Internal derangement of the temporomandibular joint: radiographic and histologic changes associated with severe pain.

In 20 temporomandibular joints (TMJs) (15 patients) with internal derangement associated with severe pain, the presurgical radiographic findings were compared with the morphologic and histologic alterations. Disc extirpation was performed in 17 joints, and in three joints the disc was surgically repositioned. Deformation of the disc observed by double-contrast arthrotomography was verified histologically. Perforation of the posterior disc attachment was seen in two joints; both were associated with osteophyte formation and flattening of the articular eminence. The white disc-like structure in 11 cases was composed of an anterior, stiff, bulgy, biconvex structure combined with a posterior flattened portion that grossly was incorrectly determined to be part of the disc, but that was identified histologically as a posterior disc attachment that had undergone adaptive change characterized by connective tissue hyalinization. In the arthrotomogram the disc position could easily be determined. However, the disc-like clinical appearance of the posterior disc attachment in these cases made determination of disc position at surgery uncertain or impossible. The nonhyalinized posterior disc attachment was intensely red and showed advanced histologic alterations of the vessels, deposits of extravasated erythrocytes and fibrin, and altered composition of the connective tissue. Thus, signs of inflammation were present but without activation of the local immune system since no major inflammatory cell infiltrates were seen. Small accumulations of lymphocytes were seen in only two cases. The surgically extirpated posterior attachments were innervated by silver-positive nerve fibers ranging in diameter from 1 to 15 micron. The severe pain in the TMJs is likely to have originated from this innervated posterior disc attachment or capsule and to have been triggered by the vascular reaction.