking, chewing), TMJ noises and pain, and craniomandibular dysfunction (CMD) (1, 2, 3, 15). The main reason for treating condylar hyperplasia is facial asymmetry (15, 17) (Figure 2). In around one third of cases, however, facial asymmetry goes unnoticed by those affected; primary symptoms are pain and TMJ dysfunction (1, 15, 19), which can also develop in the contralateral joint (14, 15). Examination for the presence of facial asymmetry should be conducted in patients with symptoms of a TMJ disorder to identify any signs of disorders of condylar growth (A, ↑↑, 4/k+). Depending on the stage in which condylar hyperplasia is diagnosed, therapeutic objectives include either preventing progression of the disorder (20, 21, 22) or restoration of normal occlusion and articulation (18), improvement of mandibular mobility (21) and function (22) as well as correction of facial deformities with their associated functional and esthetic impairments (18, 22).

Figure 2

Case example of seemingly only discrete facial asymmetry in a patient with condylar hyperplasia on the right side of the face (a). The extent of the asymmetry becomes clear on intraoral inspection (b) revealing the oblique occlusal plane. The teeth of the right upper jaw are elongated to compensate; note the caudal position of the mandibular basal arch on the right, which will require complex corrective measures.

Mandibular hyperplasia, facial syndromes, and benign and malignant neoplasms must be distinguished from condylar hyperplasia in the differential diagnosis (14, 18).

Diagnosis

The diagnosis of condylar hyperplasia should be established early in order to prevent progression of the disorder and to recognize in time its effects on facial growth (B, ↑↑, 4/k++). Apart from the history and clinical examination (inspection, palpation, assessing occlusion), basic diagnostics for suspected condylar hyperplasia should also include imaging studies in the form of an orthopantomogram (OPG, panoramic view of the jaw, Figure 3), which can be supplemented by nuclear medicine examinations if required (A, ↑↑, 4/k++). The OPG serves as a screening examination. Three-dimensional imaging using computed tomography (CT) or digital volume tomography (DVT) should be considered for more exact analysis, classification, and clinical monitoring (B, ↑, 4/k++). In Europe, nuclear medicine procedures (usually single-photon emission computed tomography, SPECT) are the modalities of choice for detecting growth activity in condylar hyperplasia, even though scintigraphy is not yet established internationally as generally recognized diagnostic best practice (2, 23, 24). With this in mind, the German S3 guideline issued a grade B recommendation for SPECT bone scanning to determine the activity level of condylar hyperplasia (B, ↑↑, 4/k++). A comparison between the two condyles and measurement of an external control (for example, the healthy condyle of a healthy person) are recommended for quantitative evaluation of SPECT scans for unilateral condylar hyperplasia (2, 6, 23, 25). Condylar uptake of at least 55% or a difference of at least 10% between both sides is interpreted as a sign of active unilateral condylar hyperplasia. Values between 5% and 10% are an indication of possible condylar hyperplasia (1, 2, 5, 6, 16, 26, 27, 28). The result of the diagnostic assessment determines to a large extent the further course of action, although there is no uniform consensus on this in the international literature. The guideline group recommends that in the first instance monitoring of disease progression be conducted when the SPECT result is borderline (i.e., around the cut-off level, defined as uptake of at least 55% or a difference between the condylar values of at least 10%) and unremarkable clinical findings (B, ↑↑, 4/k+).

Treatment

Of the 257 identified literature sources, around 200 refer to treatment, of which the majority correspond to the evidence class 4 (eBox 1). The choice of therapeutic procedure should therefore be decided on an individual basis. Once diagnosed, the treatment approach for condylar hyperplasia is based on the activity of condylar growth, progression of asymmetries, the degree of facial deformity and malocclusion, age, and other symptoms (2, 14, 26). Conflicting results between scintigraphic examination and clinical progression of asymmetry present a particular problem here.

