[Axiographic functional parameters after dysgnathia operations with special reference to the position of the...

This follow-up study was designed to identify the differences between the TMJ movements of individuals undergoing orthognathic surgery, with and without positioning of the mandibular proximal segment. A further aim was to assess the location of the terminal hinge axis before and after surgery regarding variations due to mandibular advancement or set back, respectively combined two jaw osteotomy. Mechanical axiographic tracings were documented in 14 patients undergoing orthognatic surgery without positioning of the mandibular proximal segment. The terminal hinge axis position was marked by a tattoo. After surgery two more axiographic tracings were recorded over a follow-up period of 24 months. Changes to the terminal hinge axis position were also documented. Condylar guidance angles showed no differences, whereas Bennett angles decreased by an average of 25%. Subjective or objective TMJ symptoms after surgery could be observed in 64% of the patients, compared to 50% before surgery. Considerable variations in the position of the terminal hinge axis were observed nine months after surgery, especially in the two jaw group. In Class II individuals the terminal hinge axis was found in a cranial position both after 9 and 24 months. Class III individuals with two jaw surgery also gained a long term cranial localisation, whereas Class III patients with mandibular setback only demonstrated a hinge axis position inferior and anterior compared to the preoperative reference. No statistically significant differences were apparent between the axiographic condylar movement parameters in the present group as compared to data published employing condylar positioning.