Abdominal vascular compression syndromes prevail in females. In daily practice over 90% of the afflicted ones are pre- and postpubertal girls or women. This is due to the prepubertal growth spurt and the specific changes of the female pelvis during puberty.
Female puberty, in comparison to males, leads to a wider and deeper pelvis. Women develop a significantly stronger lumbar lordosis as a consequence of a variety of specific changes.
Firstly, the greater depth of the pelvis causes its anterior tilt.
Secondly, the wider hips stretch the basis of the psoas triangle, consisting of both psoas muscles and a virtual connecting line of their femoral insertion. Elongation of this basis with a constant length of both muscles forces a reduction of the height of this triangle. The height can be reduced only by a stronger anterior curvature of the lumbar spine.
Both mechanisms add to the general human lordogenesis which is unique in the evolution and is basically a consequence of the “physiological” overstretching of the hip joints. Human hip joints, as all other mammalian hip joints, has a range of motion which is restricted by the tight ligaments of its capsule. A femoral position of 90° towards the lumbar spine is regarded the pendulum line of a resting hip joint. Unrestricted hip flexion and extension is then possible up to about 45°cranially and caudally to the pendulum line., So, a human newborn can never touch the matrass with its knees in a supine position, since it cannot yet overstretch its hips. Only with the beginning of human bipedal gait after about 12 months the adult position of the hip joints is gradually achieved – and defined as “normal”. But this can be achieved only by overstretching the hip joints more caudally than 45°. Since a pure articular motion cannot yield such a position due to bondage of the femur by the ischiofemoral ligament, the only way to achive a perpendicular position of the femur is an anterior tilt of the human pelvis. This tilt encompasses the sacral bone too. The lumbar spine, inserting at the sacral bone has to compensate this anterior tilt by an equivalent dorsal curvature – the human lumbar lordosis, which is not inborn.
In summary, the unique human answer to gravitation is a lumbar lordosis. It is much more prominent in females than in males, causing a number of vascular compression syndromes (MALS, Nutcracker syndrome, Superior mesenteric artery syndrome, May-Thurner-syndrome, Lumbar artery syndrome and others), predominantly in females.
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