Lecture 4.2: The Shoulder Joint Flashcards
Shoulder Joint: Glenohumeral Joint
- Head of humerus fits into Glenoid Cavity of the Scapula
- Lined by hyaline cartilage
- Glenoid Cavity deepened by Glenoid Labrum (fibrocartilage)
Is the Shoulder Joint stable? Why?
- Inherently unstable!
- Glenoid cavity shallow
- Disproportion of articular surfaces
- Multiplanar movements
- Lax capsule
How is the stability of the Shoulder Joint increased? (4)
1) Capsule
2) Ligaments (Extracapsular and Intracapsular)
3) Muscles of the rotator cuff (4) –> these are very important!
4) Other muscles
What is the Shoulder Capsule attached to?
• Glenoid Labrum & margins of Glenoid Cavity
• Anatomical neck of humerus
• Bridges intertubercular groove & dips down medially to surgical neck
(provides laxity for full abduction)
Why does the Shoulder Capsule have a small anterior opening?
• Communication between synovial shoulder joint and subscapular bursa
Shoulder Joint: Synovial Membrane
Lines capsule & Lines bone within capsule up to edge of articulating surfaces
Where is the tendon of the long head of biceps located?
- Tendon of long head of biceps lies within joint cavity
- Tendon acquires a tubular sleeve of synovium as it enters joint
- This synovium surrounds the tendon up to its insertion on scapula
Extracapsular Ligaments: Coracoacromial Ligament
- MOST important
* Between acromion and coracoid process
Extracapsular Ligaments: Coracohumeral Ligament
• From base of coracoid process to anterior part of greater tubercle
Extracapsular Ligaments: Coracoclavicular Ligament
• Can be torn from AC joint dislocation
Extracapsular Ligaments: Transverse Humeral Ligament
• Holds tendon of long head of biceps in place during movement
Intracapsular Ligaments
- 3 Glenohumeral Ligaments (Superior, Middle, Inferior)
- Fibrous bands extending between Glenoid Labrum and Humerus
- Part of Fibrous Capsule and reinforces capsule anteriorly
- Can only be seen from inside the capsule
Coracoacromial Arch (CAA)
- Formed by: Coracoacromial Ligament + Acromion + Coracoid Process
- Strong bony and ligamentous structure
- Overlies humeral head
- Prevents upper displacement
Rotator Cuff Muscles: SITS
S: upraspinatus
I: nfraspinatus
T: eres Minor
S: ubscapularis
Importance of Rotator Cuff Muscles
They are the most important structures that give stability to the shoulder joint
What do Tendons of Rotator Cuff Muscles do?
- Tendons BLEND to form a cuff
- Cuff fuses with fibrous capsule (of joint) and strengthens it
- Tone in muscles holds humeral head close to Glenoid Cavity
What separates the Supraspinatus Tendon from the Coracoacromial Arch?
The Subacromial Bursa
Actions of the Rotator Cuff and Nerve: Supraspinatus
- Initiation and first 15 degrees of abduction
* Suprascapular Nerve (C5,6)
Actions of the Rotator Cuff and Nerve: Infraspinatus
- Lateral rotation of arm
* Suprascapular Nerve (C5,6)
Actions of the Rotator Cuff and Nerve: Teres Minor
- Lateral rotation of arm/weak adductor
* Axillary nerve (C5,6)
Actions of the Rotator Cuff and Nerve: Subscapularis
- Medial rotation of arm
* Upper and Lower Subscapular Nerve
Other Muscles that help stabilise the Shoulder Joint (3)
- Deltoid
- Long Head of Biceps
- Long head of Triceps
Where does the Long Head of Biceps attach on the Shoulder Joint?
• Attaches to Supraglenoid Tubercle
Where does the Long Head of Triceps attach on the Shoulder Joint?
• Attaches to Infraglenoid Tubercle
Where does the Deltoid attach on the Shoulder Joint?
Attaches to lateral clavicle, acromion, scapula spine and humerus
Importance of Subacromial Bursa in Movement?
Facilitates movement of:
• Supraspinatus tendon under CAA
• Deltoid muscle over the shoulder joint capsule & greater tubercle of humerus
What happens if the Subacromial Bursa becomes Inflammed?
- Subacromial Bursitis
- Causes pain on abduction of arm between 50-130 degrees
- ‘Painful arc’ Syndrome
Importance of Subscapular Bursa in Movement?
• Facilitates movement of subscapularis tendon over scapula
[• Communicates with joint cavity]
What is the most common dislocation of the Glenohumeral Joint? What usually causes it?
- Anterior Dislocation
- Humeral head comes to lie below coracoid process
- Usually caused by trauma on a fully abducted arm
What does an Anterior Dislocation look like externally?
Loss of round contour of shoulder —> appears square
When is Axillary Nerve Damage caused?
- Injured in dislocation
* Injured during fracture of surgical neck of humerus
What area experiences a loss of sensation during Axillary Nerve Damage?
• Loss of sensation in “Regimental Badge Area
• Area over central part of Deltoid
[• Supplied by Axillary Nerve (C5,6)]
What is a more extreme effect of Axillary Nerve Damage?
- Motor function loss
* Loss of Deltoid muscle (no abduction of arm)
What is ‘Painful Arc’ Syndrome?
It is when the Supraspinatus Tendon rubs under CAA (Coracoacromial Arch)
What can ‘Painful Arc’ Syndrome lead to? (3)
- Subacromial Bursitis (+/- calcification)
- Supraspinatus Tendonitis (+/- calcification)
- Degeneration and rupture of tendons
Risk Factors for ‘Painful Arc’ Syndrome (4)
- Repetitive overuse (sports, work involving overhead use of arms)
- Ageing (degeneration of tendons)
- Avascularity of supraspinatus tendon
- Slight differences in anatomy = may increase chances of impingement
Symptoms of ‘Painful Arc’ Syndrome (2)
- Irritation and inflammation of the supraspinatus tendon/subacromial bursa
- Pain during 60-120 degrees of abduction arc
What is the first spinal ligament you encounter in deep skin and subcutaneous tissue during a Lumbar puncture?
Supraspinous Ligament
What is the role of the Ligamentum Nuchae?
It maintains the secondary structure of neck and supports the head
What is Lordosis?
Lordosis refers to the normal inward curvatures of the spine at the cervical and lumbar regions
What is Kyphosis?
Kyphosis refers to the normal outward curvature of the spine specifically at the thoracic region
What is Carpal Tunnel Syndrome?
- Pressure on a nerve in your wrist
* It causes tingling, numbness and pain in your hand and fingers
Cutaneous Nerve Area vs Dermatome
Cutaneous innervation refers to the area of the skin which is supplied by a specific cutaneous nerve
Dermatomes are similar; however, a dermatome only specifies the area served by a spinal nerve
