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PubMed2004

The effect of anterior cruciate ligament surgery on bone mineral in the calcaneus: a prospective study with a 2-year follow-up evaluation.

PURPOSE: The goal of this study was to evaluate the effect of anterior cruciate ligament (ACL) reconstruction on the bone mineral area mass (BMA) in the calcaneus on the injured and noninjured sides. TYPE OF STUDY: A prospective cohort study with sequential assessments of bone mineral in the calcaneus before and after ACL reconstruction. METHODS: Thirty-four consecutive patients with a unilateral ACL rupture underwent arthroscopic reconstruction using patellar tendon autografts. The BMA was assessed bilaterally in the calcaneus using a gamma camera according to the dual-energy photon absorptiometry technique, before surgery and after 6 and 26 months. RESULTS: Thirty-one of 34 patients (20 men and 11 women) underwent all BMA measurements. The median age at index surgery was 27 (16 to 50) years, and the reconstruction was performed 12 (2 to 192) months after the injury. The median preoperative Tegner activity level increased from 3 (2 to 8) to 7 (2 to 9) at 26 months (P <.0001). The BMA in the calcaneus on both the injured and noninjured side decreased by 16% and 17% respectively from the preoperative measurement to the 26-month control (P =.0014; P =.0006). On all occasions, the BMA was lower on the injured side than on the noninjured side (P =.012). CONCLUSIONS: Patients with a unilateral ACL rupture had a lower BMA in the calcaneus on the injured side compared with the noninjured side. Although patients increased activity levels after reconstruction, the BMA in the calcaneus decreased on both the injured and the noninjured side up to 2 years after surgery. LEVEL OF EVIDENCE: Level II-1, prospective cohort study.

Absorptiometry, Photon↗

PubMed2004

Wheat bran fiber supplementation and bone loss among older people.

OBJECTIVE: The purpose of this study was to investigate the effect of wheat bran fiber (WBF) supplementation on bone loss in older people. METHODS: Two hundred thirty-seven men and women ages 40 to 80 y were included in this study. They constituted a subgroup of participants from a 3-y WBF intervention trial for preventing recurrence of colorectal adenomas. These participants were randomized into a high (13.5 g/d) or a low (2 g/d) WBF supplementation group. Bone mineral density at the forearm was measured by single photon absorptiometry at baseline and yearly during the intervention to monitor possible toxic effects of fiber supplementation on bone metabolism. RESULTS: Baseline characteristics of this subgroup of participants from the WBF trial were similar between the high and low supplementation groups. The annual amounts of bone loss at the radial third site were -0.017 +/- 0.018 g/cm2 and -0.013 +/- 0.021 g/cm2, respectively, for the low and high WBF groups; and the annual bone losses at the ultra-distal site were was -0.005 +/- 0.020 g/cm2 and -0.006 +/- 0.027 g/cm2, respectively, for the low and high WBF groups. After controlling for confounding factors, we found no significant differences in bone loss between groups (P > 0.05). CONCLUSION: WBF supplementation at the level given in this study may not have a significant effect on bone loss among older people.

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PubMed1997

Skeletal status of men with early and late ankylosing spondylitis.

