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Biomechanics > Shoulder > Flashcards

Shoulder Flashcards

1
Q

What are the 4 joints of the shoulder complex?

A

Sternoclavicular (SC)
Acromioclavicular (AC)
Scapulothoracic (ST)
Glenohumeral (GH)

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2
Q

What are the kinematics of the SC joint?

A

elevation and depression (frontal plane)
protraction and retraction (horizontal plane)
posterior clavicular rotation (sagittal plane)

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3
Q

What are the kinematics of the SC joint during elevation?

A

superior roll, inferior slide
AP AOR
stretched costoclavicular ligament produces downward force in direction of slide

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4
Q

What are the kinematics of the SC joint during depression?

A

inferior roll, superior glide

AP AOR

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5
Q

What are the kinematics of the SC joint during retraction?

A

vertical AOR throught sternum

concave on convex: roll and slide both in posterior direction

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6
Q

What are the kinematics of the SC joint during protraction?

A

vertical AOR throught sternum

concave on convex: roll and slide both in anterior direction

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7
Q

What are the primary motions of the AC joint?

A

upward and downward rotation

AP AOR

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8
Q

What are the secondary motions of the AC joint?

A

internal and external rotation, anterior and posterior tilting

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9
Q

What are the motions of the Scapulothoracic Joint?

A

elevation and depression, protraction and retraction, upward and downward rotation

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10
Q

What motions compose Scapulothoracic Elevation?

A

elevation (upward rotation) of SC joint: superior roll, inferior glide
downward rotation at AC joint

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11
Q

What motions compose Scapulothoracic protraction?

A

Protraction (anterior roll and anterior slide) at SC joint

horizontal place adjustments at AC joint

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12
Q

What motions compose Scapulothoracic upward rotation?

A

SC joint elevation (superior toll, inferior slide)????

AC upward rotation

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13
Q

What motions compose Scapulothoracic depression?

A

depression at SC joint: inferior roll, superior slide + upward rotation at AC joint

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14
Q

What motions compose Scapulothoracic retraction?

A

retraction at SC joint: posterior roll, posterior slide + slight horizontal plan adjustments of AC joint

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15
Q

What motions compose Scapulothoracic downward rotation?

A

depression of SC joint: interior roll, superior slide + downward rotation at AC joint

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16
Q

What 3 important functions do upward rotation of scapula during full shoulder abduction in plane of scapula serve?

A
  1. projects glenoid fossa upward and anterior-laterally, providing structural base to maximize upward and lateral reach of upper limb
  2. preserves optimal length-tension relationship of abductor muscles of GH joint, such as middle deltoid and supraspinatus
  3. helps maintain volume within subacromial space
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17
Q

How much articular surface does the glenoid fossa cover?

A

About 1/3 of articular surface of humeral head

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18
Q

In what positions is most excessive motions in an instable GH joint?

A

anteriorly and inferiorly

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19
Q

What are the primary motions drawing the middle glenohumeral ligament taut?

A

Anterior translation of the humeral head, especially in about 45-60° of abduction; external rotation

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20
Q

What are the primary motions drawing the Inferior glenohumeral ligament (three parts: anterior band, posterior band, and connecting axillary pouch)?

A

Axillary pouch: 90° of abduction, combined with anterior-posterior and inferior translations
Anterior band: 90° of abduction and full external rotation; anterior translation of humeral head
Posterior band: 90° of abduction and full internal rotation

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21
Q

GIRD is indicated by what?

A

20° or greater loss of internal rotation of throwing shoulder compared with non-dominant shoulder

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22
Q

What are some common findings in overhead athletes?

A

Associated with GH and scapulothoracic deficiency

Associated with rotator cuff tears and labral pathology

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23
Q

What are primary motions drawing superior glenohumeral ligament taut?

A

Adduction, inferior and anterior-posterior translation of humeral head

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24
Q

What are primary motions drawing coracohumeral ligament taut?

A

Adduction; inferior translation of the humeral head; external rotation

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25
Q

What are the osteokinematics of the GH joint?

A

abduction and adduction, flexion and extension, internal and external rotation

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26
Q

What are the kinematics of the GH joint during abduction?

A

inferior slide, superior roll, AP AOR, longitudinal diameter

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27
Q

What are the kinematics of the GH joint during adduction?

A

superior slide, inferior roll, AP AOR, longitudinal diameter

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28
Q

What are the kinematics of the GH joint during external rotation?

