Bone
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The aim of this study was to investigate the incidence and epidemiology in 1994 of hip fracture in Shenyang, a large city in the northeast of The People's Republic of China, using register information and medical records collected from the 36 hospitals in Shenyang. The hip fracture data were restricted to cervical or trochanteric types. A subset (59% of total) of medical records of hip fracture was used to investigate the causes of hip fracture. ⋯ Simple fall accounted for 70% hip fractures in women but caused only 49% in men (chi2 = 11.2, degrees of freedom [df] = 1,p = 0.0008). The frequency of hip fractures caused by a fall from a bicycle was higher in men (28%) than women (10%) (chi2 = 13.0, df = 1,p = 0.0003). The results of this study indicate (1) a low incidence of hip fracture in a Chinese population compared with more affluent countries, and (b) a higher incidence in men than women that is related in part to a higher incidence of accidents, especially bicycle-related ones.
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Droloxifene (DRO) is a selective estrogen receptor modulator that prevents bone loss by inhibition of bone turnover associated with estrogen deficiency in both growing and aged female rats. The purposes of this study were to test: (a) whether DRO can maintain prostaglandin E2 (PGE2)-restored bone after discontinuation of PGE2 in aged, ovariectomized (ovx) rats; (b) if an inhibition of bone turnover by DRO reduces bone anabolic effects of PGE2; and (c) whether bone mass restored by PGE2 plus DRO can be maintained after discontinuation of both agents. Female rats at 12 months of age were sham-operated (sham) or ovx. ⋯ Treatment with DRO in the maintenance phase inhibited bone turnover and prevented bone loss induced by withdrawal of PGE2. Trabecular bone mass was maintained in the PGE2 plus DRO followed by vehicle group and further increased in the PGE2 plus DRO followed by DRO groups. We found that: (a) DRO is efficacious in maintaining PGE2-restored bone after discontinuation of PGE2; (b) DRO did not blunt the anabolic effects of PGE2; (c) bone loss occurred after cessation of treatment in the PGE2-alone group, whereas it was maintained after cessation of treatment in PGE2 plus DRO group; and (d) an additional anabolic effect was found in ovx rats treated with PGE2 plus DRO followed by DRO.
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We modified the noninvasive, in vivo technique for strain application in the tibiae of rats (Turner et al., Bone 12:73-79, 1991). The original model applies four-point bending to right tibiae via an open-loop, stepper-motor-driven spring linkage. Depending on the magnitude of applied load, the model produces new bone formation at periosteal (Ps) or endocortical surfaces (Ec. ⋯ Bending strains above a loading threshold of 40 N increased Ec lamellar bone formation rate, bone forming surface, and mineral apposition rate with a dose response similar to that reported by Turner et al. (J Bone Miner Res 9:87-97, 1994). We conclude that the modified loading system offers precision for applied loads of between 0 and 70 N, versatility in the selection of loading rates up to 20 Hz, and a reproducible bone formation response in the rat tibia. Adjustment of the loader also enables study of mechanical usage in murine tibia, an advantage with respect to the increasing variety of transgenic strains available in bone and mineral research.
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The mineral, lean, and fat contents of the human body may be not only allometrically but also functionally associated. This report evaluates the influence of muscle mass on bone mass and its age-related changes by investigating these and other variables in both genders in the different stages of reproductive life. We have analyzed the dual-energy X-ray absorptiometry (DEXA)-determined whole-body mineral content (TBMC), lean body mass (LBM), and fat body mass data (FBM) of 778 children and adolescents of both genders, aged 2-20 years [previously reported in Bone 16(Suppl.): 393S-399S; 1995], and of 672 age-matched men and women, aged 20-87 years. ⋯ A biomechanical explanation of those differences is suggested. Sex hormones or related factors could affect the threshold of the feedback system that controls bone remodeling to adapt bone structure to the strains derived from customary mechanical usage in each region of the skeleton (bone "mechanostat"). Questions concerning whether the mineral accumulation in women during the reproductive period is related or not to an eventual role in pregnancy or lactation, or whether the new bone is stored in mechanically optimal or less optimal regions of the skeleton, are open to discussion.
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African teenagers with slipped capital femoral epiphysis (SCFE) not infrequently also have genu valgum (knock-knee). Because we had previously demonstrated metabolic bone disease attributable to dietary calcium deficiency in black teenagers with genu valgum, we examined 29 black teenagers (15 male, 14 female) with SCFE for metabolic bone disease. Each patient had an iliac crest bone biopsy taken (after double tetracycline labeling) for routine histomorphometry, and blood and urine samples for bone biochemistry. ⋯ Parathyroid hormone correlated with Aj. AR (r = 0.661, p = 0.038) and serum phosphorus (r = -0.764, p = 0.010). We conclude that sexual immaturity and possibly past dietary calcium deficiency contributed to osteopenia, and that this, together with obesity, led to the development of more severe and more frequently bilateral SCFE in our patients than in reported series of black and white children.