Assessment of chin surgery by a coordinate free method.

A quantitative description of the changes and stability after genioplasty in a cross-sectional sample of 19 patients who had advancement genioplasty is presented. Euclidean distance matrix analysis (EDMA) of five cephalometric landmarks was used to assess these changes. During the first 6 months after surgery, bone deposition occurred at B point and pogonion, with bone resorption at the superior and posteroinferior aspects of the advanced segment. The genial segment rotated slightly anticlockwise. The authors believe this to be due to the action of the mentalis muscles. The stability of the advanced segment was excellent when assessed 1 year after surgery. The Euclidean distance matrix method can be used to assess shape changes and does not require cephalographic superimposition. It can also distinguish repositioning from remodelling and the changes of genioplasty from those of concomitant orthognathic surgery.