Biomechanical aspects of modern models of pelvis stability. Part II: symphysis pubis and anterior oblique muscle sling

Rafał Gnat, Edward Saulicz, Mirosław Kokosz, Michał Kuszewski

Rafał Gnat, Edward Saulicz, Mirosław Kokosz, Michał Kuszewski – Biomechanical aspects of modern models of pelvis stability. Part II: symphysis pubis and anterior oblique muscle sling. Fizjoterapia Polska 2006; 6(4); 328-333

Abstract
Biomechanical model of pelvis stability based on self-bracing mechanism contributed to certain discrimination of previous proposals mentioning the pelvic ring and ascribing important stabilizing role to pubic symphysis. However, the paper presents some arguments challenging thesis about complete lack of significance of the symphysis and anterior part of the pelvic stabilising system in process of maintaining stability. Both the symphysis itself as well as anterior oblique muscle sling seem to find their own, meaningful place there. Maybe this role could not be considered primary, but surely it is supplementary one. Observations of biomechanical, clinical and evolutional nature seem to support such a point of view. Spreading of the effective range of self-bracing due to compressive forces acting on the sacroiliac joint and increased friction between its surfaces divides the burden of maintaining stability on bigger number of muscles. The adductor longus that belongs to anterior oblique muscle sling seems to locate its attach-ment in the proper area. Moreover, a view of the pelvis, where the force closure mechanism is executed by posterior muscle slings exclusively brings about compelling impression of shearing forces arising within the sacroiliac joints. Activation of the anterior portion of the stabilizing system heads off the incoming threat immediately. Also assuming the upright body posture resulted in humans in more frequent, in comparison with other species, backward excursions of the centre of gravity. In such conditions the anterior part of the pelvic stabilizing system will always be activated in order to maintain stability.

Key words:
pelvis, symphysis pubis, anterior oblique muscle sling

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