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Biomechanics Winter 2024 > Elbow & forearm > Flashcards

Elbow & forearm Flashcards

1
Q

What is the normal “carry angle” for the elbow?

A

13 degrees

women greater than men

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2
Q

What constitutes cubitus valgus?

A

greater than 20-25 degrees carry angle

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3
Q

What constitutes cubitus varus?

A
  • forearm angled toward midline
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4
Q

Why does the carrying angle disappear with full elbow flexion?

A
  • the trochlear groove determines path of the forearm
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5
Q

List all the ligaments that surround the elbow joint and their jobs

A

Medial collateral ligament (UCL):
- Ant. fibers: resists valgus (taut thru ROM)
- post. fibers: resists valgus (taut w/ elbow flexion)
- transverse fibers

Lateral collateral ligament (RCL):
- RCL & lateral ulnar collateral ligament (resist varus)

LUCL forms sling for radial head to protect against excessive ER of proximal forearm

Annular ligament:
- wraps around radial head

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6
Q

What is the axis of rotation for pronation and supination?

A
  • from radial head to ulnar head
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7
Q

What are the arthrokinematics of humeroulnar flexion?

A

Moving ulna: concave
- rolls and slides anteriorly

Moving humerus: convex
- rolls anterior
- slides posterior

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8
Q

What are the arthrokinematics of humeroulnar extension?

A

Moving ulna: concave
- rolls and slides posteriorly

Moving humerus: convex
- rolls posterior
- slides anterior

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9
Q

What are the arthrokinematics of humeroradial flexion?

A

Moving radius: concave
- rolls and slides anteriorly

Moving humerus: convex
- rolls anteriorly
- slides posteriorly

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10
Q

What are the arthrokinematics of humeroradial extension?

A

Moving radius: concave
- rolls and slides posteriorly

Moving humerus: convex
- rolls posteriorly
- slides anteriorly

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11
Q

What are the arthrokinematics of PRUJ pronation?

A

Moving radius:
- spin

Moving ulna: concave
- rolls and slides volar (anterior)

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12
Q

What are the arthrokinematics of PRUJ supination?

A

Moving radius:
- spin

Moving ulna: concave
- rolls and slides dorsal (posterior)

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13
Q

What are the arthrokinematics of DRUJ pronation?

A

Moving radius: concave
- rolls and slides volar (palmar)

Moving ulna: convex
- rolls volar
- slides dorsal

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14
Q

What are the arthrokinematics of DRUJ supination?

A

Moving radius: concave
- rolls and slides dorsally

Moving ulna: convex
- rolls dorsal
- slides volar

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15
Q

What are the arthrokinematics of humeroradial pronation/supination?

A

Moving radius & humerus:
- spin

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16
Q

What are some consequences of a torn interosseous membrane?

A
  • proximal drift of the radius
  • bony asymmetry
  • will cause wrist pain/loss of function
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17
Q

What are some consequences of a torn TFCC?

A
  • multidirectional joint instability
  • pain/difficulty in motions of forearm/wrist
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18
Q

What structures are responsible for stabilizing the DRUJ?

A
  • TFCC
  • pronator quadratus
  • FCU tendon
  • distal oblique fibers of interosseous membrane
19
Q

Explain the screw home mechanism of the elbow?

A
  • pronator teres compresses radial head against capitulum
20
Q

What muscles perform elbow flexion?

A
  • brachialis
  • biceps brachii
  • brachioradialis
  • pronator teres
21
Q

What muscles perform elbow extension?

A
  • triceps brachii
  • anconeus
22
Q

What muscles perform forearm pronation?

A
  • pronator teres
  • pronator quadratus

Secondary:
- FCR
- palmaris longus
- brachioradialis (from supinated position)

23
Q

What muscles perform forearm supination?

A
  • supinator
  • biceps brachii

Secondary:
- EPL
- EI
- brachioradialis (from pronated position)

24
Q

What muscles perform wrist flexion?

A
  • FCU
  • FCR
  • palmaris longus

Secondary:
- FDP
- FDS
- FPL
- APL
- EPB

25
Q

What muscles perform wrist extension?

A
  • ECRB
  • ERCL
  • ECU

Secondary:
- ED
- EDM
- EI
- EPL

26
Q

What muscles perform radial deviation?

A
  • ECRL/B
  • EPL/B
  • FCR
  • APL
27
Q

What muscles perform ulnar deviation?

A
  • ECU
  • FCU
  • FDP/S
  • ED
28
Q

What ROM does elbow flexion have the best torque?

A

80-90 degrees

29
Q

What ROM does elbow extension have the best torque?

A

80-90 degrees

30
Q

What ROM does wrist flexion have the best torque?

A

40 degrees

31
Q

What ROM does wrist extension have the best torque?

A

30-35 degrees

32
Q

What ROM does gripping have the best torque?

A

30-35 degrees wrist ext.

33
Q

Which positions make the biceps brachii and triceps brachii actively insufficient?

A

BB: shoulder flexion & elbow flexion

TB: shoulder ext & elbow ext

34
Q

Which positions make the biceps brachii and triceps brachii passively insufficient?

A

BB: elbow ext & shoulder ext

TB: shoulder flexion & elbow flexion

35
Q

What is the best UE positioning for the optimal length-tension relationship of the biceps brachii?

A
  • shoulder ext & elbow flexion
36
Q

What is the best UE positioning for the optimal length-tension relationship of the triceps brachii?

A
  • shoulder flex & elbow ext
37
Q

What is the law of parsimony?

A
  • nervous system tends to activate the fewest muscles/fibers possible for control of a given joint action
  • this decreases energy expenditure
38
Q

What is the terrible triad of the elbow?

A
  • dislocation
  • radial head fracture
  • coronoid fracture
39
Q

What is posterolateral rotary instability?

A
  • tearing/rupturing of LUCL ligament
  • from compression & valgus & supination
  • radial head dislocates posteriorly
40
Q

What is nursemaids elbow?

A
  • radial head dislocates out from the annular ligament
  • comes from a sudden pulling from the hand in an upward direction
  • common in children due to lack of strength and ligament laxity
41
Q

How can a person with a C6 lesion transfer from supine to sit?

A
  • tricep is paralyzed so have to use shoulder muscles to help extend the arm
  • if wrist is fixed on bed then they can use working elbow flexors to help get from supine to sitting
42
Q

Explain the pathomechanics of lateral epicondylalgia

A
  • Tennis elbow
  • repetitive microtrauma usually involving ECRB
  • incomplete reparative process

S & S:
- painful & weak grip
- painful passive wrist flexion & forearm pronation
- TTP over lateral epicondyle

Treatment:
- splinting/bracing
- manual therapy
- ECC training of wrist ext

43
Q

What are AAOS norms for elbow flexion and extension?

A

Flexion:
- 150

Ext:
- 0

44
Q

What are AAOS norms for elbow supination and pronation?

A

Supination:
- 80

Pronation:
- 80

Biomechanics Winter 2024 (6 decks)

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