Shoulder Anatomy Flashcards
The Shoulder Joint
Glenohumeral (glenoid fossa and humeral head)- Ball in socket
The Shoulder Girdle
- Acromioclavicular Joint (gliding joint)
- Sternoclavicular Joint (saddle joint)
- Scapulothoracic Interface (no classified as a joint but the movement is vitally important for normal shoulder joint motion
Shoulder Capsule
- Capsule is ~2x larger than the humeral head
- Inferior portion is the weakest
Clavicle
- Lateral 1/3 is flattened and concave anteriorly, increasing its resilience
Clavicle
Elevation/Depression - Elevation: 45 - Depression: 5-15 Protraction/Retraction - 15 Rotation - 30-45 (posterior only- the only time it does anterior rot. is to return to resting position)
Sternoclavicular Joint
Capsular Reinforced
- Superiorly by interclavicular ligament
- A/P and inferiorly by the A/P sternoclavicular ligament
Costoclavicular Ligament
- Attaches clavicle to 1st rib
- Restricts movement of the medial and of the clavicle (any movement of the clavicle, except inferior, tightens its fibers)
Acromioclavicular Ligament
- Weak capsule
- Reinforced superiorly by aponeurotic fibers of traps and deltoid
- Controls horizontal stability
Coracoclavicular Ligament
- Conoid = medial
- Trapezoid = lateral
- Contributes to vertical and horizontal stability
- Assist in transmission of compression from scapula to clavicle
- Also functions to produce longitudinal rotation in clavicle during elevation
AC Joint Seperation
3 Grades
- 1: damage to AC joint capsule and ligament
- 2: joint capsule and trapezoid ligament
- 3: joint capsule, trapezoid and conoid ligament damage
Coracoacromial Arch
- Prevents superior dislocation
- Arch includes the anterior acromion, coracoacromial ligament and coracoid process
Capsular Ligaments
- 3 ligaments help support the anterior capsule
- Superior, Middle, and Inferior glenohumeral ligaments
- IGHL has 2 bands
- Inferior band has to give out for a dislocation to occur
- 3/4 bands are anterior and help limit ER and create more anterior stability
SGHL Ligament Function
Helps resist inferior translation when the arm is hanging or adducted
MGHL Ligament Function
Some help with inferior translation when arm is adducted. Helps resist anterior translation (maximal effect at about 45 degrees abduction)
IGHL Ligament Function
Anterior stabilization with arm in 90 degrees abduction. Tighten when the arm is abducted and externally rotated and cradle inferior head. This is theorized to also add to the posterior/superior shift of the humeral head in throwing
Shoulder Bursae
- Subacromial and subdeltoid are the most referenced and critical bursae
- Usually not distinct from one another
What is the labrum?
- A fibrocartilaginous rim that helps to deepen the glenoid
- Almost triangular in shape
- Bottom portion is firmly attached to underlying bone
- Top portion is loosely connected
- Superior portion is attached to the biceps tendon (long head)
Glenoid Labrum Depth
- Increases depth to 5 mm A/P, 9 mm S/I
- Depth is only 2.5 mm w/out labrum
Muscles Crossing the Shoulder Joint
- Deltoid
- Supra/Infraspinatus
- Teres Major/Minor
- Pectoralis Major
- Subscapularis
- Long head of Biceps and Triceps
- Coracobrachialis
- Latissimus Dorsi (when shoulder is fully flexed)
Muscles attaching to Scapula
- Deltoid
- Trapezius
- Supra/Infraspinatus
- Teres Minor/Major
- Subscapularis
- Serratus Anterior
- Latissimus Dorsi
- Rhomboids
- Pectoralis Minor
- Coracobrachialis
- Biceps (both heads)
- Long head of Triceps
- Levator Scapulae
- Inferior belly of Omohyoid
Rotator Cuff Muscles
- Supraspinatus: Abduction
- Infraspinatus: ER
- Teres Minor: ER
- Subscapularis: IR
Insertions for Rotator Cuff Muscles
- Greater Tubercle of the Humerus: S.I.T. (supraspinatus, infraspinatus, and teres minor)
- Lesser Tubercle of the Humerus: Subscapularis
