The standard treatment consists of oral supplementation of large doses of phosphorus along with administration of vitamin D. Studies have revealed that longitudinal growth is superior in children who receive vitamin D treatment [4]. Furthermore, treatment by growth hormone administration also increases height and has positive influence on bone density [9]. Recently, analogs of vitamin D3 (1,25-dihydroxy-vitamin D3) have been proved to be more effective than the previously used supplements [10].

The orthotic management of skeletal deformities in patients with vitamin D-resistant rickets has not been successful. If patients complain of increasing pain and difficulty walking, angular deformities should be surgically corrected [4, 11]. The postoperative management should be done in close collaboration with the attending nephrologist or endocrinologist, since calcium levels tend to suddenly increase with postoperative immobilization period. The most common deformity seen in this patient group is a gradual anterolateral bowing of the femur accompanied by tibia vara (Figs. 15.6 and 15.7). In order to reach a physiologic lower extremity alignment, multilevel osteotomies are often necessary [4, 11, 12]. The mechanical axis can be slightly overcorrected during surgery. The suggested fixation modality varies among reports. While external fixation allows fine-tuning of the alignment postoperatively [13] (Fig. 15.8), intramedullary fixation and plate fixation have also been reported [12, 14–16] (Fig. 15.9; Table 15.2). Regardless of type of implants utilized, careful preoperative planning of the surgery for these multiplanar deformities is obligatory to successfully reestablish the alignment of the lower extremity.

Recurrent deformity is a common sequela of osteotomies in patients with hypophosphatemic rickets [4, 12, 14] (Fig. 15.10). As expected, younger patients have a higher risk of recurrence. Therefore, milder deformities should not be operated early in the infancy. At this stage guided growth by hemiepiphyseodesis is an advisable alternative [17]. Only when gait is compromised by a thrust, or symptoms such as pain start, a corrective osteotomy should be done.

Short stature is also noted amongst children with hypophosphatemic rickets. The common indication for long bone lengthening is a shortening of the entire or segment of limb in one or both legs [11]. The procedure can be performed by monolateral or circular external fixators or by lengthening over an intramedullary nail (LON) (Fig. 15.11) [12]. The application of flexible intramedullary nails in limb lengthening for children is also an alternative with multiple advantages [18]. This technique also respects the bone biology that is essential during the limb lengthening.

The pathological change caused by hypophosphatemic rickets occurs very close to the growth plate, often leading to juxta-articular multiplanar deformities and severe malalignment. Preoperative assessment usually reveals multiple centers of rotation of angulation (CORA) (Fig. 15.12); thus several osteotomies may be required to fully correct the multiapical deformities. Many methods of treatment have been described. The most common involve acute or gradual correction, using either circular or monolateral external fixators, which can secure accurate correction of the deformity and address the limb-length discrepancy. However, these methods are uncomfortable for the patient, especially when both legs are involved. There are further disadvantages, such as the need for daily adjustments, weekly follow-ups, a high rate of pin-track infection, and a long duration of external fixation.