Quantification of skeletal, muscular and kinematics parameters in scoliosis : methodological and clinical studies
Author: Diab, Khaled Mohamed
Date: 1998-09-11
Location: Föreläsningssal C187, plan 8 Hus C, Huddinge sjukhus
Time: 9.00
Abstract
This dissertation presents new methods derived for precise evaluation of
a number of anatomical and functional variables of the complex
thoracospinal deformity in scoliosis.
By consensus the scoliotic angle at the frontal plane is measured on
radiographs using the Cobb method. Another way of measuring this angle,
the Ferguson method, although evidently more accurate than the Cobb, is
not in use. The Cobb method uses only the declination of the upper and
the lower vertebra of the curve to measure the degree of the curve. The
Ferguson method uses the centroid of these two vertebrae and of the
apical one to define the angle. In a derived new method the geometrical,
i.e., the true, centre of the three vertebrae is defined on
antero-posterior radiographs of the spine to delineate the scoliotic
angle. Comparison of the measurements by the three methods in three
groups of radiographs with different degrees of scoliosis shows that the
new method gives higher accuracy and better repeatability than the two
other methods.
Studies on the vertebral growth under normal and pathological conditions
are based on measurements of the vertebral height at different points of
interest on radiographs, since there is no method for evaluation of the
vertebral volume. A new stereological method is presented which allows
estimation of the vertebral volume in vivo. The volume of one isolated
normal and one scoliotic vertebra was measured in a model study using
frontal and lateral radiographs and one CT-scan of each. The height of
the vertebrae was measured at five points on the radiographs and was
expressed as weighted circumferential height. Then the area of the
vertebral body was measured using a grid on the CT-scan of the vertebra
and the volume was calculated using the Cavallieri method. The accuracy
of the measurements with the new method was high compared with serial
CT-scans ofthe whole vertebra. The applicability of the method was
evaluated in a series of scoliotic patients who had undergone posterior
spinal instrumentation and fusion. The results showed that the weighted
circumferential height of the three vertebrae had increased significantly
at the last follow up on average 3 years after the operation. Also the
volume of the apical vertebra was found to have increased, though not
significantly. It is concluded that the proposed method provides accurate
evaluation of vertebral body volume changes.
The role of the intercostal muscles in the development of the
thoracospinal deformity in scoliosis and of the respiratory movements of
the thoracic cage is well recognised, but poorly studied because of lack
of an accurate method for measurement of the surface area of the muscles
and hence, indirectly, their function. In a model study the surface area
of the intercostal muscles was evaluated in ultrasonographs and CT-scans
by measurement of the area of their image either from the perpendiculars
or by tracing. In both cases measurements of the surface area from the
perpendiculars gave more accurate results than by tracing. The
applicability of the method was tested in one healthy person during
maximal inhalation and exhalation and no significant difference was found
between the left and the right side during maximal inhalation or at full
exhalation nor between full inhalation and exhalation for either side.
To investigate if quantitative whole body movement analysis is a suitable
method for motor control research a model study was developed to evaluate
the kinematics of different spinal segments and of shoulder-link and
pelvis displacement. Fourteen girls participated in the study; eight with
right convex adolescent idiopathic scoliosis and six age-matched normal
controls. The subjects were asked to stand on two force plates, and
seventeen passive reflective markers were attached to certain anatomical
landmarks on the dorsal aspect of their body. Six surface EMG electrodes
were attached to the paraspinal and hip abductor muscles. The subjects
were instructed to perform standardised voluntary trunk rotation and side
bending to the left and right side. Simultaneous recording of the
displacement of the markers with signals from plate forms recording the
ground reaction force and the muscle activity was done. The results
showed that the scoliotic group had a different way and strategy for
orientation of different spinal segments displacement during voluntary
trunk movements with a significant difference in the amplitude of the
displacement of the centre of mass during side bending and during
rotation of the trunk, compared with the control group. The resulting
horizontal shear forces showed a significant difference between the two
groups during side bending of the trunk, which was not the same during
trunk rotation. The EMG study of the recorded activities from the
paraspinal muscles and hip abductor muscles showed a different patterns
and large variability between subjects and between the trials of each
subject. In conclusion, this type of investigation helps to understand
better the co-ordination of different body segments during voluntary
movements and provides an adequate tool for investigation of spine
movements and other trunk movements in normal as well as in scoliotic
subjects.
Issue date: 1998-08-21
Publication year: 1998
ISBN: 91-628-3103-8
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