Biomedical subjects

C E Webber

Publications and source records attributed to C E Webber.

At least 19 recordsLinked to original sources

PubMed2006

Accuracy and test-retest precision of quantitative cartilage morphology on a 1.0 T peripheral magnetic resonance imaging system.

OBJECTIVE: Quantitative magnetic resonance imaging (qMRI) of knee cartilage morphology is a powerful research tool but relies on expensive and often inaccessible 1.5 T whole-body equipment. Here we examine the reproducibility and accuracy of qMRI at 1.0 T by direct comparison with previously validated technology. METHODS: Coronal images of the knee were obtained in six healthy and six osteoarthritic participants. Two data sets were acquired with a 1.5T whole-body magnetic resonance imaging (MRI) system and two with a 1.0 T peripheral MRI system, with repositioning between scans. Proprietary software was used to analyze surface area, volume, and thickness of femoral and tibial cartilage. RESULTS: At 1.0 T, precision errors for surface areas (root-mean-square (RMS) coefficient of variation (CV%)=1.7-2.6%) were higher than those at 1.5 T (1.0-2.1%). For volume and thickness, precision errors were 2.9-5.5% at 1.0 T compared to 1.6-3.4% at 1.5 T. High levels of agreement were found between the two scanners over all plates. With the exception of lateral femoral cartilage (volume and thickness), no statistically significant systematic bias was found between 1.0 T and 1.5 T. CONCLUSIONS: This is the first reported study to show that knee cartilage morphology can be determined with a reasonable degree of accuracy and precision using a 1.0 T peripheral scanner. Peripheral MRI is less costly, can be performed in clinical offices, and is associated with higher patient comfort and tolerance than 1.5 T whole-body MRI. Implementation of qMRI with peripheral systems may thus permit its more widespread use in clinical research and patient care.

Adult↗

PubMed2005

Abnormalities identified in the knees of asymptomatic volunteers using peripheral magnetic resonance imaging.

OBJECTIVE: To estimate the prevalence of bone and soft tissue abnormalities in asymptomatic knees using peripheral magnetic resonance imaging (pMRI) and to examine the relationship between these abnormalities and Kellgren-Lawrence (K-L) graded X-rays. METHOD: Volunteers (20-68 years) with no history of knee pain, injury or bone or joint disease were recruited. Individuals underwent a single MRI scan and radiograph of their non-dominant knee. pMR images were acquired in sagittal plane using a 3-D gradient-echo protocol. Two radiologists graded the presence and severity of cartilage degeneration, osteophytosis, meniscal and ligamentous abnormalities, bone marrow edema and subchondral cysts. X-rays were acquired using a fixed-flexion technique and graded using the K-L scale. RESULTS: Forty-four individuals, mean age (SD) 41.1 (14.2) years, participated. K-L grading of X-rays revealed 29 individuals were grade 0, 12 were grade 1 and 3 were grade 2. Five individuals showed evidence of cartilage lesions, the femoral trochlea, medial femur and patella being those regions most commonly affected. Twelve individuals (27.3%) showed evidence of osteophytosis, nine of whom did not show evidence on X-ray. Forty-three individuals showed evidence of at least one meniscal abnormality while 27 individuals (61.4%) had abnormalities in at least three of the four regions of the knee. CONCLUSION: Our results suggest that osteophytes may be more prevalent in this population than radiographic data suggests due to the limitations of two-dimensional imaging. Meniscal degeneration or tears, a risk factor for knee osteoarthritis, are highly prevalent in asymptomatic individuals with the medial anterior and posterior horns being the most commonly affected regions.

Adult↗

PubMed2005

The relationships between bone mineral density in the spine, hip, distal femur and proximal tibia and medial minimum joint space width in the knees of healthy females.

