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Biomedical subjects

R R Recker

Publications and source records attributed to R R Recker.

At least 91 records · Page 5Linked to original sources
PubMed1995

Ultrasound velocity, through bone predicts incident vertebral deformity.

We followed 130 postmenopausal women without evidence of vertebral deformity by lateral spine radiographs on entry into study for 2 years, and repeat spine radiographs were taken at the end of that time. Incident deformities occurring within this 2 year period were detected by two methods, a level-specific radiogrammetric approach and visual inspection by skilled clinicians. Fourteen incident deformities were detected by the radiogrammetric method, and 19 by the clinicians. Ultrasound transmission velocity was measured at the patella in each subject on entry. Values for ultrasound velocity were significantly correlated with incident fracture occurrence, with individuals having velocity values more than one standard deviation below the mean for the group exhibiting from 3.3 to 4.6 times the probability of incident fracture as individuals with velocity values more than one standard deviation above the mean. Thus, low values for ultrasound transmission velocity at the patella detect yet-unexpressed bony fragility at the spine and predict future fracture.

Adult↗
PubMed1995

Comparison of speed of sound ultrasound with single photon absorptiometry for determining fracture odds ratios.

The purpose of this study was to compare the ability of ultrasound velocity measurement with that of single photon absorptiometry to determine the odds of history of fracture since age 40, for a population-based study. To do this we computed odds ratios and 95% confidence intervals for 809 women and 502 men, aged 50 years and older, who are participants in the prospective phase of the Saunders County Bone Quality Study. These participants received both the ultrasound and single photon absorptiometry bone measurements at the initiation of the study. In addition, a history of all fractures that had occurred to participants since age 40 was obtained. The two bone assessment methods were compared by examining the magnitude of the odds ratios, to determine which produces the highest estimate of the probability of odds of fracture, and by examining widths of the respective confidence intervals to show which estimate of odds ratio is the most precise. Ultrasound velocity estimates a higher probability of odds of both low-trauma fractures and all fractures than distal radius and ulna bone mineral content, but lower than bone mineral density at the same sites for both women and men. However, the ultrasound measure is more precise than bone mineral density, but less precise than bone mineral content. We conclude that ultrasound velocity is as good as single photon absorptiometry in estimating odds of fracture.

Absorptiometry, Photon↗
PubMed1995

Bone structure in postmenopausal hyperparathyroid, osteoporotic, and normal women.

The purpose of this study was to test the hypothesis that patients with mild primary hyperparathyroidism are protected against postmenopausal (PM) loss of cancellous bone architecture. To achieve this, we compared bone structure and turnover in iliac bone biopsies from three groups: 16 women with mild primary hyperparathyroidism (PHPT; 58.2 +/- 2.2 years, 11.5 +/- 1.7 years PM), 17 women with untreated primary osteoporosis (OP; 65.1 +/- 2.0 years, 17.2 +/- 2.3 years PM), and 31 healthy women (N; 59.8 +/- 1.4 years, 13.4 +/- 1.5 years PM). The bone formation rate was significantly higher in PHPT than in either OP or N, and not different between OP and N. Cancellous bone volume, total strut length, and indices of connectivity (node number, node to node strut length, and node to terminus ratio) were significantly lower in OP than in either PHPT or N but were the same or higher in PHPT than in N. Indices of disconnectivity were significantly lower in PHPT than in N, whereas they were the same or higher in OP than N. The data were also analyzed in subgroups matched by years PM with no changes in the results. These findings indicate that osteoporotic patients with normal bone turnover have low bone volume and microarchitectural deterioration, while patients with mild PHPT have normal bone volume and normal or greater trabecular connectivity despite higher bone turnover. These findings suggest that mild PHPT protects against the loss of cancellous bone structure that normally follows menopause.

Bone and Bones↗
PubMed1995

Ultrasound, densitometry, and extraskeletal appendicular fracture risk factors: a cross-sectional report on the Saunders County Bone Quality Study.

