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Biomechanics I > Elbow and forearm > Flashcards

Elbow and forearm Flashcards

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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
can problems occur with surgery on the elbow if so, what injuries are common
yes persistent instability, nerve damage, heterotropic ossification, stiffness
26
when can a flexion contracture occur
after immobilization heterotropic ossification osteophyte formation inflammation/effusion elbow joint muscle spasticity triceps paralysis scarring of the skin anterior elbow
27
what is the functional arc of the elbow
145-150 flexion -5 degrees extension
28
what is the primary plane of motion of the humero-ulnar joint
saggital
29
explain full extension of the humero-ulnar joint
extensible anterior tissues and some fibers MCL olecranon process able to wedge into olecranon fossa
30
explain flexion of the humeral-ulnar joint
concave surface of trochlear notch rolls and slides on convex trochlea elongation fo ulnar nerve posterior MCL
31
where does motion occur with the humeroradial arthrokinematics what are the arthrokinematics
between cuplike fovea of radial head and capitulum radius rolls and slides
32
describe the active flexion of the humeroradial arthrokinematics
radial fovea pulled against capitulum by contracting muscles
33
humeroradial joint provides __% lateral stability
50%
34
t/f changes with the radial head such as fracture, malunion, surgical removal change valgus alignment
true
35
what is the function of the interosseous membrane
radius and ulna bound together attachment site transmits force to share load
36
the tensile strength of the interosseous membrane is similar to what other structure
patellar tendon
37
a tear of the interosseus membrane will result in..
proximal migration fo radius
38
what structure connects the ulna to the humerus
interosseus membrane
39
in full pronation, how does the radius and ulna move
radius crosses over the ulna
40
where is the axis of rotation located in the FA during pronation
obliquely across the forearm from radial head to ulnar head
41
what causes a "pulled elbow", "nursemaids elbow", or "babysitter's elbow"
strenuous pull on pronated hand causes radial head to slip out
42
what makes up the distal radio-ulnar joint
convex head of ulna on shallow concave radius triangular fibrocartilage (TFC) holds head of ulna
43
what are the stabilizers of the distal radio-ulnar joint
triangular fibrocartilage (TFCC) pronator teres ECU tendon distal oblique fibers interosseous membrane
44
what is the average motion of pronation/supination
pronation: 75 degrees supination: 85 degrees
45
t/f supination/pronation both require simultaneous movements at only proximal or distal radio-ulna joint or humeroradial joint
false supination/pronation both requires simultaneous movements at both proximal and distal radio-ulna joint and humeroradial joint
46
what happens during supination with the radius and carpal bones
radius and carpal bones rotate around the fixed humerus and ulna
47
proximally, describe supination
rotation of radial head in fibro-osseus ring no slide/roll
48
distally, describe pronation
radius rolls/slides in the same direction articular discs proximal surface slides across ulan head
49
during pronation, how do the radius and carpal bones move
radius and carpal bones rotate around the fixed humerus and ulna
50
where is the axis of rotation located during rotation
axis is nearly parallel to membrane limits tension
51
t/f the humeroradial joint is linked with any movement of elbow and forearm
true
52
how does the fovea of the radial head move during pronation
the fovea of the radial head spins against the capitulum
53
how does the pronator teres function during forearm pronation
pronates the forearm pulls radius proximally against the capitulum
54
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
ulna rotates around the foxed radius infraspinatus and pronator quadratus closed chain
55
what is the innervation of the brachialis
55
what is the innervation of the brachialis
55
what elbow flexors are innervated by the musculocutaneous nerve (C5-C6)
brachialis, biceps
56
what forearm supinators are innervated by the musculocutaneous nerve (C5-C6)
biceps
57
what elbow flexors are innervated by the radial nerve (C5-C6)
bracioradialis
58
what elbow flexors are innervated by the median never (C6-C7)
pronator teres
59
what elbow extensors are innervated by the radial nerve (C7-C8)
triceps anconeus
60
what forearm pronators are innervated by the median nerve
pronator quadratus pronator teres
61
what forearm supinators are innervated by the radial nerve
supinator

Biomechanics I (4 decks)

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