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39 notecards = 10 pages (4 cards per page)

Viewing:

Biomechanics Exam #2 (The elbow and forearm)

front 1

  • Elbow/forearm complex: 3 bones, 4 joints
    • Elbow:

back 1

  • humeroulnar & humeroradial joints
    • Flexion & extension => alter the functional length of the UE

front 2

  • Elbow/forearm complex: 3 bones, 4 joints
    • Forearm

back 2

  • proximal & distal radioulnar joints
  • Supination & pronation
    • allows the position of the hand to change without altering the glenoid humeral joint position

front 3

Osteology

back 3

  • Mid-to-distal humerus
  • Ulna
  • Radius

front 4

Mid-to-distal humerus

back 4

front 5

Humerus (inferior/bottom view)

back 5

front 6

Lateral view of trochlear notch

back 6

front 7

Radius

back 7

front 8

Ulna

back 8

front 9

Elbow Arthrology: General Features

back 9

  • humeroulnar & humeroradial
    • Tight fit between the trochlea notch provides MOST of the elbow/s structural stability
    • small amounts of axial rotation & side-to-side motion

front 10

Normal Valgus

back 10

  • Asymmetry of trochlea causes frontal deviation (colloquially called “carrying angle”; cubitus valgus)
    • 13 +/- 6 degrees; women have about 2deg
      more

front 11

humeroulnar & humeroradial joints

back 11

front 12

Elbow Arthrology: Connective Tissue

back 12

  • Articular capsule is relatively thin; reinforced anteriorly by oblique
    bands of fibrous tissue
  • Collateral ligaments
  • Wrist flexor and pronator group

front 13

Collateral ligaments

back 13

  • provide much (passive) stability
    • Medial collateral ligament => anterior, posterior, and transverse fiber bundles
      • Anterior is the stiffest provide the most resistance to force

front 14

Wrist flexor & pronator group

back 14

  • provide much (active) stability
    • Most notably the flexor carpi ulnaris

front 15

Elbow Osteokinematics

back 15

  • Flexion & extension
  • PROM:
    • 5 degrees beyond neutral in extension
    • 145 degrees flexion
      • Often noted as (-5-145)
  • AROM
    • 0-145

front 16

Arthrokinematics: Humeroulnar Joint (bicep flex)

back 16

  • concave on convex
  • SLIDE UP + ROLL UP

front 17

Arthrokinematics: Humeroradial Joint (radius and ulna)

Sagital section=

back 17

  • concave on convex
  • SLIDE UP + ROLL UP

front 18

The Interosseus Membrane

back 18

  • central band binding radius and ulnar together
  • site for extrinsic muscles of the hand

front 19

The Interosseus Membrane: Compression force

back 19

  1. radiocarpal joint to radius
  2. compression force to ulna (pulls on tight of IMem)
  3. across elbow at humero-ulnar joint
  4. cross elbow toward shoulder

front 20

the IOM with holding an suitecase

back 20

  • distal-directed distracting force through the radius
  • oblique cord, angular ligaments, and brachioradialis support load
  • distraction slackens central and of IOM

front 21

Forearm Arthrology: General Features

back 21

front 22

Pronation

back 22

front 23

Forearm Arthrology: Connective Tissue

back 23

  • proximal radioulnar joint is within the joint capsule of the elbow
    • radial head is held against the ulnar via: the radial notch & the annular ligament
      • ~75% is from the ligament, 25% from the bony notch

front 24

Forearm Arthrology: Connective Tissue

Distal radioulnar joint

back 24

front 25

Forearm Osteokinematics

back 25

  • Pronation & supination
    • “zero” point is the thumbs-up position

front 26

Elbow Arthrokinematics (fixed/no moving ulna!)

SUPINATION

back 26

  • roll + slide in SAME DIRECTION of supination (down or up)

front 27

Elbow Arthrokinematics (fixed ulna)!

PRONATION

back 27

  • roll + slide in SAME DIRECTION of pronation(down or up)
  • RADIUS CROSSES

front 28

Full Supination when weight is pushing on one hand

back 28

  1. Radius is fixed // humerus and ulna can move
  2. H and U has rotated 80-90* externally => forearm pronation

front 29

Muscular Actions

back 29

  • Elbow flexion
  • Biceps Brachii
  • Brachialis
  • Brachioradialis
  • Pronator Teres

front 30

Muscular actions: movmentd

back 30

Maximal isometric internal torques (greatest to lowest)

  1. FLEXION
  2. EXTENSION
  3. SUPINATION
  4. PRONATION

front 31

Muscular actions: peak levels

back 31

  1. Flexor torque vs elbow join angle (=90*)
  2. Flexor force vs elbow joint angle (=80*)
  3. Flexor moment arm vs. elbow joint angle (100*)

front 32

Synergy: Elbow Flexion + Shoulder Extension

back 32

  • Contracting biceps(front): elbow flexion (90*) and shoulder flexion (45*)
  • Pulling arm back: elbow flextion (90*), shoulder extention (45*)

front 33

Muscular Action: Elbow Extension

back 33

  • Triceps Brachii
  • Anconeus

front 34

**(recheck) Muscular Actions: Elbow extensor torque

back 34

  • Largest at 90*
  • Internal muscular action @largest point = flexor (90*) // = extensor (near full extension)
  • muscle length NOT leverage

front 35

Extension Synergy: Shoulder Flexion & Elbow Extension

back 35

  • Flexion: anterior deltoid
  • Extension: elbow

front 36

Muscular Actions: Supination

back 36

  1. Supinators
  2. Biceps Brachii
  3. brachioradialis(always pulls the forearm into neutral)

front 37

Muscular actions: Pronation

back 37

  1. Pronator Teres
  2. Pronator Quadratus
  3. brachioradialis(always pulls the forearm into neutral)

front 38

Muscular Action: Supination and Pronation

back 38

front 39

Muscular Action: Pronators (2)

back 39

  1. Pronator teres
    • 2heads // Median nerve runs between(in most people)
    • Highpower
  2. Pronator Quadratus
    • Workhorse
    • On for all pronation
    • compresses distal radioulnar joint