PURPOSE: To assess the influence of extent of disease on the skeletal status of men with ankylosing spondylitis (AS). PATIENTS AND METHODS: Fourteen men with AS were studied at entry and again after 15 months. Bone mineral density (BMD) was assessed by single photon absorptiometry (SPA), dual energy x-ray absorptiometry (DXA), and quantitative computed tomography (QCT). Calciotropic hormones and bone turnover were also assessed, and biopsies of iliac crest and skin were taken after tetracycline double-labeling from 10 subjects. Clinical evaluation and Health Assessment Questionnaires were used to assess functional status. RESULTS: Of the 14 participants, 7 had sacroiliitis alone without radiologic evidence of spinal involvement (early disease) and 7 had sacroiliitis with extensive vertebral calcifications and immobilization (late disease). QCT baseline lumbar spine BMD was very low in both groups compared with normative standards (Z score = -3.08 +/- 1.83, P < 0.0001) and did not change significantly over 15 months. This low BMD was more marked in late disease than in early disease subjects (P < 0.01). DXA BMD at the lumbar spine was lower than predicted in early disease subjects (Z score = -1.08 +/- 0.67, P = 0.005) but not in the late disease group. DXA BMD was also low at the all three hip sites (Z score = -0.96 +/- 0.86, P < 0.01). Significant differences between late disease group and normative values were apparent at all hip sites. Values in early disease subjects, however, did not differ from age-predicted norms. Bone mineral status did not change significantly over the 15-month period of observation. Circulating parathyroid hormone (PTH) and vitamin D metabolites were normal in both groups as were creatinine clearance and urinary excretion of calcium and hydroxyproline. Osteocalcin levels were normal in all but the two youngest subjects in the early disease group. Histomorphometry of the iliac crest showed no consistent change in bone turnover. Bone volume and trabecular width were low in many cases. Cancellous bone volume correlated with lumbar spine BMD by QCT (r = 0.69, P = 0.026) but not with DXA. Although beneficial changes occurred in exercise tolerance and pain over time, anthropometric measurements did not improve. CONCLUSION: BMD is low in both the axial and peripheral skeleton in men with AS and is independent of spinal immobilization. Anterioposterior lumbar spine DXA in late AS is less useful than QCT in determining the degree of osteopenia in late AS. Bone mineral deficits in AS do not reflect measurable metabolic derangement or hypogonadism. Although bone histomorphometry suggests both trabecular thinning and loss of structural elements as mechanisms involved in low bone volume, the exact cause of osteopenia in AS remains to be determined.

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PubMed1996

The relative contribution of disc and vertebral morphometry to the angle of kyphosis in asymptomatic subjects.

In order to investigate the relative contributions of vertebra and inter-vertebral disk to kyphosis, a series of 100 asymptomatic healthy women (age range 39-91 years) were studied to evaluate lateral dorsal appearances and possible related parameters of bone loss. Subjects underwent lateral dorsal spine radiography and single photon absorptiometry of the radius. There was a significant decrease in physical height in relation to age (P < 0.001) and this was directly related to an increasing thoracic kyphosis (P < 0.005). The angle of kyphosis was better related to the average anterior disc height (P < 0.001) than to average anterior vertebral height. The vertebral body ratio, however (anterior/posterior height), was more strongly related to angle of kyphosis than was disk ratio. The results also showed a fall in the proximal and distal radial bone mineral content with age (P < 0.001). These findings suggest that dorsal kyphosis as part of the ageing process may be as closely related to the physical integrity of the disc as to the vertebral body. Hence, therapy for age related bone mineral loss may have limited effect on a kyphotic deformity of the dorsal spine in otherwise asymptomatic patients.

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PubMed1992

Bone mineral density of the lumbar vertebrae in children and adolescents with insulin-dependent diabetes mellitus.

To test the hypothesis that bone mineral density (BMD) is lower in children with insulin-dependent diabetes mellitus (IDDM), we measured BMD of the lumbar vertebrae (L-2 to L-4) by dual-photon absorptiometry in 31 boys and 25 girls, mean age 12.3 years, with IDDM of varying clinical duration (range 0.1 to 14.8 years). Mean standard deviation scores (z scores) were determined for L-2-L-4 BMD, weight, height, weight percentile, and weight-adjusted L-2-L-4 BMD index (L-2-L-4 BMD/weight), with reference data from a previously described white, nondiabetic, age-matched control group (n = 221). Compared with nondiabetic control subjects, male patients with short-term IDDM and all female patients with IDDM did not have significantly different L-2-L-4 BMD, weight, weight percentile, height, or BMD index. Boys with IDDM longer than 1 year had significantly lower weight, weight percentile, and height than did age-matched control subjects. When L-2-L-4 BMD of boys with long-term diabetes was corrected for weight, the L-2-L-4 BMD index was significantly greater than that of control subjects, indicating that weight was disproportionately lower than BMD. There were no significant linear correlations between metabolic control and L-2-L-4 BMD. When L-2-L-4 BMD was adjusted for differences in body weight, spinal BMD values in children with IDDM were not lower than in control subjects. These findings indicate that in children with IDDM, as in previously studied nondiabetic youths, body weight and spinal BMD are highly correlated; although BMD is reduced in some children with diabetes, the reduction parallels reductions in growth, and may simply reflect a normal response of the skeleton to a lower weight-bearing load.

