Morphologic features of the fetal mandibular condyle: Layers, canals and microvascular pattern

During organogenesis the mandibular condyle is divided by a fibrovascular septum, the persistence of which in the growing cartilage can lead to a bifid condyle. In this study we have evaluated the morphology of 3rd trimester human fetal temporomandibular (TMJ) specimens in order to determine the pattern of the vascular morphology associated with the layers and vascular canals (VCs) of the developing condyle (covering layers and condyle proper). Eleven human fetuses of 27–38 cm crown-rump length were used for histological (hematoxylin-eosin, Van Gieson stain) and immunohistochemical evaluation (antibodies for bcl2 and CD34) and another two of 24 and 31 cm, for TMJ microvasculature studies after black ink injections. With increasing fetal age, the intermediate loose lamina (LL) of the condylar proliferative layer evolves from a vascular-mesenchymal to a fibrillar pattern, via a transitory stage of a clear space that may be misdiagnosed as lower joint cavity (LJC). Within the condyle proper VCs may be present on its entire sagittal length, deepening variably towards the erosive zone and opened superiorly in the LL loose layer. Vessels of the evolving LL enter the condyle, directly or through the VCs; these vessels retract peripherally with increasing age and the intrinsic vessels of the condyle supplied from the erosive zone become prevalent. Vascular morphogenesis at the level of the LL seems comparable to that at the level of the LJC where characteristic glomeruli regress with increasing age. Lack of vascular regression and closure of central V-shaped defects of the condyle, as observed in 2/22 condyles, may represent a developmental substrate for condylar bifidism or a predisposing condition weakening the condyle, and making it more sensitive to trauma in childhood.