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Biomedical subjects

A Kapasouri

Publications and source records attributed to A Kapasouri.

8 recordsLinked to original sources
PubMed1986

Centrode characteristics of the lumbar spine as a function of segmental instability.

A cadaveric study provides a quantitative measurement of early degenerative disc disease before significant radiographic changes are present. Accurate assessment of spinal motion is hampered by the inaccessibility of the lumbar joints and because of the small range of motion at each motion segment. Using Moiré fringes and, more recently, computerized digitization of spinal motion, the authors have developed a technique of measuring centers of rotation for small ranges of motion. The centers of rotation when joined form a locus that has characteristics that allow one to identify spines with degenerative disc disease. These loci, or centrodes, are longest in the earliest stages of degeneration, but maintain their length through moderate degenerative disc disease. Furthermore, radiographic changes consistent with moderate disc disease are associated with inferior migration of the centrode.

Biomechanical Phenomena↗
PubMed1985

Moiré patterns: an accurate technique for determination of the locus of the centres of rotation.

This study describes an accurate technique for the determination of the centre of rotation of small angles. The moiré fringe method localizes the centre of rotation by defining two primary fringes, each of which is found by the intersection of three lines. The primary fringes intersect at the centre of rotation at 90 degrees to each other, the angle least likely to produce an error in measurement. By utilizing joints with known centres of rotation, we have found that the method is extremely accurate and reproducible to within 2 mm of the real centre for angular changes as small as 3 degrees. This technique is useful in evaluating whether a joint is a simple hinge, i.e. rotating about a single axis of rotation or whether the joint moves about a changing axis of rotation referred to as a locus or centrode.

Arthrography↗
PubMed1985

Centrode patterns and segmental instability in degenerative disc disease.

Moiré fringes were used to determine centrode patterns in cadaveric spines with degenerative disc disease. The normal centrodes were compared with those with minor, mild, moderate, and severe degenerative disc disease. The most complex loci noted were those discs that showed minimal radiographic evidence of degeneration, that is, the minor and mild groups. The loci lengthened significantly (P less than 0.001) when compared with normal controls. The position of the centrode shifted downward into the body of L5 in the moderate group.

Adult↗
PubMed1984

Computer analysis of spinal segment motion in degenerative disc disease with and without axial loading.

The center of rotation of the spinal motion segment is an indicator of spinal instability. However, the motion segment does not move about a single fixed axis of rotation, but rather a locus of instantaneous axes of rotation, the centrode. This paper studies centrodes in various stages of degenerative disc disease comparing them with normal spines. Computer analysis is undertaken in 47 cadaveric spines, 22 of which also were evaluated with axial loading. The normal centrode fell within the posterior half of the disc space and averaged 21 mm in ten specimens. In the earliest stages of degenerative disc disease, the centrode lengths increased significantly (average 116 mm). Specimens with moderate disc degeneration also migrated inferiorly into the L5 vertebra. Axial loading did not appear to influence the centrode lengths or position. This technique is highly sensitive, detecting 94% of the abnormal spines as compared with only 25% detected by means of measuring an excessive range of motion on flexion and extension radiographs. This method provides a highly reliable and quantifiable method of detecting early changes in spinal motion in degenerative disc disease prior to the well recognized radiographic abnormalities.

Biomechanical Phenomena↗
PubMedDate not supplied

Determination of a locus of instantaneous centers of rotation of the lumbar disc by moiré fringes. A new technique.

The aim of this study was to define the motion of the L4-5 spinal segment moving from full extension to full flexion. A new technique using moiré fringes was applied to measure angles of 3-degree change, a technique proven to be highly accurate for small angular changes. This investigation has identified a locus of centers of rotation (centrode) that is located in the posterior half of the intervertebral disc. The direction of the locus passes from posterior to anterior and back to posterior. The technique can be adapted for evaluation of in vivo radiographs. This technique may prove useful in identifying aberrations in movement associated with spinal segment instability in its earliest stages.

Biomechanical Phenomena↗
PubMedDate not supplied

Centrode patterns in the lumbar spine. Baseline studies in normal subjects.

Segmental spinal instability is a known cause of back pain, but no method of accurately quantifying instability exists. The movement of complex joints with rotational and translational components (such as the lumbar motion segment) is tracked by a pathway of instantaneous centers of rotation, or a centrode. Instability, ie, excessive and/or erratic movement, is reflected by increased centrode length in cadaver studies. This study describes an in vivo method that precisely determines the centrode pattern and reports the results for 21 normal male volunteers who were studied at the L4-5 and L5-S1 levels. Each volunteer underwent lateral radiographs of the lumbar spine. High speed films were used and six positions, from full extension to full flexion, were recorded. Acetate tracings and contour matching techniques recorded the relative positions of the vertebral bodies on each film. Multiple tracings of each radiograph, combined with a digitizer and computer, were used to improve precision in the calculated centrode patterns. Centrode lengths measured 43.7 mm and 55.9 mm, respectively, for the L4-5 and L5-S1 levels. This study demonstrates that precise centrode pattern analysis for sagittal plane motion of the lumbar spine is possible in vivo. Studies are under way to determine whether this technique will be useful as a clinical test in diagnosing early segmental instability of the lumbar spine in patients with low-back pain.

Adult↗
PubMedDate not supplied

Altered lymphocyte response in adjuvant-induced arthritis.

Evaluation of lymphocyte response has been undertaken in adjuvant-induced arthritis in rats. Lymphocyte reactivity was studied by evaluating lymphocyte transformation in mixed lymphocyte-chondrocyte cultures as well as the response to PHA and M. tuberculosis. It was found that animals immunized with Freund's complete adjuvant showed increased transformation when challenged with M. tuberculosis powder. However, there was a depressed response to PHA and a markedly depressed response in mixed lymphocyte-chondrocyte cultures.

Animals↗