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Pelvic girdle
Last reviewed: 20.11.2021
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Bones of the pelvic girdle are joined together in front of the pubic half-joint, and behind them with the sacrum they form the sacroiliac joints.
The sacroiliac joint is formed by the ear-shaped surfaces of the sacrum and the ilium and is a flat joint. The joint capsule in front and behind is supported by strong short ligaments. In the strengthening of the joint plays a large role sacroiliac joint between the bone, stretched between the ileum tuberosity and tuberosity of the sacrum. The movements in the joint are insignificant and occur around this ligament, which acts as the axis of the joint. Mobility in the sacroiliac joint provides elastic buffer function of the pelvis. In the innervation of the articulation, the branches of the lumbosacral plexus participate. The peculiarity of this joint is the absence of muscles, which specifically would drive this joint.
The pubic joint (pubic articulation) is formed by the pubic bones, which are firmly connected with the fibrous-cartilaginous interlobic disc located between them. Among the ligaments of the pelvis, it is necessary to note iliac-lumbar, sacro-tubercular and sacral-ligament ligament.
In the vertical position of the body, the pelvis always has an anterior inclination, which is measured by the angle of the pelvic incline. It is formed by a line passing through the spine and the upper edge of the frontal fusion, and a line located in the horizontal plane.
This angle is usually 50-60 ° and can change with a change in the character of standing.
During the examination, the doctor should remember that the pelvis together with the presacral disc, the lumbar and paired or sacral joints, hip joints and the musculoskeletal apparatus is a buffer for the movement of the kinematic chain "spine-legs".
There are three main types of pelvis (Lewit K., 1993):
- middle type (normal) pelvis. The angle of the sacrum to the vertical from the body's BMP is 130-145 °, the vertical passes through the apex of the muscles behind the axis of the hip joints. Lumbar lordosis is 18 mm;
- assimilated, or liberated, pelvis with elongated sacrum and high-lying cape, lumbosacral disk higher than L1-L2. The sacrum approaches the vertical line, the angle of inclination is 150-165 °, the lumbar lordosis is flattened to 6 mm. There is a great mobility of vertebrae L1 and sacroiliac joints;
- The "overloaded" pelvis has a deep-set and forward-facing cape. The angle of the sacrum tilt approaches the horizontal line, reaching 110-130 °. The steep line C 7 runs in front of the cape and the axis of the hip joints. The patient's head is most often pushed forward, the pelvis is back. The structures of the lumbosacral PDS, the sacroiliac joint and the hip joints are overloaded, the abdominal muscles are overgrown. Hyperlordosis (30 mm) is combined with the tonic tension of the multi-sectional and gluteal muscles. When the
pelvis is overloaded , lumbar and orosocular articular blockages, interstitial ligamentoses and apiarthroses (Baastrup syndrome) often occur.
[Plane and axis of movement of the pelvis
To study and record the state of the human body and its parts, it is customary to distinguish between the plane of the body and the axis of motion. There are three main planes.
The sagittal or anteroposterior (imaginary) plane divides the human body or any part of it into the left and right halves (divisions), the sagittal plane passing through the middle of the body being called the median plane.
The horizontal plane crosses the body transversely, dividing it into the cephalic (cranial) and caudal (caudal) divisions. The horizontal plane, drawn on any limb, divides it into the proximal (closer to the trunk) and distal (further from the trunk) sections.
The frontal (parallel to the surface of the forehead) plane divides the body or its parts into the anterior (ventral) and posterior (dorsal) divisions. All three planes are perpendicular to each other. Any other plane can be only intermediate with respect to the planes mentioned.
All three planes, when intersected with each other, form lines called rotation axes. When the sagittal and horizontal planes intersect, a sagittal axis is formed and movement around this axis occurs in the frontal plane. When crossing the front and horizontal planes a transverse axis is formed. Movement around this axis is carried out in the sagittal plane. When crossing the sagittal and frontal planes a vertical axis is formed. Movement around the vertical axis occurs in the horizontal plane.
Biomechanics considers the device of human movement as controlled biokinetic chains, consisting of links connected by joints and attached to them muscles. Together they constitute a biomechanism capable of performing the given motions. In the biokinetic chain, movements can be maintained in all joints, only in part of them or this can be the movements of all links as a whole. Biokinetic chains can be open or closed (with associated end links) and therefore have different properties. Thus, a closed biokinetic chain does not have a free terminal link, it is impossible to have isolated motions in only one joint.