300 © Soeidt~ d'Edition de l'Association d'Enseignement M~dical des Hdpitaux de Paris, 1998 Congenital radioulnar synostosis Study of a series of 37 children and adolescents K. YAMMINE, A. SALON, J.C. POULIQUEN SUMMARY: The authors report a retrospective series of 37 patients (49 forearms) with congenital radioulnar synostosis followed and treated at Raymond Poincar6 University Hospital. This disease is rare, but much more frequent than post- traumatic or humeroradial synostosis. A genetic factor was incriminated in 25 % of patients. The clinical study was based on 31 files (40 forearms) with a subjective finding of hypermobility of the wrist in all patients. Shortening of the ipsilateral upper extremity < 2 cm was also observed in one third of patients, and a defect of elbow extension was observed in 35 %. The radiological study, conducted on 30 files (38 forearms), confirmed the existence of several degrees of fusion within the synostosis and revealed an associated radiological abnormality in 92 % of cases. The only valid correlation revealed was between the degree of fusion of the synostosis and the presence of a morphological abnormality of the radial head (r - 0.87), hence the proposal of a new radiological classification essentially based on this element. Functional adaptation was excellent in the majority of cases. The authors propose two main indications for surgery: hyperpronation > 90 ° and bilateral synostosis ; in both cases, the disability must be very severe. The operative technique used appeared to be very well adapted to this disease: << reed >> radial osteotomy and transverse ulnar osteotomy. No complications or relapses were observed in six operated patients with a mean follow-up of 10 years, with a mean loss of derotation of only 5 °. Ann Chir Main (Ann Hand Surg), 1998, 17, n ° 4, 300-308. KEY-WORDS : Congenital radioulnar synostosis. Forearm. - Pronation-supination. INTRODUCTION Congenital radioulnar synostosis (CRUS) is a rare malformation of the upper extremity. In 1932, Fahlstrom [1] reviewed all cases reported in the international literature and found only 185 cases since the first anatomical description by Sandifort in 1793. Correspondence." K. Yammine, 1, square Marcel-Toussaint, 75015 PARIS. Manuscrit rec~u ~ la R~daction le 3 aofit 1998. Service d'OrthopOdie et de Traumatologie POdiatriques, H@ital Accepte le 23 septembre 1998. Universitaire Raymond-Poincar~, 92 GARCHES.