Pediatric Metabolic and Vascular Disorders: An Introduction

Rickets is a common disorder of children, caused by inadequate supply or metabolism of calcium, phosphorous, or vitamin D, all of which are necessary elements for the development of healthy growing bones. While nutritional rickets (poor dietary intake) remains the most common cause of this disease worldwide, sex-linked vitamin D-resistant hypophosphatemic rickets is believed to be the most common cause of this disorder in North America. Pathologically, rickets is characterized by deficient mineralization of newly formed bone (preformed osteoid is unmineralized), and the endochondral calcification at the growth plate is absent or reduced leading to growth deformity. Clinically, this results in stunted growth and soft and weak bones causing multiple generalized deformities, specifically around the knee in the form of bow legs, knock knees, and windswept knees. As this is a systemic disorder, deformities are typically bilateral, multi-apical, multi-planar, and multi-segmental. Rotational deformities, often severe, are also very common (three of the four cases presented in this section). Medical treatment (oral phosphate and vitamin D) remains the cornerstone of management of these conditions. However, in some cases, the deformities are not fully corrected despite adequate medical treatment and can even progress or recur. In such cases, surgical treatment is indicated. High recurrence rate of deformities and a tendency toward delayed and nonunions of osteotomies are two potential complications largely dependent on the age at which surgery was performed and is generally independent of the type of corrective osteotomy or type of fixation used.