A Case of Synovial Chondromatosis in the Temporomandibular Joint Accompanied by Progressive Occlusal Changes

Abstract

Synovial chondromatosis (SC) is an uncommon progressive cartilaginous metaplasia of residual mesenchymal cells in synovial tissue. This disorder usually affects large joints and is rarely observed in the temporomandibular joint (TMJ). SC in TMJ is difficult to diagnose early owing to non-specific clinical symptoms. In this article, we report a patient with SC on the right TMJ, who presented with pain in the right TMJ and progressive occlusal changes, not responsive to conventional conservative temporomandibular disorder treatment for several months. This case emphasizes the importance of an accurate specific diagnosis for TMJ problems before the delivery of any treatment.

INTRODUCTION

Synovial chondromatosis (SC) is an uncommon, generally benign metaplastic condition characterized by the formation of cartilaginous nodules [1]. It is mainly found in large joints, such as the hip, knee, and shoulder. However, it very rarely affects the temporomandibular joint (TMJ), as understood from more than 200 cases that have been reported since Axhausen first reported in 1933 [2,3].

The pathology and the etiology of SC still remain unclear. However, some authors have reported a possible relationship with past trauma history [1]. Therefore, SC was commonly classified into the primary and secondary forms according to its cause. While primary SC has no obvious etiological factors, secondary SC is associated with obvious causes including internal derangement, inflammatory joint disease, repetitive microtrauma, and past trauma [4].

It is characterized mainly by non-specific clinical signs and symptoms, namely arthralgia, preauricular swelling, mouth opening limitation, joint noise and progressive occlusal change, which makes it challenging to achieve an accurate diagnosis [4,5]. Especially, occlusal change presented with progressive accumulation of loose bodies and a subsequent displacement of condyle [6].

In this case report, we describe a patient with SC in the right TMJ, who presented with limited mouth opening and progressive occlusal change.

CASE REPORT

A 54-year-old female visited the Department of Oral Medicine, Kyungpook National University Hospital, with the chief complaints of pain in her right TMJ and mouth opening limitation. Especially, she presented with such a progressive occlusal alteration that she had experienced difficulty in chewing food on the right side. She described that she had to position her mandible toward the right side in order to occlude her right posterior teeth. Her past history revealed that her pain and discomfort started 3-4 years ago without any known cause and gradually worsened despite of conservative treatments including physiotherapy, medication, and occlusal splint therapy, administered at a local dental clinic, based on the clinical impression of internal derangement in her right TMJ. Moreover, she described a slight swelling on the right preauricular area (Fig. 1). Pain severity fluctuated during the day, but her pain score on a 100-mm visual analogue scale was usually around 30. Despite investigating her history thoroughly, no specific medical and dental history that could be linked with onset and progression of her symptoms was noted.

Fig. 1. Right preauricular swelling in the patient (arrowheads).

Clinical examination revealed slight disocclusion of the right posterior teeth with premature contact, when determined using shimstock occlusion foils (Fig. 2). It was also observed that the mandibular midline was slightly shifted toward the left. The maximum mouth opening range was 34 mm with deflection to the right side, as measured between maxillary and mandibular incisors. She reported tenderness on digital palpation in the right TMJ. However, no joint noise was detected on the right TMJ. Conventional radiograph views including the panoramic and TMJ panoramic views did not demonstrate any significant pathological bony changes on her right TMJ (Fig. 3). Therefore, for further evaluation, magnetic resonance imaging (MRI) was performed after careful consultation with her. MRI revealed that there were multiple small loose bodies within the articular cavity of the right TMJ, which present with a distinct dark signal. In addition, excessive joint effusion was also found in the right TMJ, which was sufficiently bulging to displace the right condyle anterior-inferiorly within the mandibular fossa. However, the discal position and the condylar shape were evaluated to be normal (Fig. 4).

Fig. 2. Photographs showing pretreatment occlusion: (A) right, (B) front, and (C) left.

Fig. 3. Radiographic images show no remarkable pathologic findings except that the sliding movement of the right condyle is insufficient: (A) panoramic view and (B) temporomandibular joint panoramic view.​​​​​​​

Fig. 4. Proton density-weighted magnetic resonance imaging T2 images of the right temporomandibular joint in a closed jaw position. The white arrow indicates a large amount of joint effusion that bulge into the joint cavity. Three white arrowheads indicate multiple small intra-articular cartilaginous bodies.​​​​​​​

Fig. 5. (A) Preauricular incision and exposure of a cartilaginous loose body. (B) A number of loose bodies (approximately 50) were observed.

Based on clinical and diagnostic imaging findings, it was suggested that the occlusal changes might be caused by excessive joint effusion surrounding multiple loose bodies within the right TMJ, and premature contacts on the right posterior teeth might be associated with anterior displacement of the right condyle; subsequently, this causes a disturbance in the cusp–fossa occlusal relationship.

For surgical intervention on the affected joint, she was referred to the Department of Oral and Maxillofacial Surgery, Kyungpook National University Dental Hospital. Surgical removal of the intra-articular bodies was performed by adopting a preauricular approach under general anesthesia (Fig. 5). Based on tissue biopsy specimens, the histopathological examination confirmed SC diagnosis. Postoperative panorama showed no morphologic changes in the right condyle. At 1-month follow-up, occlusion was found to be normalized with simultaneous occlusal contacts on both sides while her mouth opening was preserved with interincisor distance of approximately 4 cm without any feeling of pain.

