Arthrology: Shoulder Complex Learning Objectives Flashcards
Describe the morphology (convex/concave) of the articular surface of bones of the sternoclavicular (SC) joints.
sellar/saddle joint
Clavicle is convex superior to inferior; concave anterior to posterior
Manubrium is concave superior to inferior; convex anterior to posterior
Describe the morphology (convex/concave) of the articular surface of bones of the acromioclavicular (AC) joint.
Plane (gliding) joint
No convexity/concavity (?)
Describe the morphology (convex/concave) of the articular surface of bones of the glenohumeral (GH) joint.
Multiaxial ball and socket joint
Convex humerus on concave glenoid fossa/labrum
Synovial joint type: sternocostal
Sellar/saddle
Synovial joint type: acromioclavicular
plane (gliding)
Synovial joint type: glenohumeral
multiaxial ball and socket
Glenohumeral restraints to external rotation
- 0 degrees abduction
o Subscapularis
o Superior glenohumeral ligament (SGHL) - 45 degrees abduction
o Superior glenohumeral ligament (SGHL)
o Middle glenohumeral ligament (MGHL) - 90 degrees abduction
o Anterior band, inferior glenohumeral ligament complex (IGHLC)
Glenohumeral restraints to internal rotation
- 0 degrees abduction
o Posterior band, Inferior glenohumeral ligament complex (IGHLC) - 45 and 90 degrees abduction
o Anterior and posterior band, inferior glenohumeral ligament complex (IGHLC)
Glenohumeral restraints to inferior translation
- 0 degrees abduction
o Superior glenohumeral ligament (SGHL)
o Coracohumeral ligament - 90 degrees abduction
o Inferior glenohumeral ligament complex
Glenohumeral static stabilizers
Labrum, joint capsule, ligament complex
Glenohumeral static stabilizers: labrum
o Increases concavity of glenoid fossa
o Deepens socket 50-75%
Glenohumeral static stabilizers: joint capsule
o Tissue anterior and posterior continues laterally on the humerus into the neck of humerus
o Anterior and inferior capsule much thicker than posterior
Glenohumeral static stabilizers: ligament complex
o Anterior: GH ligaments
o Inferior: pliable redundant(?) ligamentous complex
Glenohumeral muscular/dynamic stabilizers
- Rotator cuff
o Pulls head of humerus into glenoid fossa - Deltoid
o Large stabilizing component in all humeral positions
o Primary function to swing humerus
Discuss the concept of concave-convex in relation to motion of the SC joint
Protraction = anterior roll and glide of concave clavicle
Retraction = posterior roll and glide of concave clavicle
Elevation = superior roll and inferior glide of convex clavicle
Depression = inferior roll and superior glide of convex clavicle
Discuss the concept of concave-convex in relation to motion of the AC joint
Protraction-retraction of scapula = anterior-posterior glide
Abduction-adduction = rotation of acromion on clavicle
Discuss the concept of concave-convex in relation to motion of the GH joint
Convex on concave rule: roll and glide happen in opposite directions
o ER = posterior roll, anterior glide
o IR = anterior roll, posterior glide
o Flexion = superior roll, inferior glide
Sternoclavicular joint dislocation
anterior or posterior
Rare
Direct trauma or FOOSH
Clavicle fracture is more common
Posterior dislocation risks injury to other critical structures (vasculature)
Acromioclavicular joint sprain
Separated shoulder
Fall on tip of the shoulder (acromion)
Progressive disruption of ligaments
- AC joint ligaments
- Trapezoid
- Conoid
Graded by displacement (see image)
Grades 1-3 can be managed non-surgically in most cases
Subacromial impingement (GH joint)
RTC tendon and/or LHB may get repeatedly compressed, along with the bursa
Potential causes
- RTC dysfunction
- Scapular positioning
- Shape of acromion
- GH joint hypo/hypermobility