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PubMed1995

Effect of physical activity on bone mineralization in premature infants.

OBJECTIVE: A 4-week pilot study was done with 26 preterm infants to evaluate whether a physical activity program would result in greater bone mineralization. DESIGN: Subjects were matched by birth weight, gender, and gestational age, and randomly assigned to the physical activity program (group EX; n = 13) or to the control group (group C; n = 13). Physical activity consisted of range of motion with passive resistance to all extremities for 5 to 10 minutes daily. Baseline and 4-week values were determined for both bone mineral analyses and serum levels of calcium, phosphate, alkaline phosphatase, parathyroid hormone, and 25-hydroxy-vitamin D. RESULTS: Despite similar nutrient intake at advised levels for preterm infants, EX infants gained more weight than control subjects (17.8 vs 13.4 gm/kg body weight per day; p = 0.01). A difference in radial bone mass and density change as determined by single-beam photon absorptiometry (+/- 2% error) was found between groups (p = 0.006 by analysis of covariance). Changes in bone width and in bone mineral content and density were enhanced by physical activity. Group EX infants had 12%, 18%, and 34% gains in bone width and in bone mineral density and content, respectively; group C infants had only a 2% gain in bone width and 11% and 14% losses from baseline in bone mineral content and density, respectively, during the 4-week study. Serum biochemical values were similar in the groups except for lower alkaline phosphatase levels in group EX. There was a negative association between bone mineral content and parathyroid hormone values: r = -0.83, p = 0.01. CONCLUSIONS: A physical activity program may increase the effects of adequate nutrition in healthy preterm very low birth weight infants by promoting weight gain and bone mass and by decreasing the risk of osteopenia.

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PubMed1991

Vertebral mineral content in diet-dependent and diet-independent hypercalciuria.

The vertebral mineral content was measured using dual photon absorptiometry in 41 calcium stone patients with idiopathic hypercalciuria. These patients had been previously divided into 2 groups (diet-dependent and diet-independent hypercalciuria) during a low sodium and low calcium diet. In some of the patients (11 with diet-dependent and 11 with diet-independent hypercalciuria) the vertebral mineral content was evaluated in relation to serum ionized calcium, intact parathyroid hormone, alkaline phosphatase and osteocalcin determined after a low sodium and low calcium diet. The vertebral mineral content, expressed as Z-VMD, was normal in diet-dependent and lower in diet-independent hypercalciuric stone patients (-0.30 +/- 1.19 versus -0.26 +/- 1.18, p less than 0.02). In 7 of 21 patients (33.3%) the vertebral mineral content was less than 2 standard deviations of the normal value, indicating a true involvement in bone metabolism. Serum intact parathyroid hormone and osteocalcin levels were not different from the controls in both groups, while alkaline phosphatase activity and ionized calcium were higher in diet-independent hypercalciuric patients. Serum ionized calcium was negatively correlated with bone vertebral density. The results suggest that an increased bone turnover may be a primary event in causing hypercalciuria in calcium stone patients unable to decrease urinary calcium to less than the calcium intake.

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PubMed1998

Bone mineral density in prepubertal children with beta-thalassemia: correlation with growth and hormonal data.

