X-linked hypophosphatemic rickets. What the orthopedic surgeon needs to know

Purpose: X-linked hypophosphatemic rickets (XLH) is a rare genetic disease characterized by an increase in fibroblast growth factor 23 (FGF23) expression. The skeleton is one of the systems most affected and deformities of the lower limbs are one of the first reasons for consulting an orthopedic surgeon. The aim of the present study was to offer practical advice for a comprehensive orthopedic approach to XLH. Materials: A literature search was conducted in PubMed, a freely available and cost-effective database. The articles included in the study were discussed by a research group with specific expertise in bone metabolism and pediatric deformities, in order to answer three fundamental questions and thus provide the orthopedic specialist with guidance on XLH: (1) How should the physician complete the diagnosis of XLH?; (2) When might a surgical procedure be recommended?; (3) What kind of surgical procedure should be performed? Results: Sixty-three articles were included and discussed by the research group. Conclusions: A correct and timely diagnosis of XLH is essential to appropriately manage affected patients. To complete this diagnosis a detailed medical history of the patient, a comprehensive clinical and radiographic evaluation, and specific biochemical tests are needed. Pharmacological treatment is based on supplementation of both phosphate and vitamin D, however, a monoclonal antibody that inactivates FGF23 (burosumab), has recently been introduced with promising results. Orthopedic surgery is needed in cases of moderate or severe deformities, to allow physiological growth and prevent early osteoarthritis and gait alterations. Surgical options are osteotomies and hemiepiphysiodesis, which is preferred whenever possible. Three different devices for temporary hemiepiphysiodesis are available (staples, transphyseal screws and tension band plates). Obviously, surgical procedures need an appropriate medical therapy to be effective. In conclusion, the diagnosis, treatment and follow-up of XLH require a multidisciplinary approach and a comprehensive evaluation of anamnestic, clinical and radiographic data.