OBJECTIVE: To investigate the relationships between bone mineral density (BMD) in the hip, spine, distal femur and proximal tibia and minimum joint space width (mJSW) in the knees of healthy women. METHODS: Women 22-68 years old without a history of knee pain, bone or joint disease or injury underwent a single, fixed-flexion knee X-ray. Radiographs were graded according to the Kellgren-Lawrence scale and analyzed for mJSW using a computer algorithm. Dual X-ray absorptiometry scans of the spine, hip, distal femur and proximal tibia were also acquired for each participant. Femur and tibia scans were acquired and analyzed using a modified version of the lumbar spine software. RESULTS: Forty-five females, mean [standard deviation (SD)] age and body mass index (BMI) of 40.1 (13.9) years and 24.6 (4.5)kg/m(2), respectively, participated. The mean (SD) mJSW was 4.64 (0.68)mm. Linear regression analyses controlling for age and BMI revealed that BMD in the femoral trochanter and the central two regions of the tibia (T2 and T3) was significantly related to mJSW in the knee. A backwards regression analysis performed to determine which region of interest is most significantly related to mJSW revealed that femoral trochanter BMD (beta-value=0.416) is the most significant. CONCLUSIONS: In contrast to the suggestion that BMD is negatively correlated with mJSW in the knees of osteoarthritic individuals, these results suggest that increasing BMD in the femoral trochanter and tibia is significantly associated with increasing mJSW in healthy females. Further investigation of this relationship is warranted.

Absorptiometry, Photon↗

PubMed2005

Body weight supported treadmill training in acute spinal cord injury: impact on muscle and bone.

DESIGN: Longitudinal prospective case series. OBJECTIVE: To evaluate the impact of early introduction post-spinal cord injury (SCI) of twice-weekly body-weight supported treadmill training (BWSTT) on muscle and bone. SETTING: Centre for Health Promotion and Rehabilitation, McMaster University, Canada. METHODS: Five individuals who had sustained traumatic SCI within 2-6 months participated in the study. Bone mineral densities (BMD) of proximal femur, distal femur, proximal tibia and lumbar spine were measured before and after training, as well as muscle cross-sectional area (CSA), BMD and bone geometry at mid-femur and proximal tibia. Serum osteocalcin and urinary deoxypyridinoline were measured at baseline, and after 24 and 48 sessions of training. RESULTS: All participants experienced increased muscle CSAs, ranging from 3.8 to 56.9%. Reductions in BMD were evident in all participants at almost all lower limb sites after training, ranging in magnitude from -1.2 to -26.7%. Lumbar spine BMD changes ranged from 0.2 to -7.4%. No consistent changes were observed in bone geometry. BWSTT did not alter the expected pattern of change in bone biochemical markers over time. The individual with the greatest improvement in ambulatory ability demonstrated the smallest reduction in lower limb BMD. Conversely, the individual who completed the fewest BWSTT sessions demonstrated the greatest reductions in BMD. CONCLUSIONS: Twice-weekly BWSTT appeared to partially reverse muscle atrophy after SCI, but did not prevent bone loss. Larger, controlled trials should evaluate whether relative preservation of bone loss occurs with regular BWSTT following acute SCI. SPONSORSHIP: Ontario Neurotrauma Foundation.

Adult↗

PubMed2004

Speed of sound in bone at the tibia: is it related to lower limb bone mineral density in spinal-cord-injured individuals?

STUDY DESIGN: A cross-sectional study evaluating BMD at the hip and tibia, and SOS at the radius and mid-tibia in individuals with spinal cord injury (SCI) and a subgroup of non-SCI individuals. OBJECTIVES: To investigate the speed of sound (SOS) in bone in relation to bone mineral density (BMD). SETTING: Kinesiology Department, McMaster University, Ontario, Canada. METHODS: In 14 individuals with SCI and 10 non-SCI individuals, proximal femur and tibia BMD were measured using dual energy X-ray absorptiometry, and radius and tibia SOS were measured with an ultrasonometer. T-scores were calculated using healthy reference databases. Inter-relationships between measurement techniques were determined using Pearson's correlation coefficients. P-values less than 0.05 were considered statistically significant. RESULTS: : The average ages of the SCI and non-SCI groups were 33+/-9 and 27+/-6 years, respectively. Lesion level ranged from C4 to T12 and average time postinjury was 12 years, with a range of 1.6-25 years. Using the WHO criteria for osteoporosis, nine of 14 SCI subjects were osteoporotic at the hip, with the remainder in the osteopenic range. Tibia SOS T-scores were in the osteoporotic range for one subject with SCI, and two were in the osteopenic range. Among non-SCI individuals, one male had a tibia SOS T-score of -1.4, all others were within the normal range. Hip BMD and tibia SOS were significantly correlated (r=0.46, P<0.01). Hip BMD and tibia BMD were more strongly correlated (r=0.80, P<0.0005). Tibia BMD was not significantly correlated with SOS at the tibia (r=0.35, P=0.09). Radius SOS T-scores were positive and not significantly correlated with any lower limb variable. CONCLUSION: Lower-limb bone mass is reduced in spinal cord-injured individuals, but SOS at the mid-tibia is not. It remains to be determined whether ultrasound measurements can predict fracture in the SCI population.

