Osteoarthritis in temporomandibular joint internal derangement

Abstract

Internal derangement of the temporomandibular joint is the most common diagnosis leading to joint surgery. Two variants of internal derangement exist, painful clicking and chronic closed lock. Painful clicking is characterized by no or minor arthritic changes. Joints with chronic closed lock, on the other hand, frequently exhibit osteoarthritic degeneration of the disc and fibrocartilage. This study was done in order to elucidate some of the underlying biologic processes during disc displacement.

The occurrence of fibroblasts, chondrocytes and blood vessels was studied morphologically in the tissue of temporomandibular joint disc, the intermediate zone and the posterior disc attachment region in control autopsy specimens and compared with corresponding tissues from patients with temporomandibular joint internal derangement. The volume density of blood vessels was significantly higher in the posterior disc attachment region in patient specimens than in autopsy controls. Whether this reflects a role for the vessels in the pathogenesis of temporomandibular joint internal derangement or merely is a reaction to another type of injury remains to be settled. In both the autopsy control and the patient specimens, chondrocytes and fibroblasts were characteristic for disc respective posterior disc attachment region. Thus it appears that occurrence of these cells can be used to distinguish temporomandibular joint disc from posterior disc attachment in small biopsy specimens.

The glycosaminoglycans of the extracellular matrix were analysed by means of capillary zone electrophoresis in specimens from temporomandibular joint disc and posterior disc attachment in patients with internal derangement of the temporomandibular joint. There were significant differences in the amount of glycosaminoglycans between the two groups of patients with internal derangement - painful clicking and chronic closed lock. Values in patients with painful clicking were comparable to those of normal individuals, while patients having chronic closed lock showed significantly reduced values. Both groups showed higher values in the posterior disc attachment when compared to the disc and similar pattern of glycosaminoglycan sulphation. Based on the close correlation between the osteoarthritis associated degradation in the temporomandibular joint disc and in the posterior disc attachment, it is suggested, that once osteoarthritis develops in patients with painful clicking, the effects on the attachments will lead to chronic closed lock.

RT-PCR was used to analyze the expressions of a series of mRNAs coding for proteoglycans in specimens obtained during discectomy of the temporomandibular joint in patients with signs and symptoms of painful clicking and chronic closed lock. The degradation of matrix in patients with chronic closed lock of the temporomandibular joint seems not to be caused by a reduced synthesis and the degenerative process seen in these patients is one with low turnover similar to the situation in primary osteoarthrosis of hyaline cartilage.

An indirect microimmunofluorescence test for detecting antibodies against Chlamydia trachomatis was used to analyse serum samples from a subgroup of patients with chronic closed lock. This subgroup of patients showed monoarthritis without any signs of degenerative joint disease. The occurrence of serum antibodies to Chlamydia trachomatis was significantly higher in patients than in controls. However, this occurrence did not correlate with severity of observed tissue changes.