Introduction
Our aim was to describe 3-dimensional condylar deformation of the temporomandibular joint (TMJ) and symptoms and signs of temporomandibular dysfunction (TMD) in patients with idiopathic condylar resorption (ICR).
Methods
We included 25 patients with ICR and 25 controls. We performed cone-beam computed tomographic scans and analyzed condylar width, length, and height as well as the condylar axial angle and the condylar neck angle. TMJ cross sections were evaluated for degenerative characteristics and location of bony deformations. Furthermore, symptoms and signs of TMD were described in the ICR group.
Results
In the ICR group, we found statistically significantly reduced condylar width (mean difference, 2.0 mm), height (mean difference, 4.9 mm), and condylar axial angle (mean difference, 10.6°); 84% of the TMJs had a posterior condylar neck angle (control group, 22%). The most common degenerative changes were noncongruent shape of the condyle-fossa relationship (72%), condylar resorption (56%), and nonintact cortex (40%). More than 70% of the joints with bony deformations showed changes along the entire condylar head. Most patients with ICR showed symptoms and signs of TMD; nevertheless, 12% had no signs or symptoms of TMD.
Conclusions
ICR in the TMJ changes the shape and reduces the size of the condyle. Deformity locations are unspecified, and the entire condyle is often affected. Most patients with ICR have signs or symptoms of TMD; however, a small group was asymptomatic and without clinical signs.
Highlights
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Idiopathic condylar resorption (ICR) changes the size and shape of the condyle.
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The localization is unspecified, and often the entire condyle is affected.
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Most patients will have nonspecific symptoms or signs of TMD, but some are asymptomatic.
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Epidemiologic and radiographic parameters to diagnose ICR are presented.
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Distinct clinical diagnostic criteria for ICR were not found.
Idiopathic condylar resorption (ICR) is a pathologic condition of unknown origin that affects the temporomandibular joint (TMJ). It is characterized by bony deformation of the mandibular condyles causing loss of condylar volume and mass. Maxillofacial morphologic changes comprise sagittal and posterior vertical deficiency of the lower facial third, most likely causing decreased ramus height and reduced mandibular length combined with posterior mandibular rotational growth bringing about a retrognathic profile and an open bite. In a growing patient, condylar growth may be affected, leading to a change in mandibular morphology.
The etiology of ICR is unknown but is often classified as severe forms of degenerative joint disease, osteoarthritis, osteoarthrosis, and arthrosis deformans or dysfunctional remodeling. Several studies on condylar resorption have used the terms progressive condylar resorption, aggressive condylar resorption, and condylysis. However, these studies often included patients who developed condylar resorptions after maxillofacial surgery; therefore, these patients did not have ICR. Other less commonly used names include avascular necrosis, osteonecrosis, condylar atrophy, and condylar osteolysis.
ICR is commonly classified under low-inflammatory arthritic disorders and is considered to be a severe form of osteoarthritis. The group of low-inflammatory arthritic disorders (noninflammatory arthritic disorders) also comprises osteoarthritis, arthrosis, and degenerative joint disease. The group of high-inflammatory arthritic disorders (inflammatory arthritic disorders) includes rheumatoid arthritis, juvenile idiopathic arthritis, and other arthritic conditions that affect the TMJ with a similar clinical picture. Others classify ICR in a TMJ category of its own to stress its idiopathic etiology.
ICR occurs more frequently in females than in males; according to Wolford, the female-to-male ratio is 9:1. Since ICR frequently affects adolescent girls, it has been coined the “cheerleaders’ syndrome.”
The symptoms of temporomandibular dysfunction (TMD) may be severe, mild, or nonexistent; 25% of patients with ICR have no symptoms of TMD. Handelman and Greene observed that a high percentage of ICR patients reported pain or another symptom of TMD. However, no data were presented to support either of these clinical observations.
The aims of this article were to describe the condylar morphologic changes and localization of these changes in a group of ICR patients and to describe symptoms and signs of TMD and mandibular function.
Materials and methods
The ICR group comprised 25 patients from the Section of Orthodontics, Faculty of Health Sciences, Aarhus University, and the Department of Oral and Maxillofacial Surgery, Aarhus University Hospital, in Denmark. They had been referred for diagnosis or treatment of malocclusions, skeletal deviations, or TMD, and were included in this study if they appeared to have changes of the mandibular condyle evaluated on cone-beam computed tomography (CBCT). The patients were included from November 2005 to January 2014. Those with any of the following characteristics were excluded: (1) history of arthritis, immune disease, or systemic disease confirmed by a rheumatologist, or patients under investigation for such diseases; (2) congenital syndrome; (3) craniofacial trauma; and (4) previous orthognathic surgery.
The control group included age- and sex-matched patients enrolled for general orthodontic treatment at the Section of Orthodontics, Faculty of Health Sciences, Aarhus University. Only patients who had a full-face CBCT image in their diagnostic records were included. Excluded were patients with (1) history of orofacial pain or TMD; (2) history of arthritis, immune disease, or systemic disease confirmed by a rheumatologist, or patients under investigation for these diseases; (3) congenital syndrome; (4) craniofacial trauma; and (5) previous orthognathic surgery.
