Shoulder Flashcards
Functional articulations of Shoulder complex
- Shoulder girdle increases ROM with less compromise of stability (scapula humeral rhythm) (4 joints vs. 1 joint)
Combined roll and slide mechanism
- Maintains joint congruity through range of movement
- GH is an example of convex on concave; where the moving bone (humerus) is convex and the stationary bone (scapular) is concave.
- The humerus superior rolls, whilst scapular slides inferiorly during abduction.
- During flexion/extension, the head of the humerus spins along with accompanying upward rotation of the scapulothoracic joint. Assisted by rotation of the clavicle.
Force Coupling around a pivot point:
- 2 opposing forces rotating around a pivot point.
- Pivot point = middle, medial scapula.
- Trapezius internally rotates scapula
- Deltoid externally rotates scapula
- Serratus anterior protract the scapula
- There are multiple forces at any given moment. These can be equal or unequal, depending on the function required and balance of moving elements such as muscles and balance of stabilising elements such as ligaments.
- E.g., Upper traps being way too tight – pulls shoulders into elevation, not enough counter compression to bring shoulders down.
Scapulo-humeral rhythm
- Relationship of movement between the GH and the scapula.
First 30 Gh, 2;1 ratio from GH to scap
120 by GH 60 by the scap. - The rate that the scapula moves depends on how the humorous moves
- Permits largest ROM of any complex in the body. Compare this with Hip
- Shoulder girdle increases ROM with less compromise of stability (scapula humeral rhythm) (4 joints vs. 1 joint)
- Facilitate movements of the upper extremity by positioning GH favourably
3 phases during arm abduction
Phase1. 30deg humeral abduction
0-5deg clavicle
minimal scapula movement
Phase 2. Humerus abduction 40deg
Scapula 20deg lateral rot
Clavicle 15deg elevation
Phase 3. Humerus 60deg abduction and 90deg laterally rotated
Scapula 30deg lateral rotated
Clavicle 30-50 post rot& 15deg elevated
Role of the clavicle
- The clavicle is the only axial attachment for the entire upper extremity.
- The clavicle elevates, depresses, rotates, protracts and retracts. All movements are passive accessory movements.
- All clavicular movements are essential to position the scapular in the optimal position to accept the head of the humerus.
- Essentially all movements of the glenohumeral joint involve some movement of the clavicle around the pivot point of the sternoclavicular joint.
- Otherwise humerous would rise to high and come into conntact with the acromion process
Role of Long and Short Head of Biceps in humeral head stability
- Provides anterior stability to the GH, therefore failure of the stabilisation of the LHB can have damaging effects on GH and Rotator Cuff (RC) function
- LHB attaches onto glenoid labarum, not scapula itself – potential weakness/vulnerability but big stabiliser for movement in all vectors
- Transverse ligament helps LHB run true through the bicipital groove, if it loosens (commonly through swimming, throwing sports) it can escape the bicipital groove and cause big problems for the GH and dysfunction to the rotator cuff as it has to work harder to stabilise the shoulder.
- Achieved through compression of the humeral head against the glenoid fossa. LBH and SBH acts in tandem with the LHB to make sure the humorus stays down and away from the sub-acromial space.
- Observations that the tendon of LHB hypertrophies in patients with RC tears confirms that it has a role in GH stability.
- SHB attaches onto the coracoid process. Common cause of stiffness in that area, compressing the surrounding structures.
Importance of sub acromial space
- Key to avoiding impingement syndromes
- Coracoid process – attachment point of coracobrachialis and pec minor. Big anterior anchor of the scapula
- Acromion process – very little space, tendon of supraspinatus has to pass under the acromion process. Most commonly damaged tendon of rotator cuff. Should be reasonably flat, in some people it curves or becomes hooked
Movers vs Stabilisers
Movers
* Deltoid
* Supraspinatus
* Biceps Brachii
* Brachioradialis
* Pectoralis major
Joint stabilising tissues
* Capsule
* Ligaments
* Articular disc (AC/SC jts)
Stabilising muscles
* Subscapularis
* Serratus anterior
* Latissimus
* Coracobrachialis
* Pectoralis minor
Scapular stability
Latissimus and subscapularis the unsung heroes
- One of the best ways to stabilise a Pts shoulder is to teach them how to engage the latissimus dorsi
- Any Pts with hypermobile shoulders, or have dislocated them or have general instability, get them training subscapularis and latissimus dorsi to stabilise the shoulder.
When it goes wrong: Dysfunctions of the shoulder
Painful and weak
E.g., Pt can’t raise both arms into abduction, may side bend to assist
* Rotator cuff related shoulder pain – muscle issue
* Subacrominal- impingement Syndrome
* SLAP Lesion – Tear of the long biceps head – tears off some of the glenoid labarum
Painful and stiff
Pain Vs stiffness - Difference between the active and passive exam:
Stiffness - Limited ROM actively and passively
* Adhesive Capsilitis.
* Osteoarthritis (Bony remodelling) of GH, AC
Painful and unstable
- Dislocations
- Repeated dislocations
- Common to see semi dislocations of the AC where Pt is unaware e.g., from repetitive strain
Common rotator cuff injuries
A lot of Rotator cuff issues occur because the anterior shoulder is too tight in relation to the posterior, e.g., hunched at computers or driving, pecs become too tight. Pulling scapula and rotator cuff anteriorly which puts stress on it.
Good way to help this is stretch the anterior muscles, pecs and biceps.
3 phases during arm abduction
Phase1. 30deg humeral abduction
0-5deg clavicle
minimal scapula movement
Phase 2. Humerus abduction 40deg
Scapula 20deg lateral rot
Clavicle 15deg elevation
Phase 3. Humerus 60deg abduction and 90deg laterally rotated
Scapula 30deg lateral rotated
Clavicle 30-50 post rot& 15deg elevated