The Saunders Bone Quality Study was designed to determine the feasibility of ultrasonic bone measurement, at the patella, as a predictor of low-trauma fractures in a rural population-based study. At the first visit of this 4-year longitudinal study, anthropometric and clinical measurements and medical, surgical and fracture histories were obtained for the 1428 participants 9899 women and 529 men). Explored risk factors for low-trauma fractures included age, sex, calcium intake, alcohol and caffeine ingestion, tobacco use, body mass and grip strength, age of menopause, estrogen replacement therapy, propensity to fall, distal radius and ulna bone mineral content, and bone density. Forward multivariate logistic regression analysis showed that lower ultrasound values are more consistently associated with reported low-trauma appendicular fractures than the commonly reported forearm absorptiometry measures of radius mineral content and density. When ultrasound, age, and the extra skeletal risk factors were included in an additional multivariate model, only age and ultrasound were significantly associated with appendicular fracture history in women (P = 0.0003), whereas only ultrasound was associated in the men (P = 0.001). We conclude that ultrasound is a better measure as association with reported low-trauma fractures than the commonly reported forearm SPA measures. Even after adjustment for many of the extra skeletal risk factors, low AVU is highly associated with low-trauma fracture status for both men and women.

Age Factors↗
PubMed1995

Patellar ultrasound transmission velocity in healthy children and adolescents.

Apparent velocity of ultrasound (AVU) (Signet, Osteo-Technology Cambridge, MA) at the patella was measured on 568 children and adolescents, aged 8 to 18 years. Trend analysis revealed a significant trend (p < 0.004) toward increasing AVU with increasing age and increasing Tanner stage. Height and weight were positively correlated with AVU in both sexes, while dietary intake of calories, protein, and calcium were positively correlated with AVU in males, but not in females. Multiple linear regression revealed that 29% of the variance of AVU in females was described by Tanner stage (p < 0.002) and height (p < 0.007). The best regression model for males accounted for 48% of the variance in AVU and included age (p < 0.0001) and protein intake (p < 0.01). Bone quality has a distribution in children which is similar to the distribution of bone mass and density. Our patellar AVU values can be used as a baseline for much-needed prospective research with children and adolescents.

Adolescent↗
PubMed1995

Elastic properties of osteoporotic bone measured by scanning acoustic microscopy.

A combination of low bone mass and decreased bone quality underlies osteoporotic fracture. We used scanning acoustic microscopy, a nondestructive method for assessing bone elasticity at a resolution of about 60 microns, to estimate the quality of biopsied iliac bones. We compared the acoustic velocities and bone volumes among premenopausal normal (n = 10), osteoporotic (n = 20), and postmenopausal normal (n = 10) subjects, the latter age-matched to the osteoporotic subjects. The acoustic measurements were highly reproducible (coefficient of variation = 0.32%). Bone volume of osteoporotic subjects (BV/TV = 13.3%) was lower than that of premenopausal and age-matched normals (BV/TV = 22.8%, p = 0.0007; BV/TV = 24.8%, p = 0.0004, respectively). Acoustic velocity of osteoporotic bone was 6.2% lower than that of age-matched normal bone (p < 0.02), but 3.4% higher than that of bone from premenopausal normal women. The lower acoustic velocity of osteoporotic bone than that of age-matched normal subjects implies that osteoporosis involves altered tissue elasticity. However, the lowest acoustic velocities were measured in premenopausal normal subjects. This unexpected result may indicate a complex relationship between tissue level properties and fragility in bone.

Aged↗
PubMed1995

Patient care of osteoporosis.

Osteoporosis is a condition of excessive skeletal fragility that afflicts more than 25 million Americans and results in over one half million fractures per year in the United States. Evaluation of patients presenting with symptoms of osteoporosis includes measurement of serum 25 hydroxy, vitamin D, thyroxine, thyroid-stimulating hormone, serum protein electrophoresis, in addition to blood count, urinalysis, and multichannel screen. Spine and other films are indicated as necessary, and although bone density measurements are useful, they are somewhat restricted in availability. There are lifestyle measures that influence the cause as well as the treatment of osteoporosis. Symptomatic patients benefit most by interventions that include nutrition, physical fitness, calcium, and vitamin D.

Aged↗
PubMed1994

Velocity of ultrasound and its association with fracture history in a rural population.

