Shoulder complex Flashcards
GH joint
Multiaxial, ball and socket synovial joint
Depends on the muscles and ligaments for support, rather than the bones (sacrifices stability for more movement)
—- this is why OA is less likely in GH joint as there is less stability
Labrum:
– ring of fibrous cartilage, surrounds and deepens the glenoid cavity of the scapula about 50%
– only part of the humeral head is in contact with the glenoid at any one time
Rotator cuff muscles
Supraspinatus (superior), subscapularis (anterior), infraspinatus and teres minor (posterior)
– plays an integral role in shoulder movement
– controls osteokinematics and arthrokinematics movement of the humeral head in the glenoid.
– and along with the biceps it depresses the humeral head during movements into elevation.
Ligaments of GH
Primary ligaments:
– superior, middle and inferior glenohumeral ligaments
– play an important role in stabilising the shoulder
Superior glenohumeral ligament:
- primary role- limiting inferior translation in adduction, also restrains anterior translation and lateral rotation up to 45 degrees of adduction.
– excessive external rotation (as seen in throwing), may lead to damage of the anterior portion of the ligament (and capsule), thereby increasing the GH laxity
Middle glenohumeral ligament:
- absent in 30% of the population
- primary role- limits lateral rotation between 45 and 90 degrees abduction
Inferior glenohumeral ligament:
– most important out of the 3
– has an anterior and posterior band and an axillary pouch in the middle
– acts more as a sling or a hammock for the joint
- primary role- supports the humeral head above 90 degrees abduction, limiting inferior translation
—- the anterior band tightens on lateral rotation and the posterior band tightens on medial rotation
Coracohumeral ligament
Connects from the coracoid process to the lesser and greater tubercles of the humeral head
primary role- limits inferior translation and helps limit external rotation below 60 degrees abduction
Injuries to the rotator interval
Rotator interval- shows the relationship between:
– supraspinatus tendon
– subscapularis tendon
– coracohumeral ligament
Injuries to rotator interval can cause:
– contractures
– biceps tendon instability
– anterior glenohumeral instability
Coracoacromial ligament
Connects from coracoid process to the acromion
Forms an arch over the humeral head stopping superior translation of the humeral head
Transverse humeral ligament
Forms a roof over the bicipital groove, holding the bicep tendon into the bicipital groove
GH innervation
Branches of the posterior cord of the brachial plexus, and the sub scapular, axillary and lateral pectoral nerves
AC joint
Made up of acromion and lateral end of clavicle
Synovial plane joint that increases the range of motion of the GH joint
Joint surrounded by a fibrous capsule with an articular disc inside
The joint depends on ligaments for its strength
The acromioclavicular ligaments surround the joint:
– control horizontal movement of the clavicle
– these ligaments will commonly be the first ones damaged if the joint is stressed
types of acromion process shapes
Flat (17%)
Curved (43%)
Hooked (39%):
– about 70% of rotator cuff tears or impingement are associated with a hooked acromion
– however some people dont believe a hooked acromion is a real anatomical defect, however formed from ossification of the coracoacromial ligament
Convex ‘upturned’ (1%)
Coracoclavicular ligament
Primary support of the acromioclavicular joint.
Has 2 portions- coined (medial) and trapezoid (lateral)
If a step deformity occurs (where the clavicle steps off of the acromion), the the costoclavicular ligament has been torn
SC joint
Enables the humerus to move through full 180 degrees of abduction
Saddle shaped synovial joint with 3 degrees of freedom
Location- medial end of clavicle, the manubrium sternum, and the cartilage of the 1st rib
—- connects appendicular skeleton to the axial skeleton
Joint depends on ligaments for strength
Ligaments of SC joint
Anterior and posterior sternoclavicular ligaments:
– support the joint anteriorly and posteriorly
Interclavicular ligament
Costoclavicular ligament (clavicle to first rib and its costal cartilage):
– main ligament maintaining the integrity of the SC joint
Scapulothoracic joint
Even though it is not a real joint, always needs to be considered in any assessment of the shoulder.
– because a stable scapula enables the rest of the shoulder to function correctly
—- think about the scapulohumeral rhythm
Way to differentiate between nerve root pain and inflammatory intrinsic
Nerve root pain- elevating arm over head may relieve symptoms
Intrinsic- elevating arms over head may exacerbate symptoms
