Early diagnosis of osteoarthrosis of the temporomandibular joint: Correlation between arthroscopic diagnosis and keratan sulfate levels in the synovial fluid

712

DISCUSSION

J Oral Maxillofac Surg 49 :712. 1991

Discussion Early Diagnosis of Osteoarthrosis of the Temporomandibular Joint: Correlation Between Arthroscopic Diagnosis and Keratan Sulfate Levels in the Synovial Fluid

Sigvard Kopp, DDS, PhD Karolinska lnstitutet, Stockholm

The topic of early diagnosis or detection of osteoarthrosis (OA) of the temporomandibular joint (TMJ) and other joint diseases is relevant. Up to now , radiologic or clinical methods have been the main source of information. However, the radiologic picture does not tell anything of the catabolic changes taking place in the TMJ at the moment of examination and may not correlate at all with the subjective symptoms and clinical signs. This article , therefore , is a valuable contribution towards a biological assessment of what is really happening in the joint at the moment of examination. We should remember in the following discussion, however, that protcoglycan degradation and the release of glycosaminoglycans (GAGs) into the syno vial fluid are not specific for OA, but occur in all joint diseases with cartilage breakdown, eg, rheumatoid arthritis . I Keratan sulfate (KS) is an import ant component, especially of hyaline cartilage proteoglycans, but is less abundant in the type of fibrocartilage present in the TMJ. 2 •3 Therefore, the question arise s: Why investigate KS? The preoperative diagnosis' of the patients was based on clinical examination, panoramic radiographs, and magnetic resonance imaging (!\tRI) examination. What were the radiologic and MRI findings? Nothing is presented about the preoperative distribution of clinical signs or criteria of OA (3 joints), internal derangement (24 joints), or fibrosis (2 joints). What kind of diagnostic entity is internal derangement when the number of joints with OA increased to 17 after arthroscopy? It seems that

internal derangement is a rather nonspecific diagnosis. Another question that arises is: How long was the time between injection of saline and aspiration, and was it standardized? This que stion is important since time is needed for equilibration between synovial fluid and saline with respect to KS. One purpose of the study was to determine if the early diagnosis of OA could be established by arthroscopy. There is no clear answer to this question in the article. On the other hand, arthroscopy was used to allocate the patients into the OA and NON-OA groups, which were subjected to analysis of difference in level of KS in the synovial fluid. To summarize, the biochemical detection of increased amounts of KS, as performed in this study, or chondroitin sulfate or dermatan sulfate a nd their use as markers of TMJ disea se, would certainly be a significant step forward in the early assessment ofTMJ disease. However, it is not specific for OA; it might just as well be an indication of rheumatoid arthritis or any other of the diseases that involve the TMJ. The diagnosis of OA, therefore, can hardly be based on increased levels of keratan sulfate alone. Nevertheless,joint disease activity, at least in the early stage, is only detectable by a biochemical approach . The choice of KS can be questioned , however, because the articular fibrocartilagcs of the TMJ has been shown to consist to a large degree of dermatan sulfate and chondroitin sulfate .

References I. Saxne T, Heinegard D, Wollheim FA: Therapeutic effects on

cartilage metabolism in arthritis as measured by release of proteoglycan structures into the synovial fluid. Ann Rheum Dis 45:491, 1986 2. Granstrom G, Linde A: Glycosaminoglycans of temporomandibular articular discs. Scand J Dent Res 81:462, 1973 3. Habuchi H, Ymagata T, Iwata H, et al: The occurrence ofa wide variety of dermatan sulfate-chondroitin sulfate copolymers in fibrous cartilage. J BioI Chern 248:6019, 1973