Absorptiometry, Photon↗

PubMed2004

Quantification of bone strontium levels in humans by in vivo x-ray fluorescence.

The need for in vivo bone strontium assessment arises because strontium may exert a number of effects on bone, which may be either beneficial or toxic. Measurements discussed here are noninvasive, no sample is taken, nor is there discomfort to patients. The developed source excited x-ray fluorescence system employs a 109Cd source to excite the strontium K x rays, with the source and detector in approximately 90 degree geometry relative to the sample position. The factors affecting the accuracy and minimal detectable limit for bone strontium in vivo measurements are discussed. A system calibration revealed a minimum detectible limit of approximately 0.25 mg Sr/g Ca, which is sufficient for the monitoring of strontium levels in healthy subjects and patients with elevated bone strontium concentrations. Preliminary in vivo measurements in ten healthy subjects at two bone sites (phalanx and tibia) indicated that this system can be applied for cumulative bone strontium estimation while delivering a low effective dose of 80 nSv during the measurement time. Future work will involve attempts to enhance system precision with alternative fluorescing sources and further optimization of the detection system.

Bone and Bones↗

PubMed2001

Longitudinal changes in bone lead concentration: implications for modelling of human bone lead metabolism.

In this study, 539 occupationally exposed subjects received in vivo bone lead measurements using 109Cd excited K X-ray fluorescence (109Cd K XRF). Of these subjects, 327 had previously been measured five years earlier. Measurements were made from both tibia and calcaneus samples, taken to reflect cortical and trabecular bone, respectively. Changes in tibia lead concentration related negatively to initial tibia lead concentration and positively to both lead exposure between the measurement dates and initial calcaneus lead concentration. This finding confirmed and strengthened the interpretation of an earlier study involving fewer subjects. With the larger data set it was possible to examine subgroups of subjects. This showed that people aged less than 40 years had a shorter half-life for the release of lead from the tibia (4.9, 95% CI 3.6-7.8 years) than did those older than 40 (13.8, 95% CI 9.7-23.8 years). Similarly, less intensely exposed subjects (lifetime average blood lead < or = 25 micrograms dL-1) had a shorter tibia lead half-life (6.2, 95% CI 4.7-9.0 years) than those with a lifetime average blood lead > 25 micrograms dL-1 (14.7, 95% CI 9.7-29.9 years). Age and measures of lead exposure were strongly correlated; nevertheless, age matched subgroups with high and low intensity exposures showed clearance rates that were significantly different at the 10% level, with the lower exposure intensity again being associated with the faster clearance. These findings imply that current models of human lead metabolism should be examined with a view to adjusting them to account for kinetic rates varying with age and probably also with exposure level.

Adult↗

PubMed2001

Effect of altered physical loading on bone and muscle in the forearm.

Cast immobilization of injured forearms is common clinical practice yet little is known about the effect of reduced skeletal loading in the absence of pathology. This study reports the changes in the forearms of nine healthy young adults owing to six weeks in a plaster cast followed by 1 year of either habitual activity or a strengthening program. Both groups exhibited similar patterns of change in wrist mobility, forearm muscle strength, and bone variables. Because of small sample size and poor compliance with the exercise protocol, no conclusions can be drawn about the effect of exercise. In all subjects, reduced loading caused a decrease in wrist mobility (p < 0.02) and grip strength (p = 0.01) with full recovery following 3 months of remobilization. Six months after removing the cast, bone size was reduced in the middle region of the radius (p = 0.02) and recovered after 1 year of remobilization. Given that radial bone mass tended to decrease while bone density was unchanged, we conclude that the effect of casting was modulated by changes in gross bone morphology rather than in material characteristics.

Absorptiometry, Photon↗

PubMed2000

Study of the relationships between bone lead levels and its variation with time and the cumulative blood lead index, in a repeated bone lead survey.

