A classification system for conditions causing condylar hyperplasia.

A classification system was developed to place patients with condylar hyperplasia (CH) into categories based on histology, clinical and imaging characteristics, effects on the jaws and facial structures, and rate of occurrence. Four major categories were defined. CH type 1 is an accelerated and prolonged growth aberration of the "normal" mandibular condylar growth mechanism, causing a predominantly horizontal growth vector, resulting in prognathism that can occur bilaterally (CH type 1A) or unilaterally (CH type 1B). CH type 2 refers to enlargement of the mandibular condyle caused by an osteochondroma, resulting in predominantly unilateral vertical overgrowth and elongation of the mandible and face. One of the forms has predominantly a vertical growth vector and condylar enlargement, but without exophytic tumor extensions (type 2A), whereas the other primary form grows vertically but develops horizontal exophytic tumor growth off of the condyle (CH type 2B). CH type 3 includes other rare, benign tumors and CH type 4 includes malignant conditions that originate in the mandibular condyle causing enlargement. The order of classification is based on occurrence rates and type of pathology, where CH type 1A is the most commonly occurring form and CH type 4 is the rarest. This classification system for CH pathology should help the clinician understand the nature of the pathology, progression if untreated, recommended ages for surgical intervention to minimize adverse effects on subsequent facial growth and development in younger patients, and the surgical protocols to comprehensively and predictably treat these conditions.