J Orthopaed Traumatol (2008) 9:11–15 DOI 10.1007/s10195-008-0098-z O R I G I N A L Correction of knee and ankle valgus in hereditary multiple exostoses using the Ilizarov apparatus E. Ofiram · S. Eylon · S. Porat Received: 27 July 2007 / Accepted: 1 December 2007 / Published online: 17 March 2008 Abstract Background Hereditary multiple exostoses (HME) is a genetic disorder that causes limb deformities due to distur- bance at the growth plates. Materials and methods Six adolescents, whith sympto- matic valgus deformity at the ankle and knee (seven affected legs) underwent correction procedures using the Ilizarov apparatus. In 5 legs, a bifocal Ilizarov apparatus was used, whereas in 2 legs the use of a monofocal appa- ratus was sufficient. Results Correction of the mechanical axis was achieved in all cases, and limb length discrepancy was equalized in the 3 cases that underwent limb elogation. The average knee and ankle corrections were 15° and 18°, respectively. The aver- age time from application to removal of the Ilizarove appa- ratus was 4.6 months. No major complication occurred. Conclusions The use of the Ilizarov method in adolescents with HME enables successful simultaneous correction of multiplanar, multifocal complex limb deformities. Keywords Hereditary multiple exostosis · Ilizarov appara- tus · Osteochondroma · Limb deformity E. Ofiram ( ) Department of Orthopaedic Surgery Kaplan Medical Center P.O. Box 1, Rehovot 76100, Israel e-mail: eofiram@gmail.com S. Eylon · S. Porat Orthopaedic Surgery Department The Hadassah - Hebrew University Medical School Jerusalem, Israel Introduction Hereditary multiple exostoses (HME) is a dominantly inherited genetic disorder, caused by point mutations in the exostosin gene family and characterized by multiple benign cartilage-capped tumors, primarily on long bones [1]. HME has a wide spectrum of clinical manifestations, the most common presentation being exostosis in the lower limbs, which is expressed by pain, disruption of osseous growth, bowing of long bones, limb length dis- crepancy, genu valgum, short fibula, valgus ankle, coxa valga and acetabular dysplasia [2, 3]. Various methods have been described to correct the valgus deformity at the ankle [4–6] but there is only one case report on the use of the Ilizarov method [7]. We present a series of six adolescents (seven affected legs) with HME, who were treated for valgus deformities of the knee and ankle using the Ilizarov apparatus. Materials and methods Six adolescents (seven affected legs) with an average age of 14.3 years (range, 10–17.5), who had valgus deformity as a result of osteochondromas at the knee and ankle (Fig. 1), underwent surgical correction using the Ilizarov method (Table 1). The average knee valgus was 13.7° (range, 9°–18°) and the average ankle valgus was 18.4° (range, 10°–30°). Preoperative planning based on long standing radiographs included a malalignment test [8], center of rotation and angulation (CORA) definition, and assembling of the Ilizarov apparatus. In two of the seven legs, monofocal correction was sufficient to achieve mechanical alignment of the lower limb. In one of these cases the knee valgus (9°) did not