The study aims were to: (i) investigate long term human lead metabolism by measuring the change of lead concentration in the tibia and calcaneus; and (ii) assess whether improved industrial hygiene was resulting in a slow accumulation of lead in an exposed workforce. 109Cd excited K X-ray fluorescence was used to measure tibia lead and calcaneus lead concentrations in 101 workers in a secondary lead smelter. 51 subjects had had similar bone lead measurements 5 years previously. Most of the other subjects had been hired since the first survey. Measurements of whole blood lead were available for the large majority of subjects. Tibia lead concentrations fell significantly (p<0.001) in the 51 subjects with repeated bone lead measurements, from a mean of 39 microg Pb (g bone mineral)(-1) to 33 microg Pb (g bone mineral)(-1). The change correlated negatively with the initial tibia lead concentration, producing an estimate for an overall half-life of 15 years, with a 95% confidence interval of 9 to 55 years. Adding continuing lead exposure and recirculation of bone lead stores to the regression models produced half-life estimates of 12 and 9 years, respectively, for release of lead from the tibia. The repeat subjects showed no net change in calcaneus lead (64 microg Pb (g bone mineral)(-1) initially, 65 microg Pb (g bone mineral)(-1) 5 years later). Subjects not measured previously had average lead concentrations of 15 microg Pb (g bone mincral)(-1) in the tibia and 13 microg Pb (g bone mineral)(-1) in the calcaneus. The rate of clearance of lead from the tibia (9 to 15 years) is towards the more rapid end of previous estimates. The lack of a significant fall in the calcaneus lead was surprising. Attempts should be made to repeat this observation. If confirmed, it would have implications for models of lead metabolism. The relatively low lead concentrations in the non-repeat subjects are reassuring. However, observation after a longer period of employment would be desirable.

Adult↗

PubMed1999

The O'Flaherty model of lead kinetics: an evaluation using data from a lead smelter population.

The O'Flaherty model of lead kinetics is a physiologically based computer model of lead disposition in humans. The model is based on an age-dependent approach to human growth, with particular attention devoted to bone metabolism. As such, model output is well suited for comparison with noninvasive bone lead measurements made via X-ray fluorescence. A subset of workers from a lead smelter population were selected for an initial evaluation of the O'Flaherty model. Detailed blood lead records were used to define input. Simulated bone lead and blood lead output were compared with observation, enabling a refinement of model parameters. A revised version of the O'Flaherty model was then evaluated for the smelter population as a whole. Previously observed trends for the accumulation of lead in cortical bone and the release of lead from bone stores were well explained by the revised model. Model predictions for the accumulation of lead in trabecular bone were not in accord with observed levels in the calcaneus. Model results from the smelter population are consistent with the hypothesis that a polymorphism in the delta-aminolevulinate dehydratase enzyme modifies the kinetics of lead in humans. Further refinements are suggested, which may enhance the ability of the model to explain the underlying relationships between lead exposure and the distribution of lead in the body.

Aging↗

PubMed1999

In vivo detection of structural differences between dominant and nondominant radii using peripheral quantitative computed tomography.

This cross-sectional study identifies differences in distal radial trabecular bone structure related to habitual loading patterns in the upper extremities using high-resolution peripheral quantitative computed tomography. As well, it determines whether measurements of these indices in one limb serve as satisfactory surrogates for the contralateral limb. The dominant and nondominant forearms of 106 adult volunteers (mean age [SD], 44.3[17.5] yr) were scanned and indices of trabecular bone structure (connectivity index [CI], maximum hole size [H(M)], and mean hole size [H(A)]) were determined at the distal radius. The images were also analyzed to determine bone density. For all subjects, H(M) is significantly smaller in the dominant radius (p < 0.01). Right-handed subjects (n = 96) have greater CI (p < 0.05) and smaller H(M) (p < 0.01) in the dominant radius. For the total group, the dominant limb has a greater mass (total and cortical bone mineral content, p < 0.01 and p < 0.05, respectively) and greater total bone volumetric density (p < 0.05). There are no significant differences between limbs for the group of left-handed subjects &lapr;n = 10). As expected, significant associations exist between side-to-side measurements of bone structure and density (p < 0.001). The correlation coefficients for connectivity index, H(M), and H(A) are 0.86, 0.85, and 0.87, respectively. For bone density, the between-limb associations are 0. 90, 0.73, and 0.92 for the total, cortical, and trabecular bone compartments at the distal radius. Differences in the structure of the trabecular bone network suggest that differential loading of the dominant limb preserves bone strength.

