Shoulder Biomechanics Flashcards
How many degrees of freedom does the shoulder have
3… Can argue 4 (Horizontal ADD/ABD)
Which ways does the UE elevate (3)
- Flexion
- Abduction
- Scaption
What are the 7 motions of the UE
- Elevation
- ER
- IR
- Extension
- Adduction
- H ADD
- H ABD
What is the amount of elevation of the UE
170-180
What plane and axis does scaption occur in
Plane of the scapula and perpendicular axis
What is the angle for the POS
30 degrees anterior to coronal plane
What is ER at base of UE
40-60
What is ER at 90 ABD
90-100
What is IR at 90 ABD
45-60
What motions occur with FIR (3)
IR, Ext, ADD
What motions occur with FER (3)
ER, Flx, ABD
What is normal FIR
Spinous process T5
What is normal FER
Spinous process T3
What is horizontal ABD of UE
120-140
What is horizontal ADD of UE
40-60
What is extension of the UE
60-80
What position does the long head prevent the most motion
Elbow extension and pronation
What are the 4 joints of the shoulder
- GH
- ST
- AC
- SC
Where is the superior angle located in relation to spine
T2
Where is the inferior angle located in relation to spine
T7
What is the distance between spine of scapula and T3
2”
What is normal upward rotation of scapula at rest
3-5 degrees
Which rotation of the scapula is pathologic
Downward rotation
Upward rotation promotes what
Inferior stability
What happens with a downward rotated shoulder
Adaptive lengthening
What ligaments are adaptively lengthened with downward rotated shoulder (2)
- Superior GH
2. Coracohumeral
What is scapular dumping
Humeral head out of glenoid
What become tension loaded during scapular dumping (2)
- Superior GH
2. Coracohumeral
What does scapular dumping potentially cause
False positive sulcus test
What is the surgery for inferior instability
Vest over pants
What does AMBRI stand for
Atraumatic Multidirectional Bilateral Rehabilitation and rarely requires Inferior capsular shift
What does TUBS stand for
Traumatic Unilateral with Bankart lesion requires Surgery
What position normally causes scapular dumping
Kyphotic psture
What is the anterior tilt of the scapula
9-20
What is another name for anterior tilt
Anteflexion
Does the anterior tilt of scapula increase or decrease with age
Increase
What does exaggerated thoracic kyphosis and/or an abnormally elevated scapula cause
Increased anterior tilt of scapula
How big is the subacromial space
5 dimes
What 3 things are housed in the subacromial space
- RC muscles
- Long head of biceps
- Subacromial bursa
What type of impingement occurs at the subacromial space
External
How does anterior tilting effect impingement
Increases the chances of impingement
Where does internal impingement occur
Between humeral head and glenoid (posterior side)
What is the scapulo-clavicular angle at rest
50 degrees
What is the clavicular retraction angle at rest
20 degrees
What is the purpose of the scapula
Position the glenoid to allow optimal motion
What are the 5 motions of the scapulothoracic joint
- Elevation/Depression
- Protraction/Retraction
- Upward/Downward rotation
- Anterior/Posterior tilting
- Medial/Lateral rotation
Do the motions of the scapulothoracic joint occur separate
No, they occur together
What occurs with scapular elevation
Clavicular elevation and anterior tilt of scapula
What occurs with scapular depression
Clavicular depression and posterior tilt of scapula
What occurs with scapular protraction
Clavicular protraction and medial rotation of the scapula
What occurs with scapular retraction
Clavicular retraction and lateral rotation of the scapula
What axis does sagittal plane motion occur about in the scapula
M-L axis at the AC joint
What axis does rotary motion occur about in the scapula
Vertical axis in region of AC joint
What does scapular winging result in
Posterior displacement of the medial border of the scapula
What causes scapula winging
Pathology of the serratus anterior
What causes pathology to the serratus anterior most commonly
Long thoracic nerve palsy
What clavicular motion occurs with upward rotation of the scapula
Elevation of the clavicle
What clavicular motion occurs with downward rotation of the scapula
Depression of the clavicle
What is the normal configuration of the AC joint
Convex clavicle and concave acromion
What type of joint is the AC joint
Synovial joint with fibrocartilage disc
What scapular motions occur with UE elevation
Elevation, anterior tilting, upward rotation, protraction, and medial rotation
What are the rotary scapular motions (3)
- Anterior/Posterior tilting
- Medial/Lateral rotation
- Upward/Downward rotation
What type of joint is the SC joint
Synovial joint with articular disc
What SC joints movements occur with scapular motion (3)
- Elevation/Depression
- Protraction/Retraction
- Posterior/Anterior tilting
What is the configuration of the clavicle and sternum in the frontal plane
Convex clavicle on concave sternum
What is the configuration of the clavicle and sternum in the sagittal plane