Conservative treatment methods

Conservative treatment options include both dental prosthetic solutions (29) as well as orthodontic and functional therapeutic measures (for example, occlusal splints) (2, 14, 18). Since no randomized controlled studies dealing with the assessment of conservative approaches for treating condylar hyperplasia are available, the guideline group expresses the open recommendation that conservative measures may be a treatment alternative for inactive condylar hyperplasia, especially for deformities and malocclusions of a lesser degree (0, ↑↑, 4/k++).

Surgical treatment

Surgical treatment of condylar hyperplasia includes various forms of condylar surgery (high/proportional/low condylectomy) and orthognathic surgery.

There is no exact definition for the term “high condylectomy” for treating condylar hyperplasia. In the literature, this is usually understood to mean resection of the joint surface by 3 to 5 mm or less than 5 mm including the growth region (30, 31). Resection of up to 3 mm is also referred to as “condylar shaving” (30, 31).

With proportional condylectomy, the degree of resection corresponds to the height difference between the affected and contralateral (“healthy”) condyle, so the height of reduction is determined individually, and it is not a matter of standardized values (27, 32).

There is some controversy concerning the choice of condylectomy procedure. Whereas high condylectomy was for a long time considered the standard procedure for treating active condylar hyperplasia, proportional condylectomy has more recently been increasingly discussed as an alternative, while deep condylectomy is now reserved for individual cases (27). With regard to recurrence prophylaxis, removal of at least 5 mm potentially offers more reliability than condylar shaving (30). However, a thicker ablation layer may produce postoperative occlusion disorders (26, 27, 30). Some authors, on the other hand, recommend high condylectomy as the procedure of choice due to its lower complication rate, satisfactory esthetic results, and cessation of the condition after surgery (20, 22, 32, 33). Another aspect under discussion is whether proportional condylectomy significantly reduces the need for secondary orthognathic surgery in comparison with high condylectomy (34, 35). Yet, following this line of thought, other authors recommend proportional condylectomy as the optimal therapeutic procedure (35) (Table).

Table

Evidence table of the principal studies on the treatment of mandibular condylar hyperplasia

Given the conflicting study results and expert opinions and at the same time small numbers of patients involved in studies, no evidence-based recommendation has so far been offered to help decide between high and proportional condylectomy as the surgical procedure of choice for condylar hyperplasia (↑↑, EC [expert consensus]).

A further point of discussion in the international literature is the question of whether supplementary procedures in the form of articular disc repositioning, possibly together with discopexy, should be regularly performed in addition to condylectomy. Following detailed and controversial discussion within the guideline group, the decision statement was released that an intervention in the form of routine articular disc repositioning and discopexy for both asymptomatic and symptomatic internal derangement (disc dysfunction) is not usually necessary (↑↑, 1+).

An established surgical procedure as a supplement to condylectomy is orthognathic surgery to correct malocclusion while at the same time improving facial deformities (Figure 4). Both single-stage (18, 20, 22, 33) and two-stage procedures (2, 27, 32) are available for this. So, an orthognathic surgical repositioning operation may be indicated to correct the resulting malocclusion and deformities after high or proportional condylectomy (0, ↑↑, 4/k++). Given the conflicting results and small case figures presented in various studies, no evidence-based recommendation has been provided so far on the optimum time point for orthognathic surgery after condylectomy (↑↑, EC).

Figure 4

a) corrected occlusal plane after surgery; b) restored bony facial asymmetry after surgery

Orthognathic surgery is also a treatment option as the sole surgical procedure during the inactive phase (17, 22). See eBox 2 for possible complications arising from surgical treatment.

eBox 2

Sick leave and complications associated with surgical treatment for condylar hyperplasia

Operative approach for active condylar hyperplasia

Active condylar hyperplasia is present when the SPECT scan is positive and associated with clinically progressive asymmetry (22, 27). The guideline group recommends high condylectomy with removal of the condylar growth region for patients with active condylar hyperplasia and less marked asymmetry to arrest excessive condylar growth and its associated progressive symptoms (B, ↑↑, 4/k++). On the other hand, the indication for proportional condylectomy should be considered for patients with active condylar hyperplasia and clinically increased condylar growth activity and strongly marked asymmetry (B, ↑↑, 5/k++).

