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Biomechanics Winter 2024 > Elbow & forearm > Flashcards

Elbow & forearm Flashcards

(44 cards)

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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?

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

Explain the screw home mechanism of the elbow?

Study These Flashcards
A
  • pronator teres compresses radial head against capitulum
20
Q

What muscles perform elbow flexion?

Study These Flashcards
A
  • brachialis
  • biceps brachii
  • brachioradialis
  • pronator teres
21
Q

What muscles perform elbow extension?

Study These Flashcards
A
  • triceps brachii
  • anconeus
22
Q

What muscles perform forearm pronation?

Study These Flashcards
A
  • pronator teres
  • pronator quadratus

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

23
Q

What muscles perform forearm supination?

Study These Flashcards
A
  • supinator
  • biceps brachii

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

24
Q

What muscles perform wrist flexion?

Study These Flashcards
A
  • FCU
  • FCR
  • palmaris longus

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

25
What muscles perform wrist extension?
- ECRB - ERCL - ECU Secondary: - ED - EDM - EI - EPL
26
What muscles perform radial deviation?
- ECRL/B - EPL/B - FCR - APL
27
What muscles perform ulnar deviation?
- ECU - FCU - FDP/S - ED
28
What ROM does elbow flexion have the best torque?
80-90 degrees
29
What ROM does elbow extension have the best torque?
80-90 degrees
30
What ROM does wrist flexion have the best torque?
40 degrees
31
What ROM does wrist extension have the best torque?
30-35 degrees
32
What ROM does gripping have the best torque?
30-35 degrees wrist ext.
33
Which positions make the biceps brachii and triceps brachii actively insufficient?
BB: shoulder flexion & elbow flexion TB: shoulder ext & elbow ext
34
Which positions make the biceps brachii and triceps brachii passively insufficient?
BB: elbow ext & shoulder ext TB: shoulder flexion & elbow flexion
35
What is the best UE positioning for the optimal length-tension relationship of the biceps brachii?
- shoulder ext & elbow flexion
36
What is the best UE positioning for the optimal length-tension relationship of the triceps brachii?
- shoulder flex & elbow ext
37
What is the law of parsimony?
- nervous system tends to activate the fewest muscles/fibers possible for control of a given joint action - this decreases energy expenditure
38
What is the terrible triad of the elbow?
- dislocation - radial head fracture - coronoid fracture
39
What is posterolateral rotary instability?
- tearing/rupturing of LUCL ligament - from compression & valgus & supination - radial head dislocates posteriorly
40
What is nursemaids elbow?
- 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
How can a person with a C6 lesion transfer from supine to sit?
- 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
Explain the pathomechanics of lateral epicondylalgia
- 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
What are AAOS norms for elbow flexion and extension?
Flexion: - 150 Ext: - 0
44
What are AAOS norms for elbow supination and pronation?
Supination: - 80 Pronation: - 80

Biomechanics Winter 2024 (6 decks)

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