Biomedical subjects

Ian H Parkinson

Publications and source records attributed to Ian H Parkinson.

5 recordsLinked to original sources

PubMed2006

Trabecular rod buckling index in thoraco-lumbar vertebral bonedagger.

The need for improved mechanistic understanding of cancellous bone failure is at the core of important clinical problems such as osteoporosis, as well as basic biological issues such as bone formation and adaptation. Three-dimensional (3D) anaglyphs were produced from 15 T12 and L1 vertebral bodies, which encompass the adult life span in both sexes. The anaglyphs were viewed with red-green stereo glasses, using an image analyzer, and trabecular thickness and trabecular length were measured. From biomechanical principles, the strength of individual trabeculae can be estimated from measurement of trabecular rod thickness and trabecular rod length as the load to buckling index. The distribution of the load to buckling index was best described by a log normal curve. Trabecular rod thickness, trabecular rod length, and load to buckling index for males were consistently greater than for females. With aging, trabecular rod thickness, and the load to buckling index decrease for males while trabecular rod length increases for females. In this study, the load to buckling index for thoraco-lumbar vertebral trabecular rods potentially quantifies a greater risk of vertebral fracture for females. Decreased trabecular rod thickness or increased trabecular rod length result in the strength of trabeculae shifting closer to a putative fracture threshold. The corollary being that there is a reduced safety margin for resistance to mechanical loads for the vertebral bodies. The 3D anaglyph technique for measuring trabecular dimensions provides an accurate and precise methodology by which these morphological studies can be undertaken.

Adolescent↗

PubMed2005

Antero-postero differences in cortical thickness and cortical porosity of T12 to L5 vertebral bodies.

OBJECTIVE: This study will investigate interrelationships between the cortical shell and cancellous bone trabecular thickness, in vertebral bodies. METHODS: One hundred and sixty vertebral bodies from T12 to L5 were obtained at autopsy. The average age of the cohort was 59.3+/-22.1 years (range = 20-94 years). Cortical thickness, cortical porosity and trabecular thickness from the adjacent cancellous bone were measured. RESULTS: At the mid-vertebral body anterior cortical thickness was significantly greater than posterior cortical thickness (524 +/- 352 vs. 370 +/- 283 microm, respectively, P < 0.0001) and mid-anterior cortical porosity was significantly less than mid-posterior cortical porosity (24 +/- 14% vs. 32 +/- 16%, respectively, P < 0.0001). There were no anterior/posterior differences in trabecular thickness of the cancellous bone adjacent to the cortical walls. CONCLUSION: This study provides a novel perspective of T12 to L5 vertebral body bone, where measurement of cortical thickness and cortical porosity in a cohort of skeletally normal individuals revealed structural differences between load bearing anterior and posterior cortical walls. The data suggest that modulators of change to vertebral body bone may affect the cortical and trabecular bone differently. The relationships between cortical and cancellous bone suggest that the middle sectors of the vertebral body play a critical role in load bearing.

Adult↗

PubMed2004

Effectiveness of AutoPap system location-guided screening in the evaluation of cervical cytology smears.

Location-guided screening is a feature of the AutoPap primary screening software. Areas of the smear most likely to contain an abnormality are identified for prompt review by the cytotechnologist, thereby facilitating diagnostic accuracy and reducing laboratory workload. A two-armed retrospective study comprising 6,000 conventional smears was undertaken to compare this approach with the current practice of full manual screening of conventional smears. Discrepant diagnoses between the two study arms were subject to an internal discrepancy review process to determine the final truth diagnosis. Analysis of the results show that AutoPap location-guided screening is at least equivalent to current practice when detecting high-grade or suspected high-grade smears. However, the device does not detect low-grade abnormalities, unsatisfactory smears, an endocervical component or organisms, as well as standard screening. The device also assigns a numerical score to each slide, with abnormal smears allocated a higher rank. Slide ranking was found to be of value in triaging abnormal smears for prompt screening and reporting. The performance of the primary screening software was found to be comparable to previous studies, with the majority of abnormal smears being selected by the instrument for manual review.