Alternatively, in cases of (less marked) active condylar hyperplasia, the end of progression may be awaited before undertaking any necessary or desired correction of deformities and malocclusion (0, ↑↑, 4/k++). With this expectant approach, however, neither the duration of the excessive growth phase nor the ultimate degree of deformity and change in symmetry are predictable. It is therefore possible that the final conditions for correction will be less favorable than after early growth stop.

Due to the poor epidemiological availability of data, no evidence-based recommendation can be given at present for the optimal time point of therapy for condylar hyperplasia. Disease activity must therefore be assessed and treatment determined on an individual basis.

Operative approach for inactive condylar hyperplasia

Abnormal condylar growth is considered to have ceased and condylar hyperplasia to be inactive once the SPECT scan is negative and there is no further progression of asymmetry. If it is not possible to clearly determine the activity level of condylar hyperplasia using appropriate diagnostic examinations, for example, because of conflicting or borderline clinical and nuclear medical findings, then further follow-up diagnostics should be performed before reaching any indication for surgery (B, ↑↑, 4/k+).

On the whole, recommendations in the literature for the treatment of inactive condylar hyperplasia are not uniform. The guideline group recommends that with inactive condylar hyperplasia the indication for orthodontic-surgical treatment to correct malocclusion and deformities should be carefully assessed (B, ↑↑, 4/k++).

Summary and outlook

Condylar hyperplasia is one of the most common causes of facial asymmetry, yet it is often not diagnosed correctly. Early diagnosis and treatment can avoid severe disease and secondary damage. This guideline update has contributed towards standardizing patient care and avoiding complications based on the best possible evidence.

Despite increased interest in research over recent years, further studies would be desirable, for example, in order to determine the optimum time point for treating condylar hyperplasia or for conducting orthognathic surgery after high condylectomy.

Acknowledgments

We would like to thank Univ.-Prof. Dr. Dr. Johannes Kleinheinz, Univ.-Prof. Dr. Dr. Andreas Kolk, Prof. Dr. Dr. Pautke, Dr. Dr. Andreas Schön, Dr. Dr. Marcus Teschke, and Dr. Dr. Astrid Toferer for supporting the guideline work. We also thank Dr. Dr. Axel Meisgeier for his support with image material.

Conflict of interest statement
NCG is involved in the surgical treatment of patients with condylar hyperplasia.

BK was appointed by the German Society of Neuroradiology (DGNR) and the German Radiology Society (DRG) to prepare the guideline.

AN has received lecture fees and third-party research funding from the Karl Storz company. He is a member of the European Society of Temporomandibular Joint Surgeons, Osteosynthesis Research Group, and the International Bone Research Group. He is involved in the surgical treatment of patients with condylar hyperplasia.

The other authors declare that no conflict of interest exists.

Manuscript received on 10 April 2024, revised version accepted on 30 September 2024.

Translated from the original German by Dr Grahame Larkin.

As with many other professional journals, clinical guidelines in the German Medical Journal Deutsches Ärzteblatt are not subject to the peer review process, as S3 guidelines are already texts that have been assessed and discussed by experts (peers) and have a broad consensus.

Corresponding author:
Univ.-Prof. Dr. med. Dr. med. dent. Andreas Neff

Klinik und Poliklinik für Mund-, Kiefer und

plastische Gesichtschirurgie

UKGM GmbH, Universitätsklinikum Marburg

Baldingerstraße

35043 Marburg

Cite this as:
Riechmann M, Gellrich NC, Kress B, Schmidt C, Schröder C, Neff A: Clinical practice guideline: Condylar hyperplasia of the mandible—diagnosis and treatment. Dtsch Arztebl Int 2024; 121: 816–23. DOI: 10.3238/arztebl.m2024.0210

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