The rotational angle of the trunk during different positions is affected by pelvis position. Two studies used different techniques and devices to control the trunk rotation of subjects as reproducibly as possible depending on controlling the pelvis rotational angle. (Rogers et al. 2002)used a rotating table in which the patient was positioned with the head and thorax on the longer part of the table, while the hip was placed on the shorter part of the table. (Fujii et al. 2007)used a different technique depending on a rotating device consisting of many angled pelvic holders (15°, 30°, 45° and maximum). However, these techniques were valid to produce only 8° of passively trunk rotation in
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the case of techniques introduced by (Rogers et al. 2002), while the (Fujii et al. 2007) technique was designed to rotate the subjects’ trunks passively.
On the other hand, (Sprigle et al. 2003; Prushansky et al. 2008; Preece et al. 2008) used goniometers, digital inclinometer and palmeters to measure pelvic tilt by determining both anterior superior iliac spine and posterior superior iliac spine positions. (Alsancak et al. 1998)used a plurimeter and callipers to determine the pelvic tilt on the horizontal and sagittal plane by placing the callipers on a line drawn which joined the right and left posterior superior iliac spines. However, these devices could not be used in supine and rotation positions.
As the current study will be based on the three actively lower trunk rotational positions with accurately controlled angle of rotation of each lower trunk rotational position, the current study will use a novel lower trunk holder (MRI holder) and a modified goniometer. A modified goniometer and a novel lower trunk holder (MRI holder) will be used to obtain and maintain the accurate measurements of the lower trunk rotational angle depending on controlling and measuring the pelvis angle of rotation. In such way that the modified goniometer will be used to measure the rotational angle of the right and left posterior superior iliac spines while the novel lower trunk holder will be used to fix the pelvic to maintain the performed active angle of rotation. In addition the novel lower trunk holder (MRI holder) will be used to prevent the motion artifacts during long MRI scan as a result of fixing the subjects pelvic during MRI.
To evaluate the hypothesis that the pelvis angle of rotation depending on measuring the rotational angle of the right and left posterior superior iliac spine relative to the horizon will be accurately controlled by using a reliable an adaptive goniometer and MRI holder, the measurements of the angle of rotation of the right and left posterior superior iliac spines relative to the horizon by using the adaptive goniometer will be compared to those will obtain by using MRI at three sections of the ilium (3.4.2).
3.3.3 The relation between the right and left posterior superior iliac spines and the last lumbar vertebrae during trunk rotation
The position of the spine, pelvis, and hip balances the mass of the trunk above it, and the mobility of these articulations allows for coordinated motion during activities such as moving from standing to sitting or bending forward at the waist.
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The functional linkage between pelvis and spine has been translated by many researchers. Some of those researchers defined this linkage as pelvic incidence which represents the sum of two positional parameters, sacral slope and pelvic tilt. In this definition, the pelvic incidence is tightly correlated with the degree of lumbar lordosis (Tardieu et al. 2017; Ike et al. 2018).
The pelvic incidence was defined as an angle formed by a line from femoral head to the centre of the S1 end plate and a line tangent to the S1 end plate. In turn, sacral slope defined as the angle between the horizontal and the sacral plate. While, pelvic tilt angle was drawn by the angle between the vertical and the line through the midpoint of the sacral plate to femoral heads axis (Lavignolle et al. 1983).
Other researchers showed that lumbo-sacro-pelvic structure plays an important role in determining the shear and compressive forces applied on the anterior (vertebral body and intervertebral discs) and posterior (facet joints) elements of the lumbar vertebral column. Those researchers analysed the relation between the lumbar, sacral and pelvic structures as the sacral angle and sacral curvature. The sacral angle was defined as a straight line along the superior margin of the sacrum, drawn to meet the horizontal line. While sacral curvature represented by the angle between the first and the last sacral vertebrae (Ghasemi et al. 2016).
On the other hand, as mentioned in 3.4, (Gracovetsky and Farfan 1986; LaFiandra et al. 2002; Montgomery 2008; Park et al. 2012) stated that the fifth lumbar vertebrae with the pelvis and lower trunk will rotate in a clockwise direction, while the upper trunk and shoulders rotate in an anti-clockwise direction when the spine bends laterally and forward when clockwise torque is applied. However, it seems that these studies did not take into account the difference in the rotational degree between the pelvis and the fifth lumbar vertebrae. Based on the previously mentioned studies, the current study will introduce a new definition of the relation between the spine and the pelvic as the relation between the rotational angle of the last lumbar vertebra (L5) and the rotational angle of the posterior superior iliac spines in three anatomical sections related to the horizon during lower trunk rotational positions.
To investigate the hypothesis that there will be a significant difference between the rotational angle of the left and right posterior superior iliac spines and the rotational angle of the last lumbar spine during all performed lower trunk rotational positions, the
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rotational angle of the left and right posterior superior iliac spines in three sections relative to the horizontal plane will be measured using a new technique by determining the lowest attached points of the erector spinae muscle tendons to the posterior superior iliac spines depending on using the pixel intensity values between 091-094 per cent. While the rotational angle of the last lumbar vertebrae (L5) will be measured at the convex posterior disc margins relative to the horizontal plane.
The coordination between the trunk, the shoulder and pelvis movements are very important in understanding rehabilitation strategies for lower back pain. Nonetheless, no study has yet examined the position of the scapula (as the position of bilateral posterior borders of the acromion processes) and the motions of the posterior superior iliac spines related to the L5 angular motion during different rotational positions of the