Automation↗

PubMed2003

Trabecular rod thickness by direct measurement from 3D SEM anaglyphs.

This study presents a methodology for measuring the thickness of trabecular rods directly from anaglyphs. Macerated sagittal slices of T12 vertebral bodies from 15 subjects were examined by scanning electron microscopy (SEM). Two digital images (the second image tilted 5 degrees ) were recorded, and a 3D anaglyph was created. The thickness of the trabecular rods (Tb.Th((rods))), and the anatomical orientation of the trabecular rods were measured using an image analyser. Conventional 2D histomorphometry was performed on adjacent bone slices. A total of 1559 rod measurements were made from the 15 vertebral bone slices, with a mean Tb.Th((rods)) of 123 +/- 36 microm. The rod thickness in males (128 +/- 34 microm) was significantly greater than that in females (119 +/- 37 microm, P < 0.001). Tb.Th((rods)) changed significantly with age in the males: the thicker rods in the younger men reduced with age to a thickness similar to that in women. 3D measurements were significantly larger than the 2D estimates, and there was no correlation between the two methods of measurement. An inverse correlation was found between the number of rods and the bone volume fraction (BV/TV), indicating that decreased BV/TV is associated with an increased number of rods. The vertical rods (132 +/- 39 microm) were significantly thicker than the horizontal rods (116 +/- 33 microm, P < 0.001). The determination of rod numbers, and their orientation and individual thicknesses enables a greater understanding of cancellous bone architecture in both individuals and populations, and will allow more reliable finite element modelling. Direct measurements from 3D anaglyphs of intact specimens provide new data that show previously unrecognised age- and sex-related changes.

Adolescent↗

PubMed2003

Interrelationships between structural parameters of cancellous bone reveal accelerated structural change at low bone volume.

UNLABELLED: This study shows that change to cancellous bone structure is bone volume-dependent in a nonlinear manner. At low bone volume (< 15%), trabecular thickness and trabecular separation change at a much greater rate than at higher bone volume. This suggests that the structural integrity of the cancellous bone may become rapidly compromised when bone volume falls below a critical value. INTRODUCTION: While bone mass is the major determinant of bone strength, this mass-based paradigm does not fully account for the contribution of the bone microstructure to mechanical efficiency. Geometric models of cancellous bone structure have been formulated based on stylized representations of the trabecular elements, where the relationships between bone volume and bone surface of cancellous bone are complex and reflect the modulating effect on the cancellous bone structure of bone remodeling at the trabecular surfaces. Using the plate model of cancellous bone structure, the interrelationships between parameters of cancellous bone structure have been studied. MATERIALS AND METHODS: Two hundred eighty histological sections of human cancellous bone from eight skeletal sites were analyzed. The structural parameters of cancellous bone (BV/TV, BS/TV, BS/BV, Tb.Th, Tb.Sp, Tb.N, and TBPf) were obtained. RESULTS AND CONCLUSIONS: This study shows that change to cancellous bone structure is bone volume-dependent in a nonlinear manner. At low bone volume (< 15%), structural parameters of cancellous bone, such as trabecular thickness and trabecular separation, change at a much greater rate than at higher bone volume. This suggests that the structural integrity of the cancellous bone may become rapidly compromised when bone volume falls below a critical value. These data describe the complex relationships between bone mass and structure in cancellous bone that are often overlooked in the mass-based paradigm of bone strength. Histomorphometric descriptors of cancellous bone structure highlight the potential for accelerated deterioration of the structure with low bone volume, which leads to increased risk of fracture. From a clinical viewpoint, estimation of an individual's fracture risk is constrained to noninvasive techniques, which only provide bone mineral density or bone mineral content. Therefore, there is a need to better correlate measurement of bone mass with measurements of structural parameters.

Bone Density↗