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S1 Biomechanics > Biomechanics Shoulder > Flashcards

Biomechanics Shoulder Flashcards

1
Q

shoulder complex mobility/stability

A

greatest mobility of any joint

inherently unstable

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2
Q

how does the shoulder serve the hand through mobility and stability

A

mobility
-shoulder motion (w/ elbow) allows for infinite possibilities of hand positioning
stability
-must be capable of stability to maximize hand function

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3
Q

clavicle position

A

20 degrees posterior to frontal plane

10 degrees superior to transverse plane

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4
Q

what muscles attach to acromion

A

deltoid

lower/mid trap

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5
Q

glenoid fossa

  • shape
  • % surface area of humeral head
  • what attaches around outside?
A

pear shaped
25% surface area
glenoid labrum attaches around bony rim

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6
Q

glenoid labrum

  • function
  • what attaches at superior glenoid
A

deepens glenoid

LHBT attaches at superior glenoid

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7
Q

SLAP lesion

  • what is it?
  • what population typically?
A

superior labral lesion
seen in overhead athletes
(superior labrum ant-post)

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8
Q

normal glenoid fossa orientation frontal plane

-when is the risk of should instability increased?

A

4 upward tilt
adult range
-7 downward tilt to 16 upward tilt
<5 superior tilt = increase in risk of shoulder instability

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9
Q

normal glenoid fossa orientation transverse plane

A

35 degrees anterior to frontal plane

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10
Q

humeral head angle of inclination

  • range
  • shoulder instability above what angle?
A

135
range: 130-135
shoulder instability above 140

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11
Q

humeral head angle of torsion

A

30-50 retroversion

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12
Q

shoulder complex joints

A

SC
AC
GH
scapulothoracic (not true joint)

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13
Q

movement of scapula on thorax controlled by motion at…

A

AC and SC joints

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14
Q

terms used to describe static postural scapular position

A 
elevated/depressed
protracted/retracted
upwardly/downwardly rotated
anteriorly/posteriorly tilted
-involuntary; occurs to stay with thorax
internally/externally rotated scapula
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15
Q

scapular winging is a consequence of what scapular position

A

IR

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16
Q

SC joint

  • links shoulder complex to _____
  • why does it have a paradoximal function?
A

axial skeleton

has to be stable, but mobile

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17
Q

SC joint

  • type of joint
  • -describe
A 
synovial joint: saddle (modified)
proximal clavicle
-convex along long diameter
-concave along transverse diameter
stermum: reciprocal shapes
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18
Q

SC joint articular disc

  • composition
  • function
A 
fibrocartilage
functions
-improves congruity
-shock absorber
separates SC joint into two joint cavities
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19
Q

SC joint connective tissues

A 
joint capsule
SC ligament
costoclavicular ligament
-limits all motions but depression
interclavicular ligament
-limits depression
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20
Q

SC stability assisted by what muscles

A

SCM
sternothyroid
sternohyoid
subclavius

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21
Q

SC joint degrees of freedom

A

3

  • elevation/depression
  • protraction/retraction
  • axial rotation
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22
Q

clavicle elevation/depression (SC joint)

-available range

A

45 elevation

10 depression

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23
Q

clavicle elevation/depression arthrokinematics

  • elevation roll and glide direction
  • depression roll and glide direction
A

elevation
-superior roll, inferior glide
depression
-inferior roll, superior glide

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24
Q

clavicular protraction/retraction (SC joint)

  • available range
  • driver of what motion
A

range
-15-30 degrees each direction
drives of scapular pro/retraction

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25
Q

clavicular protraction/retraction arthrokinematics

A

retraction
-posterior roll and glide
protraction
-anterior roll and glide

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26
Q

clavicular axial rotation (SC joint)

-superior aspect of clavicle rotates _____ (direction and amount) with shoulder abduction or flexion

A

posterior 20-35 degrees

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27
Q

clavicular axial rotation arthrokinematics

A

spin of clavicle on sternum

mechanically linked with abduction/flexion of shoulder

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28
Q

AC joint connective tissues

  • names
  • which is primary stabilizer
  • reinforced by…
A 
joint capsule
AC ligament
coracoclavicular ligament
-trapezoid portion
-conoid portion
-primary static stabilizer
reinforced by
-deltoid and trapezius attachments
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29
Q

