Computed tomography was used to find a sensitive parameter for bone mineralization. A precision scanning instrument was constructed for determination of the mineral distribution in sections of the forearm. The quality of the reconstructed images allows separate quantification of compact and spongy bone even when gamma rays are used. Computer simulation and measured of models and macerated human bones showed that under clinical conditions it is possible to quantify spongy bone density within an accuracy of +/-2%.

Gamma-ray computed tomography (gamma-ray CT), using a special purpose scanner, enables in-vivo quantitative analysis of bone mineralization. Trabecular bone density (TBD), the relative amount of compact bone (bone density, BD) and the total absorption (TA) for a cross-section of the radius are determined from measurements of local linear absorption coefficients. A preliminary study of normal children (n = 49) and adults (n = 34) indicated that TBD is independent of age and sex in the age range 4 to 40 years. DB remains constant throughout childhood but increases after puberty in both women and men. TA is higher for adults than for children, and also higher for men than for women. A correlation between TA and parameters relating to body size indicates a relationship between body weight and bone mass.

Medical Research Societyquently the non-disruptive spectrophotometric method, based on the absorption a t 280m by tyrosileresidues, has been investigated. Full spectra (320-24Onm) of synovial f l u i d s showed variations due t o light-scattering t h a t were only p a r t i a l l y diminished by treatment w i t h hyaluronidase or centrifugation. However, since light-scattering increases as the fourth power of the wavelength, the extinction ( E~g o ) due to protein can be corrected f o r s c a t t e r by measuring a t 310nm (E310) i . e . corrected E z~o = measured E2g0-E310(3104/2804) . This relationship gave values f o r d i f f e r e n t concentrations of serum albumin and of human serum t h a t agreed w i t h measurements done both by the biuret and by the Lomy method. Similar comparative measurements of human synovial f l u i d showed t h a t normal serum can be used f o r calibrating spectrophotometric measurements of synovial fluid. T h i s method is very rapid and reproducible to within * 4%, w i t h a l i m i t of measurement of 0.05 m g / m l .Contamination by blood can be assessed from t h e absorption a t 420nm.

SUMMARY 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 wes 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.

During a 15-month period, 47 elderly female patients admitted to hospital with a fractured neck of femur were studied immediately prior to discharge, in comparison with 34 elderly female control patients undergoing elective surgery who had been admitted over the same period to the same orthopaedic wards. The principal differences between the two populations were that the fracture patients had a lower forearm trabecular bone density, with lower bodyweight (both lower muscle mass and lower fat content), increased body sway, worse eyesight and reduced mental acuity. The serum biochemistry of the two groups was almost indistinguishable except that the fracture patients tended to have slightly lower concentrations of proteins. There was no evidence to implicate dietary vitamin D deficiency, osteomalacia, oestrogen deficiency or alcoholism in the aetiology of the fracture, nor was there evidence to suggest alterations in endocrine function with respect to cacitonin or parathyroid hormone.