Full ethical approval was obtained from the Danish Data Protection Agency (reference 1-16-02-36-15) and the Danish Health Authority (reference 3-3013-848/1); the study was conducted according to the Helsinki declaration.
A CBCT with a 12-in field of view was conducted in all patients (model 3G or 5G; NewTom, Verona, Italy). Radiographic material was obtained from the Section of Orthodontics of Aarhus University and from the Oral and Maxillofacial Department of Aarhus University Hospital. Primary scans and subsequent study reconstructions of volumetric data were performed according to the indications and standard protocol of the Section of Radiology of Aarhus University and Aarhus University Hospital, respectively. Secondary CBCT study reconstructions were made for each patient to conduct a radiologic assessment suitable for this study.
Three-dimensional reconstructions were processed and analyzed using the NewTom software NNT (version 4.6; Newtom). The reconstructions were standardized and reorientated in the frontal view to the upper orbital crest, and in the sagittal view according to the horizontal occlusal plane.
All landmarks and radiologic outcome variables were identified and verified in 3 planes of space. Table I presents defined landmarks and constructed lines and measurements.
| Landmarks and constructed points | Definition |
|---|---|
| Nasion, N | Most anterior point of the fronto-nasial suture, axial plane |
| Basion, B | Most posterior point of the occipital bone, anterior border of foramen magnum, axial plane |
| Lateral condylar point, LCo | Most lateral point of the condyle |
| Medial condylar point, MCo | Most medial point of the condyle |
| Anterior condylar point, ACo | Most anterior point of the condyle |
| Superior condylar point, SCo | Most superior point of the condyle |
| Posterior condylar point, PCo | Most posterior point of the condyle |
| Constructed lines | |
| Midsagittal reference line, NB | Line from N to B |
| Condylar axis, LCo-MCo | Line from LCo to MCo |
| Ramus tangent line, R-tan | Tangent to the posterior border of the ramus |
| Ramus tangent line perpendicular, R-tan-P | Line perpendicular to R-tan tanging the deepest point of the mandibular incisura |
| Radiologic outcome variables | |
| Condylar width | Distance from LCO to MCo |
| Condylar length | Distance from ACo to PCo |
| Condylar height | Distance from SCo perpendicular to R-tan-P |
| Condylar axial angle | Angle between LCo-MCo and N-B |
The radiologic outcome variables were analyzed as follows : (1) mandibular condyle width, length, and height ( Fig 1 ); (2) condylar axial angle ( Fig 2 ); and (3) condylar neck angle ( Fig 3 ). Width was defined as the distance from the lateral condylar point to the medial condylar point (LCo-MCo), length as the distance from the anterior condylar point to the posterior condylar point (ACo-PCo), and height as the distance from the superior condylar point (SCo) to the ramus tangent line perpendicular (R-tan-P). The condylar axial angle was the angle between the axial condylar line (lateral condylar point to medial condylar point [LCo-MCo]) and the midsagittal reference line (nasion-basion [N-B]). The condylar neck angle was divided into categorical data in posterior, normal, and anterior inclinations ( Fig 3 ).
Qualitative data from the TMJs were obtained by evaluating 2-dimensional cross sections for the presence or absence of the pathologic characteristics described by Hatcher ( Table II ). The radiologic assessment was conducted in a blinded fashion.
| Characteristic | Definition | Presence |
|---|---|---|
| Intact cortical border | Well-defined cortical border | +/− |
| Nonintact cortical border | Broken cortical border | +/− |
| Cavitation defect | A cup-shaped defect in the superior surface of the condyle | +/− |
| Flattening | Superior surface of the condyle is flatted | +/− |
| Resorption | Loss of condylar volume defined as the imaginary equator circumferential line being superiorly positioned | +/− |
| Congruency | Congruent shape of the articular surfaces | +/− |
The condylar characteristics were evaluated in both the sagittal and coronal planes to address the size and localization of the changes. In the sagittal plane, tomographic sections were made at a 90° angle to a line from the coronoid tip and to the anterior external auditor meatus. The condylar head was assessed for structural changes after dividing it into thirds: anterior, superior, and posterior. Likewise, cross sections in the coronal plane were done in a 90° angle to the condylar width line, and the tomographic sections were evaluated after dividing the condylar head into medial, middle, and lateral thirds.
Patients were described by age at CBCT, sex, and number of TMJs involved (unilateral or bilateral).
Symptoms, clinical signs of TMD, and mandibular function were obtained from the patients’ clinical records (≤6 months before or after CBCT) to evaluate the relationship between ICR and clinical signs of TMD.
The self-reported outcome measures were (1) TMJ: history of locking, clicking, crepitation, or combined; (2) orofacial pain: TMJ pain constant (yes/no), TMJ pain on opening (yes/no), or muscular pain (yes/no); and (3) TMJ function: reduced mouth-opening capacity (yes/no).