The authors set out to determine the distribution of bone quality, as measured by ultrasound, in a rural Nebraska population of women and men. Noninstitutionalized residents of Saunders County, Nebraska, who were age 50 years or older as of January 1, 1992, were enumerated. From this sampling frame, a randomized proportionate stratified sample was selected. The response rate to this random sampling was 58%. Bone quality was measured using the apparent velocity of ultrasound (AVU) through the patella. In addition to demographic information, participants were asked to describe all fractures that had occurred since age 40 years. Fractures were classified as resulting from low or high trauma. Like bone mass, previously studied extensively, AVU was lower among successively older strata for both sexes. AVU discriminated between those with and those without low-trauma or any fractures for both sexes, whether unadjusted or adjusted for nonresponse. AVU is a faster, cheaper, and less time-consuming procedure than bone mass. The measuring device is portable and is well suited for population-based studies. It remains to be determined, by prospective methods, whether AVU is a predictor of low-trauma or osteoporotic fracture in this population.

Accidental Falls↗
PubMed1994

Bone response to alternate-day mechanical loading of the rat tibia.

Mechanical loading of the living skeleton influences bone formation, mass, and strength. The primary purpose of the present study was to examine the influence of different loading schedules (days/week) on the bone response to external loading using an in vivo rat tibia four-point bending model. Three studies were conducted to (1) characterize the loaded region, (2) examine the variation of the response within the loaded region, and (3) test the response to different loading schedules. In all studies adult female retired breeder Sprague-Dawley rats were used (6 months, 285 g). First, the location of the loaded region during four-point bending was determined by radiogrammetry of 7 rats. Second, 5 rats were externally loaded for 8 of 10 days at 31 N, 36 cycles, and 2 Hz (1349 +/- 244 mu epsilon). The extent of labeled (forming) periosteal and endocortical surface in the loaded region was compared both among four serial sections from the same tibia and between the loaded and the contralateral tibiae. Finally, 50 rats were randomized into five groups: two nonloaded, control and sham, and three loaded, alternate day, Monday, Wednesday, and Friday, and daily. The rats were externally loaded for 3 weeks at 35 N, 36 cycles, and 2 Hz (1533 +/- 308 mu epsilon). The tibia and fibula were studied for labeled surfaces and mineral apposition rate. For adult female rats with tibial length 39 mm, the loaded region was located 3.5-14 (+/- 0.7) mm proximal to the tibia-fibula junction (TFJ).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Periosteal bone formation stimulated by externally induced bending strains.

The rat tibia four-point bending model is a new mechanical loading model in which force is applied through external pads to the rat lower limb. The advantages of the model are controlled force application to a well-defined bone, noninvasive external loading, and the addition of loads to normal daily activity. A disadvantage of the model is that the pads create local pressure on the leg at the contact sites. This study examined the differences in tibial response to bending strains and to local pressure under the pads. A total of 30 adult Sprague-Dawley rats were randomized into three external loading groups: bending, cyclic pressure, and static pressure. The right leg of each rat was externally loaded to create either bending or local pressure without bending; the left leg served as a control. Strains on the lateral surface averaged 1200 mu epsilon in compression during bending load application and < 200 mu epsilon in compression during pressure loading. Histomorphometric data were collected from three regions: the maximal bending region, under the loading pads, and outside the maximal bending region. In the maximal bending region, bending loads created greater mineral apposition rate (MAR) on the lateral surface and greater MAR and formation surface on the medial surface of loaded than control tibiae. The region under the bending pad was exposed to similar bending strains and showed the same pattern of increased MAR as sections from the maximal bending region. Cyclic pressure had no effect on periosteal MAR or formation surface. Static pressure increased MAR only on the lateral tibial surface. Bending stimulates bone formation in regions with the highest bending strains. Similar forces applied only in the form of pressure loading do not stimulate tibial formation either at the contact site or between loading pads. These results suggest that externally applied forces of moderate magnitude stimulate bone formation primarily as a result of increased bending strains, not local pressure at the contact site.

Animals↗
PubMed1994

Determinants of endogenous fecal calcium in healthy women.

Endogenous fecal calcium (EFC) excretion was measured in 518 studies in 191 normal perimenopausal women, most studied two to three times over a 15 year period. EFC averaged 102 +/- 25 mg/day. Absorption fraction was simultaneously determined by both double-isotope and balance methods. EFC was found to vary inversely with absorption fraction, and the observed relationship was used to calculate the total amount of calcium (TIC) entering the gut from endogenous sources. TIC averaged 140 +/- 34 mg/day and was found to be correlated with a number of intake and body size variables. Phosphorus intake was the most strongly correlated of all the variables (r = 0.404; P < 0.0001), each increment of 0.1 g phosphorus intake being associated with an increase in TIC of 6 mg. Lean body mass was the best correlated of the body size variables, with TIC rising by 1.6 mg/day for every kg lean mass. There were also small but significant correlations with protein and energy intakes, the latter suggesting that some of the variation of TIC is related to the amount of food consumed. Caffeine, previously reported as elevating TIC, did not exhibit a significant relationship in this study.

