Biomechanics Shoulder Flashcards
1
Q
shoulder complex mobility/stability
A
greatest mobility of any joint
inherently unstable
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
3
Q
clavicle position
A
20 degrees posterior to frontal plane
10 degrees superior to transverse plane
4
Q
what muscles attach to acromion
A
deltoid
lower/mid trap
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
6
Q
glenoid labrum
- function
- what attaches at superior glenoid
A
deepens glenoid
LHBT attaches at superior glenoid
7
Q
SLAP lesion
- what is it?
- what population typically?
A
superior labral lesion
seen in overhead athletes
(superior labrum ant-post)
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
9
Q
normal glenoid fossa orientation transverse plane
A
35 degrees anterior to frontal plane
10
Q
humeral head angle of inclination
- range
- shoulder instability above what angle?
A
135
range: 130-135
shoulder instability above 140
11
Q
humeral head angle of torsion
A
30-50 retroversion
12
Q
shoulder complex joints
A
SC
AC
GH
scapulothoracic (not true joint)
13
Q
movement of scapula on thorax controlled by motion at…
A
AC and SC joints
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
15
Q
scapular winging is a consequence of what scapular position
A
IR
16
Q
SC joint
- links shoulder complex to _____
- why does it have a paradoximal function?
A
axial skeleton
has to be stable, but mobile
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
18
Q
SC joint articular disc
- composition
- function
A
fibrocartilage functions -improves congruity -shock absorber separates SC joint into two joint cavities
19
Q
SC joint connective tissues
A
joint capsule SC ligament costoclavicular ligament -limits all motions but depression interclavicular ligament -limits depression
20
Q
SC stability assisted by what muscles
A
SCM
sternothyroid
sternohyoid
subclavius
21
Q
SC joint degrees of freedom
A
3
- elevation/depression
- protraction/retraction
- axial rotation
22
Q
clavicle elevation/depression (SC joint)
-available range
A
45 elevation
10 depression
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
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
25
clavicular protraction/retraction arthrokinematics
retraction
-posterior roll and glide
protraction
-anterior roll and glide
26
clavicular axial rotation (SC joint)
| -superior aspect of clavicle rotates _____ (direction and amount) with shoulder abduction or flexion
posterior 20-35 degrees
27
clavicular axial rotation arthrokinematics
spin of clavicle on sternum
| mechanically linked with abduction/flexion of shoulder
28
AC joint connective tissues
- names
- which is primary stabilizer
- reinforced by...
```
joint capsule
AC ligament
coracoclavicular ligament
-trapezoid portion
-conoid portion
-primary static stabilizer
reinforced by
-deltoid and trapezius attachments
```
29
AC motions
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
30
scapular position (normal)
between ribs 2 and 7
medial border 6 cm from t-spine
10 degree anterior tilt
slight upward rotation
31
what occurs during scapular elevation
elevation of clavicle at SC
downward rotation at AC
fine tuning at AC
depression = opposite movments
32
what occurs during scapular protraction
protraction of clavicle at SC
| horizontal plane adjustment at AC to keep scapula in contact with thorax
33
what occurs during scapular upward elevation
SC clavicular elevation
AC upward rotation
critical motion to allow normal raising of arm over head
34
GH joint capsule
- encloses...
- attachments
```
encloses GH joint
-fibrous capsule
-synovial capsule
attachments
-glenoid rim
-anatomic neck
```
35
GH joint capsule
- how tight it is?
- what is the inferior portion called
```
loose fitting
-allows for mobility
inferior portion
-axillary pouch
-involved in frozen shoulder
```
36
RC tendons
- blend into...
