Search PubMed⌕ Search

Biomedical subjects

J E Block

Publications and source records attributed to J E Block.

33 records · Page 2Linked to original sources
PubMed1989

Determinants of bone density among athletes engaged in weight-bearing and non-weight-bearing activity.

To identify the factors associated with greater bone density among athletic individuals, we recruited three distinct groups of young male subjects. Twenty were nationally ranked water polo players, 19 were engaged in weight-training programs, and 20 subjects comprised a nonexercising comparison group. All participants had measurements of spinal trabecular and integral bone density by quantitative computed tomography as well as a determination of hip bone density by dual photon absorptiometry. A series of potential predictor variables included maximal O2 uptake, back strength, leg strength, total kilocalories expended per day, body mass index, paraspinous muscle cross-sectional area, percent body fat, daily calcium intake, and age. We found no significant differences for any of the bone density measures between the two groups of athletic subjects, whereas bone density was generally significantly lower among the nonexercisers compared with either exercise group. Correlation analysis found only weak and somewhat inconsistent relationships when each of the subgroups was examined separately; however, when all subjects were assessed collectively, many more correlations reached significance. Paraspinous muscular area was found to be most robust in this regard, being significantly correlated with all three bone density measures (r = 0.33-0.55). By using step-wise regression analysis in each subgroup, we observed a consistent significant contribution (R2 = 0.18-0.44) of paraspinous muscle area to the variability in bone density at the spine and the hip. When the data of all three subgroups were pooled, regression analysis reconfirmed the importance of the muscle parameter (R2 = 0.06-0.27) to bone density variation, but more importantly it showed that differentiation based on exercise status was most significant (R2 = 0.18-0.22).

Adolescent↗
PubMed1988

An examination of the association between vertebral deformities, physical disabilities and psychosocial problems.

In order to measure the clinical consequences of spinal osteoporosis, we correlated a number of physical and psychosocial dysfunctions with the degree of vertebral deformity in 204 women aged 55-75 yr. We employed 5 standardized questionnaire instruments: the physical dimension of the Sickness Impact Profile (SIP), an analog back pain scale, a 24-question instrument eliciting back-related disabilities, and assessments of self-esteem and mastery. Using these results as the dependent variables, we performed 5 separate stepwise regression analyses; independent variables were vertebral deformity score and 11 possible confounders. Using Pearson correlation coefficients, we found a high degree of correlation between each of the 5 primary outcome variables. Vertebral deformity score played a small but statistically significant role in the 3 models whose dependent variable was related to physical dysfunction, but it accounted for only 4-10% of the variance of these models. Mastery and self-esteem were related to overall poor health and attendant physical disabilities but not to vertebral deformity score. In this selected cohort of women, the occurrence of mild to moderate vertebral deformities caused little loss of physical function or function of psychosocial problems because of vertebral deformity. Although we were able to demonstrate a statistically significant handicap related to the total vertebral deformity score, several other clinical variables appeared to have a greater impact.

Aged↗
PubMed1988

Avascular necrosis of the femoral head: high-field-strength MR imaging with histologic correlation.

Magnetic resonance (MR) images, contact radiographs, and histologic sections of six femoral head specimens with avascular necrosis were correlated. A low-signal-intensity band or ring represented the repair tissue interface surrounding a high-signal-intensity necrotic marrow segment. Large segmental areas of low signal intensity were observed on T1-weighted images when the lesion consisted of necrotic bone with amorphous marrow debris and adjacent thickened trabecular bone with mesenchymal repair tissue infiltration. On intermediate-weighted images, however, mesenchymal repair tissue, which was located inferior to the necrotic zone, increased markedly in signal intensity, permitting distinction from low-intensity necrotic bone with amorphous marrow debris. When trabecular thickening with collapse predominated, segmental areas of low signal intensity with both sequences were found. MR signal intensities used in combination with anatomic configuration and location may provide information of potential therapeutic importance regarding tissue composition and stage of disease.

Adult↗
PubMed1987

Quantitative computed tomography in assessment of osteoporosis.