A

anterior slide, posterior roll, Horizontal plane/vertical AOR, transverse diameter

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29
Q

What are the kinematics of the GH joint during internal rotation?

A

posterior slide, anterior roll; Horizontal plane/vertical AOR, transverse diameter

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30
Q

What are the kinematics of the GH joint during flexion?

A

anterior spin, Near sagittal plane/near ML AOR

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31
Q

What are the kinematics of the GH joint during extension?

A

posterior spin, Near sagittal plane/near ML AOR

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32
Q

What is kinematics?

A

branch of mechanics that describes the motion of a body, without regard to the forces or torques that may produce the motion; assessed by goniometer and accelerator etc

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33
Q

What is kinetics?

A

branch of mechanics that describes the effect of forces and torques on the body as measured by transducer etc.

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34
Q

What is a moment arm?

A

perpendicular distance between an axis of rotation and the line of force.

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35
Q

What is torque?

A

a force multiplied by its moment arm; tends to rotate a body or segment around an axis of rotation, hence rotary force.

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36
Q

What is internal force?

A

push or pull produced by a structure located within the body. Most often, internal force refers to the force produced by an active muscle.

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37
Q

What is internal/external torque?

A

product of an internal/external force and its internal/external moment arm.

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38
Q

What is joint reaction force?

A

force that exists at a joint, developed in reaction to the net effect of internal and external forces.

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39
Q

What is mechanical advantage?

A

ratio of the internal moment arm to the external moment arm or of the output force to the input force.

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40
Q

Class 1 Lever

A

Fulcrum in the middle; MA can be greater/less/equal to 1. Designed for speed and range of motion

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41
Q

Class 2 Lever

A

Resistance in the middle; MA is greater than 1. Has advantage in force

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42
Q

Class 3 Lever

A

Effort in the middle; MA is less than 1. Has advantage in speed and range of motion

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43
Q

Functional design of Class 1 lever with axis near the middle:

A

Balanced movements

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44
Q

Functional design of class 1 lever with axis near force

A

speed and range of motion

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45
Q

Functional design of class 1 lever with near resistance

A

force/strength

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46
Q

Functional design of class 2 lever with axis near resistance

A

force/strength

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47
Q

Functional design of class 3 lever with axis near force

A

speed and range of motion

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48
Q

What is translation?

A

describes linear motion in which all parts of rigid body move parallel to and in same direction as every other part of body. Can occur in straight or curved line

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49
Q

What is rotation?

A

describes motion in which assumed rigid body moves in circular path around some pivot point. All points in body simultaneously rotate in same angular direction across the same number of degrees.

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50
Q

What are active movements?

A

caused by stimulated muscle, such as lifting glass of water toward mouth

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51
Q

What are passive movements?

A

caused by sources other than active muscle contraction, such as a push from another person, the pull of gravity, tension in stretched connective tissues, and so forth

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52
Q

What movements occur in the sagittal plane?

A

Flexion and extension

Dorsiflexion and plantar flexion

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53
Q

What movements occur in the frontal plane?

A

Abduction and adduction

Lateral flexion

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54
Q

What movements occur in the horizontal plane?

A

Internal (medial) and external (lateral) rotation

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55
Q

What is the axis of rotation of flexion and extension?

A

medial-lateral axis of rotation

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56
Q

What is the axis of rotation of abduction and adduction?

A

anterior-posterior axis of rotation

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57
Q

What is the axis of rotation of internal and external rotation?

A

vertical axis of rotation

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58
Q

What is degrees of freedom for a joint?

A

number of independent directions of movements allowed at a joint

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59
Q

How many degrees of freedom can joints have?

A

Joint can have up to three degrees of angular freedom, corresponding to three cardinal planes

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60
Q

What is a roll?

A

Multiple points along one rotating articular surface contact multiple points on another articular. Example: A tire rotating across a stretch of pavement

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61
Q

What is a slide/glide?

A

A single point on one articular surface contacts multiple points on another articular surface. Example: A non-rotating tire skidding across a stretch of icy pavement

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62
Q

What is a spin?

A

A single point on one articular surface rotates on a single point on another articular surface.. Example: A toy top rotating on one spot on the floor

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63
Q

Convex on cave movement occurs in what direction?

A

opposite direction

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64
Q

Concave on convex movement occurs in what direction?

A

the same direction

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65
Q

What is a closed pack position?

A

most ligaments and parts of capsule pulled taut providing stability to joint. Accessory movements typically minimal in close-packed position
-maximum contact between surfaces

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66
Q

What is loose packed position?

