Spinal Biomechanics: Pelvis Flashcards
Anatomy of the Pelvis
What are the bones and joints of the pelvis?
Bones: Two innominate bones, sacrum
Joints: Pubic symphysis, sacroiliac, lumbosacral, acetabular-femoral (hip)
Anatomy of the Pelvis
Innominate bone is a fusion of what 3 bones?
Ilium, ischium, pubis
Anatomy of the Pelvis
Pubic symphysis is what type of joint? How moveable? What type of disc material?
Amphiarthrosis
Slightly moveable
Fibrocartilagenous disc
Anatomy of Pelvis
Sacroiliac joints are what type of joint? Typical or atypical?
Diarthrosis (synovial) joints
Atypical joint surfaces
SI Joint: Sacrum or Innominate? A. Articular surface is concave B. Articular surface is convex C. Fibrocartilage D. Hyaline cartilage
A. Sacrum
B. Innominate
C. Innominate
D. Sacrum
Anatomy of Pelvis
Joint between L5 and S1 is called _____
Z joint = zygapophysial joint
Statics
Describe self-locking mechanism of SI joints related to shape.
Wedge shape of sacrum Interlocking groove (sacrum) and ridge (ilium) "S" shaped joint surfaces
Statics
Describe self-locking mechanism of SI joints related to forces.
Tension in muscles, ligaments, and fascia aids in stabilizing.
Creates lateral to medial pressure from ilium to sacrum
Creates anterior closure of pubic symphysis.
Dynamics
Pelvis transmits forces between _____ and ______
Decreases stress to _____ spine and opposite _____ joint
Lower extremity and axial skeleton
lumbar spine and opposite SI joint
Dynamics: Nutation or Counternutation?
A. Sacral base rotates anteriorly on ilium
B. Sacral base rotates posteriorly on ilium
C. Ilium rotates posteriorly on sacral base
D. Ilium rotates anteriorly on sacral base
A. Nutation
B. Counternutation
C. Nutation
D. Counternutation
Dynamics: Nutation or Counternutation
A. Moving into _____ decreases lumbar lordotic curve
B. Moving into _____ increases lumbar lordotic curve
A. Counternutation
B. Nutation
Dynamics
What are the movements of the pubic symphysis?
Compression
Distraction
Rotation in sagittal plane with SI joint motion
Gliding (translation) – ant-post, sup-inf
Dynamics
Flexion of the hip and ilium (posterior inferior movement of the PSIS) is accompanied by what kind of movement in the sacral base?
Ispilateral anterior inferior movement
Pelvic Tilt
Anterior pelvic tilt uses hip flexors ___ and ___.
It also uses back extensors _____
Iliopsoas and rectus femoris
Erector spinae
Pelvic Tilt
Posterior pelvic tilt uses hip extensors ___ and ____.
It also uses abdominal muscles ____ and _____.
Gluteus maximus and hamstrings
Rectus abdominus and external obliques
