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Commentary |
1 Department of Radiology, University of California Davis Medical Center, 4860 Y St., Suite 3100, Sacramento, CA 95817.
Received October 11, 2006; accepted after revision October 20, 2006.
Address correspondence to R. W. Katzberg
(richard.katzberg{at}ucdmc.ucdavis.edu).
Keywords: arthrography • CT • MRI • temporomandibular joint
—Acquisition of a paradigm and of the more esoteric type of research it permits is a sign of maturity in the development of any given scientific field.—Thomas S. Kuhn [1]
Signs and symptoms of temporomandibular joint (TMJ) dysfunction are a common clinical problem. The prevalence is reported to be in the range of 4%–28% of the adult population, predominantly women [2]. Before the 1980s, patients with the four cardinal symptoms—pain, joint noise, tenderness, and locking—were classified as having nonspecific functional mechanisms, masticatory muscle spasm being considered the primary factor responsible for the signs and symptoms [3]. In 1978 in the New England Journal of Medicine, an extensive review [4] of the state of knowledge of TMJ disorders made no mention of internal derangement of the joint as a causative factor in TMJ pain and dysfunction. In addition, a strong psychological component was considered an important etiologic factor. The clinical approach was nonspecific, and it was not possible at that time to depict the soft-tissue anatomic features of the TMJ.
In the late 1970s, Wilkes [5] and Farrar and McCarty [6] made the iconoclastic suggestion that abnormalities of the disk (or meniscus), both anatomic and functional, could be the cause of specific signs, symptoms, and chronic sequelae. The influence of the clinical research described in 1980 in "Arthrotomography of the Temporomandibular Joint" [7] was that the imaging technique showed substantial evidence to "support the contention that a fundamental pathophysiologic abnormality in the temporomandibular joint is anterior meniscus displacement." This article was preceded by a preliminary report in 1979 [8]. The new paradigm, along with the simultaneous introduction of concepts for conservative and surgical therapy for correction of anterior disk displacement based on an accurate definition of disk abnormalities, stimulated an explosion in interest in the specificity of diagnosis and treatment as well as research into the pathophysiologic mechanism of this painful disorder. This paradigm shift is a prime example of the profoundly critical role of diagnostic imaging in revolutionizing medical diagnosis and therapeutics.
After the advent of arthrotomography of the TMJ, revolutionary developments in imaging technology continued to increase sophistication in diagnosis and to decrease the need for invasive techniques such as arthrotomography [9]. The first CT scans showed the displaced disk, accurately depicted degenerative joint disease, and could be used to assess histologic changes in the disk material itself [10–12]. These advances were soon followed by yet another revolutionary development, the application of MRI, which depicted structures in fine detail, including not only the basic positional abnormalities of the disk but also morphologic and configurational derangements [9, 13]. Morphologic derangements in cadavers had been methodically defined in 1982 by Westesson [14] in his doctoral dissertation. These abnormalities can now be easily depicted in vivo with MRI.
The need for imaging of the TMJ continues to decrease because of greater confidence in conservative management of internal derangement of the TMJ in conjunction with better appreciation of the pathophysiologic mechanism and outcome of the disease. The improvement in conservative management has substantially reduced the need for widespread use of surgical procedures, which are reserved for patients with intractable and intense pain.
What is happening now and what is in store for the future? For patients with TMJ pain and dysfunction, research is being conducted into the mechanisms of pain, inflammation of the joint, and development of degenerative joint disease. Causative factors in the development of internal derangement of the TMJ and estimation of the role of early or asymptomatic internal derangement as risk factors for progressive disease, facial and mandibular deformities, and occlusal instability are under investigation. Occlusal instability is especially important in young patients undergoing orthodontic treatment. An exciting opportunity for radiology is the use of less-expensive MRI techniques for preorthodontic screening for asymptomatic internal derangements. The findings should lead to better understanding of the role of the derangements in occlusal changes, facial asymmetry, pain, and the pathophysiologic mechanism of degenerative joint disease.
Acknowledgments
The following radiologists, in alphabetical order, have made seminal contributions to the study of the TMJ: Quentin Anderson, Ken Bell, Bill Carrera, David Collier, Steve Harms, Clyde Helms, Phoebe Kaplan, Larry Manco, Jim Manzione, Bill Murphy, Vijay Rao, Kurt Schellhas, Joe Thompson, and Per-Lennart Westesson.
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