Scapula/shoulder Flashcards
Elevators of the scapula (4)
Upper trapezius
Levator scapulae
Rhomboid minor
Rhomboid major
Depressors of the scapula (6)
Levator scapula Rhomboid minor Rhomboid major?? Pectoralis minor Lower pectoralis major Latissimus dorsi
Upward rotators of the scapula (3)
Upper trapezius
Lower trapezius
Serratus anterior
Downward rotators of the scapula (7)
Anterior:
Lower pectoralis major
Pectoralis minor
Subclavius
Posterior: Latissimus dorsi Lower serratus anterior Lower trapezius Rhomboids
Shoulder facts
- Mobility at the expense of stability
- Shoulder girdle is composed of seven joints
- There are structures within the suprahumeral space
Clavicle facts
- clavical stability–> from ligaments
- clavical mobility–> from crank shape
Scapulohumeral rhythm
- scapular rotation
- glenohumeral movements
Shoulder girdle 7 joints
- glenohumeral
- scapulothoracic (or scapulocostal)
- suprahumeral* (pseudo-joint)
- acromioclavicular
- sternoclavicular
- costosternal
- costovertebral
Suprahumeral
*pseudo-joint
between head of humerus and arch formed by coracoacromial ligament (CA ligament)
Joint definition
union of two bones that permit movement at their junction
Suprahumeral “joint” function
- prevents upward dislocation of humerus
- protects glenohumeral joint from trauma above
Structures within the suprahumeral “joint”
- portion of subacromial bursa
- subcoracoid bursa
- supraspinatus muscle and tendon
- superior portion glenohumeral capsule
- portion of biceps tendon
- loose connective tissue
*vulnerable to compression by greater tuberosity during abduction (need to externally rotate)
Role of clavicle
- to keep the arm away from the body
- strong ligaments for stability
- “crank” shape of clavicle for mobility
Clavicular ligaments
- coracoclavicular ligment: trapezoid ligament & conoid ligament
- costroclavicular ligament: important fulcrum for shoulder girdle; between the clavicle and the underlying rib
- sternoclavicular ligament
Coracoacromial (CA) ligament
often cut out in athletes to give more room
AC joint separations (“shoulder separations”)
I- AC ligament partially torn
II- AC ligament completely torn
III- AC ligament and CC ligament completely torn
IV- type III with avulsion of CC ligament from clavicle
V- type III with vertical displacement of the clavicle and 100% increased of the coraco-clavicular space
VI- type III with inferior dislocation of distal clavicle
AC joint separations (“shoulder separations”) MCC?
Direct impact to the shoulder from a fall
Crank shape of the clavicle for mobility
Rotation of the clavicle begins after 90 degrees of abduction of the arm
- 60 degrees glenohumeral
- 30 degrees scapular rotation (2:1 ratio)
As scapula rotates next 30 degrees, the clavicle must rotate about its long axis.
In movements of the arm, sternoclavicular joint motion is a/w reciprocal motion in the AC joint.
TRUE
A congenital absence of the clavicle will result in little or no loss of functional ability in use of the shoulder.
TRUE
Glenohumeral abduction
supraspinatus
deltoid
*BOTH muscles are active throughout abduction
What happens when supraspinatus is paralyzed?
There is no difficulty raising arm above head, there is simply a decrease in strength and endurance.
What happens when deltoid is paralyzed?
- They attempt to raise arm by upward rotation of scapula and lateral bending of truck.
- Also frequently externally rotate so can use long head of biceps.
*Important: always check shoulder abduction with both internal and external rotation of shoulder!
Long head of biceps in external rotation
If the biceps long head is the muscle causing abduction (and thus, covering up loss of deltoid and supraspinatus), the patient will be able to abduct ONLY when in external rotation.
*All abduction will be lost when the shoulder is internally rotation!
Codman scapulohumeral movement
2:1 ratio
For every 15 degrees of abduction of the arm…
- 10 degrees occur at glenohumeral
- 5 degrees from rotation of scapula upon chest wall
Scapular rotation purpose
- mechanical stability of the glenohumeral joint
- to maintain optimal deltoid length (length-tension relationship)
Rotation of the scapula as in full abduction of the arm is produced by..?
trapezius and serratus anterior
Glenohumeral movement
- gliding of two incongruous surfaces
- large humeral head/small glenoid fossa
- glenoid fossa faces lateral/anterior/upward–> VERY important for this to be facing the correct way!
Glenoid capsule
- Arm at side hanging: superior capsule is taut, inferior is loose
- Arm in full abduction: superior capsule is loose, inferior is taut
- Arm half abducted: both superior and inferior capsule are slack so this is a position of instability
Scapula position affects inclined plane
-Ball compressed against inclined plane (glenoid fossa)
-Compressive forces created by:
superior capsular ligament
coracohumeral ligament
tendon of supraspinatus
Anterior capsule of the glenoid
- loose (humerus can be drawn 3 cm from fossa)
- reinforced by ligaments:
1. superior glenohumeral ligament
2. middle glenohumeral ligament
3. inferior glenohumeral ligament
*Between the superior and middle ligament is an opening called the Foramen of Weitbrecht