A

ligaments and capsule relatively slackened allowing increase in accessory movements. Joint generally least congruent near its midrange

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67
Q

The stress-strain curve changes as a function of:

A

Time of loading

Rate of loading

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68
Q

What is creep?

A

Creep describes progressive strain of material when exposed to constant load over time
-reversible

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69
Q

What two outcomes can forces have on the body?

A
  • Translate a body segment

- produce potential rotation of joint

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70
Q

What is the moment arm?

A

perpendicular distance between axis of rotation and force

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71
Q

A muscle is capable of producing torque at a joint only if:

A
  • produces a force in plane perpendicular to AOR of interest

- acts with associated moment arm distance greater than zero

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72
Q

External torque equals internal torque:

A

isometric activation; no muscle shortening or rotation at joint

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73
Q

Internal torque is greater than external torque

A 
concentric activation (muscle contracts/shortens)
creates rotation of joint in direction of pull of activated muscle
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74
Q

External torque is greater than internal torque

A

Eccentric activation: muscle produces pulling force as it is being elongated by another dominant force

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75
Q

Osteoblasts:

A

cells that create bone

76
Q

Osteoclasts

A

cells that reabsorb bone

77
Q

cortical

A

compact, very dense, outer later

78
Q

cancellous

A

spongy, very porous, inner layer

79
Q

Types of bone:

A
  1. long (ulna, clavicle, femur)
  2. short (tarsals, carpals)
  3. flat (ribs, scapula, sternum)
  4. Irregular (skulls, vertebrae)
  5. sesamoid (patella)
80
Q

Wolff’s Law

A 
Resorption
-response to decreased stree
-osteoclasts dominate
-disue, immobilization
Deposition
-response to increased stress
-osteoblasts dominate
-weight bearing exercise
81
Q

Osteoporosis

A

resorption exceeds deposition

82
Q

Anisotropic

A

response depends on direction of load application

83
Q

Visoelastic

A

response depends on rate & duration of loading

84
Q

Elastic response

A

deformation in response to loading

load removed -return to original shape/length

85
Q

Plastic response

A

microtears & debonding

load removed- permanently deformed

86
Q

Failure is caused by

A
  • single traumatic event

- accumulation of microfractures

87
Q

Types of loading

A
  1. compression
  2. tension
  3. shear
  4. bending
  5. torisonal
88
Q

Compression

A

presses ends of bones together

89
Q

Tension

A

pulls or stretches bone apart

90
Q

Shear

A

parallel to the surface of object

91
Q

Bending

A

applied to area having no direct support

92
Q

Torsional

A

twisting force

93
Q

Two types of cartilage

A
  1. articular

2. fibrocartilage

94
Q

Fibrocartilage

A
  • improves fit between bones

- intermediary between hyaline cartilage and other connective tissue

95
Q

Articular cartilage

A
  • aka hyaline
  • converts joints ends at articulations
  • contains collage & proteoglycan
  • 60-80% water
96
Q

Ligaments connect what?

A

bone to bone

97
Q

Ligaments consist of:

A
  1. collagen
  2. elastin
  3. reticulin
98
Q

What happens to ligaments during loading?

A

ligaments become stronger and stiffer

99
Q

Where is arthritis seen?

A

in articular cartilage

100
Q

What is joint stability created by?

A
  • ligaments
  • gravity
  • vacuum
101
Q

What joints are typically most stable?

A

synovial joint

102
Q

What is a simple joint?

A

connects two articulating surfaces

103
Q

What is a compound joint?

A

connects three or more articulating surfaces

104
Q

What is a complex joint?

A

connects two surfaces with articular disc or fibrocartilage

105
Q

What is an example of closed -packed position?

A

full extension at knee

106
Q

What are the functions of muscle?

A
  • produce movement
  • maintain postures & positions
  • stabilize joints
  • support & protect visceral organs
  • alter & control cavity pressure
  • maintain body temperature
  • control entrances/exits to body
107
Q