Patients with beta-thalassemia major (beta-thalassemia) frequently have bone disorders of multifactorial etiology. We attempted to analyze the relationship between the bone mineral density ([BMD] measured by dual-photon absorptiometry) and auxanologic parameters, degree of siderosis, function of the growth hormone (GH)/insulin-like growth factor-I (IGF-I)/IGF-binding protein-3 (IGFBP3) axis, calcium-phosphate balance, parathyroid hormone (PTH), and cytokines (interleukin-1beta [IL-1] and tumor necrosis factor-alpha [TNF-alpha]) in 30 prepubertal children with beta-thalassemia major and 15 age-matched children with constitutional short stature (CSS), who have normal glucose tolerance and thyroid function. Children with beta-thalassemia had a significantly decreased BMD and mean BMD% for age and sex (0.75+/-0.24 g/cm2 and 71%+/-10%, respectively) versus children with CSS (1.06+/-0.3 g/cm2 and 92%+/-7%, respectively). Thalassemic patients had significantly lower circulating concentrations of IGF-I and IGFBP3 (49+/-21 ng/mL and 1.2+/-0.25 mg/L, respectively) compared with control children (153+/-42 ng/mL and 2.1+/-0.37 mg/L, respectively). The GH response to provocation by clonidine and glucagon was defective (peak GH < 7 microg/L) in 12 of the 30 thalassemic children. Serum concentrations of IL-1beta and TNF-alpha did not differ among the two study groups. Hypocalcemia was detected in five of the 30 thalassemic patients: hypoparathyroidism was diagnosed in two of the five and rickets in the other three. BMD was highly correlated with the circulating concentrations of IGF-I and IGFBP3, as well as with the auxanologic parameters (age, weight, height, height standard deviation score [HSDS], and body mass index [BMI]). It is suggested that increasing the circulating IGF-I concentration through aggressive nutritional therapy and/or GH/IGF-I therapy with supplementation with vitamin D and/or calcium might improve bone growth and mineralization and prevent the development of osteoporosis and consequent fractures in these patients. Such therapy requires blinded controlled trials.

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PubMed1998

Bone loss in young women with karyotypically normal spontaneous premature ovarian failure.

OBJECTIVE: To evaluate the effects of karotypically normal spontaneous premature ovarian failure on femoral neck bone mineral density. METHODS: Eighty-nine women with karyotypically normal spontaneous premature ovarian failure who desired fertility were evaluated at a tertiary care academic center and underwent hip and spinal bone density measurements by conventional dual-photon absorptiometry. Seventy-seven of the women (87%) had sought medical advice previously and had taken a variety of estrogen and progestin replacement regimens at least intermittently. The median (range) age was 32 (20-39) years, and the median (range) time since diagnosis was 1.5 (0.5-11) years. Findings were compared with a reference group of 218 regularly menstruating women of similar age. RESULTS: Sixty of the 89 women with premature ovarian failure (67%, 95% confidence interval 57, 77) had a femoral neck bone mineral density more than 1 standard deviation (SD) below the mean of the reference group (P < .001, chi2 with Yates correction). Even in women in whom the bone mineral density measurement was made within just 1.5 years of the diagnosis, nearly one-half (47%) had a femoral neck bone mineral density more than 1 SD below the mean of the reference group (P < .01). CONCLUSION: Two-thirds of young women with karyotypically normal spontaneous premature ovarian failure have a femoral neck bone mineral density more than 1 SD below the mean of a reference group. These young women need early education regarding strategies to maintain their bone mass and ongoing medical evaluation to maintain compliance with these strategies.

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PubMed1999

Environmental exposure to cadmium, forearm bone density, and risk of fractures: prospective population study. Public Health and Environmental Exposure to Cadmium (PheeCad) Study Group.

