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95 Cards in this Set

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Define the bones of the shoulder complex
clavicle, scapula, humerus
Most mobile joint in the body
glenohumeral joint
Primary mechanism of stability in the UE
Muscles; the arm is only connected to the axial skeleton at the SC joint
Describe dynamic stabilization
Situation where passive elements (bones, etc) provide little support and stability of structure is dependent on active muscle contraction forces.
Advantages of dynamic stabilization
Wide range of mobility, good stability when function is normal.
Movement at the scapulothoracic interface is dependent on movement at what joint(s)?
The stenoclavicular and/or acromioclavicular joints
Relative contributions of the SC, AC and GH joints for movement of UE in flexion or abduction
2/3 glenohumeral
1/3 SC and AC (scapular)
List the main components of the sternoclavicular joint
- medial clavicle with manubrium and first costal cartilage
- plane/mild saddle
- synovial
- 3 rotary degrees of freedom
- 3 translatory degrees of freedom
- capsule
- joint disk
- 3 major ligaments
Describe the shape of the SC joint at rest
wedge-shaped open superiorly
Attachments at superior portion of medial clavicle
- SC joint disck
- interclavicular ligament
Attachments of the sternoclavicular disk
- upper portion to postereosuperior clavicle
- lower portion to manubrium, 1st costal cartilage, anterior and posterior capsule
- Therefore, the disk acts like a hinge/pivot
Position of strenoclavicular disk in the joint space
Diagonally transects the SC joint space and divides into 2 cavities
Describe different pivot points in sternoclavicular joint based on movement
- elevation/depression clavicle: upper attachment as pivot
- protraction/retraction: lower attachment as pivot
Axis of motion of the sternoclavicular joint
At location of the costoclavicular ligament (lat and ant to joint)
List the three major ligaments of the SC joint
- sternoclavicular ligaments
- costoclavicular ligament
- interclavicular ligament
Describe clavicular rotation with elevation and depression
- elevation: lat clavicle rotates upward
- deperession: lat clavicle rotates downward
Possible ROM at the SC joint
- 50 degrees of elevation
- 15 degrees of depression
- 15 degrees protraction
- 20 degrees of retraction
- min/10 degrees of ant rotation
- 50 degrees posterior rotation
This ROM is usually not used functionally
Describe clavicular rotation with protraction and retraction
- protraction: lat clavicle rotates anteriorly
- retraction: lat clavicle rotates posteriorly
From resting, which direction (in A/P) can the clavicle rotate around the long axis?
Posteriorly (bring inferior surface anteriorly)
Describe the balance of incongruence and joint degeneration in the sternoclavicular joint
SC joint is incongruent BUT with disc matches well, dissipates force and RARELY have degenerative changes.
SC joint dislocations represent what % of joint dislocations in the body?
~1%
The AC joint attaches...
the scapula to the clavicle
Describe the AC joint
- plane
- synovial
- 3 rotational degrees of freedom
- 3 translational degrees of freedom
- joint capsule
- 2 major ligaments
- may or may not have a disk
3 general purposes of the AC joint
- allow additional rotation of scapula on thorax
- allow adjustments in tipping on thorax as arm moves
- transmission of forces from upper extremity to clavicle
Describe the articular facets of the AC joint
- incongruent
- large range and may be flat, concave-convex or reversed
- intra-articular mvnts at this joint are not predictable
Describe relationship between AC joint facet shape and shear forces
The more vertical the facet shape, the more prone to joint wear from shear forces.
Describe the development (age2...) of the AC joint
Fibrocartilaginous union until age 2. As UE is used the joint space develops and there may or may not be a "meniscoid" fibrocartilage remnant (disk) within the joint
AC joint capsule strength
It is weak
3 ligaments of the AC joint
- superior acromioclavicular
- inferior acromioclavicular
- coracoclavicular
Why is the superior support of the AC joint better than the inferior?
- fibers of superior AC ligament are reinforced by fibers of the deltoid and trapezius
The clavicle and scapula are most most strongly connected by the
coracoclavicular ligament; provides most of the joint's stability
2 parts of the coracoclavicular ligament:
- trapezoid laterally (more horizontal) resists posterior
- conoid medially (more vertical) resists sup/inf
- both limit upward rotation of the scapula at AC joint
What separates the trapezoid and conoid ligaments of the AC joint?
