and Angular Bone Deformity

Differential Diagnosis

Physiological bilateral genu vara in otherwise healthy infants will spontaneously correct by 2–3 years of age, after which genu valga can develop and resolve by age 5–7. The differential of pathologic pediatric angular deformities includes (1) posttraumatic or post-infectious, (2) Blount’s disease, (3) vitamin D-resistant rickets, (4) nutritional (calcium or Vitamin D deficiency) rickets, (5) skeletal dysplasias, and (6) idiopathic.

Posttraumatic or Post-infectious

Inadequate access to primary treatment of osteomyelitis and fractures results in metaphyseal or diaphyseal malunion or deformity or asymmetric physeal arrest (Fig. 12.2). The deformity is usually unilateral and often accompanied by leg-length discrepancy.

../images/270913_2_En_12_Chapter/270913_2_En_12_Fig2_HTML.jpg — Fig. 12.2

Healed osteomyelitis of the femoral diaphyses with physeal growth arrest and varus angulation in a 7-year-old

Blount’s Disease

Blount’s disease is a developmental abnormality caused by disordered endochondral ossification of the medial proximal tibial physis, resulting in a multi-planar deformity, most commonly characterized as tibia varus. Blount’s disease is thought to be caused by mechanical abnormalities, not metabolic ones. It occurs in infantile and adolescent forms. The infantile form is often bilateral but asymmetric, distinguishing it from physiological genu vara. Careful evaluation of the radiograph reveals typical physeal changes confined to the medial half of the proximal tibial physis (Fig. 12.3). The distal femoral physis is often normal, but in some cases an adaptive valgus deformity is seen. An alternate diagnosis should be sought if varus deformity is seen in the distal femur.

../images/270913_2_En_12_Chapter/270913_2_En_12_Fig3_HTML.jpg — Fig. 12.3

X-ray of a knee with the typical bony changes of Blount’s disease: medial tibial physeal changes with adaptive valgus at the distal femur

This condition is more common in children of African origin and should be distinguished from the Blount’s seen in higher-income countries in obese patients. A review of 110 African children with Blount’s disease found no evidence to support age of walking or weight as risk factors [2]. (See Chap. 41 for discussion of osteotomies.)

Rickets

For children in the developing world, rickets is the most common noncommunicable disease [3]. Rickets is caused by a failure of endochondral calcification resulting in widened and deformed growth plates. Though there are no internationally accepted diagnostic criteria, the usual findings are widened epiphysis at multiple locations (particularly the wrist), rachitic rosary, swollen knees, angular deformities of the lower limbs, bone pain with ambulation, and frontal bossing [4]. A wrist x-ray should be taken as non-rickets forms of angular bone deformity seldom affect the wrist (Fig. 12.4).

../images/270913_2_En_12_Chapter/270913_2_En_12_Fig4_HTML.png — Fig. 12.4

(a) This infant presented with delayed motor milestones and was noted to have swelling at the costochondral junction (“rachitic rosary”). (b) A 4-year-old child with rickets and wrist swelling, a clinical sign of active rickets, (c) also had bowing of the lower extremities. (d) Classic radiographic findings in rickets include widening of the physes and flaring of the metaphyses

Worldwide, the most common cause of rickets is vitamin D deficiency; however, this is not the case in a variety of countries in sub-Saharan Africa and Asia. In these low-income countries, calcium deficiency is the major cause of nutritional rickets [5].

Vitamin D-Resistant Rickets

Vitamin D-resistant rickets results from genetic abnormalities causing a defect of renal tubular function. Children present as toddlers with weakness and delayed walking, angular deformities, and enlarged epiphyses. Biochemical screening to differentiate nutritional from vitamin D-resistant rickets should be done if available. All children should be treated initially with vitamin D and calcium supplements as a trial. Treatment of vitamin D-resistant rickets is complex and requires a multidisciplinary approach with specialized medical colleagues.

Vitamin D-Deficient Rickets

True vitamin D-deficient rickets was previously thought to be rare in tropical countries due to abundant sunlight, except in cultures where individuals are covered or veiled. Recent studies show that in some environments where children are kept inside much of the day—informal settlements in Kenya for safety reasons or houses with few windows—vitamin D-deficient rickets is a problem [6, 7].

Calcium Deficiency

Calcium-deficiency rickets is the most common cause of angular deformity in lower-income countries yet is the least understood and is probably underdiagnosed [8, 9]. The past cases were likely to have been classified as idiopathic. Studies in Africa and South Asia show that calcium deficiency results from malnutrition due to a monotonous carbohydrate diet deficient in calcium and micronutrients while high in phytates—compounds found in whole grains, legumes, nuts, and seeds that bind to certain essential dietary minerals and slow their absorption [10–12]. Large deformities are common. Radiographs may show some widening or flaring of the metaphyses, but these changes are not as profound as in vitamin D-resistant rickets. Angular deformities occur in the metaphyses and diaphyses of long bones, especially at the knee, presenting as genu valga, genu vara, or windswept deformity. Upper extremity and other weight-bearing joint involvement is rare. The presentation of windswept deformity should create a high index of suspicion of calcium deficiency. Biochemical analysis will be normal (Fig. 12.5).