1. INTERNAL MEDICINE SERIES
OMM LECTURE
Sacrum and Innominates
Julia Faller, D.O., PGY1

2. ANATOMY Innominate: 3 bones; ilium, ischium and pubis
Sacrum: 5 fused vertebrae
Sacral base: top part of the sacrum
Sacral promontory: anterior portion of 1st segment
Sacral apex: bottom part of the sacrum
Sacral sulci: superior lateral part of sacrum
Inferior lateral angles (ILA’s): inferior lateral part of sacrum

3. ANATOMY

4. ANATOMY

5. LIGAMENTS
True pelvic ligaments: sacroiliac ligaments that surround and help stabilize the SI joint
Anterior
Posterior
Interosseous

6. LIGAMENTS Accessory pelvic ligaments
Sacrotuberous—originates at ILA and attaches to ischial tuberosity
Sacrospinous—originates at sacrum and attaches to ischial spines
Iliolumbar—originates from transverse processes of L4 and L5 and attaches to medial side of iliac crest

7. LIGAMENTS

8. LIGAMENTS

9. Board Points
The sacrospinous ligament divides the greater and lesser sciatic foramen
The iliolumbar ligament is often the first ligament to become painful in lumbosacral decompensation

10. MUSCLES
Primary pelvic muscles: levator ani and coccygeus (pelvic diaphragm)
Secondary: muscles that have partial attachment to the true pelvis
Iliopsoas
Obturator internus
Piriformis

11. Clinical Point
Approximately 11% of the population will have the entire peroneal portion of the sciatic nerve running through the belly of the piriformis.
Piriformis hypertonicity can cause buttock pain that radiates down the thigh, but not usually below the knee.

12. MECHANICS
Innominates: rotate about an inferior transverse axis of the sacrum during the walking cycle.
Sacrum: four types of motion
Respiratory
Craniosacral
Postural
Dynamic

13. AXIS

14. RESPIRATORY AXIS
Respiratory motion occurs about the superior transverse axis of the sacrum.
Located at S2
During inhalation the sacral base moves posterior.
During exhalation the sacral base moves anterior

15. RESPIRATORY AXIS

16. CRANIOSACRAL AXIS
Motion occurs about the superior transverse axis of the sacrum
AKA inherent motion
During craniosacral flexion the sacral base rotates posteriorly, counernutation
During craniosacral extension the sacral base rotates anteriorly, nutation

17. CRANIOSACRAL AXIS

18. POSTURAL AXIS
Motion occurs about the middle transverse axis of the sacrum.
As a person begins to bend forward, the sacral base moves anteriorly.
At terminal flexion the sacrotuberous ligaments become taut and the sacral base will move posteriorly.

19. POSTURAL AXIS

20. OBLIQUE AXIS Motion that occurs during ambulation. Dynamic motion
As weight bearing shifts from one side to the other while walking, the sacrum engages two sacral oblique axes.
Stepping forward with the right leg will cause a left sacral axis to be engaged.

21. OBLIQUE AXIS

22. INNOMINATE DYSFUNCTION
The side of the positive standing flexion test is the side of the dysfunction.
Types:
Anterior/posterior rotation
Superior/inferior innominate shear
Superior/inferior pubic shear
Inflare/outflare

23. INNOMINATE DYSFUNCTION
Anterior innominate rotation: one innominate will rotate anteriorly
Inferior transverse axis
Tight quadriceps
ASIS inferior/PSIS superior
Longer leg ipsilaterally
ASIS restricted to compression

24. ANTERIOR INNOMINATE

25. INNOMINATE DYSFUNCTION
Posterior innominate rotation: one innominate will rotate posteriorly
Inferior transverse axis
Tight hamstrings
ASIS superior/PSIS inferior
Shorter leg ipsilaterally
ASIS restricted to compression

26. POSTERIOR INNOMINATE

27. INNOMINATE DYSFUNCTION
Superior innominate shear: one innominate will slip superiorly
ASIS and PSIS superior
Pubic rami superior
Short leg ipsilaterally
ASIS restricted to compression

28. SUPERIOR INNOMINATE SHEAR

29. INNOMINATE DYSFUNCTION
Inferior innominate shear: one innominate will slip inferiorly
ASIS and PSIS inferior
Pubic rami inferior
Long leg ipsilaterally
ASIS restricted to compression

30. INFERIOR INNOMINATE SHEAR

31. INNOMINATE DYSFUNCTION
Superior pubic shear: one pubic bone is displaced superiorly compared to the other
Trauma or tight rectus abdominus
ASIS/PSIS level
Pubic bones superior ipsilaterally
ASIS restricted to compression

32. SUPERIOR PUBIC SHEAR

33. INNOMINATE DYSFUNCTION
Inferior pubic shear: one pubic bone is displaced inferiorly compared to the other
Trauma or tight abductors
ASIS/PSIS level
Pubic bones inferior ipsilaterally
ASIS restricted to compression

34. INFERIOR PUBIC SHEAR

35. INNOMINATE DYSFUNCTION
Innominate inflare: innominate rotates laterally
ASIS more lateral ipsilaterally therefore the distance between the ASIS and umbilicus is greater on the affected side
Ischial tuberosity more medial ipsilaterally
ASIS restricted to compression ipsilaterally

