The Hip: Preservation, Replacement and Revision

Rickets


- See:
    - Osteomalacia:
    - Vit D Abnormalities:

- Discussion:
    - rickets is an osteomalacic syndrome in which there is an inability to mineralize chondroid and osteoid;
          - lack of available calcium or phosphorus (or both) for mineralization of newly formed osteoid;
    - osseous changes in both adults and children reflect that either ionized Ca or phos, or both, is insufficient in concentration to mineralize the skeleton fully;
          - there is less mineralized bone per unit volume of bone;
    - osseous changes in the rapidly growing skeleton of a young child w/ rickets may result in bowing deformities due to the decreased resistance of the
          skeleton to bending and shearing moments;
          - as consequence, stress frxs w/ resultant deformities occur;
          - note that the classic changes of rickets will typically occur in children younger than 6-7 years of age;

- Causes of Rickets and Osteomalacia
    - deficiency states
    - gastrointestinal causes
    - renal osteodystrophy
    - hypophosphatemic vitamin d-resistant rickets;
    - vitamin-D deficiet rickets:
          - may see hypophosphatemia, low level of vitamin D, and normal level of PTH hormone;
    - vit D dependent rickets: type I and II
    - idiopathic hypophosphatemic rickets:
          - new syndrome of hypophosphatemic rickets has been described that is unusual in that symptoms include hyper-calciuria and a normal serum calcium level;
          - high 1,25 vit D levels & hyperabsorption of Ca distinguish this new disorder from more common X linked familial hypophos-phatemic rickets, in which
                 defective 1,25 Vit D production is usual feature;
          - it is probably that both X linked and hypophosphatemic forms have a similar renal tubular defect in phosphate reabsorption;
    - renal tubular acidosis:
          - increased phosphate retention causes increased binding of Ca in the gut;
          - patients get a secondary hyperparathyroidism;
    - tumors: (see soft tissue and bone tumors)
          - may present as late onset rickets in a patient without family history of metabolic disease;
          - many of these tumors secrete phosphatonin, which will inhibit tubular resorption of phosphate and which converts hydroxylation of 25 Vit D to 1-25 Vit D;
    - medications:
          - chronic use of anticonvulsant medication:
          - lasix, heparin, steroids, INH, tetracycline;


- Differential Dx:
    - hypophosphatasia:
          - it is important to note that in young children hypophosphatasia may cause hypercalcemia, and therefore it would be inappropriate to prescribe Vit D or
                    calcium supplementation (which might be given if the condition was mistaken for rickets);
    - metaphyseal chondrodysplasia:
          - many pts initially to have been considered to have Vit D resistant rickets, have actually been found to have metaphyseal chondrodysplasia, 
                 & has led to innappropriate administration of vitamin D in some patients;
    - fibrous dysplasia or neurofibromatosis:
    - fanconi syndrome:  
          - autosomal recessive syndrome w/ a hypokalemic, hyperchloremic acidosis;
          - patients show hypocalcemia, hypophosphatemia, and increase alk phos;
          - urine is alkaline instead of being acidotic;


- Clinical Presentation:
    - classically brittle bones w/ physeal cupping/widening, bowing of long bones, transverse radiolucent (Looser's) lines, ligamentous laxity, flattening of skull,
           enlargment of the costal cartilages (rachitic rosary), and dorsal kyphosis characterize this disorder;
    - personality:
           - children may show apathy and irritability;
           - they may be hypokinetic and may prefer to sit rather than to stand or to walk;
    - growth disturbance:
           - most children who have florid rickets, regardless of etiology, have some stunting of growth, and the height sometimes falls far below the normal range;
    - face and skull:
           - skull in very young children may show softening (craniotabes) and prominence of suture lines (hot-cross-bun skull) and frontal bones (frontal bossing);
           - defects of the dental enamel and extensive caries are common;
    - spine and thorax:
           - exam of spine frequently shows a thoracic kyphosis (rachitic cat-back)
           - exam of thorax may show prominence of the costochondral junctions (rachitic rosary) and, not uncommonly, pectus carinatum;
           - indentation of lower part of the rib cage, at the insertion of diaphragm, is referred to as Harrison groove.
           - the resultant deformities may cause a "pot belly" abdominal deformity;
    - extremities:
           - examination of extremities is likely to show rather marked enlargement of the wrists, ankles,
                  knees, and elbows and bowing deformity of long bones, especially of the lower limbs.
                  - see: coxa vara and genu varum;
           - frxs are common in children w/ rickets and in those with renal osteodystrophy;
           - slipped capital femoral epiphysis is sometimes a serious problem;


- Histologic Changes in Rickets:

- Radiographic Findings:


- Treatment:
    - if disorder is detected early in life, skeleton may develope normally;
    - treatment w/ phosphate and 1,25 Vit D can usually maintain normal growth in such disorders as sex linked dominant hypophosphatemic rickets;
    - prevention:
           - premature infants: require 2,000 IU/day for first 3 months;
           - full term infants: require   400 IU/day
    - treatment:
           - vitamin D 1,500 to 5,000 IU/day for 6-10 weeks;
           - w/ in 2-4 weeks, x-rays demonstrate evidence of healing



Principles and results of corrective lower limb osteotomies for patients with vitamin D-resistant hypophosphatemic rickets.

Primary hypophosphatemic rickets. Effect of oral phosphate and vitamin D on growth and surgical treatment.

Adult-onset vitamin D-resistant hypophosphatemic osteomalacia. A possible variant of vitamin D-resistant rickets.



Original Text by Clifford R. Wheeless, III, MD.

Last updated by Data Trace Staff on Monday, May 21, 2012 4:19 pm