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Biomechanics I > Elbow and forearm > Flashcards

Elbow and forearm Flashcards

1
Q

describe the osteology of the forearm

A

3 bones/4 joints
humeral-ulnar
humeroradial
proximal/distal radio-ulnar

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2
Q

t/f
flexion/extension and supination/pronation of the forearm si independent of each other in the GH joint

A

true

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3
Q

describe the trochlear notch

A

jawlike
has longitudinal crest

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4
Q

which ligament in the body runs from the ulna to the ulna

A

MCL transverse fibers

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5
Q

describe the radial head

A

disc-like
articular cartilage covers at 280 degrees of the rim
contact radial nots on ulna

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6
Q

describe the fovea
what does the fovea articulate with

A

shallow cup-shaped depression
articulates with capitulum

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7
Q

what motions does the humero-ulnar joint contribute to

A

flexion/extension
contributes to much of the stability

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8
Q

what motions does the humeroradial joint contribute to

A

flexion/extension
ligaments buttress the radial head against the capitulum

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9
Q

does the ulna have axial rotation

A

yes, modified hinge joint

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10
Q

how does the medial lip of the trochlea affect flexion/extension of the elbow

A

medial lip of trochlea is larger so ulna deviates laterally relative to humerus

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11
Q

what is the frontal plane angle called in regard to elbow flexion/extension

A

normal cubitus of carrying angle

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12
Q

what is the average normal cubitus valgus or carrying angle

when is it higher

A

13 degrees

higher on dominant side, higher with age

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13
Q

what is excessive cubitus valgus or carrying angle

A

20-25 degrees

cubitus varus secondary to growth plate injury

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14
Q

what ligaments are present in the elbow joint

A

medial collateral ligament (MCL)
radial collateral ligament (RCL)
lateral collateral ligament (LCL)
annular ligament

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15
Q

describe the MCL anterior fibers
-strength
-resists
-how does it run
-function

A

strongest
resists valgus
medial epicondyle to coronoid process
9 separate divisions
stability in sagittal plane

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16
Q

describe the MCL posterior fibers
-location
-where does it run
-what does it resist

A

fan-like thickening of posterior/med capsule
medial epicondyle to olecranon
resists valgus forces and tight in extreme flexion

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17
Q

describe the MCL transverse fibers
-where does it run
-what does it limit

A

olecranon to coronoid process (ulna to ulna)
only limited articular stability

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18
Q

explain how a WB injury to the MCL can occur

what injuries can occur

A

extended and valgus force WB
can cause compression fracture, ulnar nerve injury
anterior capsule, medial musculature at epicondyle

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19
Q

explain how a NWB injury to the MCL can occur

A

repetitive valgus producing strain, overhead athletes

most common in baseball pitchers d/t late cocking and acceleration phase

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20
Q

what is tommy john surgery

A

repair of the anterior fibers through a tendon graft from palmaris longus, gracilis, or plantaris

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21
Q

what 3 structures does the RCL merge with

A

annular ligament
supinator
extensor carpi radialis brevis (ECRB)

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22
Q

describe the lateral ulnar collateral ligament (LUCL)
-attachment site
-when is it taut
-what structure is the guidewires in frontal plane

A

thicker
attaches supinator crest of ulna
taut in full FXT
MCL are guidewires in frontal plane during full FLX/EXTn

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23
Q

when is intracapsular pressure the lowest or the “position of comfort”

what does the “position of comfort” mean

A

80 degrees flexion

pts with swollen elbow may hold this position, but may get a flexion contractor

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24
Q

what is the terrible triad injury

A

fall on outstretched/supinated arm
elbow joint dislocation (ligament injury)
fracture on radial head or coronoid process

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25
Q

can problems occur with surgery on the elbow

if so, what injuries are common

A

yes

persistent instability, nerve damage, heterotropic ossification, stiffness

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26
Q

when can a flexion contracture occur

A

after immobilization
heterotropic ossification
osteophyte formation
inflammation/effusion elbow joint
muscle spasticity
triceps paralysis
scarring of the skin anterior elbow