prime mover

A

muscle(s) primarily responsible for a given movement

108
Q

assistant mover

A

other muscles contributing to movement

109
Q

agonist

A

muscles creating same joint movement

110
Q

antagoinst

A

muscles opposing joint movement

111
Q

stabilizer

A

holds one segment still so specific movement in an adjacent segment can occur

112
Q

neutralizer

A

muscle working to eliminate undesired joint movement of another muscle

113
Q

belly

A

thick central portion

114
Q

epimysium

A

outside covering of a muscle

115
Q

fascicles

A

bundles of muscle fibers

116
Q

perimysium

A

dense connective sheath covering a fasicle

117
Q

fibers

A

cells of a skeletal muscle

118
Q

endomysium

A

very fine sheath covering individual fibers

119
Q

sarcolemma

A

thin plasma membrane branching into muscle

120
Q

myofibrils

A
  • rodlike strands of contractile filaments

- many sarcomeres in series

121
Q

sacroplasma

A

cytoplasm of muscle cell

122
Q

sarcoplasmic reticulum

A

speacialized endoplasmic reticulum of muscle cells

123
Q

T-tubules

A

extension of sarcolemma that protrudes into muscle cell

124
Q

myosin

A

thick, dark filament

125
Q

actin

A

thing, light filament

126
Q

sacromere

A

unit of myosin an actin

contractile unit of muscle

127
Q

Fibers run in what direction in fusiform muscles

A

parallel to each other and central tendon

128
Q

Fibers run in what direction in pennate muscles

A

approach central tendon obliquely = more fibers into a given length of muscle=large cross sectional area and higher capability for generating force

129
Q

PEC

A

parallel elastic component
allows the muscle to be stretched
associated with fascia surrounding muscle

130
Q

Contractile

A

converts stimulation into force

131
Q

SEC

A

series elastic

transfers muscle force to bone

132
Q

critical length

A

muscle begins to generate passive tension

133
Q

Henneman Size Principle

A

smaller neurons generally recruited before larger motor neurons

134
Q

Type I Fiber

A

slow twitch, oxidative
red (high myoglobin)
endurance athletes

135
Q

Type IIA Fiber

A

intermediate fast-twitch, oxidative-glycolytic

136
Q

Type IIX Fiber

A

fast twitch, white
glycolytic
sprinters

137
Q

Muscles attach to bone:

A
  1. directly
  2. via a tendon
  3. via an aponeurosis
138
Q

Tendon

A

inelastic bundle of collagen fibers

139
Q

Aponeurosis

A

sheath of fibrous tissue

140
Q

Characteristics of a Tendon

A
  1. transmits muscle fore to associated bone
  2. Can withstand high tensile loads
  3. Visoelastic stress-strain response
  4. myotendinous junction (where tendon and muscle join)
141
Q

Principle 1

A

Based on generalized 2 : 1 scapulohumeral rhythm, active shoulder abduction of about 180° occurs as result of simultaneous 120° GH joint abduction and 60° of scapulothoracic upward rotation.

142
Q

Principle 2

A

60° of upward rotation of scapula during full shoulder abduction is result of simultaneous elevation at SC joint combined with upward rotation at AC joint.

143
Q

Principle 3

A

Clavicle retracts at SC joint during shoulder abduction.

144
Q

Principle 4

A

Scapula posteriorly tilts and externally rotates during full shoulder abduction.

145
Q

Principle 5

A

Clavicle posteriorly rotates around its own axis during shoulder abduction.

146
Q

Principle 6

A

GH joint externally rotates during shoulder abduction.

147
Q

What is SICK scapula?

A

S=scapular malposition
I=inferior medial border prominence
C=coracoid pain and malposition
K=dykinesis of the scapula

148
Q

What are the three types of dykinesis?

A

Type I: Inferior medial scapular prominence
Type II: Medial scapular border prominence
Type III: Superomedial border prominence

149
Q

Type I and II dyskinesis associated with what?

A

SLAP lesions

150
Q

Type III associated with what?

A

impingement and rotator cuff lesion

151
Q

Dyskinesis shows what compared to normal patients?

A

Dyskinesis showed less scapular upward rotation, less clavicular elevation, and greater clavicular protraction

152
Q

What are the two categories of muscles of the shoulder complex?

A

proximal stabilizers and distal mobilizers

153
Q

Proximal stabilizers

A

originate on spine, ribs and cranium and insert on scapula and clavicle

154
Q

Distal mobilizers

A

originate on scapula and clavicle and insert on humerus and forearm

155
Q

What are the elevators for the ST joint?

A

Upper trapezius
Levator scapulae
Rhomboids

156
Q

What are the depressors of the ST joint?

A

Lower trapezius
Latissimus dorsi
Pectoralis minor
Subclavius

157
Q

What are the categories of muscles of the STJ?

A

elevator or depressor, protractor or retractors, upward and downward rotators

158
Q

What are the protractors of the STJ?

A

-serratus anterior

159
Q

What are the retractors of the STJ?

