Measurement of bone density around the Oxford medial compartment knee replacement using iDXA. A precision study.

The goal of this study was to evaluate whether the Lunar iDXA densitometer can accurately measure the bone mineral density (BMD) around the tibial component of the Oxford unicompartment knee replacement (UKR). Both knees in 20 patients were measured 3 times in the supine position with repositioning between each scan. We chose 7 regions of interest to evaluate the bone density around the implant. Small but significant differences between the implant and nonimplanted knee were noticed with the nonimplanted knee having slightly higher BMD and bone mineral content (BMC) in areas 1-3 (p≤0.001) and area 6 (p=0.002). There was higher BMD in area 4 (p=0.028). The precision for BMD in the 7 areas of interest in the implanted knee varied between 0.55% and 4.04% and BMC between 1.8% and 5.3%. There was no significant difference in the precision between the nonimplanted and implanted knees. Prospective serial measurements around the Oxford UKR using iDXA will be able to assess specific areas of stress shielding and potential implant stability, which is likely to help predict the survival of the implant.

Recruitment strategies for an osteoporosis clinical trial: analysis of effectiveness.

AIM: To examine the effectiveness of a planned rapid recruitment strategy in an osteoporosis clinical trial. METHODS: Multiple recruitment methods were explored, including media advertising, searching bone density scan and X-ray results in specialist and primary practice databases, community initiatives, and generation of research centre and study-specific pamphlets. RESULTS: Of 246 women screened, 41 consenting to the study, only 14 were randomised. Thus, 232 (94%) volunteers were screen failures, ineligible or declined to participate. With regard to the cost-effectiveness of all recruitment strategies, searching the research centre database was the most successful, with four women randomised at a cost of approximately NZ$302 per volunteer. Other strategies were less cost-effective. CONCLUSION: Obtaining a specific study cohort can be achieved by a comprehensive, targeted, rapid recruitment program. A research centre database search was the most successful and cost-effective recruitment modality in this small study.

The effects of a high calcium dairy food on bone health in pre-pubertal children in New Zealand.

Childhood and adolescence is the period of most rapid skeletal growth in an individual's lifetime. A greater peak bone mass achieved in the first 2-3 decades of life, may protect against the risk of osteoporotic fracture in later life. The aim of this randomized, controlled study was to assess in pre-pubertal boys and girls (aged 8-10 years) the effect of 18 months of a calcium enriched, cocoa flavoured product on bone density, bone growth and bone size in New Zealand children. One hundred and fifty four pre-pubertal boys and girls (aged 8-10 years) were randomized to receive a high calcium dairy drink or a control drink reconstituted with water for 18 months. They were assessed at baseline and then every 6 months for the first 18 months, while they were having the supplement; they were then followed up 12 months after supplementation had finished. Bone mineral density and bone mineral content were assessed at the total body, hip and spine. Indicators of bone size (vertebral width and height) were also measured at the spine. Anthropometric data was collected, medical history questionnaires were administered (including the Tanner or pubertal stage questionnaire), dietary calcium intake was assessed with a calcium food frequency questionnaire and calcium supplement compliance was determined. There was no significant difference between the 2 groups for bone mineral density or bone mineral content at any time point. There was no difference in vertebral height or width at any stage of the study, indicating no additional influence on bone size at the lumbar vertebrae. There were no significant differences between height, weight, lean mass or fat mass at any time point. Both groups had higher habitual calcium intakes than recommended for this age group going into the study and throughout the study. In this 2(1/2) year study (18 months supplementation, 1 year follow-up) we did not observe a difference in bone mineral density in pre-pubertal children. This was probably due to their high habitual dietary calcium intake whereby minimal addition of calcium to the diet reached the threshold level where no further benefit was seen. There were no significant differences between the two groups in body composition. Growth and the mean height and weight remained between the 50th and 75th percentile for their age. We have shown calcium supplementation in children with high habitual dietary calcium intake appears not to have additional effects on bone mass. Calcium supplementation needs to be targeted in those children with low habitual dietary calcium intake.

The hemorheological effects of raloxifene in postmenopausal women with osteoporosis. Results of a 3-year placebo-controlled clinical trial.

Raloxifene, the prototype of the selective estrogen receptor modulators, has been associated with an increased risk of venous thromboembolism. As hemorheological factors may be involved in thrombus formation this placebo-controlled study investigated whether raloxifene was associated with changes in determinants of blood viscosity. Fifty-seven post-menopausal women were randomly assigned to receive placebo, raloxifene 60 mg/day, or raloxifene 120 mg/day for 36 months. Venous blood samples were collected at baseline and at 12-monthly intervals and used to measure hematocrit, whole blood and plasma viscosity and plasma fibrinogen concentration. Time- and treatment-related changes in the grouped and pooled data was analysed using ANOVA with repeated measures and correlation matrices. The mean values of all the hemorheological indices showed small inconsistent changes within the normal reference range over the 36-month period of the study. There was a small but significant decrease over time in high shear rate blood viscosity and plasma viscosity in raloxifene-treated subjects compared to those receiving placebo (p<0.05). Correlation analyses showed the anticipated relationships between blood viscosity and hematocrit and plasma viscosity levels and also between plasma viscosity and plasma fibrinogen concentration. No subject developed a thromboembolic vascular event during the study. These results show that compared with placebo treated-subjects, long-term raloxifene treatment in post-menopausal women, at a dose of either 60 or 120 mg daily, was not associated with adverse changes in hemorheological factors that may contribute to venous thromboembolism.