Surgical treatment of the varus knee caused by vitamin D-resistant rickets. Report of two cases and review of the literature

Introduction: Hypophosphatemic rickets is a rare X-linked genetic disorder clinically characterized by bone deformities, especially localized in the lower limbs, such as varus and valgus knees. Diagnosis is based on clinical observation and biochemical parameters. Treatment is pharmacological, however, if the skeletal deformities are severe, it is necessary a surgical correction. Presentation of cases: We report two patients with hypophosphatemic rickets and severe varus knee. Both patients were surgically treated by bilateral femoral and tibial osteotomy, and stabilized with a uniplanar external fixator. No complications occurred in the post-operative period. The patients were clinically and radiographically checked thereafter over time. At last follow-up, 2 and 19 years after surgery, both patients were asymptomatic without recurrence of the deformity. Discussion: In case of severe bone deformities caused by hypophosphatemic rickets, surgical approach is mandatory. Most authors agree that the ideal time to perform the operation is close to the end of bone maturity, to avoid the risk of recurrence of the deformities. However, in some young patients, with severe and progressive deformity, it is necessary to plan an early surgical correction in two or more stages, and multiple osteotomies should be planned. Conclusion: According to our results, we believe that surgical treatment should ideally be performed close to skeletal maturity, but in one of our cases with serious deformities of both lower limbs, an early surgical correction was necessary despite the young age.