Sacrum 2/4 Flashcards
when does sacrum fuse?
around the age of 25
- in its center is the sacral canal with the caudaequina and 4 sacral spinal nn. which exit from the sacral foramina
- top of sacrum is the base: the bottom of the sacrum is the apex
sacral promontory
anterior portion of S1
anatomy of weight bearing of sacrum? Which ligament is most likely the first to get tight?
The weight of the upper body is transmitted through the sacrum and its ligamentous attachments to the pelvis via the iliolumbar, sacrospinous (to sacral spine), & sacrotuberous ligaments (to ischial tuberosity).
The anterior and posterior sacroiliac ligaments are extremely strong and connect the sacrum to the pelvis
The first ligament to get really tight is the iliolumbar ligament. Always seen with sacral dysfunction
What muscles move the sacrum?
- none directly move the sacrum*
- possibly piriformis (attaches to 2-4th sacral segments) - externally rotates leg when hip is in flexion
- illiacus
- pelvic diaphragm (supports everything - if this is off, can have prolapse and hernias and pain)
- aponeurosis of erector spine
Piriformis
Attachments:S2-4 and inserts into the greater trochanter of the femur
Action:External rot of thigh; abductor of the hip when the hip is flexed
Innervation: S1-2
*** Sciatic n. often passes through the piriformis, or over piriformis, or splits through piriformis: can result in sciatica
Lumbosacral angle
25-35 degrees, increase in angle cause lumbosacral sprain
- can be the result of pregnant women, and obese people
landmarks of sacrum? how do you find sacral sulci?
sacral sulci: found medial and slightly superior to PSIS
Physician places the palm of his/her hand on the sacrum. The most posterior aspect of the sacrum is the level of the Inferior Lateral Angles. The thumbs are then placed on each ILA.
7 axes of sacral motion?
1 vertical axis: allows for left/right rotation (“queens wave”)
1 Anterior-posterior: allows for sidebending (small motion)
3 Transverse: Allows for flexion and extension.
2 oblique axes: Combines rotation and sidebending.
Vertical axis
Right oblique axis
Left oblique axis
1. Respiratory axis (superior transverse axis)
2. Sacroiliac axis (middle transverse axis)
3. Iliosacral axis (inferior transverse axis)
Anteroposterior axis
superior transverse/respiratory axis
Superior transverse / Respiratory axis. (S2)
- Flexion and Extension occurs with respiration.
- The sacrum flexes when lumbar lordosis increases (exhalation)
- The sacrum extends when lumbar lordosis decreases (inhalation)
Sacroiliac (sacrum on ilium)/middle transverse
S3
Flexion and extension occurs with motion of the sacrum on the illium.
Oblique sacral axes
Named for the SUPERIOR aspect they exit.
The axis that runs from the right inferior aspect of the sacrum(right ILA) to the left superior aspect of the sacrum(left sacral sulcus) is the left oblique axis.
The axis that runs from the left inferior aspect of the sacrum(left ILA) to the right superior aspect of the sacrum(right sacral sulcus) is the right oblique axis.
Iliosacral (ilium on sacrum)/inferior transverse
S4
Flexion and extension occurs with motion of the ilium on the sacrum.
Vertical axis
Sacral side bending via an AP axis
L5 Rules/Sacral Torsion rules (always true for high yield exam)
- The sacral oblique axis will be to the same side as L5 side bending
- So if L5 is FRSL then the sacral axis will be left - The sacrum rotates opposite of L5
- So if L5 is FRSL then the sacrum will rotate right (R on L) - The seated flexion test is positive on the opposite side of the oblique axis
- So +SeFT on the right, we will have a left oblique axis
What is dynamic sacral motion with walking?
Torsional motion occurs during the walking cycle, depending on which phase of gait we are in. When we place weight on our left foot the sacrum rotates to the Right, on the Right oblique axis at midstance.
The lumbar spine sidebends Right because of QL contraction.
This motion is normal, however, when this motion is limited or fixed in a non-neutral position dysfunction occurs.