AC motions

A

upward/downward rotation
-“frontal plane” but really scapular plane
anterior/posterior tipping
-sagittal plane
scapular int/ext rotation
-transverse plane
motions fine tune scapular position through subtle motions

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30
Q

scapular position (normal)

A

between ribs 2 and 7
medial border 6 cm from t-spine
10 degree anterior tilt
slight upward rotation

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31
Q

what occurs during scapular elevation

A

elevation of clavicle at SC
downward rotation at AC
fine tuning at AC
depression = opposite movments

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32
Q

what occurs during scapular protraction

A

protraction of clavicle at SC

horizontal plane adjustment at AC to keep scapula in contact with thorax

33
Q

what occurs during scapular upward elevation

A

SC clavicular elevation
AC upward rotation
critical motion to allow normal raising of arm over head

34
Q

GH joint capsule

  • encloses…
  • attachments
A 
encloses GH joint
-fibrous capsule
-synovial capsule
attachments
-glenoid rim
-anatomic neck
35
Q

GH joint capsule

  • how tight it is?
  • what is the inferior portion called
A 
loose fitting
-allows for mobility
inferior portion
-axillary pouch
-involved in frozen shoulder
36
Q

RC tendons

  • blend into…
  • function
A

blend into capsule
when they contract, they tension capsule
creates dynamic tension in capsule
centers humeral head in glenoid

37
Q

GH capsular ligaments (bands)

A

superior GH ligament
middle GH ligament
inferior GH ligament
review table 5-1, p. 139

38
Q

inferior GH ligament portions

A

anterior
posterior
axillary pouch

39
Q

other GH ligaments

-functions

A

coracohumeral ligament
-superior location
-tightens with ER, extension, and inferior humeral translation
transverse humeral ligament
-tethers long head of biceps tendon in bicipital groove

40
Q

what provides GH stability with the arm at the side

A 
SGHL and CHL
-limit inferior and A/P translation
-limit ER
posterior capsule
-limits posterior translation
41
Q

what provides GH stability with arm in mid-elevation (45-60)

A

MGHL
-limits anterior translation and ER
posterior capsule
-limits posterior translation

42
Q

what provides GH stability with arm above 90 elevation

A 
IGHL anterior band
-limits anterior translation and ER
IGHL axillary pouch
-limits inferior, anterior, and posterior translation
IGHL posterior band
-limits posterior translation and IR
43
Q

GH capsuloligamentous complex summary

A

arm at side: superior capsule and ligaments are taught
as arm is elevated, gradual shift of ligamentous tension from superior capsule and ligaments to inferior capsule and ligaments
arm overhead: the “hammock” (IGHL) is primary static support

44
Q

other GH non-contractile stability mechanisms

A

negative intra-articular pressure in joint creates relative vacuum
presence of intact glenoid labrum
-deepens socket
-suction cup effect

45
Q

coracoacromial arch

  • formed by
  • structures in subacromial space
A 
formed by acromion and CA ligament
structures
-LHBT
-supraspinatus
-superior capsule
-subacromial bursa
46
Q

bursae of shoulder

-location

A

subscapular
-extension of GH synovial capsule
-lies deep to subscapularis
subacromial

47
Q

GH close-packed positioin

A

GH abduction and ER

48
Q

GH loose-packed position

A

55 abduction

30 horizontal adduction

49
Q

shoulder impingement

-caused by…

A

contact between humeral head against inferior acromion

50
Q

scaption

  • what
  • benefit
A

abduction in scapular plane

better fit of humeral head in glenoid - less potential for pinching

51
Q

why do you have less ER at the GH joint with the arm at the side compared to in 90 abduction

A

less motion due to coracohumeral ligament

52
Q

GH IR/ER arthrokinematics

A

IR
-anterior roll, posterior glide
ER
-posterior roll, anterior glide

53
Q

scapulohumeral rhythm purpose

A

distributes motion between multiple joints
maintains optimal glenoid position for stability
maintains effective muscle length-tension relationship

54
Q

kinematic principles of should abduction (6)

A

180 shoulder complex abduction is result of 120 GH abduction and 60 ST upward rotation
60 ST upward rotation is result of SC elevation and AC upward rotation
clavicle retracts at SC during shoulder abduction
scapula posteriorly tilts and externally rotates at AC joint during shoulder abduction
clavicle posteriorly rotates at SC during abduction
GH externally rotates during abduction

