Histologic Study of Adhesions in the Upper Joint Compartment of the Temporomandibular Joint

PurposeThe aim of this study was to observe the histologic characteristics of adhesions in the upper joint compartment of the temporomandibular joint and investigate the mechanism of genesis.Patients and MethodsDuring arthroscopic surgery, we obtained 42 biopsy specimens of different grades of adhesions, ranging from grade I to grade IV, from 21 joints in 21 patients with internal derangement. Two biopsy specimens from each temporomandibular joint were obtained in this study; one was immediately fixed in 4% formalin and examined under a light microscope, and the other was fixed in 2% glutaraldehyde solution and examined under a transmission electron microscope.ResultsDifferent grades of adhesions had uniform dense connective tissue under the light microscope, and a number of fibrocytic cells were scattered within the extracellular matrix. However, in grade II adhesions, synovial membrane and some elastic fibers were shown. Under the transmission electron microscope, orderly arranged collagen bundles were prominent in grade I and grade III adhesions. Elastic fibers were abundant in grade II adhesions with orderly arranged collagen bundles; a small number of inactive fibroblasts were scattered about these adhesions. Randomly arranged collagen bundles and elastic fibers were also observed in grade IV adhesions, in which synovial membrane cells and cartilaginoid cells were detected. In addition, fibroblasts with active secretion were observed, and a considerable amount of rough endoplasmic reticulum was noted.ConclusionsDifferent arrangements of collagen fibers with or without elastic fibers were observed in the 4 types of adhesions. These findings could enable further exploration into the mechanism of adhesion formation.