[Modifications to the skin profile following facial osteotomy]

Soft tissue changes resulting of maxillary and/or mandibular osteotomies need to be evaluated with a great accuracy for a better prediction of the post-operative profile. As the aesthetic result seems to be most important for our patients, it is necessary to study the relations between the displacements of characteristic cutaneous points and hard structures below, osseous or dental. Then, a retrospective statistical computerized study was performed on 45 patients who underwent facial osteotomies at least three months before. The vertical and horizontal positions of 14 osseous or dental landmarks and 16 cutaneous points were recorded. Corresponding displacements were calculated for each of these, but only six cutaneous and 9 osseous displacements were selectionned for this study. A first correlation research was made, with determination of the lineary regression equations, when it was possible. Then a multivariate study was performed for each cutaneous point, with determination of multiple regression equations. Comparison between the two methods of prediction shows a S.D. over 2 mm for the simple regression versus a S.D. of about 1 mm for the multiple regression. On the other hand, it seems that it is possible to predict the horizontal displacements with the first method without important error. But the vertical displacements cannot be evaluated with good prediction, and particulary the stomion movements. It will be necessary to consider other parameters to obtain better correlation coefficient. But it is obvious that one can join together different groups of patients for a soft tissue changes study with the same results than after separation of those. In fact, the soft tissue reactions are the same although the surgical procedures are different.