36. INNOMINATE DYSFUNCTION
Innominate outflare: innominate rotates medially
ASIS more medial ipsilaterally therefore the distance between the ASIS and umbilicus is less on the affected side
Ischial tuberosity more lateral ipsilaterally
ASIS restricted to compression ipsilaterally

37. SACRAL DYSFUNCTION Three types of dysfunction
Sacral torsion on an oblique axis
Sacral shear (unilateral sacral flexion/extension)
Bilateral sacral flexion/extension

38. SACRAL TORSION
Sacral rotation about an oblique axis along with somatic dysfunction at L5
The axis is named for the side of the superior pole it runs through

39. SACRAL TORSION RULES
When L5 is sidebent, a sacral oblique axis is engaged on the same side as the sidebending
When L5 is rotated, the sacrum rotates the opposite way on an oblique axis
The seated flexion test is positive on the opposite side of the oblique axis

40. Board Points
Know the rules of L5 on the sacrum

41. MOTION OF TORSIONS
Motion present over the part of the sacrum that moved anteriorly
Motion restricted over the part of the sacrum that moved posteriorly
Motion restricted over the poles that make up the oblique axis

42. SACRAL TORSION Forward sacral torsion AKA anterior sacral torsion.
Rotation is on the same side of the axis.
Left on left/right on right
Negative lumbosacral spring test

43. SACRAL TORSION: L on L Left on left Right sulcus deeper
Left ILA posterior and inferior
Lumbar curve convex to the right
Motion at right base only

44. SACRAL TORSION: R on R Right on right Left sulcus deeper
Right ILA posterior and inferior
Lumbar curve convex to the left
Motion at left base only

45. SACRAL TORSION Backward sacral torsion AKA posterior sacral torsion
Rotation is on the opposite side of the axis
Right on left/left on right
Positive lumbosacral spring test
Positive backward bending test
L5 will be non-neutral

46. SACRAL TORSION: R on L
Right superior sulcus moves posterior and the left ILA moves anterior
Right sulcus shallow
Left ILA anterior and superior
Lumbar curve convex to the right
Motion at left ILA only

47. SACRAL TORSION: L on R
Left superior sulcus moves posterior and the right ILA moves anterior
Left sulcus shallow
Right ILA anterior and superior
Lumbar curve convex to the left
Motion at right ILA only

48. BILATERAL SACRUM Bilateral flexion and extension
The entire sacral base moves anterior or posterior about a middle transverse axis
Common in the postpartum female

49. BILATERAL SACRAL FLEXION
Right and left sulci deep
ILA’s shallow bilaterally
Increased lumbar curve
False negative seated flexion test
Motion at base
Negative spring test

50. BILATERAL SACRAL EXTENSION
Right and left sulci shallow
ILA’s deep bilaterally
Decreased lumbar curve
False negative seated flexion test
Motion at both ILA’s
Positive spring test

51. SACRAL SHEARS AKA unilateral sacral flexion/extension
The sacrum will shift anteriorly or posteriorly around a transverse axis

52. UNILATERAL SACRAL FLEXION
Ipsilateral deep sulcus
Ipsilateral inferior ILA
Ipsilateral ILA posterior
Ipsilateral positive seated flexion test
Ipsilateral motion at sulcus
Ipsilateral restriction at ILA
Negative lumbosacral spring test

53. UNILATERAL SACRAL EXTENSION
Ipsilateral shallow sulcus
Ipsilateral superior ILA
Ipsilateral ILA anterior
Ipsilateral positive seated flexion test
Ipsilateral motion at ILA
Ipsilateral restriction at sulcus
Positive lumbosacral spring test

54. Question 1
Which structure divides the greater and lesser sciatic foramen?
a. Sacrotuberous ligament
b. Sacrospinous ligament
c. Sacroiliac ligament
d. Tendon of the obturator internus
e. Tendon of the piriformis

55. Question 1
Which structure divides the greater and lesser sciatic foramen?
a. Sacrotuberous ligament
b. Sacrospinous ligament
c. Sacroiliac ligament
d. Tendon of the obturator internus
e. Tendon of the piriformis

56. Question 2
Which of the following movements will cause the sacral base to move anterior?
a. Cranial extension
b. Counternutation
c. Exhalation
d. Weight bearing on right leg
e. Weight bearing on left leg

57. Question 2
Which of the following movements will cause the sacral base to move anterior?
a. Cranial extension
b. Counternutation
c. Exhalation
d. Weight bearing on right leg
e. Weight bearing on left leg

58. Question 3
Which of the following findings is present in a left innominate anterior rotation?
a. PSIS inferior on left
b. PSIS superior on right
c. PSIS superior on left
d. ASIS superior on left
e. PSIS and ASIS posterior on left

59. Question 3
Which of the following findings is present in a left innominate anterior rotation?
a. PSIS inferior on left
b. PSIS superior on right
c. PSIS superior on left
d. ASIS superior on left
e. PSIS and ASIS posterior on left