The Shoulder- Palastanga Flashcards
Shoulder is also known as what
The glenohumeral joint
Classification of the shoulder joint
Synovial ball and socket
Articular surfaces
Head of humerus and shallow glenoid fossa
Angle of inclination of the humerus
135 degrees
Between axis of head and neck and anatomical axis of shaft
Angle of retroversion of the humerus
30-40 degrees
Rotated backwards against the shaft (opposite of the femur which is anterverted)
Describe the articular surfaces facings
Glenoid fossa faces laterally, anteriorly and slightly superiorly, is pear shaped and only slightly concave
Head of humerus faces medially, posteriorly and superiorly, represents 2/5 of a sphere
What increases the congruency of the joint
The presence of the glenoid labrum
Describe the joint capsule
Is thick and strong only really anteriorly where is strengthened by ligaments, otherwise is very lax and confers little stability
Has 2 openings, one to allow long head of biceps through, one to communicate with subscapular bura (deep to tendon suscapularis)
What is the role of rotator cuff muscles regarding the shoulder joint
Act as extensible ligaments and fan over the joint capsule
Are of tantamount importance in maintaining/ creating joint stability and integrity
Where are the glenohumeral ligaments
Anteriorly over the joint and only seen from the inside of the capsule
Describe the glenohumeral ligaments
Superior
Middle
Inferior - usually most well developed
Have no real stabilising function but certain movements such as lateral rotation in particular, put them under increased tension
Features of the synovial membrane
Hangs down in a lil pouch when arm is hanging by its side - due to lax capsule
Encloses the long head of biceps tendon as it passes through
Associated with a number of bursae
Clinically significant bursa of the shoulder
The subacromial bursa which sits under the acromion and deltoid and over the rotator tendons
Adhesions can form and prevent free sliding mvoement, may affect underlying supraspinatous tendon
Describe the glenoid labrum
Triangular in cross section, fibrocartilagenous rim, site of attachment for long head of biceps
What are the accessory ligaments of the shoulder
Coracohumeral and coracoacromial
What function does the coracoacromial ligament serve
Forms a ligamentous arch and together with the bony processes of the coracoid and acromion increases the surface on which head of humerus is supported during upward force transmission through the humerus
How stable is the shoulder joint and what is the main contributor to this
Very unstable
Low bony congruency and little supporting ligaments
Tone of rotator cuff muscles most important in conferring stability
Why does the shoulder dislocate relatively easily compared to other joints
Low stability as sacrificed for high mobility
Long humerus has great leverage in dislocating forces
Which type of dislocation is most common and why
Anterior dislocation more common due to anterolateral facing of glenoid which is better suited to resist posterior forces, posteriorly capsule also reinforced by infraspinatous and teres minor
Define the axes about which movement of the shoulder joint can occur
About the cardinal planes e.g. sagittal, coronal etc
OR
With respect to the plane of the glenoid fossa aka in the scapular plane (inclined approx 45 degrees to the frontal and sagittal planes
Movement at the shoulder joint occurs through a combination of?
Gliding and rolling
EXCEPT for axial rotation
Describe flexion/extension of the shoulder joint
Occurs about an axis perpendicular to the plane of the glenoid fossa so that in flexion arm moves anteromedially and in extension is opposite
ROM of flexion extension
Flexion 110d
Extension 70d
Can be extended when combined with movement of the pectoral girdle to
Flexion 180d
Extension 90d
Limits to flexion/ extension
Flexion has no limit really as moves through its full arc of 180d
Extension is limited by the greater tubercle of the humerus coming into contact with the coracoacromial arch
Describe abduction and adduction of the shoulder
Occur in an oblique horizontal axis in the same plane as the glenoid fossa so that in abduction the arm moves anterolaterally away from the trunk and vice versa in adduction
Abduction and adduction is accompanied by what other movement of the shoulder joint?
Is pure abduction for the first 25d of the arc then is accompanied by concomitant (lateral) rotation of the scapula between 30 and 180d
What is the total ROM for abduction/ adduction at the shoulder joint
120d
Is augmented by scapular rotation to take this to 180d
The terminal phase of abduction is accompanied by what movement
Lateral rotation of the humerus
What produces the movement of abduction at the shoulder joint
Is initiated by supraspinatous and then deltoid takes over after the first 20d to produce the rest of the movement
The accompanying lateral rotation of the scapula is produced by lower part serratus anterior and upper fibres trapezius
Describe medial and lateral rotation of the shoulder joint
Takes place about the longitudinal axis of the humerus, best seen with the elbow flexed. In lateral rotation the hand and forearm move outwards and anterior surface of the humerus is turned laterally
What are the ROMs for medial/ lateral rotation
Medial rotation = in excess of 90d if forearm pulled behind trunk
Lateral rotation= 80d
What limits medial/ lateral rotation
Limited by the extent of the articular surfaces as well as tension is the joint capsule and appropriate musculature
Muscles medially rotating the arm at the shoulder
Subscapularis, pec major, lat dorsi, teres major and ant fibres deltoid
Muscles laterally rotating the shoulder
Infraspinatous, teres minor, post fibres deltoid
Muscles adducting the shoulder
Eccentric contraction of the abductor msucles-
serratus anterior, trapezius, deltoid and supraspinatous
Muscles flexing the shoulder joint
Ant fibres deltoid, clavicular head pec major, coracobrachialis and biceps
Muscles extending the shoulder
From flexed position is eccentric contraction of flexing muscles
Beyond neutral position is post fibres deltoid, teres major, lat dorsi