55
Q

scapulohumeral rhythm early phase

  • what range is this?
  • what occurs
A

initial 90 elevation
initial 30-50: setting
-minimal ST motion, most GH motion
-scapula is “seeking stability”
overall, 2 humeral elevation for each 1 of scapular motion
-30 ST upward rotation (20-25 SC elevation; 5-10 AC upward rotation)
-60 GH motion

56
Q

scapulohumeral rhythm late phase

  • what range is this
  • what occurs
A

elevation above 90
2 humeral elevation of each 1 scapular motion
-30 upward rotation at ST joint (5 SC elevation; 25 AC upward rotation)
-60 GH motion
25 posterior rotation of clavicle as SC
posterior tilting and ER at AC
15 retraction of clavicle at SC

57
Q

scapulohumeral rhythm summary

A

overall 180 elevation
-120 GH
-60 ST
early range: SC joint is greatest contributor to ST motion
late range: SC posterior rotation and AC upward rotation contribute to ST motion

58
Q

possible contributors to abnormal shoulder kinematics

A

muscle fatigue: rotator cuff and periscapular muscles
muscle length issues (e.g. short pec minor)
abnormal T-spine posture/movmenet
intra-articular shoulder pathology
-adhesive capsulitis
-RC tear
-labral tear

59
Q

for test, be able to answer following (review anatomy)

A

if _____ nerve is damaged, _____ muscle/movmeent might be affected

60
Q

sensory supply to shoulder region

A 
midcervical nerve roots (C3-C6)
-SC: C3-4
-AC and GH: C5-6
peripheral nerves
-axillary
-suprascapular
61
Q

elevators of ST joint

A

upper trap
levator scapulae
rhomboids

62
Q

why might CN XI palsy lead to instability of GH joint

A

CH XI innervates UT

UT gives scapula its upward tilt

63
Q

depressors of ST joint

A

lat
LT
pec minor
subclavius

64
Q

CKC action of scapular depressors

A

can elevate the thorax

65
Q

ST joint protractor

-why

A

serratus anterior

  • long moment arm
  • critical in shoulder complex function to properly position scapula
66
Q

ST joint retractors

-co-contraction will…

A

middle trap
rhomboids
LT
con-contraction: neutralization of scapular rotation and elevation/depression

67
Q

GH abductors

A

middle delt
supraspinatus
upper fibers of infraspinatus and subscap

68
Q

shoulder flexors

A

anterior delt
coracobrachialis
LHBT

69
Q

middle deltoid and supraspinatus

  • explain relationship
  • what occurs when one or both is paralyzed
A

similar moment arms
contribute = shares of total abductor torque
without deltoid: weak but full abduction
without supra: weak abduction and not full ROM
without both: no abduction

70
Q

ST joint upward rotators

A

UT
LT
serratus anterior

71
Q

UT, LT, and SA force couple

-explain

A

all three upwardly rotate

elevation/depression is neutralized

72
Q

which part of the RC causes…

  • superior roll
  • inferior glide
  • ER
  • IR
A 
superior roll
-supraspinatus
inferior glide
-lower cuff
ER
-posterior cuff
IR
-anterior cuff
73
Q 
shoulder complex abduction
muscles that...
-move humerus
-control scapular motion
-control humeral head
A 
move humerus
-deltoid
-supra
control scapular motion
-trap
-SA
control humeral head
-RC
74
Q

muscles that adduct and extend arm

-which shoulder girdle muscles participate in adduction/extension

A 
posterior delt
lat
teres major
LH triceps brachii
pec major
teres minor and infra
downward rotators participate in adduction/extension
75
Q

GH IR muscles

A 
subscap
pec major
lat
teres major
larger muscle mass than ER
greater torque
76
Q

GH ER muscles

-function

A

infra
teres minor
posterior delt
decelerators of high velocity IR contractions

77
Q

function of the following muscles for dynamic stability

  • ST muscles
  • RC
A

ST muscles
-critical for providing stable base for shoulder function and appropriately positioning scapula
RC
-co-contraction of RC is key
-creates dynamic stability
-compresses and centers humeral head in glenoid fossa

78
Q

ideal shoulder profile during static observation

A 
anterior
-clavicle angle (10 upward)
scapular position
-between T2 and T7
-35 anterior to frontal plane
-5-6 cm from midline thorax
-flat against thorax
-medial border relatively parallel to T-spine (NOT downwardly rotated)
humeral head
-<1/3 anterior to acromion
-neutral rotation

S1 Biomechanics (12 decks)

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