These are the 2 components of the coracoclavicular joint
- separated by adipose tissue and a large bursa
Where on the clavicle does the coracoclavicular ligament attach?
- undersurface
- the conoid attaches very posteriorly
2 most important roles of the coracoclavicular ligament
- Transfer forces from bearing weight on arm to strong SC joint
- coupling posterior rotation of clavicle to scapula rotation during elevation of upper extremity.
Movements at the AC joint occur in relation to what?
The plane of the scapula
Helpful to focus on the position of _____ for external and internal rotation at the AC joint
position of the glenoid fossa secondary to movement of scapula
List 4 important reasons to maintain correct position of the glenoid fossa
- maintain congruency with humeral head
- maximize function of GH muscles, capsule and ligaments
- maximize stability of GH joint
- maximize ROM of arm
ROM at AC joint
- 30 degrees of internal/external roation
- 30 degrees of ant/post tipping
- 30 degress of upward rotation
- 15 degree of downward rotation
Describe the relationship between rotation of the scapula and rotation of the GH fossa
They are the same; upward rotation of the scapula rotates the glenoid fossa up
Upward/downward rotation of the scapula is limited by the
coracoclavicular ligament
Describe the process of the coracoclavicular ligament "allowing" the scapula to rotate upward
- The coracoclavicular ligamnet attaches inferiorly and posteriorly on the clavicle.
- the clavicle rotates posteriorly
- the coracoclavicular ligament then has slack and allow the AC joint to "open up"
Describe general progression of AC joint degeneration
- degeneration starts in 20s
- joint space commonly narrowed in 60s
Why is AC joint vulnerable to degeneration?
Incongruent facets lead to high pressure per surface area
General description of AC joint dislocation classification
- graded on amount and direction of displacement
-Usually VI types
- Types I-III result from inferior displacement of the acromion from loss of support of coracoclavicular ligaments
- Type IV-VI injuries have posteriorly displaced lateral clavicle and are surgical
% of residual symptom rates in non-surgical AC joint injuries
40-70% (type I-type III) of people still have symptoms
How to tell a person had an old type III unilateral AC joint dislocation
On physical exam, the injured shoulder will have a step down to the acromion (relative clavicle is more superior)
Is the scapulothoracic joint a closed chain or open?
Closed; any movement at the scapulothoracic junction MUST cause movement at the acromioclavicular and/or the sternovclavicular joints.
What is the resting position of the scapula
- medial edge aprox 5 cm from midline
- internally rotated 40 degrees
- tipped anteriorly 15 degrees
- upwardly rotated 15 degrees from AC axis (or 2 degrees compared to vertebral line)
What is the primary scapular motion that occurs at the AC joint?
upward/downward rotation
List the primary translatory motions of the scapula
- elevation/depression
- protraction/retraction
Does the scapula ever have a pure movement?
No; the linkage to both the acromion and the clavicle prevents isolated movements.
What is the primary movement of the scapula when the arm is elevated?
upward rotation (of the scapula on the thorax)
ROM of the scapula
- 60 degrees of upward rotation
- others not well defined
Shrugging the shoulders occurs primarily through what?
Elevation of the clavicle at the SC joint; subtle changes in this joint also keep the scapula on the thorax during shrug
Scapular protraction/retraction is a combination of what movements?
- internal/external rotation at the AC joint
- protraction/retraction at the SC joint
Upward rotation of the scapula is a combination of what movements?
- elevation of the clavicle
- Posterior rotation at the SC joint
- Rotation at AC joint
Anterior/posterior tipping of the scapula typically occur ______ and in association with _________
- at the AC joint
- in association with ant/post rotation of the clavicle at the SC joint
Stability of the scapula depends on
- stability of SC and AC joints
- Muscle attachments pulling the scapula into the thorax
Which is bigger: the glenoid fossa or the humeral head?
The humeral head is bigger
What is the most common orientation of the glenoid fossa in relation to the scapula
7 degrees of retroversion (although may be larger or even anteverted)
Which direction of the glenoid fossa is most curved?
It is typically more curved in its LENGTH
Shape of articular cartilage of the glenoid fossa
- Increased radius of curvature over just bone
- Thinner in middle and thick at periphery of cartilage
Proximal and distal components of the GH joint
- proximal: glenoid fossa
- distal: the humeral head
Shape of the humeral head
1/3-1/2 of a sphere
Where is the head of the humerus in relation to the shaft and humeral condyles?
