The influence of mandibular condyle morphology on TMJ anterior dislocations

Temporomandibular Joint Space in Mandibular Prognathism

This study compared the temporomandibular joint (TMJ) space between patients with normal and prognathic mandibles. The study included a total of 68 Korean individuals, and the TMJ space was measured using computed tomography. Patients with normal SNB values (normal mandible) were classified into Group 1. Patients with high SNB values (prognathic mandibles) were categorized into Group 2. The TMJ space was defined as the distance between the condylar process and the mandibular fossa, and it was significantly different between Groups 1 and 2 (1.94±0.07 mm versus 1.50±0.05 mm, P< 0.01). This study confirmed that the TMJ space in patients with prognathic mandibles is narrower than that in patients with normal mandibles.

Increased Prevalence of Generalized Joint Hypermobility Observed in Patients With Recurrent Temporomandibular Joint Dislocation

BACKGROUND

Generalized joint hypermobility (GJH), determined by the Beighton score, is a fundamental part of diagnosing benign joint hypermobility syndrome (BJHS), which may also present extra-articular manifestations, and is determined by the Brighton criteria.

PURPOSE

This study was designed to investigate whether there is an association between recurrent temporomandibular joint (TMJ) dislocation and these disorders.

STUDY DESIGN, SETTING, AND SAMPLE

A retrospective cross-sectional study was conducted. Hospital-based patients with a history of recurrent TMJ dislocation were compared to population-based patients that did not experience TMJ dislocations or any other TMJ disorders. Age and sex matching were performed between the study groups. All subjects reached the age of skeletal maturity.

PREDICTOR VARIABLE

A history of recurrent TMJ dislocations.

MAIN OUTCOME VARIABLES

Measurements of Beighton score (range from 0 to 9 with a score of ≥ 4 indicating GJH) and correspondence to the Brighton criteria (with at least two "major" criteria or one "major" criterion plus two "minor" criteria or four "minor" criteria indicating BJHS).

COVARIATES

Included age and sex.

ANALYSES

Mann-Whitney U-test for continuous variables and the χ² test or Fisher's exact test for categorical variables. Statistical significance was set at P < .05.

RESULTS

A total of 68 participants were included, of whom 34 patients presented with recurrent TMJ dislocations compared with a control population of 34. The Mean participants were 31.35 ± 8.06 years, and 29.4% (n = 20) were males. Of the dislocation group, 16 (47.0%) patients had a Beighton score of 4 or higher. The Beighton sum score was significantly higher, with a TMJ dislocation group mean score of 3.06 ± 2.8, compared with a control score of 0.82 ± 1.1 (P = .001). A total of 58.8% (n = 20) of the TMJ dislocation group participants met the Brighton criteria versus none (0.0%) of the control group (P = .001).

CONCLUSION

We found an association between recurrent TMJ dislocation and GJH. An association with BJHS was also found, based mainly on articular manifestations. Early detection of these disorders in patients suffering from recurrent TMJ dislocation may help identify individuals at increased risk for joint instabilities and allow the implementation of appropriate preventive management strategies.

Evaluation of congruency of condyle convexity and fossa concavity and interrelationship bony components in temporomandibular joint anterior dislocation

OBJECTIVES

This study aimed to compare the congruency of surface geometry of the articulating bones and morphologic differences in temporomandibular joint (TMJ) structure, between patients with TMJ anterior dislocation and healthy controls.

METHODS

The study included 15 patients with TMJ anterior dislocation and 15 controls who underwent cone-beam computed tomography. The surface angle of the articular fossa (fossa-concavity) and condyle (condyle-convexity) and joint spaces were measured from both sagittal and coronal views. The articular eminence morphology and horizontal condyle position were also evaluated.

RESULTS

Coronal fossa angles were significantly lower in controls than in patients (p < 0.05). There was a positive correlation between coronal condyle and fossa angle values in controls and in patients' joints (p < 0.05), however, the fossa-condylar congruence was higher in controls than in patients. Superior joint space was significantly higher in controls than in patients (p < 0.05). There were no significant differences in articular eminence measurements, mean condyle angle variables and condyle position between the patients and controls (p > 0.05).

CONCLUSIONS

The findings of this study which include lower joint congruency, higher fossa concavity and superior joint space distance in patients with anterior dislocation may be related to the inferior positioning of the condyle away from the fossa and potentially the elongation of the capsular ligament.