Concave clavicle on convex sternum
What 2 motions are you most likely to have trouble with at the sternoclavicular joint
Elevation and retraction
What is the amount of elevation at the SC joint
45
What is the amount of depression at the SC joint
15
What is the amount of elevation at the SC joint from full depression
60
What is the amount of protraction and retraction at the SC joint
15
Rotation of the clavicle occurs about what type of axis
Longitudinal axis
What type of clavicular motion occurs with scapular upward rotation
Posterior rotation and elevation
When does the posterior rotation of the clavicle occur during scapular upward rotation
After 30 degrees of elevation of outer clavicle
What is the max rotation of the clavicle
30-55
Is the anterior rotation of the clavicle
Not from anatomical neutral
GH joint analogy
GH joint = golf ball on a tee
What is the max amount of the humeral head that is in contact with glenoid
1/3
What is the shape of the glenoid fossa
Pear shaped
Where does the glenoid have greater concavity and dimension
Superior to inferior
Most common to least common dislocation of shoulder (3)
- Anterior
- Posterior
- Inferior
Why are anterior and posterior dislocations more common than inferior dislocations
Due to decreased concavity of glenoid anterior to posterior
What is the angle of inclination of the humeral head
130-150
Which way does the humeral head face
Medially, superiorly, and posteriorly
Which way does the glenoid fossa face
Laterally, superiorly, and anteriorly
Is the glenoid and humeral head a perfect match
No 2/3 are perfect
What is GH ER at base
40-60`
What is GH ER at 90
90-100
What is GH IR at 90
45-60
What amount of elevation is the GH responsible for
0-120
Does the glenohumeral elevate the UE
No it is entire shoulder complex and scapulothoracic joint
For full UE elevation to occur what must happen
ER of humerus
What does ER of humerus do during UE elevation (2)
- Prevents impingement of greater tuberosity against acromion
- Provides greater humeral head articulating surface
What is the amount of glide with any UE motion
2mm
What is scapulohumeral rhythm
Humerus and scapula working together to provide smooth motion of UE
what is the ratio of humeral motion to scapular motion
2:1
What is it called when the scapula doesn’t move properly
Scapulodiskinesis
What does scapulohumeral rhythm allow for (3)
- Increase elevation ROM
- Inferior stability of the GH joint
- Maintain optimal length tension relationship for scapulohumeral musculature
How much flexion or scaption makes up phase 1A of UE elevation
Scaption: 0-30
Flexion: 0-60
True or False:
The motion during phase 1A is predominantly GH motion
True
Where is the axis of rotation during phase 1A
Medial part of scapular spine
How much flexion or scaption occur during phase 1B UE elevation
Flexion: 60-90
Scaption: 30-90
True or False:
In phase 1B there is consistent upward scapular rotation
True
Where is the axis of rotation during phase 1B
Line connecting root of the spine of scapula and SC joint
During phase 2A of UE elevation how much flexion and scaption occur
90-120
What happens to clavicular elevation during phase 2A
It tension loads costoclavicular ligaments
What is the limit of costoclavicular ligament elevation
30
As the clavicle elevation slows what happens to the axis of rotation
Shifts to the AC joint
How much flexion and scaption occur during phase 2B of UE elevation
120-end rang
Where is the axis of rotation during phase 2B
The AC joint
During phase 2B what is scapular upward rotation accompanied by
Coracoid depression
Why is scapular upward depression accompanied by coracoid depression
Anterior tilting of scapula
What does the depression of the coracoid process cause
Tension load to coracoclavicular ligaments
What does the tension of the coracoclavicular ligament do to the clavicle
Imparts a downward force on the posterior clavicle through conoid ligament
What does the downward force on the posterior clavicle cause
Posterior rotation of the clavicle
What does the clavicles crank shape result in
30 further elevation of the lateral clavicle
What does posterior clavicle rotation aid in
Scapular posterior tilting/tipping
What are the muscles that cause upward rotation of the scapula (4)
- Upper trapezius
- Lower trapezius
- Upper serratus anterior
- Lower serratus anterior
During phase 1B what causes upward rotation of the scapula (2)
- Upper trapezius
2. Lower serratus anterior
During phase 2B what causes upward rotation of the scapula (2)
- Lower trapezius
2. Lower serratus anterior
What is more important for abduction serratus or trapezius
Trapezius
What is more important for flexion serratus or trapezius
Serratus
With serratus paralysis what does abduction and flexion look like
Abduction: ROM may be full
Flexion: Reduced ROM
With trapezius paralysis what does abduction and flexion look like
Abduction: ROM to 75 degrees