The head is medial, superior and posterior
What is the angle of inclincation of the humerus
- 130-150 degrees in the frontal plane
(axis through humeral head and neck in relation to longitudinal axis)
What is the angle of torsion of the humerus?
- 30 degree posteriorly
(angle through the humeral head and neck in relation to axis through the condyles)
Why is posterior torsion of the humerus beneficial?
Is helps match the resting GH joint from the internally rotated scapula
Pitchers often have increased GH external rotation and decreased GH medial rotation. What is their likely retro/anteversion of the humeral head and what would they be at risk for?
- humeral retroversion
- increased risk of posterior subluxation at end range
What is the GH joint articulation like at rest?
Little contact between joint surfaces; inferior humeral head rests on a small part of the inferior glenoid fossa
The glenoid labrum attaches where and changes GH joint how?
- Attaches around glenoid fossa
- Increases the depth of curvature by about 50%
Describe basic difference between the glenoid labrum superiorly and inferiorly
- superiorly: loose attaches
- inferiorly: firmly attached and relatively immobile
What attaches to the glenoid labrum?
- Tendon of the long head of the biceps brachii
- Glenohumeral ligaments
Characteristics of GH capusle when arm is resting at side
- large capsule
- taut superiorly
- slack anteriorly and inferiorly
Size of the GH joint capsule compared to the humeral head
Capsular surface area is twice that of the humeral head
In the loose packed position, how much distraction of the humeral head is generally allowed
2.5 cm
What is the close-packed position of the GH joint?
The humerus abducted and laterally rotated (joint capsule twists on itself)
Where does the humeral head commonly sulux through anteriorly?
* The foramen of Weitbrecht
An area of capsule between the superior and middle glenohumeral ligaments
What muscle helps reinforce the GH capsule anteriorly?
The subscapularis tendon
Define and describe the rotator interval capsule.
- Capsule of GH joint
- complex in the space between the supraspinatus and subscapularis tendons
- mad eof the upserior GH ligament, superior capsule and the coracohumeral ligament
Important characteristics of the middle GH ligament
- runs obliquely from the sup/ant labrum to the ant humerus
- blends with anterior capsule
- absent in 30% of subjects
Define and describe the inferior glenohumeral ligament complex
- called the IGHLC
- 3 components are the anterior band, axillary pouch, posterior band
- positional variation in function
- positional variation in viscoelastics
The superior GH ligament (and thus the rotator interval capsule) limit:
Anterior and inferior movements with arm at zero abduction
The middle GH ligament limits:
Anterior humeral translation with arm in 45 degrees of abduction
The IGHLC stabilizes in what position:
In abduction greater than 45 degrees and/or rotation
- reinforces when inferior capsule slack is used up
- external rot: anterior band fans out
- medial rot: posterior band fans out
When arm is abducted, how does rotation effect the capsule?
In all positions the capsule and GH ligaments tighten with rotation
Describe the structure and function of the coracohumeral ligament
- originates at the base of the coracoid process
- 2 bands: one to supraspinatus and greater tubercle; one to subscapularis and lesser tubercle
- 2 bands form a tunnel for long head of biceps brachii
- limits inferior translation of humeral head at rest
- prevents superior translation of humeral head especially when dynamic stabilizers are weak.
- resists external rotation when arm adducted
What forms the coracoacromial arch
coracoid process, acromion, coracoacromial ligament; often includes wtih inferior surface of AC joint
What is in the coracoacromial arch
- subacromial bursa
- rotator cuff tendons
- part of long head of biceps brachii
Rotator cuff impingement is typically "impingement" of _________
supraspinatus
Radiographic features of the coracoacromial arch
- measured from the acromion to the humerus
- 10mm at rest, 5mm with arm abducted
People with shoulder impingement will often mention this about their sleep...
Can't sleep on affected side (position forces the head of the humerus further into the space)
2 most important bursae in the shoulder
- subacromial and subdeltoid
- often continuous w/ each other
- separate the supraspinatus tendon and humerus from the other structures
- inferior part of bursae is superior supraspinatus tendon sheath
- does not normally communicate with the GH joint space
ROM of the GH joint
- 90 degrees (more with scapula)
- 45 degrees of extension
- med/lat rotation: 60 degrees in adduction, 120 degrees in abduction