- function
blend into capsule
when they contract, they tension capsule
creates dynamic tension in capsule
centers humeral head in glenoid
37
GH capsular ligaments (bands)
superior GH ligament
middle GH ligament
inferior GH ligament
review table 5-1, p. 139
38
inferior GH ligament portions
anterior
posterior
axillary pouch
39
other GH ligaments
| -functions
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
what provides GH stability with the arm at the side
```
SGHL and CHL
-limit inferior and A/P translation
-limit ER
posterior capsule
-limits posterior translation
```
41
what provides GH stability with arm in mid-elevation (45-60)
MGHL
-limits anterior translation and ER
posterior capsule
-limits posterior translation
42
what provides GH stability with arm above 90 elevation
```
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
GH capsuloligamentous complex summary
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
other GH non-contractile stability mechanisms
negative intra-articular pressure in joint creates relative vacuum
presence of intact glenoid labrum
-deepens socket
-suction cup effect
45
coracoacromial arch
- formed by
- structures in subacromial space
```
formed by acromion and CA ligament
structures
-LHBT
-supraspinatus
-superior capsule
-subacromial bursa
```
46
bursae of shoulder
| -location
subscapular
-extension of GH synovial capsule
-lies deep to subscapularis
subacromial
47
GH close-packed positioin
GH abduction and ER
48
GH loose-packed position
55 abduction
| 30 horizontal adduction
49
shoulder impingement
| -caused by...
contact between humeral head against inferior acromion
50
scaption
- what
- benefit
abduction in scapular plane
| better fit of humeral head in glenoid - less potential for pinching
51
why do you have less ER at the GH joint with the arm at the side compared to in 90 abduction
less motion due to coracohumeral ligament
52
GH IR/ER arthrokinematics
IR
-anterior roll, posterior glide
ER
-posterior roll, anterior glide
53
scapulohumeral rhythm purpose
distributes motion between multiple joints
maintains optimal glenoid position for stability
maintains effective muscle length-tension relationship
54
kinematic principles of should abduction (6)
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
scapulohumeral rhythm early phase
- what range is this?
- what occurs
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
scapulohumeral rhythm late phase
- what range is this
- what occurs
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
scapulohumeral rhythm summary
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
possible contributors to abnormal shoulder kinematics
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
for test, be able to answer following (review anatomy)
if _____ nerve is damaged, _____ muscle/movmeent might be affected
60
sensory supply to shoulder region
```
midcervical nerve roots (C3-C6)
-SC: C3-4
-AC and GH: C5-6
peripheral nerves
-axillary
-suprascapular
```
61
elevators of ST joint
upper trap
levator scapulae
rhomboids
62
why might CN XI palsy lead to instability of GH joint
CH XI innervates UT
| UT gives scapula its upward tilt
63
depressors of ST joint
lat
LT
pec minor
subclavius
64
CKC action of scapular depressors
can elevate the thorax
65
ST joint protractor
| -why
serratus anterior
- long moment arm
- critical in shoulder complex function to properly position scapula
66
ST joint retractors
| -co-contraction will...
middle trap
rhomboids
LT
con-contraction: neutralization of scapular rotation and elevation/depression
67
GH abductors
middle delt
supraspinatus
upper fibers of infraspinatus and subscap
68
shoulder flexors
anterior delt
coracobrachialis
LHBT
69
middle deltoid and supraspinatus
- explain relationship
- what occurs when one or both is paralyzed
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
ST joint upward rotators
UT
LT
serratus anterior
71
UT, LT, and SA force couple
| -explain
all three upwardly rotate
| elevation/depression is neutralized
72
which part of the RC causes...
- superior roll
- inferior glide
- ER
- IR
```
superior roll
-supraspinatus
inferior glide
-lower cuff
ER
-posterior cuff
IR
-anterior cuff
```
73
```
shoulder complex abduction
muscles that...
-move humerus
-control scapular motion
-control humeral head
```
```
move humerus
-deltoid
-supra
control scapular motion
-trap
-SA
control humeral head
-RC
```
74
muscles that adduct and extend arm
| -which shoulder girdle muscles participate in adduction/extension
```
posterior delt
lat
teres major
LH triceps brachii
pec major
teres minor and infra
downward rotators participate in adduction/extension
```
75
GH IR muscles
```
subscap
pec major
lat
teres major
larger muscle mass than ER
greater torque
```
76
GH ER muscles
| -function
infra
teres minor
posterior delt
decelerators of high velocity IR contractions
77
function of the following muscles for dynamic stability
- ST muscles
- RC
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
ideal shoulder profile during static observation
```
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
```