Adult↗

PubMed1999

Gender differences in normal age-dependent patterns of radial bone structure and density: a cross-sectional study using peripheral quantitative computed tomography.

This cross-sectional study determines gender differences in the age-dependent patterns in radial trabecular bone structure using high-resolution peripheral quantitative computed tomography. The nondominant forearrns of 145 adult volunteers (57 men) were scanned and indices of trabecular structure (connectivity index [CI]; mean hole size [H(A)]; and maximum hole size [H(M)]) were determined at the ultradistal radius. The images were also analyzed to determine bone density. Men had significantly higher values for CI (p < 0.01), significantly lower values for H(A) (p < 0.01), and significantly greater bone density (p < 0.001) than women. Age-dependent patterns in normal trabecular structure also displayed gender differences. CI decreased significantly with age in both men (-0.8%/yr, p < 0.05) and women &lpar-2.2%/yr, p < 0.001); however, the rate of change was more pronounced in women (p < 0.001). Similarly, the age-related increase in H(A) (+2.2%/yr) and H(M) (+1.1%/yr) was significant in women (p < 0.01) but not in men. In both sexes, when expressed as an annual percentage of change, indices of trabecular bone structure changed to a greater extent than indices of bone density. The assessment of structural indices may improve our ability to identify individuals at risk for fractures of the distal radius.

Adult↗

PubMed1999

Changes in spine and radius bone density during long-term hormone replacement.

Lumbar spine and mid-radius bone mineral density was measured repeatedly in 48 postmenopausal women who completed 7 years of taking either a 500 mg x day(-1) calcium supplement (n = 22) or calcium supplementation with hormone replacement therapy. The hormone replacement was either a low dose (n = 15) or a moderate dose (n = regime. The purpose of the measurements was to establish the long-term pattern of change in bone mineral mass produced by continued hormone replacement. The calcium-only group lost bone mineral mass at the radius, while the spine, bone was preserved. Low dose hormone replacement preserved radius bone. Moderate dose replacement increased bone mineral mass at the spine and preserved radius bone.

Aged↗

PubMed1998

Effect of the delta-aminolevulinate dehydratase polymorphism on the accumulation of lead in bone and blood in lead smelter workers.

Lead inhibition of the zinc metalloenzyme delta-aminolevulinate dehydratase (ALAD) is one of the most sensitive indicators of blood lead levels. ALAD is polymorphic, with about 20% of Caucasians expressing the rarer ALAD2 allele. Previous studies indicated that this polymorphism may be a genetic factor in lead transport, metabolism, and/or distribution. Whole blood lead, serum lead, and ALAD genotype were determined for 381 lead smelter workers, including 70 workers expressing the ALAD2 allele, whose blood lead elevations were observed for more than 20 years of employment. The same employees demonstrated higher serum lead levels. Using a cumulative blood lead index (CBLI) for each worker, based on individual blood lead histories, and in vivo X-ray fluorescence measurements of bone lead to estimate total lead body burden, the slopes of linear relations of bone lead to CBLI were greater for workers homoallelic for ALAD1, indicating more efficient uptake of lead from blood into bone. This effect was most significant in calcaneus bone and for workers hired since 1977 [ALAD1-1: 0.0528 +/- 0.0028 and ALAD1-2 or 2-2: 0.0355 +/- 0.0031 (P < 0.001)]. Decreased transfer of blood lead into bone in individuals expressing the ALAD2 allele contrasted with increased blood lead. Thus the ALAD genotype affected lead metabolism and potentially modified lead delivery to target organs including the brain; however, the ALAD genotype did not significantly affect the net accumulation of lead in bone.

Amino Acid Sequence↗

PubMed1998

Is there any association between the presence of bone disease and cumulative exposure to lead?