BACKGROUND: Chronic low-level exposure to cadmium may promote calcium loss via urinary excretion. We undertook a prospective population study to investigate whether environmental exposure to cadmium lowers bone density and increases risk of fractures. METHODS: We measured urinary cadmium excretion, a biomarker of lifetime exposure, in people from ten districts of Belgium, of which six districts bordered on three zinc smelters. We also measured cadmium in soil and in vegetables from the districts, and collected data on incidence of fractures and height loss. Bone density was measured at the forearm just above the wrist by single photon absorptiometry, and calculated as the mean of six proximal and four distal scans. FINDINGS: Mean cadmium excretion at baseline was 8.7 nmol daily. Across the ten districts, mean cadmium concentration in soil ranged from 0.8 to 14.7 mg/kg, and from 0.1 to 4.0 mg/kg dry weight in vegetables. Median follow-up was 6.6 years. Mean forearm bone density in proximal and distal scans was 0.54 g/cm2 and 0.43 g/cm2 in men, and 0.44 g/cm2 and 0.34 g/cm2 in women. In postmenopausal women, a twofold increase in urinary cadmium correlated with 0.01 g/cm2 decrease in bone density (p<0.02). The relative risks associated with doubled urinary cadmium were 1.73 (95% CI 1.16-2.57; p=0.007) for fractures in women and 1.60 (0.94-2.72, p=0.08) for height loss in men. Cadmium excretion in districts near smelters was 22.8% higher (p=0.001) than in other districts, with fracture rates of 16.0 and 10.3 cases per 1000 person-years, respectively, and a population-attributable risk of 35.0%. INTERPRETATION: Even at a low degree of environmental exposure, cadmium may promote skeletal demineralisation, which may lead to increased bone fragility and raised risk of fractures.

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PubMed1993

Bone mineral content of two populations of Chinese children with different calcium intakes.

Bone mineral content (BMC) of 5-year-old Chinese children (115 children in Jiangmen, China and 128 children in Hong Kong) was evaluated by single-photon absorptiometry at the distal 1/3 radius. The mean (S.D.) calcium intakes of children of Jiangmen and Hong Kong were 244 (46) and 542 (332) mg/day, respectively. The mean BMC, weight and height of Jiangmen children were significantly less than Hong Kong children by 14%, 10% and 4%, respectively (P < 0.001). Multiple regression analysis showed that 62% of the variance in BMC was explained by bone width (BW), weight and regional location (P < 0.0001). A regional difference in BMC of 0.0303 g/cm (P < 0.0001) still remained after adjusting for BW and weight by multiple regression analysis. When comparing sub-groups of children in the two regions with comparable low current calcium intake at 5 years, the BMC of Jiangmen children was still significantly lower than Hong Kong children even when potential confounders were adjusted (P < 0.003). The study suggests that the regional discrepancy in BMC might be explained by long-term habitual calcium intake and physical activity.

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PubMed1993

Apparent velocity of ultrasound (AVU) at the patella in comparison to bone mineral density at the lumbar spine in normal males and females.

It has been reported that apparent velocity of ultrasound (AVU) at the patella discriminates as well between osteoporotic and normal subjects as measurement of bone mineral density (BMD) using dual photon absorptiometry. To investigate the relationship between AVU and peak bone mass, we compared AVU (Signet, Osteo-Technology, Framingham, MA) at the patella and BMD (QDR 1000, Hologic, Waltham, MA) at the lumbar spine in a large sample of healthy males and females. The study population consisted of 153 males (aged 20-60 years) and 129 premenopausal females (aged 20-52 years). Vertebral BMD showed no significant difference between males and females (1.03 +/- 0.16 g/cm2 for males vs. 1.07 +/- 0.14 g/cm2 for females, NS), while AVU values were significantly higher in males compared with females (1967 +/- 64 m/s vs. 1938 +/- 76 m/s, P < 0.05). In men there was a significant decrease in BMD with aging (r = -0.27, P < 0.05), in premenopausal females we found no age-related change in BMD. Similarly in males AVU decreased significantly with age (r = -0.2, P < 0.05), whereas in females AVU values showed relative stability over the age range. There was a significant correlation between AVU and BMD (r = 0.36 for males, r = 0.34 for females, P < 0.05). Our study demonstrates only a weak correlation between AVU at that patella and BMD at the lumbar spine, supporting the view that AVU not only reflects bone quantity but possibly also qualitative properties of bone structure. The sex difference in AVU but not in BMD suggests that the trabecular bone at the patella differs significantly from axial trabecular bone. The identical peak BMD at the lumbar spine for young males and females underscores the importance of the menopause for later manifestation of vertebral fractures.