Computed tomography (CT) has been widely investigated and applied in recent years as a means for noninvasive quantitative bone mineral determination. The usefulness of computed tomography for measurement of bone mineral lies in its ability to provide a quantitative image and, thereby, measure trabecular, cortical, or integral bone, centrally or peripherally. For measuring the spine, the potential advantages of quantitative computed tomography (QCT) over dual-photon absorptiometry (DPA) are its capability for precise three-dimensional anatomic localization providing a direct density measurement, and its capability for spatial separation of highly responsive cancellous bone from less responsive compact bone. Currently, QCT vertebral mineral determination has been implemented at over 800 sites encompassing a wide geographic distribution and a wide array of commercial scanners. With a world-wide distribution of approximately 8,000 advanced CT body scanners, the capability now exists for widespread application of vertebral bone mineral determination by quantitative computed tomography. These QCT techniques for vertebral mineral determination have been used to study skeletal changes in osteoporosis and other metabolic bone diseases. Longitudinal and cross-sectional bone mass measurements have been obtained at the University of California at San Francisco (UCSF) in over 3,000 patients seen clinically or on research protocols. The results presented here illustrate the use of QCT spinal mineral measurement in the delineation of normal age-related bone loss, in the evaluation of estrogen effects on bone, in the assessment of fracture threshold and risk, and in the study of the effects of various exercise regimens on bone mineral and the determination of relationships to other techniques of bone mineral measurement. The laboratory and clinical results presented herein indicate that QCT provides a reliable means to evaluate and monitor the many forms of osteoporosis and the various interventions aimed at ameliorating this condition. The greatest advantages of spinal QCT for noninvasive bone mineral measurement lie in the high precision of the technique, the high sensitivity of the vertebral trabecular measurement site, and the potential for widespread application.

Aging↗
PubMed1986

Greater vertebral bone mineral mass in exercising young men.

Peak bone mass at skeletal maturity may be an important factor in the relative quantity of skeletal mass in old age. We have studied bone mineral in 46 young men, 28 of whom engage in regular and vigorous exercise programs. Spinal trabecular bone mineral density and spinal integral bone mineral content are significantly greater in the exercise group as compared with the 18 control subjects. Of the exercise group, subjects participating in both aerobic and weight-bearing regimens have the greatest spinal bone mineral mass, followed by those engaging in strictly weight-bearing exercise and those in a primarily aerobic program. An analysis of variance across all subject groups, including the control group, shows a significant difference in spinal trabecular bone density based on the type of physical activity.

Adult↗
PubMed1979

Is EVE ectopic.

Explore the source record for details and available documents.

Electrocardiography↗
PubMedDate not supplied

Precise determination of paraspinous musculature by quantitative CT.

The ability to quantify muscular size has important implications in monitoring the effects of muscle disorders, in assessing the efficacy of interventions aimed at abbreviating muscle atrophy, and in examining the association between muscle and bone as a correlate of osteoporosis. We have developed an autocontouring technique for the precise determination of paraspinous musculature that can be implemented as an adjunct to our current CT method of spinal trabecular densitometry without additional scanning time or radiation exposure. Using two distinct patient groups, we evaluated the validity of this technique by assessing intra- and interobserver variability. Using the average coefficient of variation (CV) as an estimate of precision, we found intraobserver variability to be essentially equivalent whether evaluated in young, healthy men (0.69%) or in older, mildly osteoporotic women (0.74%). When the muscle evaluations of two observers were compared, the variability was somewhat higher, 1.81 and 1.83% in older and younger subjects, respectively. We scanned an additional 10 subjects twice, with intermediate repositioning, and found the reproducibility (CV) of determining paraspinous muscle area to be 0.97%. Given this estimated high level of precision, we derived the approximate magnitude of change in muscle size that could be observed using two-point measurements in time. Small average changes, on the order of 1-2%, could be detected using small groups of subjects (10-20/group). Moreover, we found that, even in the individual patient, relatively small changes (3-6%) could be detected given our low imprecision estimate. We believe this quantitative approach holds promise for monitoring muscle changes in vivo as well as for rigorously exploring the relationship between muscle and bone.

Adult↗
PubMedDate not supplied

Electrically-stimulated muscle hypertrophy in paraplegia: assessment by quantitative CT.

To identify the magnitude of muscle hypertrophy following electrically stimulated exercise in paraplegic subjects, we used quantitative CT (QCT) of the midthigh prior to and following 6 weeks of bicycle ergometry. Three patients who had suffered acute spinal cord injury were examined in this pilot investigation. Average absolute changes in muscle cross-sectional area by QCT were determined to be 10.6 cm2 (p = 0.042) at a distal site located 100 mm above the tibial plateau and 18.8 cm2 (p = 0.019) at a more proximal site (175 mm). Expressed as a percentage increase, these changes were likewise found to be significant. When the total thigh musculature was segmented into anterior and posterior regions, significant increases were observed only among the anterior muscle groups at both the distal and the proximal sites. Muscle hypertrophy as determined by standard anthropometric techniques at 200 mm above the patella was not found to be significant. We conclude that QCT is a valuable technique for discerning changes in muscle size during fitness training and that, in our population, it was capable of differentiating specific muscle compartment hypertrophy secondary to electrical stimulation.

Adult↗