Flexion: ROM may be full
How much upward rotation can the trapezius produce in the sagittal plane
20 degrees
In anatomical neutral what motion occurs at the humerus due to the deltoid
Superior translation
What helps start to UE elevation
Supraspinatus
How does the supraspinatus help start UE elevation
It compresses the humeral head into the glenoid giving the humeral head something to pivot around
What muscles help with inferior glide of the humeral head (3)
- Subscapularis
- Infraspinatus
- Teres minor
True or False:
If you have shoulder instability you should strengthen all of the RC muscle
True
What is the space below the coracoacromial arch and humeral head called
Outlet view for radiographs
What is the space used for
Look at space to determine if it is narrowed and if so are osteophytes or hooking of acromion present
Why do we get superior glide of the humeral head
RC pathology or adhesive capsulitis
What happens to the RC tendon when it is torn
Retract back toward origin
What 5 things provide stability to the GH joint
- Negative intraarticular pressure
- Labral concavity compression
- Capsular constraint
- Scapulohumeral muscle
- Capsuloligamentou restraint
What is venting of the GH joint
Lose negative pressure effect due to puncture in the GH capsule
What does venting of GH joint produce
Immediate inferior subluxation
True or False:
Full thickness RC tears can cause venting
True
With the labrum in contact the GH joint resists dislocation forces up to what percent of the compressive loads
64%
With the labrum removed how much does the resistance of dislocationdecrease
20%
What is a bony bankart
Avulse anterior labrum with bone
What muscles compress the humeral head into the glenoid cavity (4)
- Deltoid
- Supraspinatus
- Infraspinatus
- Teres minor
What percent of your body weight can the GH joint resist at 90 degrees of elevation when everything is intact
90%
What is cocontraction
Contracting muscles all the way around the joint
True or False:
Closed chain allows for cocontraction
True
True or False:
Scapulohumeral musculature aides in centering the humeral head in glenoid
True
When are the GH ligaments able to restrain translation
When osteokinematic motion takes slack out of the structur
Shoulder ligaments are stressed where
End range
What are stressed at mid range
Shoulder musculature
What is isometricity
There will always be some tension in the ligament no matter the range
What does end range osteokinematic motion do
Take slack out of a specific ligament or capsule
What happens when the ligament or capsule is passively tensioned
They contribute to an obligatory humeral head translation
Which way is the humeral head translation in relation to tensioned ligament or capsule
The opposite direction
What ligament or capsule is tension loaded during IR and which way is the translation
Posterior capsule is tension loaded and an anterior translation occurs
What are the 4 main capsuloligamentous structures of the GH joint
- Superior GH ligament
- Middle GH ligament
- Inferior GH ligament
- Coracohumeral ligament
What are the 3 parts of the Inferior GH ligament
- Anterior band
- Axillary pouch (accordion folder)
- Posterior band
What is the main capsuloligamentous structures that provide stability during flexion
Anterior coracohumeral ligament
What is the main capsuloligamentous structures that provide stability during abduction
Inferior posterior capsule
What is the main capsuloligamentous structures that provide stability during IR
Middle posterior capsule
What is the main capsuloligamentous structures that provide stability during ER
Superior GH ligament
In anatomical neutral what is the primary stabilizer to ER and anterior head translation
SGHL
In anatomical neutral what is the secondary stabilizer to ER and anterior head translation
MGHL
True or False:
There is a relative lack of support by the posterior capsule against posterior translation in anatomical neutral
True
What resists anterior humeral translation at 45 degrees of scaption
MGHL
True or False:
The posterior band of IGHL provides some capsule stabilization against posterior translation of humeral head at 45 degrees scaption
True
What stabilizes against anterior humeral head translation at 90 degrees of scaption
IGHL anterior band
What stabilizes against posterior humeral head translationat 90 degrees of scaption
IGHL posterior band
What happens to the anterior and posterior bands of the IGHL during IR
Anterior band goes below the equator
Posterior band goes above the equator
What happens to the anterior and posterior bands of the IGHL during ER
Anterior band goes above the equator
Posterior band goes below the equator
True or False:
When there is a tear or laxity on one side will eventually cause laxity or a tear on the opposite side
True
What happens when you decrease the compressive force
You increase the shear force
Motivation
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