MSC week 2 Vocab (Shoulder)
musculocutaneous nerve
- From: lateral cord - Innervates 1. Biceps Brachii 2. Brachialis 3. Coracobrachialis - Sensory 1. Lateral Forearm
suprascapular nerve
- From: upper trunk - Innervates 1. Supraspinatus 2. Infraspinatus - Believed to be a source of RC impingement pain
Acromion
- Is a bony process on the scapula (shoulder blade). - Together with the coracoid process it extends laterally over the shoulder joint. - is a continuation of the scapular spine, and hooks over anteriorly.
coracoid process
- Is a small hook-like structure on the lateral edge of the superior anterior portion of the scapula - Looks "like a raven's beak" - Pointing laterally forward, it, together with the acromion, serves to stabilize the shoulder joint
glenoid labrum
- Is fibrocartilage - Attached to the bony rim of the glenoid - The labrum adds depth to the glenoid cavity by 50% - Three purposes 1. Anti-shear bumper 2. Attachment of glenohumeral ligaments 3. Increase surface contact
Humeral biomechanics & orientation
- Most people think the humerus articulates at 90 degrees - Proximal humerus is on average 30 degrees of retroversion - Neck angle is 135 degrees - Important for positioning shoulder implants
Glenoid
- Pear shaped, shallow depression on the superior-lateral aspect of the scapula - Smaller in dimensions compared to humeral head - Bone is thin; anteroposterior depth is only 2.5mm - Thin surface of articular cartilage - Average 2° anteversion to 7° retroversion and 5° of superior tilt - Thinnest in the central portion of the glenoid
Name the rotator cuff muscles and their location with respect to the scapula.
- Supraspinatours muscle (top of the Rotator Cuff) - Infraspinatours Muscle (Posterior side behind the subscapularis) Subscap - Teres Minor Muscle (Inferior muscle on the postier side of the rotator cuff)
Shoulder Abduction
0-180
Shoulder Flexion
0-180
Shoulder Extension
0-60
Shoulder Internal Rotation
0-70
Shoulder External Rotation
0-90
glenohumeral ligaments (superior, middle, inferior)
3 bands which run from the glenoid cavity to the humerus
D-E =
8mm
TERES MINOR
Attaches to inferior facet on greater tubercle of humerus Externally rotates the arm
INFRASPINATUS
Attaches to middle facet on greater tubercle of humerus Laterally rotates the arm
Supraspinatus
Attaches to superior facet on greater tubercle of humerus Initiates and assists deltoid in abduction; acts with rotator cuff muscles
SUBSCAPULARIS
Attaches to the lesser tubercle of humerus Provides internal rotation of arm and adduction
(T/F) The scapula attaches to the thoracic spine.
False
Where does most of the movement in the shoulder girdle occur?
Glenohumeral joint
B-C =
Head Thickness
Neutral plane of the scapula (scaption)
Movement of the humerus away from the body in the scapular plane. Glenohumeral abduction in a plane 30 to 45 degrees between the sagittal and frontal planes
Pectoralis
Muscles that create the bulk of the chest
F-H =
Offset
axillary nerve
Posterior cord of plexus innervates - Deltoid - Teres Minor - Long Head Triceps
Trapezius
Three functional parts: 1. An upper (descending) part which supports the weight of the arm 2. A middle region (transverse), which retracts the scapula 3. A lower (ascending) part which medially rotates and depresses the scapula
(T/F) Generally, you might expect the glenoid to be positioned with either anteversion or retroversion.
True
(T/F) The humerus is anteverted to articulate with the glenoid, similar to how the femur is positioned with the acetabulum.
True
How many bones comprise the shoulder girdle? What are the names of these bones?
clavicle, scapula, and humerus
coracoclavicular ligament
conoid and trapezoid
Deltoid
largest and strongest shoulder muscle
scapula
moves along the posterior ribs - This is the scapulothoracic articulation Many consider this a joint as it moves - However, it is not a typical joint, as it glides over fascia, muscles, and bursa
Four Muscles of Rotator Cuff
supraspinatus, infraspinatus, teres minor, subscapularis
