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EDKP-206 > Lecture 6 - Hip Biomechanics (part 1) > Flashcards

Lecture 6 - Hip Biomechanics (part 1) Flashcards

1
Q

What are the bones of the hip?

A
  1. Innominate bone
  2. Femur
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2
Q

What are the structures of the innominate bone?

A
  1. Acetabulum
  2. Labrum
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3
Q

What are the structures of the femur bone?

A

Head of the femur

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4
Q

What is the acetabulum formed by?

A

3 fused bones:
1. Ilium
2. Pubis
3. Ischium

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5
Q

What are the different surfaces of the acetabulum?

A
  1. Acetabular fossa (non articular depressed region on floor of acetabulum)
  2. Articular/lunate surface (makes contact with head of femur)
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6
Q

What is the orientation of the acetabulum?

A

Faces laterally and inferiorly

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7
Q

What is the labrum?

A

A fibrocartilaginous ring that helps…
1. Stabilize hip joint
2. Increase contact area
3. Decreases joint stress

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8
Q

What is the structure of the femur?

A

Femoral head: 2/3rds of a sphere
Articular cartilage: Makes more spherical

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9
Q

What improves joint congruence?

A

Cartilage
(Increase in congruence = Increase in stability)

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10
Q

What is the orientation of the femoral head and neck?

A
  • Large head narrows abruptly into neck
  • Neck enclosed by hip joint capsule
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11
Q

What does the orientation of the femoral head and neck influence?

A
  • Hip motion and weight bearing
    -> Frontal plane: 125 degree angle between neck and femur
    -> Transverse plane: 15 degree angle between neck and femoral condyles
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12
Q

What is Wolff’s law?

A
  • Form follows function
  • Femoral neck sustains large bending moments and tensile compressive forces
  • Neck reinforced by thickened cortical bone and trabecular bone
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13
Q

What is the important landmark of the femur?

A

Greater trochanter
- Insertion site of muscles
- Lengthens moment arm (improves mechanical advantage)

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14
Q

What do the landmarks of the femur help understand?

A
  • Hip joint anatomy
  • Muscle function
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15
Q

What type of joint is the hip joint?

A

Ball and socket joint
-> Synovial
-> Triaxial
-> 3 dof

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16
Q

What are the structures of the hip joint?

A

Joint capsule:
- Attached to bony rim of acetabulum and intertrochanteric crest
- Composed of multiple bands of fibers
- Encloses femoral neck and head

17
Q

What reinforces the joint capsule?

A

Three ligaments…
Ligament of the head of the femur (one of them)

18
Q

What is hip joint mobility?

A

The range of motion of the hip motion linked to motion of the low back and pelvis

19
Q

What is the typical hip rom in the sagittal plane for flexion?

A
  • 135 degrees
  • Largest amplitude
20
Q

What is the typical hip rom in the sagittal plane for extension?

A
  • 45 degrees
  • Limited by ligaments
21
Q

What is the typical hip rom in the frontal plane for abduction?

A
  • 45 degrees
  • Can be improved by stretching
22
Q

What is the typical hip rom in the frontal plane for adduction?

A
  • 25 degrees
  • Limited by contralateral limb
23
Q

What is the typical hip rom in the transverse plane for internal rotation?

A
  • 35 degrees
  • Limited by ligaments
24
Q

What is the typical hip rom in the transverse plane for external rotation?

A
  • 45 degrees
  • Limited by ligaments
25
Q

What are the possible orientations of the pelvis in the sagittal plane?

A

a) Retroversion (posterior tilt - extends hip)
b) Neutral
c) Anteversion (anterior tilt - flexes hip)

26
Q

What is the possible orientation of the pelvis in the frontal plane?

A
  • Pelvic tilt (hike and drop) can occur
  • Elevated side: hip adduction
  • Dropped side: hip abduction
27
Q

What is the orientation of the pelvis in the transverse plane?

A

a) Pelvic internal rotation (contralateral medial)
b) Pelvic external rotation (contralateral lateral)

28
Q

What are spine-hip interactions?

A
  • Patients/athletes compensate for lack of mobility with other joints
  • Compensations occur in frontal/sagittal plane
29
Q

What are the joint reaction forces of the articulating surfaces?

A
  • JRF on femur are transmitted from the acetabulum to the femoral head
  • JRF creates a torque on the neck of femur
  • Wider femoral necks withstand torques better
  • Men have wide necks than women
30
Q

What is the alignment of the articulating surfaces in the frontal plane?

A
  1. Femoral neck and shaft: 125 degrees (optimal)
  2. Coxa valga > 125 degrees:
    • JRF parallel to neck
    • More compression
    • Less bending
  3. Coxa vara < 125 degrees:
    • Increased bending moment
      Angle decreases with age
31
Q

What is the alignment of the articulating surfaces in the transverse plane?

A

Anteversion: 15 degrees
- Decreases during maturation
- Excessive anteversion places head of femur too anteriorly
Retroversion: less common

32
Q

What is the alignment of the articulating surfaces in the transverse plane?

A

Medial rotation: compensates for excessive femoral anteversion

33
Q

What causes lateral tibial torsion?

A

Excessive anteversion

34
Q

What is cerebral palsy?

A
  • Affects a persons ability to move and maintain balance/posture
  • Can result in femoral anteversion
  • Solution: femoral osteotomy (cut femur, realign head, stabilize)
35
Q

What are the similarities/differences between the hip and shoulder joints?

A

Difference:
- Greater stability/less mobility in hip (greater boney congruence and support from ligament/capsule)
Similarities:
- Movement limited by ligaments and muscles

EDKP-206 (16 decks)

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