Sacrum 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
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
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
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?
vertical axis: allows for left/right rotation (“queens wave”)
Anterior-posterior axis: allows for sidebending (small motion)\
Transverse axes (3): Allows for flexion and extension.
oblique axes (2): Combines rotation and sidebending.
- Right oblique axis
- Left oblique axis
Transverse Axes:
- Respiratory axis (superior transverse axis) - S2
- Sacroiliac axis (middle transverse axis) - S2 = postural
- Iliosacral axis (inferior transverse axis)Anteroposterior axis- S3 = rotational
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
S2/ S3 = rotational
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
S3/S4 = rotational
Flexion and extension occurs with motion of the ilium on the sacrum.
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.
What does sacrum do in gait?
For right leg stride
Right heel strike & propellant stance (foot flat)- Sacrum is symmetrical
At ballistic stance (midstance)- Left on left sacral torsion
At bipedal support (toe-off) & right initial swing (acel) = Sacrum is symmetrical
At midswing = Right on right sacral torsion
At right terminal swing = Sacrum symmetrical
Seated flexion test
- Seated flexion test determines the motion of the sacrum upon the ilium. (sacroilial, S3 axis)
- The side which is positive is usually the side of dysfunction (and opposite the axis)
- in sacral torsions. False positives exist due to muscle influences.
positive sacral flexion test?
The side which is positive is usually the side of dysfunction (and opposite the axis)in sacral torsions.
sacral sheers = same side of dysfunction
sacral torsions = opposite the axis
Lumbar spring test
The Spring test determines if the base of the sacrum is able to move FORWARD or if it is stuck BACKWARDS.A board like resistance or “lack of spring” to the LS junction determines that the sacrum is stuck BACKWARDS. This is a positive Spring Test.