27
Q

what is the functional arc of the elbow

A

145-150 flexion
-5 degrees extension

28
Q

what is the primary plane of motion of the humero-ulnar joint

A

saggital

29
Q

explain full extension of the humero-ulnar joint

A

extensible anterior tissues and some fibers MCL
olecranon process able to wedge into olecranon fossa

30
Q

explain flexion of the humeral-ulnar joint

A

concave surface of trochlear notch rolls and slides on convex trochlea
elongation fo ulnar nerve
posterior MCL

31
Q

where does motion occur with the humeroradial arthrokinematics

what are the arthrokinematics

A

between cuplike fovea of radial head and capitulum

radius rolls and slides

32
Q

describe the active flexion of the humeroradial arthrokinematics

A

radial fovea pulled against capitulum by contracting muscles

33
Q

humeroradial joint provides __% lateral stability

A

50%

34
Q

t/f
changes with the radial head such as fracture, malunion, surgical removal change valgus alignment

A

true

35
Q

what is the function of the interosseous membrane

A

radius and ulna bound together
attachment site
transmits force to share load

36
Q

the tensile strength of the interosseous membrane is similar to what other structure

A

patellar tendon

37
Q

a tear of the interosseus membrane will result in..

A

proximal migration fo radius

38
Q

what structure connects the ulna to the humerus

A

interosseus membrane

39
Q

in full pronation, how does the radius and ulna move

A

radius crosses over the ulna

40
Q

where is the axis of rotation located in the FA during pronation

A

obliquely across the forearm from radial head to ulnar head

41
Q

what causes a “pulled elbow”, “nursemaids elbow”, or “babysitter’s elbow”

A

strenuous pull on pronated hand causes radial head to slip out

42
Q

what makes up the distal radio-ulnar joint

A

convex head of ulna on shallow concave radius

triangular fibrocartilage (TFC) holds head of ulna

43
Q

what are the stabilizers of the distal radio-ulnar joint

A

triangular fibrocartilage (TFCC)
pronator teres
ECU tendon
distal oblique fibers interosseous membrane

44
Q

what is the average motion of pronation/supination

A

pronation: 75 degrees
supination: 85 degrees

45
Q

t/f
supination/pronation both require simultaneous movements at only proximal or distal radio-ulna joint or humeroradial joint

A

false
supination/pronation both requires simultaneous movements at both proximal and distal radio-ulna joint and humeroradial joint

46
Q

what happens during supination with the radius and carpal bones

A

radius and carpal bones rotate around the fixed humerus and ulna

47
Q

proximally, describe supination

A

rotation of radial head in fibro-osseus ring
no slide/roll

48
Q

distally, describe pronation

A

radius rolls/slides in the same direction
articular discs proximal surface slides across ulan head

49
Q

during pronation, how do the radius and carpal bones move

A

radius and carpal bones rotate around the fixed humerus and ulna

50
Q

where is the axis of rotation located during rotation

A

axis is nearly parallel to membrane

limits tension

51
Q

t/f
the humeroradial joint is linked with any movement of elbow and forearm

A

true

52
Q

how does the fovea of the radial head move during pronation

A

the fovea of the radial head spins against the capitulum

53
Q

how does the pronator teres function during forearm pronation

A

pronates the forearm
pulls radius proximally against the capitulum

54
Q

when the forearm is fixed distally during pronation (pushup position), what are the ulna/radius movements

what muscles are involved

is this a closed/open chain exercise

A

ulna rotates around the foxed radius

infraspinatus and pronator quadratus

closed chain

55
Q

what is the innervation of the brachialis

A
55
Q

what is the innervation of the brachialis

A
55
Q

what elbow flexors are innervated by the musculocutaneous nerve (C5-C6)

A

brachialis, biceps

56
Q

what forearm supinators are innervated by the musculocutaneous nerve (C5-C6)

A

biceps

57
Q

what elbow flexors are innervated by the radial nerve (C5-C6)

A

bracioradialis

58
Q

what elbow flexors are innervated by the median never (C6-C7)

A

pronator teres

59
Q

what elbow extensors are innervated by the radial nerve (C7-C8)

A

triceps
anconeus

60
Q

what forearm pronators are innervated by the median nerve

A

pronator quadratus
pronator teres

61
Q

what forearm supinators are innervated by the radial nerve

A

supinator

Biomechanics I (4 decks)

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