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J Oral Maxillofac Surg 53:241-242, 1995

Discussion

TMJ Articular Disc Position and Configuration 30 Years After Initial Diagnosis of Internal Derangement

Per-Lennar t Westesson, DDS, PhD University of Rochester School of Medicine and Dentistry, Rochester, NY

This article is interesting from many aspects. First, it shows that it is possible to identify patients with different degrees of disc displacement from old records with a rela- tively high degree of sensitivity. However, we do not know how many of the patients that were excluded from this study actually had disc displacement. Therefore, the specificity as well as the accuracy of the identification process is unknown, and the statement in the beginning of the discussion that "the methods used to select the TMJs with internal derange- ment were highly accurate" is not substantiated.

The article brings up the issue of the homogeneity of TMJ patient populations. The 46 patients who were examined represent a subset of patients with TMJ disease that is proba- bly very different from those usually seen in the practice of oral and maxillofacial surgery. I say this because these pa- tients were treated with conservative, nonsurgical methods such as reassurance, dietary advice, exercise therapy, appli- cation of superficial heat, and pain medication, la and all responded so well that none of them requested retreatment during the 30-year follow-up period. This is different from the patients referred for surgical treatment, usually after mul- tiple failed attempts with nonsurgical treatment. This illus- trates that patients with TMJ internal derangement are not a homogeneous group even if the morphology on the images appears similar. At least four subgroups can be identified: 1) asymptomatic individuals with disc displacement, 2) symptomatic patients with disc displacement who respond to conservative, nonsurgical treatment, 3) symptomatic patients with disc displacement who do not respond to nonsurgical treatment but who improve significantly with primary surgi- cal treatment, and finally, 4) those symptomatic patients with joint displacement who do not get better regardless of non- surgical or surgical treatment. The distinction between these

four groups is important, and I think the patients described in this study belong to the second group: those with minimal symptoms who respond to nonsurgical treatment. We are not able to prospectively separate patients with disc displace- ment into these four groups either on imaging or clinical grounds. It should be the goal of future studies to identify characteristics of patients with disc displacement so that eventually it becomes possible to prospectively understand to which category the individual patients belongs.

The authors' MR imaging technique included sagittal TI- weighted images. It would have been desirable to have coro- nal images, because studies have shown that there is a medial or lateral component to the disc displacement in up to about one third of cases. 3'4 Using coronal views increases the accu- racy of MR imaging over using only sagittal images. The value of coronal MR images has relatively recently become obvious and was probably not clear at the time these patients were examined.

In separating the different categories of disc displacement and internal derangement, T2-weighted images that depict the inflammatory components secondary to the disc displace- ment have been shown to be valuable. 5 Thus, a strong corre- lation between joint pain and joint effusion has been shown, and this is probably an important part of assessing patients who present with symptomatic TMJ disorders. The article would have been strengthened if T2-weighted images had been included. Again, the value of such images has become better understood only recently and was probably not ap- preciated at the time these patients were examined.

Previous studies have shown that disc displacement with reduction frequently involves only a partial dis- placement, with only a part of the disc being anteriorly displacement, while the rest is in a relatively normal position. This article also would have been strengthened if disc position had been studied in separate mediolateral sections of the joint and observations correlated to disc function. It has been my experience that disc displace- ment without reduction is associated with a total dis- placement, whereas disc displacement with reduction usually is associated with partial anterior displacement. It would be interesting to know if partial disc displacement could be present for as long as 30 years.

242 DISCUSSION

The illustrations in this paper show different degrees of disc displacement, but hardly any evidence of degenerative joint disease. This is somewhat surprising in light of the fact that the patients have had internal derangement for 30 years. It is probably another indication that there are several subcat- egories of disc displacement with different clinical and mor- phologic courses over the years. One category might be more benign, with a favorable response to treatment and no radio- logic progression, whereas another might show evidence of morphologic progression. It is not clearly understood whether this is associated with a different clinical course, and this might be another goal for future research.

In summary, this is an interesting article that shows that patients can have internal derangement for 30 years and not develop significant symptoms. The most important conclu- sion is probably that internal derangement can develop in a benign fashion and does not always lead to degenerative joint disease and progressing symptoms.

References

1. Leeuw de R, Boering G, Kuijl van der B, et al: The temporoman- dibular joint 30 years after diagnosis of osteoarthrosis and internal derangement: An imaging study of both hard and soft joint tissues, in Leeuw de R: A 30-year follow-up study of non-surgically treated temporomandibular joint os- teoarthrosis and internal derangement. Thesis, University of Groningen, Drukkerij van Denderen BV, The Netherlands, 1994, pp 61-72

2. Boering G: Temporomandibular joint arthrosis: An analysis of 400 cases. Thesis, University of Groningen, Drukkerij van Denderen BV, The Netherlands, 1966

3. Katzberg RW, Westesson P-L, Tallents RH, et al: Temporoman- dibular joint: MR assessment of rotational and sideways disk displacements. Radiology 169:741, 1988

4. Brooks SL, Westesson P-L: Temporomandibular joint: Value of coronal MR images. Radiology 188:317, 1993

5. Westesson P-L, Brooks SL: Temporomandibular joint: Relation between MR evidence of effusion and the presence of pain and disc displacement AJR 159:559, 1992