DISCUSSION

SC is a rare progressive cartilaginous metaplasia of the residual mesenchyme in the synovial tissue of the joints. The cartilaginous nodules tend to protrude from the synovial membrane as they grow in size and eventually lose their attachment, so called “loose bodies” [7]. SC was known to mainly affect the large joints, but rarely TMJ. Some differences in demographic features are known to exist between SCs in TMJ and those occurring in large joints. While the mean age of its onset in other joints was approximately 25 years, SCs were known to occur in TMJ during the age range of 39-55.4 years [8,9]. Furthermore, there was the predilection of SC for females, with a sex distribution of 1:2 ratio (male:female) [10]. Therefore, these findings indicated that SC in TMJ had a high predilection for middle-aged women.

The clinical symptoms of SC include impaired mandibular movement, joint pain, crepitation, joint swelling. These symptoms are similar to those caused by temporomandibular disorders and other TMJ benign tumors. It was known that such a clinical non-specificity frequently made the early and accurate diagnosis of SC difficult for clinicians. SC in TMJ may occasionally cause progressive occlusal changes owing to condylar shift. A previous study reported that occlusal changes occurred in 11 of 43 SC cases, mainly with a posterior open bite on the ipsilateral side [11]. It was also described that posterior cross bite could be induced when large SCs developed in the medial part of the condyle. In this case, our patient presented with a posterior open bite and premature contact on the ipsilateral side affected by SC. These occlusal changes are different from those stated by Mupparapu [12]. They described ipsilateral open bite and contralateral premature contact as typical occlusal changes in patients with SC lesions. However, occlusal changes could vary depending on the altered pattern of condylar position determining the occlusal change. When the amount of joint effusion and loose bodies would be excessive enough to displace the condyle even slightly, the cusp– fossa relationship could be disturbed at the premature contact on the slope of the cusp rather than the fossa.

For SC diagnosis, the American Academy of Orofacial Pain suggested a diagnostic guideline comprising four categories: history taking, clinical finding, imaging findings, and histological findings [6]. The past month history of the patient should be positive for at least one of the following: report of preauricular swelling, arthralgia, progressive mouth opening limitation, and joint noise. Furthermore, clinical examination must confirm at least one of the following: preauricular swelling, arthralgia, maximum assisted opening of <40 mm including the vertical incisal overlap, and crepitus. Diagnostic imaging should demonstrate the following: multiple chondroid nodules, joint effusion, and amorphous iso-intensity signal tissues within the joint space and capsule in MRI or loose calcified bodies in the soft tissues of the TMJ in computed tomography (CT). Finally, histologic examination should confirm cartilaginous metaplasia.

For the stage classification, Milgram [13] suggested three stages for SC based on histopathological studies. Stage 1 is the initial stage presenting with active metaplasia of the intrasynovial tissue, but without the formation of any loose bodies. Stage 2 is a proliferative stage in which metaplasia in the synovium and loose bodies including active chondrocyte appear simultaneously. In the Stage 3, there are multiple calcified or ossified detached loose bodies with no more active metaplastic activity. Therefore, early stages including stage 1 or 2 was seldom detected on plain radiographs, which make it difficult for many clinicians to make an early and accurate diagnosis. This was because plain radiographs had some limitations in showing the presence of lesion when cartilaginous loose bodies were not sufficiently calcified or overlapped by the condyle or cranial bone. Some authors reported that there was no significant finding in the initial plain radiographs taken for 37% to 47% of SC cases [14,15]. This case also corresponded to stage 2, when based on the findings that the joint effusion was excessive enough to displace the condyle anterior-inferiorly, while the loose bodies were not fully ossified without any radiographic detection in plain radiography. In our case, the patient was also treated with conservative treatments alone over several months after being initially misdiagnosed as disc displacement on the right TMJ.

As for treatments for SC, surgical interventions were recommended for the cases causing functional disturbances, including those that reported joint pain and mouth opening limitation. However, recurrence was not common even after surgical removal [16]. Previous researchers proposed that the metaplastic activity of synovium was a major risk factor for recurrence, which was relatively higher in stage 1 or 2. Accordingly, more careful removal of the SC-affected tissue area has been recommended for stage 1 or 2 patients. In addition, it was known that early stage SC had the tendency of not responding to conservative treatments [17]. More importantly, it is fundamental to diagnose it early for facilitating prompt and accurate treatment. CT and MRI were regarded as better diagnostic tools than plain radiograph. MRI is the most useful diagnostic image because it allows the identification of less ossified tissues such as hypodense semi-calcified loose bodies [18].

Furthermore, it was optimized to exhibit the structural changes in entire TMJ components including joint capsule, synovial membrane, disc, joint cavity, and joint effusion. Such comprehensive imaging makes it possible for the clinicians to determine the extent of surgical enucleation.

In conclusion, CT or MRI imaging should be performed to distinguish SC in patients who do not respond to conservative therapy, especially in cases of preauricular swelling or occlusal changes. MRI is a useful tool for detecting the early stage of SC, which is mainly characterized by the presence of less calcified loose bodies and joint effusion.

CONFLICT OF INTEREST

No potential conflict of interest relevant to this article was reported.