PART 1: Illustrations |
Figure 1
SIJ Ligaments Ligaments limiting nutation: sacrospinous, sacrotuberous, anterior SIJ ligament, lower two bands of the iliolumbar ligament, interosseous ligament, & short posterior ligaments.
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Figure 7
Nutation and counternutation as it appears in two dimensions In nutation, the sacral base appears to slide downward and backward. In counternutation, the sacrum appears to slide upward and forward.
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Figures 2
Sacroiliac joint surfaces: two and three dimensional views The articular part appears to be "L" shaped. Weight bearing occurs at the posterior syndesmosis, which is 1.57 times as large as the synovial part.
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Figure 8
The facets wrap around the edge of the sacrum When horizontal lines are drawn from both sides of the upper articular surfaces of the SIJ, they would converge posterior to the sacrum, and when horizontal lines are drawn from both sides of the lower...
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Figure 3
The sacroiliac joint in weight transfer & as a sensor The sacroiliac joints hold and transfer the weight of the entire upper body from the sacrum to the hips and legs. They are also important sensors of large force streams between the trunk and legs in which the largest muscles of the body are involved.
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Figure 9 - Video
The sacrum is compared to a cone The sacrum is compared to a cone, with the articular surfaces wrapping around it. This configuration allows the large anterior-posterior ...
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Figure 4 - Animation
Shock Absorption a) As the pelvis rotates posteriorly, the sacrum rotates anteriorly. b) The feet pronate, the fibulae drop, and the knees twist as the lower leg rotates internally more than the upper leg. c) The curves increase as the spine compresses.
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Figure 10 - 3D Animation
Sacral motion in three dimensions During counternutation, the sacral base pivots posteriorly and superiorly, as the sacral apex moves toward that side. At the same time, nutation occurs contralaterally, as the sacral base pivots anteriorly and inferiorly.
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Figure 5
The sacrum as a hub "The sacrum is viewed as the hub of a tension network: the model provides for stability of the sacrum when it is loaded from any direction and can be used during bipedal or quadrupedal standing and walking or even standing on one's head." (With permission from Stephen M. Levin, M.D.)
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Figure 11 - Animation
The gravitational line The gravitational line passes anterior to the sacral pivot and posterior to the innominate pivot, resulting in anterior rotation of the sacrum and posterior rotation of the ilium. When the force is greater than the restraining ligaments can withstand, they tear, resulting in the nutation lesion.
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Figure 6
Sacral movement induced by pelvis Levin accounts for movement of the hub (sacrum) within the wheel (pelvis) by a twisting action of the rim (effect of walking). "Twisting the rim of a bicycle wheel forces the hub to tilt". (With permission from Stephen M. Levin, M.D.) |
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