The objective outcome measures were (1) sounds: clicking, crepitation, or combined; (2) orofacial pain: TMJ pain on palpation (yes/no), or muscular pain on palpation (yes/no); and (3) TMJ function: maximal incisor opening (adjusting for overbite).
Statistical analysis
To measure intraexaminer reliability, duplicate measurements were done in 10 patients with 20 TMJs at a minimum 2-week interval. The smallest detectable difference (mean difference ± 2 standard deviations) was calculated for all linear data. Continuous data were evaluated using a Bland-Altman plot. The nominal data were evaluated using kappa statistics.
The normal distribution of the data was assessed graphically by Q-Q plots. The unpaired Student t test was used for all continuous data, and the Fisher exact test was used for nominal data.
Results
The ICR group comprised 25 patients (22 female, 3 male) with a mean age of 15 years 6 months (range, 5-24 years). Eighteen patients had bilateral TMJ involvement, and 7 patients had unilateral TMJ involvement. The control group was age and sex matched and comprised 25 patients (22 female, 3 male) with a mean age of 15 years 3 months (range, 11-25 years).
We measured condylar width, length, and height and found a significant 2.0 mm (95% confidence interval [CI], –2.9, –1.0 mm) intergroup difference in condylar width, a nonsignificant 0.6 mm (95% CI, –1.2, 0.1 mm) intergroup difference in condylar length, and a significant 4.9 mm (95% CI, –6.4, –3.5 mm) intergroup difference in condylar height ( Table III ). Intergroup differences in condylar width and height both exceeded the smallest detectable limit for the variables in question ( Table S1 ).
| n = 50 for each group | Mean (mm) | SD (mm) | 95% CI (mm) | P value |
|---|---|---|---|---|
| Condylar width | ||||
| ICR | 15.9 | 2.8 | 15.1, 16.7 | |
| Control | 17.9 | 1.8 | 17.4, 18.4 | |
| Difference | 2.0 | −2.9, −1.0 | <0.001 | |
| Condylar length | ||||
| ICR | 8.1 | 2.1 | 7.5, 8.7 | |
| Control | 8.7 | 1.1 | 8.4, 9.0 | |
| Difference | 0.6 | −1.2, 0.1 | NS | |
| Condylar height | ||||
| ICR | 14.8 | 4.5 | 13.5, 16.0 | |
| Control | 19.7 | 2.4 | 19.0, 20.4 | |
| Difference | 4.9 | −6.4, –3.5 | <0.000 | |
| Condylar axial angle | ||||
| ICR | 54.2 | 10.9 | −51.1, 57.2 | |
| Control | 64.6 | 6.7 | −62.9, 66.7 | |
| Difference | 10.6 | −14.1, −7.0 | <0.0000 | |
A statistically significant intergroup difference of the condylar axial angle of 10.6° was observed ( Table III ). This outcome was statistically significant and clearly exceeded the smallest detectable limit for this specific outcome variable (95% CI, –5.6°, 4.7°; Table S1 ).
A statistically significant difference in distribution of the condylar neck angle was found between the 2 groups; posterior inclination was the most frequent finding in the ICR group, and anterior inclination the most frequent finding in the control group ( Table IV ).
| n = 50 in each group | Anterior | Parallel | Posterior | P value |
|---|---|---|---|---|
| ICR | 7 | 1 | 42 | |
| Control | 24 | 15 | 11 | <0.001 |
No other posttests were conducted to further describe significant differences in the condylar neck angles between the 2 groups. The risk of subanalysis bias is present in posttests because of the limited material size.
In the TMJ cross-section evaluation, significantly higher numbers of all characteristics of bony deformations were confirmed in the ICR group compared with the control group ( Table V ).
| n = 50 | ICR | Control | P value |
|---|---|---|---|
| Nonintact cortex | 40% | 0% | <0.001 |
| Cavitation | 22% | 0% | <0.001 |
| Flattening | 22% | 2% | <0.005 |
| Resorption | 56% | 0% | <0.001 |
| Noncongruency | 72% | 0% | <0.001 |
For each of the condylar thirds in the sagittal plane, the bony deformations in the ICR group were significantly different from those of the controls ( Table VI ). In the sagittal plane, the superior part of the condyle was involved in all joints where bony deformations were found in the ICR group. The anterior part was involved in 95% and the posterior part in 81% of the joints. The entire condyle was most often involved sagittally, anteriorly, superiorly, and posteriorly (77%). The combination of the anterosuperior parts of the condyle was less frequent (18%), and the combination of the posterior and superior parts of the condyle was observed only rarely (5%).
| n = 50 | ICR | Control | P value |
|---|---|---|---|
| Sagittal | |||
| Anterior (+) | 82% | 2% | <0.0001 |
| Superior (+) | 86% | 2% | <0.0001 |
| Posterior (+) | 70% | 0% | <0.0001 |
| Coronal | |||
| Lateral (+) | 80% | 2% | <0.0001 |
| Middle (+) | 86% | 0% | <0.0001 |
| Medial (+) | 62% | 0% | <0.0001 |
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