OMM #25
Thu, 02/27/03, 11am
Dr. Dirnberger, D.O.
Robert Abbate
Page 1 of 4
Functional Anatomy of the Pelvis & Sacrum


Schedule was incorrect, this was a lecture, not PTR session
Schedule changes:
o March 5th Lumbar Roll PTR
o March 6th 1-5pm Practical
Dr. Dirnberger’s lecture went verbatim from the powerpoints. Refer to the images for
better detail
I.
The Pelvis
•The pelvis functionally consists of three bones:
–the left innominate
–the right innominate
–the sacrum
•The Male Pelvis is narrower, Female wider
•The left and right innominate connect at the pubic symphysis.
•The sacrum is suspended between the innominates posteriorly at the
sacroiliac (SI) joints
The Inominates Palpatory Landmarks
• Iliac Crest
• PSIS (posterior superior iliac spine)
• Pubic symphysis
• Pubic tubercles
• ASIS (anterior superior iliac spine)
• Ischial Tuberosity
II. Sacrum
SACRAL ANATOMICAL AXIS
• Superior: the cranial primary respiratory mechanism creates motion
around this axis
• Middle: sacral base anterior and posterior (FB/BB) occur around this
axis
• Inferior: the innominates rotate around this axis
• Reference Foundations p.1136-1137
SACRAL PHYSIOLOGIC AXIS
• Oblique: both left and right oblique axes are named for the superior pole
OMM #25
Thu, 02/27/03, 11am
Dr. Dirnberger, D.O.
Robert Abbate
Page 2 of 4
• Sagittal: includes both mid-sagittal and an infinite number of parasagittal
axes
• Horizontal: functional axis of sacral flexion/extension occur around this
axis (analogous to the middle transverse axis above)
•
Multiple axes of motion:
– Transverse (3)
• Superior S1
• Middle S2
• Inferior S3
– Vertical
– A/P
– Oblique (2)
• Left
• Right
Sacral Margins
• Sacral margins run the length of the Sacro-Iliac Articulation.
• They will rotate about a vertical midline or parasagittal axis
SACRAL MECHANICS
• Physiologic diagnoses of the sacrum occur in neutral and non-neutral
mechanics:
Neutral Mechanics a.k.a.
• Left rotation on a Left Oblique Axis
• Forward Torsion
• In neutral mechanics, the sacrum rotates in the same direction as the
oblique axis (left rotation on a left oblique axis)
Non-neutral Mechanics a.k.a.
• Right rotation on a Left Oblique Axis
• Backward Torsion
• In non-neutral mechanics, the sacrum rotates in the opposite direction
of the oblique axis (right rotation on a left oblique axis)
OMM #25
Thu, 02/27/03, 11am
Dr. Dirnberger, D.O.
Robert Abbate
Page 3 of 4
Anatomic Landmarks of the Pelvis
Patient Standing
- Iliac crest level
- PSIS
- Greater trochanters
Patient Supine
-ASIS
-Pubic symphysis
-Pubic tubercles
-Medial malleoli
Patient Prone
-PSIS
-Sacral sulcus
-Sacral base
-Inferior lateral angle
-Sacortuberous ligament
-Ischial tuberosity
-Iliac crest
-Piriformis muscle
-Iliolumbar ligament
III. Gait
• Efficient locomotion entails translation of the body’s center of gravity through space
along a path requiring the lowest expenditure of energy.
• The center of gravity is constantly displaced beyond the body’s base of support..
• Loss of balance is corrected by moving one lower extremity forward to change the
base of support.
• Repetition of this pattern creates the walking cycle.
•
•
Stance Phase
– Limb contacting ground
– 60% of walking cycle
– Of 60%, 20% is spent in double stance.
Swing Phase
– Limb advancing
– 40% of walking cycle
OMM #25
Thu, 02/27/03, 11am
Dr. Dirnberger, D.O.
Robert Abbate
Page 4 of 4
• Double stance phase shortens with increased walking speed, disappears at the onset of
running
Normal Walking Cycle
• to move the right foot the body must shift to the left
• A SL RR motion occurs in the lumbar spine.
• A left oblique axis occurs in the sacrum
• The sacrum rotates left on it’s oblique axis (this rotation is opposite that of the
lumbars)
• Right quadriceps tighten and the right ileum rotates anteriorly.
• Heel strikes the ground
• Left leg thrusts body forward
• Center of gravity shifts forward and to the right
• Right hamstrings contract
• Hamstrings pull right ileum posteriorly.
• Pubic symphsis provides a transverse axis
• As the body moves forward the center of gravity moves from above the right femur to
the right margin of the sacrum
• The lumbar spine now shifts to a SR RL
• The right superior pole of the sacrum is locked and a right oblique axis is formed
• The walking cycle now repeats itself
• Walking induces (reversible) neutral oblique axis mechanics in the sacrum with every
step e.g., right rotation on right oblique axis, then left on left oblique axis…
• It induces side bending of the lumbar spine towards the side of the weight bearing leg.
• It also causes anterior rotation of the weight bearing ilium and posterior rotation of the
opposite ilium.
•
Walking Cycle somatic dysfunction
In somatic dysfunction one or more motions become restricted leading to reduced
efficiency, vitality and function