Left-right asymmetries and other common anatomical variants of temporomandibular articular surfaces.

In this chapter, the authors describe systematically left-right asymmetries and other common anatomical variants of the temporomandibular articular surfaces as they can appear in daily clinical practice. Digital photography and macroscopic observation were used to evaluate morphologic features of TMJ surfaces of elderly subjects at 100 glenoid fossae and articular eminences of dried skull bases, and at 100 dried mandibles. Mandibular condyle shape in the horizontal plane and in the frontal plane were evaluated using a standardized classification devised by Öberg et al. (1971). Degenerative form and surface changes of the TMJ were assessed using a scale devised by Wedel et al. (1978). The antero-posterior and medio-lateral diameter of the temporomandibular articular surfaces were measured using a digital caliper. The orientation was determined using a clinical goniometer. Morphologic left-right asymmetries of the temporomandibular articular surfaces were frequently present in mandibular condyles and in glenoid fossae. In general, mandibular condyles showed more often morphologic left-right asymmetries than glenoid fossae. Anatomical variants of the articular surfaces of the left and right mandibular condyles resulted from differences in shape. The majority of the articular surfaces had an oblong horizontal outline and a rounded frontal outline. One fifth of the mandibular condyles showed pear-shaped horizontal outlines and flat or ridge-shaped frontal outlines. An important incidence of left-right asymmetries and other common anatomical variants of the temporomandibular articular joint surfaces must be considered at observation and therapy of the temporomandibular joint; arthrokinematic functional consequences may result.