To point out common patterns of malalignment and deformity in hypophosphatemic rickets and describe treatment principles and techniques as well as common obstacles.
Methods: Deformities of the lower limb in hypophosphatemic rickets do not resolve spontaneously under metabolic control of the disease. To prevent severe deformity and joint overload in the growing child guided growth has been shown to be effective in most cases. As recurrence of malalignment is common during growth, postponing surgical correction with osteotomies until or close to skeletal maturity has been recommended.
Results: The most common deformities in hypophosphatemic rickets are femur and tibia vara combined with an internal torsion deformity of the tibia. Valgus deformity is less common followed by rare cases presenting with unilateral varus-valgus (windswept deformity). Most patients present with disproportionate shortening. Acute correction of the deformities is possible. However, acute shortening for axial correction is necessary in case of severe bowing of the bone due to the relative lengthening of soft tissue (nerves/vessels) on the concave side of the bone. Additional torsional deformities of the tibia can be corrected using six-axis external fixation frames. In previously untreated cases with severe varus and torsional deformity we prefer to correct the legs sequentially using a six-axis frame on the femur and a bi-level six-axis frame on the tibia to restore full anatomic alignment and torsion in one step. At the time of frame removal rushpins can be used to protect the newly formed bone.
Conclusion: Guided growth might be repeatedly used until skeletal maturity to prevent severe deformity and joint over-load. After maturity six-axis frames allow for accurate correction of the most severe multiplanar and multiapical deformities. Less severe deformities and shortening can be corrected successfully with plates or lengthening nails.
Disclosure: Consultant Smith & Nephew Company; Consultant NuVasive Company.