MSK - Shoulder Joint And Back Muscles Flashcards
What are the two superficial muscles of the back?
Trapezius
Latissimus dorsi
What do the muscles of the back do?
Attach the limb to the trunk
What does the trapezius do?
It directly attaches the pectoral girdle to the trunk
Superior fibres - elevate scapula
Middle - retracts scapula
Inferior - depresses scapula
What does the latissimus dorsi do?
This is a powerful adductor - extends the arm at the shoulder
It is a medial rotator
What does the levator scapulae do?
This elevates the scapula
What does the rhomboid major do?
Retracts scapula and rotates it - depressing the glenoid cavity
When is scapula rotation needed, and how does it happen?
It is needed for abduction of the arm above 90’ due to the acromion preventing further rotation.
The superior and inferior parts of the trapezius act together to do this
What is the glenohumeral joint?
A ball and socket synovial joint between the articulating surfaces of the scapula and humerus.
How is glenoid cavity deepened?
By a rim of fibrocartilage called glenoid labrum
How is the joint lubricated?
Lined by synovial fluid and enclosed by fibrous capsule.
Why is this joint particularly mobile?
The GC is very shallow
What is the name of the most important ligament in the extra capsule?
The coraco acromial ligament
Between the acromion and the coraciod process
What is the coraco - acromial - arch?
This is an osseoligamentous structure which overlies the humeral head preventing the upper displacement of the humerus.
What are the rotator cuff muscles?
The supraspinatus
Infraspinatus
Teres minor
Subscapularis
Where are the rotator cuff muscles inserted to?
The posterior muscles - greater tubercule
Anterior (subscapularis) - lesser tubercule
How is the ‘cuff’ formed?
Tendons merge with each other and the capsule.
What is painful arc syndrome?
This is when the supraspinatus tendon rubs under the CAA
this causes irritation and inflammation of the supraspinatus tendon
Results in pain during 50-130 abduction
Which muscles are responsible for flexion of the shoulder?
Pectoralis major
(Anterior) Deltoid
Coracobracialis
Biceps
Which muscles are responsible for the extension of the arm?
(Post) deltoid
Latissimus dorsi
Teres major
Medial rotation of the shoulder?
Subscapularis
Teres major
Pectoralis major
Latissimus dorsi
Lateral rotation of the arm?
Intraspinous
Teres major
Adduction of the arm?
Pec major
Latissimus dorsi
Teres major
Abduction of the arm?
Supraspinatus - 20’
Deltoid -20-90
Above 90 is scapula rotation by the trapezius.
What are the main arteries supplying the shoulder joint?
Anterior and posterior circumflex humeral artery
Suprascapular artery
What is the nerve supply to shoulder?
Suprascapular, Axillary and lateral pectoral nerves
Which structures are vulnerable at fracture sites?
Axillary nerve, posterior circumflex artery.
What is the most common direction of dislocation of the glenohumeral joint?
Anterior- inferior
How is dislocation usually caused?
Trauma on an abducted arm
Where is the humeral head repositioned to after dislocation?
Below the coraciod process
What is a complication of a dislocated shoulder?
The capsule and rotator cuff may tear so poor healing leads to recurrent dislocation.
How would you test for Axillary nerve damage after dislocation?
Test for sensation in the regemental badge area
