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2 Biomechanics > Elbow > Flashcards

Elbow Flashcards

1
Q

Joints of Elbow

A

Humeroulnar
Humeroradial
Radioulnar, proximal and distal

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2
Q

Elbow joint is made of…

A

humeral ulnar and humeral radial

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3
Q

M/L axis of elbow

A

runs superior
due to asymmetry of trochlea, ulnar deviates laterally

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4
Q

Cubitus valgus

A

carrying angle
average is about 13°

generally greater on dominant arm and naturally increases with age

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5
Q

Excessive Cubitus Valgus

A

angle exceeds 20-25°

can be caused by severe fracture or growth plate injury

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6
Q

Cubits Varus

A

forearm neutral, or projects medially
can be caused by severe fracture or growth plate injury

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7
Q

Capsule of elbow

A

relatively thin, covers humeroulnar, humeroradial, and proximal radioulanar joints

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8
Q

MCL of elbow

A

has anterior fibers, posterior fibers, transverse fibers

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9
Q

Anterior fibers of MCL

A

most resistance to valgus force
taut through flexion and extension

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10
Q

Posterior fibers of MCL

A

thickening of peromedial capsule
taut in valgus and end range flexion

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11
Q

Transverse fibers of MCL

A

ulna to ulna, limited stability

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12
Q

Radial collateral ligament

A

Lateral epicondly to annular ligament
some varus resistance

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13
Q

LCL of elbow

A

lateral epicondyle to supinator crest
resists varus and end range flexion
forms a sling that prevents radial head to dislocate

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14
Q

Humeroulnar joint type

A

HINGE

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15
Q

Humeroradial joint type

A

PIVOT

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16
Q

Elbow joint characteristics

A

modified hinge
1 degree of freedom, sagittal plane
Frontal/transverse = accessory motions

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17
Q

Flexion/Extension ulna on humerus

A

Concave on convex
Flexion: roll/slide are anterior
Extension: roll/slide are posterior

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18
Q

Flexion/Extension radius on humerus

A

Concave on convex
Flexion: roll/slide are anterior
Extension: roll/slide are posterior

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19
Q

Function of interosseus membrane

A

firmly bind radius and ulna together
attachment for extrinsic hand muscles
transmit force proximally through upper limb

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20
Q

Components of interosseus membrane

A

central band: thickest
oblique cord: limits distal migration of radius to ulna
Distal oblique: only present 40% of time, stability

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21
Q

Proximally directed Force Transmission

A

closed chain force, 80% through radiocarpal joint

interosseus membrane is pulled taut, allows compressive forces to cross the elbow towards the humeroulnar joint

both joints share the compressive load

muscles will also pull the radial head towards capitulum, increases force at humeroradial joint; IM helps to transfer some force to humeroulnar

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22
Q

Distally directed force transmission

A

distal force relaxes IM
stresses oblique cord and annukar ligament
brachioradialis stops radius from moving from capitulum

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23
Q

Proximal Radioulnar Joint

A

shares capsule with elbow joints
Annular ligament helps to attach ulna to the radius

24
Q

Distal radioulnar joint

A

little osseous stability, some connective tissue
has a articular disc that is triangular
capsular ligaments are continuation of disc
tissues hold ulna against ulnar notch

25
Radioulnar joint characteristics
Modified Pivot 1 degree of freedom does pronation/supination
26
Proximal radioulnar joint movements
Axis is through heads of bones convex on concave Roll/Slide in Pronation: roll RollSlide in Supination: roll tight annular ligament prohibits standard movements
27
Distal radioulnar joint movements
Axis is through heads Cave on Vex Supination: Roll/Slide are Lateral Pronation: Roll/Slide are Medial IM stays stable during motion
28
Humeroradial joint pronation/supination
Axis through heads Cave on Vex Pronation: Medial rotation Supination: Lateral rotation
29
Closed pack position for elbow
extension and supination
30
Closed chain movement
humerus and ulna rotate relative to fixed radius and hand rotation of humerus is transferred to rotating ulna, nearly degree for degree
31
Proximal radioulnar closed chain
Cave on vex motion pronation/supination causes ulna/annular ligament on radius motion
32
Distal radioulnar joint, closed chain
Vex on cave pronation on supination is ulna on radius (ulnar notch)
33
Elbow Flexors
Biceps brachii brachialis Brachioradialis
34
Biceps brachii
maximal activation during combine flexion and supination
35
Brachioradialis
moment arm increases when active proximal attachment closer than distal attachment for joint action greater % of muscle belly over joint axis flexing muscle creates bowstring effect that increases its flexion MA
36
Moment Arms for Flexor muscles
Brachioradialis = greater at 120° Brachialis = greater at 100-120° Biceps Brachii = greater at 100° Brachioradialis has the greatest moment arm/production of force
37
Elbow Extensor
Triceps Brachii Anconeus
38
Triceps Brachii
muscles not activated all at once goes from medial to lateral to long head
39
Anconeus
Poor elbow extensor first muscle to turn on high % of type 1 fibers (ideal for stability/fatiguing)
40
Elbow extensor MAs
Triceps moment arm highest near full extension triceps torque occurs between 80-90°
41
GH adductors/horizontal adduction
Pec major and anterior deltoid can act as adductors during closed chain motion to extend elbow
42
Any muscle that supinates or pronates the forearm must have attachments where?
humerus/ulna to radius/hand
43
Supination/pronation associated with movement at shoulder
Supination --> GH ER Pronation --> GH IR
44
Supination muscles
supinator biceps brachii brachioradialis if pronated
45
Biceps brachii as a supinator
3x PCSA compared to supinator wraps around radius during pronation action as supinator greatest at 90° elbow angle MA doesn't change with supination length/tension optimized just under 90° line of pull of biceps optimized just after 90°
46
High powered supination
biceps only active during high force tasks best to perform with elbow at 90° triceps (on the ulna) acts an antagonist to prevent flexion of elbow during supination also needs extensor counter torque
47
Supinator muscle
has superficial and deep fibers weak humerus attachment and poor MA for flex/ext significant supinator at all angles and effort levels
48
Brachioradialis w/pronation & supination
brachioradialis is supinator when arm is pronated, until 10° of supination brachioradialis is a pronator past 10° of supination
49
Pronator muscles
pronator teres pronator quadratus brachioradialis
50
Pronator teres
two heads secondary elbow flexor, triceps action is needed to stabilize elbow during pronation
51
Pronator quadratus
most active and consistent pronator, regardless of force or flexion action perpendicular to axis of rotation compresses radius against ulnar head during pronation, stabilizing joint
52
UCL injury acute mechanisms
External valgus force to elbow FOOSH (extended elbow forced into valgus ulnar nerve, ant capsule, pronator/flexor muscles compression fracture to humeroradial joint
53
UCL Injury chronic mechanism
repetitive valgus strain valgus torques high during late cocking, acceleration can be fixed with tommy john surgery
54
During a FOOSH mechanism for injury, what structure helps transmit force from the medial to lateral side of the forearm?
central band of the interosseous membrane
55
The pronation/supination axis of rotation runs between which landmarks?
radial head and ulnar head

2 Biomechanics (9 decks)

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