Seventy children with juvenile chronic arthritis have had measurements of cortical and trabecular bone density in one or both radii. In 7 children with unilateral disease of one wrist, there was a substantial reduction in growth on the affected side. Trabecular bone density in the distal radius was reduced in the main group of 63 patients compared with controls, and this deficit was appreciably worse if the wrist was clinically affected by disease or if the child was being treated with steroids. Cortical bone density in the midshaft was less affected. Crush fractures of the spine were associated with more prolonged periods of bed rest, steroid therapy, radial trabecular bone density more than 2 standard deviations below normal, and subnormal 25-hydroxycholecalciferol concentrations in the serum. Since steroid therapy is often mandatory the main therapeutic implications are that the more severely affected child often needs vitamin D supplementation in \"physiological\" dosage, and that early mobilisation and reduction of steroid dosage should be constant aims.
\n \n\n \n \nUsing a modified plasma clearance technique, with 18F as a tracer, it is possible to measure blood flow to bone in man. In the normal adult skeleton, blood flow amounts to about 300 ml/min. In untreated Paget's disease of bone there is a striking increase, which is proportional to the biochemical severity of the disease : total blood flow to the skeleton is approximately doubled at an alkaline phosphatase of 50 KAu/dl (i.e. about four times the normal upper limit). Treatment with calcitonin brings a rapid return to normal, possibly before there is a detectable biochemical response. This may explain the rapid pain relief often reported on starting treatment with calcitonin.
\n \n\n \n \n1. Radiocalcium absorption was measured in duplicate in 10 subjects by the double-isotope method, with calcium as the oral carrier (2.5 mmol). Analysis of variance gave 95% confidence limits for a single measurement of fractional absorption and maximum absorption rate in a given individual of +/- 16.5% of administered dose and +/- 18.2% of dose/h respectively. 2. The size of these within individual variations suggests that alterations in the rate of calcium absorption may contribute to the week-to-week stabilization of some other controlled variable, such as plasma concentration of calcium. 3. In six of the subjects, calcium absorption was also measured with calcium loads at concentrations of 0.5, 5.0 and 20 mmol. Significant falls in fractional absorption, maximum absorption rate and mean transfer rate occurred as the load increased, together with a rise in mean transit time. Although between-individual differences at a given load were considerable, given a single-test result with a known carrier load, it is possible to predict quite accurately the results which would be obtained if a different carrier load were to be given.
\n \n\n \n \nAfter baseline studies, 21 patients with osteoporosis were treated with human parathyroid hormone fragment (PTH 1-34) given as once-daily subcutaneous injections for 6-24 months. The dose used did not cause hypercalcaemia even in the first few hours after injection. Calcium and phosphate balances improved in some patients, but there was no significant improvement in the group values. There were, however, substantial increases in iliac trabecular bone volume: the mean increase, confirmed by repeat blind measurements, was 70% above mean baseline volume. The new bone was histologically normal. Those patients who had the largest increases in 47Ca-kinetic and histomorphometric indices of new bone formation showed the greatest increases in trabecular bone volume, suggesting that treatment with human parathyroid hormone fragment caused a dissociation between formation and resorption rates that was confined to trabecular bone. Since vertebrae are four-fifths composed of trabecular bone, this hormone fragment may prove useful in treating patients with the crush fracture syndrome.
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