title: [Leg length changes after upper tibial osteotomy: analysis of different preoperative planning methods].
abstract: OBJECTIVE
  The amount of change in the length of the lower limb resulting from upper tibial osteotomy depends on the type of osteotomy performed, the preoperative length of the limb, the degree of preoperative deformity and the amount of correction obtained. Wedge resection, for example, removes bone tissue and can lead to shortening. Inversely, a lengthening effect may result from correction of deformity. The purpose of this article was to present an analysis of the differences between different types of osteotomies and compare their effect on leg length.
  
  
  METHODS
  Change in length of the lower limb was studied with a mathematical analysis in opening wedge osteotomy, closing wedge osteotomy, and dome osteotomy. Leg length was calculated for several preoperative deformity angles of the entire limb (hip-knee-ankle angle) and several values of planned correction.
  
  
  RESULTS
  The theoretical mathematical model demonstrated that the greatest changes in leg length are obtained with opening wedge osteotomy, followed by dome, then closing wedge osteotomy. Tables were established showing calculated change in leg length. Tracings on radiographs or CT scans used to measure these changes are explained. Methods applicable in case of flexion contracture of the knee are presented.
  
  
  CONCLUSIONS
  Once the initial question regarding length changes is posed, many of the points become evident on image tracings. This work points out how quickly tables can be used to recognize significant differences in leg length changes produced by different osteotomies.
authors.affiliation: Hôpital Henri-Mondor, 51, avenue de Lattre-de-Tassigny, 94010 Créteil Cedex.
authors.forename: P
authors.initials: P
authors.lastname: Hernigou
authors.forename: A
authors.initials: A
authors.lastname: Jaafar
authors.forename: A
authors.initials: A
authors.lastname: Hamdadou
mesh_terms: D000886:Anthropometry; D006801:Humans; D007870:Leg Length Inequality / Q000209:etiology*; D010027:Osteotomy / Q000379:methods*; D013977:Tibia / Q000601:surgery*