14 Fig. 5 Anteroposterior radiograph of both legs of case 6. The right leg is five years after treatment, whereas the left leg demonstrates a valgus deformity of the proximal tibia, before monofocal Ilizarov correction lization of limb length was achieved in all 3 patients that required it (cases 2–4). Discussion Osteochondromas in the proximal and distal fibula cause knee and ankle valgus in patients with HME. Ankle val- gus is a result of a sequence of events; the osteochondro- ma interferes with the normal growth of the distal fibular physis, leading to a shortened fibula. Dias et al. [9] sho- wed a correlation between a short fibula and ankle valgus in 173 cases, of which 18 had HME. The lateral support of the ankle joint is reduced due to the short fibula, enabling a sliding of the talus in the mortise, resulting in ankle valgus. In addition, the normal distribution of pres- sure applied to the distal tibial physis is altered, causing increased compression pressure on the lateral portion of the tibial physis, thus inhibiting growth. According to the Hueter-Volkmann law, the increased amount of distrac- tion pressure on the medial physis accelerates growth on this side, creating a wedge shape deformity of the epiph- ysis, further increasing the ankle valgus [10]. Another explanation for the development of ankle val- gus is inherited growth disturbance of the distal fibula rather than a mechanical etiology [11]. Solomon [12] and Fogel et al. [13] found that in both upper and lower limbs, the deformity originates from the location of the osteo- J Orthopaed Traumatol (2008) 9:11–15 chondromas on a small cross-sectional bone area, i.e. ulna and fibula, respectively. These bones are more vulnerable to growth disturbance associated with the presence of the local osteochondroma. Various surgical methods exist for correcting ankle valgus, such as epiphysiodesis of the distal medial tibial physis as described by Beals [4]. Other techniques such as transphyseal medial malleolar screws [5], screw epiphys- iodesis and medial tibial hemiepiphyseal stapling [4, 6] have been described as solutions for the correction of ankle deformity in HME. The advantages of these latter techniques are their minimal invasiveness, technical sim- plicity, and rapid recovery. Their drawbacks, however, are their inability to correct severe ankle valgus and to solve limb length discrepancy by elongation when needed. No reports in the English medical literature were found describing simultaneous surgical correction of ankle and knee valgus in HME. There was, however, a single case report by Shawen et al. [7] describing the correction of ankle valgus due to HME by the Ilizarov apparatus. The Ilizarov method enables simultaneous correction of multifocal multiplanar deformities. Therefore, it has been chosen as the treatment modality in these complex cases. The treatment of ankle valgus in our series was per- formed by osteotomy and an acute correction, unlike the 10-day progressive correction described by Shawen et al. [7]. In our series, knee valgus was corrected progressive- ly to avoid peroneal nerve injury. We are aware that correction of ankle valgus by sta- pling, for example, is much easier than the Ilizarov surgi- cal procedure. Nevertheless, acute correction using the Ilizarov apparatus immediately equalizes the forces acting on the ankle joint as well as on the physis, whereas in sta- pling unbalanced pressure continues to affect the joint. Another significant advantage of the approach advo- cated here is the immediate post-operative weight bear- ing, despite the two osteotomies performed in the same segment. According to Paley’s classification of complications [14], in this series there were three “problems”, two of “obstacles” and no “major complications”. The problems consisted of one case of neuropraxia of the common per- oneal nerve and two cases of over-correction into varus. The “obstacles” included one case with iatrogenic tran- section of the common peroneal nerve and one case of proximal fibular shifting into valgus resulting in pressure on the skin. Both cases required additional surgical inter- vention. Despite these complications, the aim of the treat- ment was accomplished. The Ilizarov method’s unique advantage is the achievement of simultaneous correction of multifocal multiplanar complex deformities of the lower limbs in patients with HME.