Complex infantile and congenital hip dislocation: assessment with MR imaging.

Twenty-five magnetic resonance hip studies were performed on 19 infants with congenital hip dislocation. These patients had a poor initial treatment response, a teratologic dislocation, or a late presentation. Detailed images of single hips obtained with small surface coils resulted in excellent visualization of all the clinically important soft-tissue and cartilaginous structures of the hip. No other imaging modality demonstrates all of these structures simultaneously.

Isolation and characterization of bone cells from a patient with osteogenesis imperfecta type 1b.

The metabolic defect(s) in bone cells which manifests itself in the disease osteogenesis imperfecta (OI) type 1 is not known. Since this form of the disease displays both a variable tissue involvement and the possibility of remission it is difficult to attribute its expression to a primary mutation in the structural gene for type I collagen (as can the perinatal lethal forms of OI). In an attempt to more fully understand OI type 1 we have isolated and characterized a subpopulation of cells obtained from a sample of bone from a patient with OI type 1b. This subpopulation of cells has been shown to morphologically resemble the osteoblast phenotype, to contain the highest level of alkaline phosphatase of the cells isolated, to synthesize collagen, to respond to bone target hormones such as 1,25(OH)2D3 and parathyroid hormone, and to proliferate rapidly. Moreover, the response of these cells to the vitamin D metabolites, from the standpoint of growth regulation, is qualitatively different from normal bone cells. We intend to use these cells as a model system for studying the defect in OI type 1b.

Congenital subluxation of the knee--an anatomic dissection.

The knee of an infant born with congenital subluxation was dissected to delineate the pathology involved. The primary findings of importance included isolated fibrosis of the vastus intermedius muscle, absence of the gastrocnemius muscle, anterior displacement of the hamstrings and contracture of the anterior joint capsule. Comparison with previously described pathology is discussed.

Assay of bone resorption in vivo with 3H-tetracycline.

3H-Tetracycline (3H-TC) was used to quantify resorption in whole bones of growing rats and dogs. After repeated isotopic labeling of actively growing embryos or neonates, 3H-TC was observed to be distributed homogeneously and in equilibrium with 45Ca. A rapid and large loss of 3H-TC and a small loss of 45Ca occurred during the early weeks of rapid bone growth, suggesting that absolute amounts of 45Ca resorbed from bone, as reflected by losses of 3H-TC, are five to ten times greater than the net amounts of 45Ca lost from bone. Minimal loss of 3H-TC occurred due to nonspecific physicochemical exchange in vivo or in vitro (5%) except with nonradioactive tetracycline, and 3H-TC was not greatly exchanged or reused (10%) in vivo. The data are considered in terms of local and systemic conservation of calcium.