Osteoarthritis (OA) is a slow progressing degenerative disease that affects the joints, including the temporomandibular joint. In the present study, transforming growth factor-β1 (TGF-β1) and matrix metalloproteinase 3 (MMP-3) in synovial fluid (SF) were examined in detecting cartilage synthesis and degradation in progression of temporomandibular joint osteoarthritis (TMJ OA) combined with disc displacement (DD) diseases. SF was obtained from 16 patients with TMJ OA combined with DD and 10 normal volunteers. TGF-β1 and MMP-3 levels were measured by enzyme-linked immunosorbent assay. In addition, TMJ OA combined with DD was classified into three stages based on radiographic signs on the preoperative tomograms and surgical findings at operation, and different treatment options were administered according to the stages. SF from TMJs with TMJ OA combined with DD showed higher levels of TGF-β1 and MMP-3 compared with the asymptomatic control TMJs. With the progression of TMJ OA combined with DD, TGF-β1 levels in SF were lower, while MMP-3 levels in SF were significantly higher. In conclusion, these data suggest that MMP-3 is not only involved in the pathological destruction process of TMJ OA combined with DD initially, but also has a positive correlation with the degree of pathological changes. Furthermore, a significant increase of TGF-β1 levels was found in the SF that were able to counteract the deleterious effects of MMP-3 at the early stage of TMJ OA combined DD, providing the scientific basis on repositioning displaced disc as early as possible for these patients.

The purpose of this study was to evaluate the diagnostic accuracy of magnetic resonance imaging (MRI) for synovial chondromatosis (SC) of the temporomandibular joint (TMJ). In this study, 1415 patients (2109 joints) with temporomandibular joint disorders were collected between January 2012 and January 2017. All patients had a preoperative MRI examination and were treated by either arthroscopy or open surgery. On reviewing all MRI images, the number of “positive”, “suspicious”, and “negative” cases was collected afterwards, then the number of reported SC cases in operative data was recorded. The SPSS software was used to process all collected data. The kappa coefficient and ROC curve (AUC-index) with sensitivity and specificity were calculated to evaluate the consistency between MRI and arthroscopy/open surgery. Compared to 156 joints with SC detected by arthroscopy and open surgery, the results of MRI examination showed “positive” in 117 joints, and “negative” in 1938 joints. The number of “true positive”, and “true negative” cases was 95, and 1897 respectively. The AUC-index was 0.86 (0.82–0.90) with a kappa coefficient of 0.74 (P < 0.05). In conclusion, the incidence of synovial chondromatosis diagnosed on MRI was in accordance with the arthroscopic and open surgery. Therefore, being a relatively non-invasive tool, MRI could be recommended as an effective diagnostic modality for SC.

Myositis ossificans (MO) is a disease where heterotropic bone forms within a muscle or other type of soft tissue. MO is classified into two groups, MO progressiva and post‑traumatic MO. It rarely occurs in the masticatory muscles and thus, only 20 cases involving the masticatory muscles have been reported since 2001. The majority of the reported cases occurred due to trauma, repeated injury or surgical manipulation. However, in a small number of cases, no specific traumatic event was identified as the cause of MO. To the best of our knowledge, this is the first case of post‑infectious MO to be reported in the medial and lateral pterygoid muscles.