Absorption↗
PubMed1994

Mechanical loading stimulates rapid changes in periosteal gene expression.

Although mechanical forces regulate bone mass and morphology, little is known about the signals involved in that regulation. External force application increases periosteal bone formation by increasing surface activation and formation rate. In this study, the early tibial periosteal response to external loads was compared between loaded and nonloaded contralateral tibia by examining the results of blot hybridization analyses of total RNA. To study the impact of external load on gene expression, RNA blots were sequentially hybridized to cDNAs encoding the protooncogene c-fos, cytoskeletal protein beta-actin, bone matrix proteins alkaline phosphatase (ALP), osteopontin (Op), and osteocalcin (Oc), and growth factors insulin-like growth factor I (IGF-I) and transforming growth factor-beta (TGF-beta). The rapid yet transient increase in levels of c-fos mRNA seen within 2 hours after load application indirectly suggests that the initial periosteal response to mechanical loading is cell proliferation. This is also supported by the concomitant decline in levels of mRNAs encoding bone matrix proteins ALP, Op, and Oc, which are typically produced by mature osteoblasts. Another early periosteal response to mechanical load appeared to be the rapid induction of growth factor synthesis as TGF-beta and IGF-I mRNA levels were increased in the loaded limb with peak levels being observed 4 hours after loading. These data indicate that the acute periosteal response to external mechanical loading was a change in the pattern of gene expression which may signal cell proliferation. The altered pattern of gene expression observed in the present study supports previous evidence of increased periosteal cell proliferation seen both in vivo and in vitro following mechanical loading.

Actins↗
PubMed1994

Bone biopsy and histomorphometry in clinical practice.

Transilial bone biopsy after tetracycline labeling coupled with histomorphometry has become an indispensable tool in the clinical research of metabolic bone disease, especially in evaluating the long-term safety and efficacy of therapeutic agents proposed for treatment of bone disease. It is probably not necessary for the majority of patients who seek medical care for bone diseases such as osteoporosis. It is particularly useful in the management of patients with end-stage renal disease who develop symptomatic bone disease because it may be the only means of deciding on proper treatment. The biopsy can be performed safely by nearly any clinician after brief training. Tetracycline labeling must be accomplished before the biopsy, and the specimen must be handled carefully to avoid removal of the mineral or disturbing the label. Embedding, sectioning, staining, and analysis must be performed without removal of the mineral. The difficulty of this methodology has limited its availability. Nevertheless, it can be applied in most situations in which there is clear benefit to patient management.

Affinity Labels↗
PubMed1993

Effect of ovariectomy on bone response to in vivo external loading.

This study was undertaken to find whether the bone response to increased external loading (EL) of the tibia in rats is affected by estrogen depletion. Female Sprague-Dawley rats 6 months were randomly assigned to four groups of 10 each: sham ovariectomy without loading (Shm-XL), ovariectomy without loading (OVX-XL), sham ovariectomy with external loading (Shm-EL), and ovariectomy with external loading (OVX-EL). In vivo external loading by a four-point bending device was initiated 4 weeks after surgery. The right lower leg of each EL rat was loaded at 31.4 +/- 0.2 N for 36 cycles at 2 Hz every other day for 21 days (11 loading days). Mean in vivo induced strain was 1305 microstrain (mu epsilon) for Shm-EL rats and 1280 mu epsilon for OVX-EL rats. With external loading of the tibia, periosteal bone formation rose equally in Shm and OVX rats. Woven bone was present around the tibia or fibula in 60% of the loaded rats and none of the control rats. No loading response occurred either at the endocortical surface or in the cancellous bone of the proximal tibial metaphysis. After OVX, cancellous bone area in the proximal metaphysis declined and formation surface rose compared to Shm rats. Although periosteal and endocortical bone formation rose after OVX, no cortical bone loss occurred. We conclude that ovariectomy and attendant loss of endogenous estrogen do not change the cortical bone response to an external load of about 1300 mu epsilon in rats. However, these results may not predict the cortical bone response to loading in animals with Haversian remodeling that display estrogen-related loss of cortical bone.