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PubMed1994

Radial bone mineral content of normal Japanese infants and prepubertal children: influence of age, sex and body size.

The present study was performed to measure appendicular bone mass of Japanese infants and children, and to assess the influence of age, sex and body size on bone mass during the period of bone growth. The bone mineral content (BMC) and bone width (BW) at the distal third of the radius were measured by single photon absorptiometry (SPA) in 229 healthy Japanese infants and children aged 0-12 years, and the BMC/BW ratio was calculated to give the bone mineral density (BMD). BMC and BW increased with age until 2 years, while BMD did not obviously change until 2 years. After 2 years of age, the overall effect of aging appeared more prominent in BMC and BMD than in BW. There were no significant differences in BMC, BW and BMD between males and females aged 0-12 years. Age, body height, and body weight were strongly correlated with three parameters of bone mass (BMC, BW, and BMD). Among the three parameters of bone mass, BMC showed the highest Pearson coefficient of correlation with age (r = 0.955), body height (r = 0.957) and body weight (r = 0.966), as compared with BW and BMD. The present cross-sectional study provides normative data of the appendicular bone mass in healthy Japanese children, which may serve as a standard for assessment of bone mineralization in Japanese infants and children with medical problems.

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PubMed1993

Bone mineral density in professional ballet dancers.

We studied the effect of physical training on the bone mineral content and soft tissue composition in 42 professional ballet dancers (17 men and 25 women). Twenty-eight of them were still actively performing and 14 had retired from professional dancing. Forty-two healthy age- and sex-matched volunteers served as controls. The bone mineral density (BMD) (g/cm2) in total body, spine, hip, arms, legs, and the proximal tibia metaphysis was measured with a Lunar DPX apparatus and the BMD of the distal forearm was measured with single-photon absorptiometry (SPA). Twelve of the now retired dancers had earlier been measured with SPA in the tibia condyle during their active career in 1975. There was no significant difference in BMD values between dancers and controls with the exception of a lower BMD in the head of the male dancers and a lower BMD in the arms of female dancers. After correcting for difference in body mass index (BMI), using analysis of covariance we found significant higher BMD in the lower extremities of female dancers and in the hip of male dancers. No correlation was found between the SPA measurements from 1975 and the corresponding measurements 15 years later. The dancers were on average 9 kg lighter but of the same height as the controls. The dancers had lower body mass index and fat content but their lean body mass was the same as the controls.

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PubMed2000

Bone metabolic analysis in patients with primary hyperparathyroidism.

Surgical treatment for primary hyperparathyroidism (PHPT) improves not only the calcium and phosphate metabolism but also the bone metabolism. This study was conducted to analyze the bone metabolism after PHPT operations. Bone mineral density (BMD) was measured by dual-photon absorptiometry in 50 patients before and after operation. Osteocalcin (OC) and alkaline-phosphatase activity (Alp) in serum were measured before and after surgery as markers of bone formation, and urinary deoxypiridinorine (DPD) as an index of osteoclast activity. The 50 patients under study were 40 women (80%) and ten men (20%). Increases in BMD at the lumbar spine were remarkable at three months following operation. Slow but steady progress was made until six months, reaching a plateau thereafter. The increase in BMD of lumbar spine was approximately 10%. Urinary DPD was the most sensitive among the three bone metabolic markers. Although serum Alp and OC remained high after operation, urinary DPD was normalized earlier. The discrepancy of bone formation and resorption was shown after operation and this contributed to the increases in BMD in the first six months.

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PubMed1995

Changes in bone mineral density of the distal femur following uncemented total knee arthroplasty.