A

Middle trapezius
Rhomboids
Lower trapezius

160
Q

What are the upward rotators of the STJ?

A

Serratus anterior

Upper and lower trapezius

161
Q

What are the downward rotators of the STJ?

A

Rhomboids

Pectoralis minor

162
Q

What is the function of the elevators?

A

support posture of shoulder girdle (scapula and clavicle) and upper extremity

163
Q

When are all retractors active?

A

during pulling activities

164
Q

Complete paralysis of the trapezius reduces what?

A

retraction potential of the scapula

165
Q

What are the three categories elevators fall into?

A
  1. muscles that elevate (abduct or flex) at the GH joint
  2. scapular muscles that control upward rotation of SC joint
  3. rotator cuff muscles that control dynamic stability & arthokinematics at GH joint
166
Q

What are the GH joint muscles primarily responsible for elevation of arm?

A

Anterior and middle deltoid
Supraspinatus
Coracobrachialis
Biceps (long head)

167
Q

What are the STJ muscles responsible for elevation of arm?

A

Serratus anterior

Trapezius (upper & lower)

168
Q

What are the rotator cuff muscles primarily responsible for elevation of arm?

A

Supraspinatus
Infraspinatus
Teres minor
Subscapularis

169
Q

Supraspinatus _________ humeral head _________ toward abduction while also compressing joint

A

rolls, superiorly

170
Q

Subscapularis, infraspinatus, and teres minor exert ___________ force on humeral head to counteract excessive superior translation, especially that caused by deltoid contraction

A

downward translational

171
Q

What does the supraspinatus do during abduction?

A

Drives superior roll of humeral head
Compresses humeral head firmly against glenoid fossa
Creates semi-rigid spacer above humeral

172
Q

What does the infraspinatus, teres minor and subscapularis do during abduction?

A

Exert depression force on humeral head

173
Q

What does the infraspinatus and teres minor do during abduction?

A

externally rotate humerus

174
Q

What are direct or indirect causes of impingement syndrom

A
  1. Abnormal kinematics at GH and scapulothoracic joints (STJs)
  2. “Slouched” posture affecting alignment of STJ
  3. Fatigue, weakness, poor control, or tightness of muscles that control GH or STJ motions
  4. Inflammation and swelling of tissues within and around subacromial space
  5. Excessive wear and subsequent degeneration of tendons of rotator cuff muscles
  6. Instability of GH joint
  7. Adhesions within inferior GH joint capsule
  8. Excessive tightness in posterior capsule of GH joint (and associated anterior migration of humeral head toward lower margin of coracoacromial arch)
  9. Osteophytes forming around AC joint
  10. Abnormal shape of acromion or coracoacromial arch
175
Q

What are theFour Articulations within Elbow
and Forearm Complex?

A

Humero-ulnar joint
Humeroradial joint
Proximal radio-ulnar joint
Distal radio-ulnar joint

176
Q

What provides most of the elbow’s structural stability?

A

Tight fit b/w trochlea and trochlear notch at humero-ulnar joint

177
Q

What causes the medial/lateral axis of the elbow to course slight superiorly?

A

owing in part to distal prolongation of medial lip of trochlea
This asymmetry in trochlea causes ulna to deviate laterally relative to humerus

178
Q

What is a valgus angle?

A

Natural frontal plane angle made by extended elbow

179
Q

What can excessive cubitus valgus damage by overstretching?

A

ulnar nerve

180
Q

What do collateral ligaments do for the elbow?

A

provide stability?

181
Q

What does the medial collateral ligaments consist of?

A

anterior, posterior, and transverse fibers

anterior fibers are strongest and stiffest

182
Q

What do the collateral ligaments resist against?

A

valgus (abduction) force to elbow

183
Q

Where do the anterior fibers of medial collateral ligament arise and insert?

A

arise from anterior part of medial epicondyle and insert on medial part of coronoid process of ulna

184
Q

Where do posterior fibers of MCL arise and insert?

A

Posterior fibers attach on posterior part of medial epicondyle and insert on medial margin of olecranon process
Posterior fibers resist valgus force, as well as become taut in extremes of elbow flexion

185
Q

Where do the transverse fibers of the MCL arise and insert?

A

olecranon to coronoid process of ulna

Because these fibers originate and insert on same bone, they do not provide significant articular stability

186
Q

Paralysis of serratus anterior can occur from injury to what?

A

long thoracic nerve, spinal cord, cervical nerve root

Biomechanics (13 decks)

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