Analysis of Variance↗
PubMed1993

Prevention of osteoporosis: calcium nutrition.

Calcium is a threshold nutrient which means that a nutritional response in terms of calcium balance or bone mass will be present at intakes below the threshold and not above. The analogy can be made with the case of iron nutrition and anemia. Estimates of the threshold intake levels can be made for all stages of life based on available calcium balance data. They range between 1.3 g/day for infants to 1.5 g/day for women past menopause. Calcium nutrition is most important during growth and development in achieving genetically programmed peak skeletal mass. It is also important in maintaining bone mass in the elderly years. Calcium needs are supplied by the breakdown of the skeleton during the first few years after menopause, and thus calcium nutrition is less important until about 5 or 6 years after cessation of menses. Optimum calcium intake is best obtained from food sources; however, the lower food intake of modern humans compared with the food intake of humans during involution has resulted in difficulty in gaining an adequate intake of calcium. Calcium supplements are destined to become and important source of dietary calcium and thus some attention must be paid to their nutritional value. Solubility of a calcium salt is not a major determinant of absorbability over a range of 5 orders of magnitude of solubility. However, there is a well-defined enhancing effect of the co-ingestion of a meal with calcium supplements. It would seem prudent to recommend that any calcium supplement be given at meal times.(ABSTRACT TRUNCATED AT 250 WORDS)

Absorption↗
PubMed1993

Revisable criteria for vertebral deformity.

In order to study vertebral fractures in various study populations, we earlier prepared a database of vertebral dimensions derived from spinal radiographs of 191 normal women seen regularly over 25 years. In this report we have expanded the range of measurements to include vertebral levels T3 to L5. We report means and standard deviations on anterior and posterior heights, on wedge shape and on heights relative to adjacent vertebrae. When one or both of the latter two quantities are 'far' below the mean, a vertebra is called deformed. We also describe a more flexible way of expressing damage using the number of deformed vertebrae, the degree of deformity of individual vertebrae, or the total damage to the entire spine. In assessing damage we use criteria for deformity adjusted to the limits detected by an experienced diagnostician, replacing an earlier approach based on 95% probability limits of normal variation. The normal women from whom these variations are ascertained are a low-prevalence group with respect to vertebral deformity, with prevalence of 2.8%. When the criteria developed from these women were applied to a moderate-prevalence group (37%) the model had a sensitivity of 97%, a specificity of 89% and an accuracy of 92% as regards the identification of subjects with damaged vertebrae. When used epidemiologically for a moderate-prevalence group the model has a known overestimation of 15%. the model is compared with other schemes for identifying vertebral deformities.

Adult↗
PubMed1993

Architecture and vertebral fracture.

Bone strength is determined by mass density, structural arrangement, and the presence of microdamage. This presentation focuses on trabecular microstructure as an element of bone strength, particularly in the syndrome of vertebral compression fracture. The base material comes from transilial biopsies from 90 patients with the crush fracture syndrome and from 34 normal volunteers who underwent transilial biopsy. Trabecular connectivity was compared in these two groups. Patients and normals were then matched for trabecular bone volume (BV/TV). To highlight measures of trabecular connectivity, three general methods for examining trabecular connectivity were applied to the 23 patient-control pairs matched for BV/TV. The conventional method of Parfitt showed that trabecular number was decreased by 11%, trabecular separation was increased by 9%, and trabecular thickness was increased by 9% in patients compared with controls. The method of counting trabecular nodes and trabecular free ends showed that in the patients, free ends were decreased by 37% and nodes were decreased by 37%. The marrow space star volume (the average volume of marrow measured from radii placed at random points within the marrow and extending to trabecular surface) was 36% greater in the patients. All three methods are measures of trabecular connectivity (the density of connections between trabeculae). All three demonstrated less trabecular connectivity in the patients versus controls for identical BV/TV. Patients with vertebral fractures had fewer trabecular elements rather than global thinning of trabeculae. Differences in measures or connectivity were not accompanied by significant differences in any of the measures of bone remodeling dynamics, as examined by tetracycline labels.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