The aim of the study was to quantitate changes in bone mineral density (BMD) in the distal femur following uncemented porous-coated total knee arthroplasty. Eight patients with total knee arthroplasties (PCA Primary, Howmedica, Rutherford, NJ) (female:male ratio, 6:2; mean age, 70 years; range, 51-77 years) were scanned by dual-photon absorptiometry within 3 months after surgery and at 2 years. An average decrease of 36% (P = .01) was found in BMD behind the anterior flange of the femoral prosthesis. Proximal to the fixation pegs, BMD increased by 22% (P = .12), but behind the posterior flange of the femoral component, BMD remained unchanged (P = .53). Stress shielding anteriorly in the distal femur occurred in all patients examined 2 years after surgery, and the increase in BMD proximal to the fixation pegs was probably a result of increased and altered mechanical loading.

Absorptiometry, Photon↗

PubMed1993

Roentgenographic procedure for selecting proximal femur allograft for use in revision arthroplasty.

A roentgenographic scoring system was developed to help orthopaedic surgeons and bone banks estimate the quality of bone stock in proximal femoral allografts intended to use in revision arthroplasty. This system scores a standardized anteroposterior roentgenograph of the proximal femur using four indices representing morphological features of cancellous and cortical bone known to be clinically associated with bone strength. The indices were combined to give a weighted score, which was thought to reflect the ability of a bone to carry in vivo loads. Thirty bones were evaluated for bone mineral density using dual-photon absorptiometry. They were then sent to another institution and evaluated using the newly devised roentgenographic scoring system. The results showed that the bone score roentgenographic method is a reasonable technique for selecting allograft femurs for transplantation. This roentgenographic technique and scoring system has now been packaged into kits and is available to orthopaedic surgeons and bone banks for evaluating bone stock quality in proximal femoral allografts intended for transplantation.

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PubMed1989

Non-invasive techniques for the measurement of bone mineral.

Non-invasive, safe and precise techniques for measuring bone mineral density are available and have an important role in the detection, prevention and treatment of bone loss associated with aging, menopause and many illnesses affecting women and men. The three most widely accessible and established techniques for measuring regional bone mineral density are single and dual photon absorptiometry and quantitative computed tomography. A technique of greater accuracy, dual energy X-ray absorptiometry, has only recently become available. These techniques have made it possible to measure the magnitude, time course and regional specificity of the skeleton's response to ageing, menopause and illness. A better understanding of the clinical epidemiology of fractures and the mechanisms responsible for bone loss has been obtained. Practical information has been obtained about the dose, duration and efficacy of oestrogen replacement therapy in preventing perimenopausal bone loss and the benefits and limitations of different forms of exercise on bone mineral density in healthy postmenopausal women. The beneficial effect of dietary calcium on peak bone mineral density and in decreasing bone loss in cortical bone has been documented. Information regarding the prevention and treatment of bone loss in exogenous hypercortisolism and the magnitude and reversibility of bone loss associated with many diseases which affect bone has been obtained. One of the most important clinical applications of these techniques is the assessment of the efficacy of treatment of patients with postmenopausal osteoporosis. As antifracture efficacy is not readily measurable, considerable information is being obtained about many potentially useful forms of therapy that may prevent bone loss and increase bone mineral density. The role of these non-invasive methods in the assessment of fracture risk and the need for oestrogen or other therapy in an individual who has attained a low peak bone mass or has risk factors predisposing to excessive bone loss, differs from broader public health initiatives of population screening. There are concerns regarding the safety, efficacy and limited number of treatment regimens available for persons found by screening to be at risk. The most economic and convenient methods for predicting fracture risk with high sensitivity and specificity are not established. There are uncertainties regarding the relative importance of bone mineral density measured at the time of screening, the amount of bone lost in the subsequent years and risk factors predisposing to falls in the pathogenesis of hip fractures.(ABSTRACT TRUNCATED AT 400 WORDS)

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