To highlight the morphodynamic anatomical mechanisms that influence the results of rhinoplasty. To present the technical modalities of nasal dorsum preservation rhinoplasties. To determine the optimized respective surgical indications of the two main techniques of rhinoplasty: interruption rhinoplasty versus conservative rhinoplasty.Based on anatomical dissections and initial morphodynamic studies carried out on 100 anatomical specimens, a prospective study of a continuous series of 400 patients operated of primary reduction rhinoplasty or septo-rhinoplasty by one of authors (YS) has been undertaken over a period of ten years (1995-2005) in order to optimize the surgical management of the nasal hump. The studied parameters were: (1) surgical safety, (2) quality of early and late aesthetic result, (3) quality of the functional result, (4) ease of the technical realization of a possible secondary rhinoplasty. The other selected criteria were function of the different nasal hump morphotypes and the expressed wishes of the patients.The anatomical and morphodynamic studies made it possible to better understand the role of the "M" double-arch shape of the nose and the role of the cartilaginous buttresses not only as a function but also the anatomy and the aesthetics of the nose. It is necessary to preserve or repair the arche structures of the septo-triangular and alo-columellar sub-units. The conservative technique, whose results appear much more natural aesthetically, functionally satisfactory and durable over the long term, must be favoured in particular in man and in cases presenting a risk of collapse of the nasal valve.The rhinoplastician must be able to propose, according to the patient's wishes and in view of the results of the morphological analysis, the most adapted procedure according to his own surgical training but by supporting conservation of the osteo-cartilaginous vault whenever possible.