There is evidence from cell culture experiments, animal studies, and from measurements in humans that lead may exert detrimental effects on bone mineral metabolism. In order to explore a possible association between lead and bone disease, both cortical and trabecular bone lead content as well as serum lead concentration was measured in 117 patients who attended a metabolic bone disease clinic (n = 92) or were undergoing dialysis for renal failure (n = 25). Cortical bone lead content was higher in patients suffering from Paget's disease than it was in controls, patients with osteoporosis, and patients on dialysis. Trabecular bone lead content was lowest in patients with Paget's disease or osteitis fibrosa. There was no association between bone lead content and serum alkaline phosphatase concentration in patients suffering from osteoporosis. No statistically significant differences in serum lead concentrations were found between groups. Our results do not distinguish between the two possibilities that increased bone turnover due to Paget's disease releases lead from trabecular bone which is then available for deposition into cortical bone or the alternative possibility that an increased lead content in cortical bone may cause increased turnover with release of lead from trabecular bone.

Aged↗

PubMed1998

A comparison of strength and muscle mass increases during resistance training in young women.

Strength gains with resistance training are due to muscle hypertrophy and nervous system adaptations. The contribution of either factor may be related to the complexity of the exercise task used during training. The purpose of this investigation was to measure the degree to which muscle hypertrophy contributes to gains in strength during exercises of varying complexity. Nineteen young women resistance trained twice a week for 20 weeks, performing exercises designed to provide whole-body training. The lean mass of the trunk, legs and arms was measured by dual energy x-ray absorptiometry and compared to strength gains (measured as the 1-repetition maximum) in bench press, leg press and arm curl exercises, pre-, mid- (10 weeks) and post-training. No changes were found in a control group of ten women. For the exercise group, increases in bench press, leg press and arm curl strength were significant from pre- to mid-, and from mid- to post-training (P < 0.05). In contrast, increases in the lean mass of the body segments used in these exercises followed a different pattern. Increases in the lean mass of the arms were significant from pre- to mid-training, while increases in the lean mass of the trunk and legs were delayed and significant from mid- to post-training only (P < 0.05). It is concluded that a more prolonged neural adaptation related to the more complex bench and leg press movements may have delayed hypertrophy in the trunk and legs. With the simpler arm curl exercise, early gains in strength were accompanied by muscle hypertrophy and, presumably, a faster neural adaptation.

Absorptiometry, Photon↗

PubMed1998

Osteopenia in children surviving brain tumours.

Osteopenia has been reported in children surviving acute lymphoblastic leukaemia, apparently as a consequence of therapy. It has been suggested that cranial irradiation may play a crucial role in this disorder. To explore that possibility, survivors of brain tumours in childhood, all of whom had received radiotherapy, were examined for evidence of bone mineral loss. 19 children were assessed, on average at 7 years after treatment. Measurements of growth velocities, plain radiography of the skeleton, bone densitometry, health-related quality of life and physical activity were undertaken. Growth hormone (GH) deficiency had been detected in 6 children and 5 had received GH replacement, for a minimum of more than 3 years. 9 children were radiographically osteopenic (including the 5 who had received GH). Z scores for bone mineral density (BMD) were negative in the majority of children. Health-related quality of life was less and pain more frequent in those with low BMD scores. Pain was correlated negatively with both free-time activity and seasonal activity (P < 0.01). Osteopenia is a common sequel of therapy in children with brain tumours. Those with osteopenia have more pain and more compromised, health-related quality of life than those who are not osteopenic, and pain significantly limits physical activity. The pathogenesis of osteopenia in these children is still uncertain, but is likely to be multifactorial.

Adolescent↗

PubMed1998

Uncertainties in bone mineral density T scores.

In the diagnosis and management of osteopenia and osteoporosis, dual photon absorptiometric measurements of lumbar spine and proximal femur bone mineral density are interpreted by calculating a T score, which is the number of standard deviations by which a result deviates from the mean bone density in young adults of the same sex. Threshold values are then used to categorize patients as having osteopenia or osteoporosis. The uncertainty associated with a single bone mineral density measurement, as well as the uncertainties in the assumed values for the bone mineral density in young adults and the population standard deviation, combine to create an uncertainty in the calculated T score. It is estimated that 95% of bone density measurements have a T score uncertainty of less than 0.4. This means that a single measurement of bone mineral density should not be used in isolation to assign a given patient to a specific diagnostic category. Rather, a bone mineral density measurement should be regarded as only one of the variables that determine the risk of fracture in a given patient.

Absorptiometry, Photon↗