Arthrology: Shoulder Complex Learning Objectives

Question 1

Describe the morphology (convex/concave) of the articular surface of bones of the sternoclavicular (SC) joints.

Answer 1

sellar/saddle joint

Clavicle is convex superior to inferior; concave anterior to posterior

Manubrium is concave superior to inferior; convex anterior to posterior

Question 2

Describe the morphology (convex/concave) of the articular surface of bones of the acromioclavicular (AC) joint.

Answer 2

Plane (gliding) joint

No convexity/concavity (?)

Question 3

Describe the morphology (convex/concave) of the articular surface of bones of the glenohumeral (GH) joint.

Answer 3

Multiaxial ball and socket joint

Convex humerus on concave glenoid fossa/labrum

Question 4

Synovial joint type: sternocostal

Answer 4

Sellar/saddle

Question 5

Synovial joint type: acromioclavicular

Answer 5

plane (gliding)

Question 6

Synovial joint type: glenohumeral

Answer 6

multiaxial ball and socket

Question 7

Glenohumeral restraints to external rotation

Answer 7

• 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)

Question 8

Glenohumeral restraints to internal rotation

Answer 8

• 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)

Question 9

Glenohumeral restraints to inferior translation

Answer 9

• 0 degrees abduction
  o Superior glenohumeral ligament (SGHL)
  o Coracohumeral ligament
• 90 degrees abduction
  o Inferior glenohumeral ligament complex

Question 10

Glenohumeral static stabilizers

Answer 10

Labrum, joint capsule, ligament complex

Question 11

Glenohumeral static stabilizers: labrum

Answer 11

o Increases concavity of glenoid fossa
o Deepens socket 50-75%

Question 12

Glenohumeral static stabilizers: joint capsule

Answer 12

o Tissue anterior and posterior continues laterally on the humerus into the neck of humerus
o Anterior and inferior capsule much thicker than posterior

Question 13

Glenohumeral static stabilizers: ligament complex

Answer 13

o Anterior: GH ligaments
o Inferior: pliable redundant(?) ligamentous complex

Question 14

Glenohumeral muscular/dynamic stabilizers

Answer 14

• 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

Question 15

Discuss the concept of concave-convex in relation to motion of the SC joint

Answer 15

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

Question 16

Discuss the concept of concave-convex in relation to motion of the AC joint

Answer 16

Protraction-retraction of scapula = anterior-posterior glide

Abduction-adduction = rotation of acromion on clavicle

Question 17

Discuss the concept of concave-convex in relation to motion of the GH joint

Answer 17

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

Question 18

Sternoclavicular joint dislocation

Answer 18

anterior or posterior

Rare
Direct trauma or FOOSH
Clavicle fracture is more common
Posterior dislocation risks injury to other critical structures (vasculature)

Question 19

Acromioclavicular joint sprain

Answer 19

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

Question 20

Subacromial impingement (GH joint)

Answer 20

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