My Shoulder

Question 1

Joints of Shoulder Complex

Answer 1

Sternoclavicular (SC) Joint
Acromioclavicular (AC) Joint
Scapulothoracic (ST) “Joint”
Glenohumeral (GH) Joint

Question 2

Characteristics of SC Joint

Answer 2

• only structural attachment between axial skeleton and shoulder/UE
• Articulation of medial clavicle w/ manubrium of sternum & costal cartilage
• Synovial, saddle joint
• At rest, it space is wedge-shaped and open superiorly

Question 3

Osteokinematics and Arthrokinematics of SC Joint (Elevation and Depression)

Answer 3

• Occur near FRONTAL PLANE
• Osteokinematics: superior and inferior translation
• Arthrokinematics: Convex on Concave (VCO)
  -> Elevation: Lateral clavicle elevates, medial clavicle rolls superiorly, slides inferiorly
  -> Depression: Lateral clavicle depresses, medial clavicle rolls inferiorly, slides superiorly

Question 4

Osteokinematics and Arthrokinematics of SC Joint (protraction and retraction)

Answer 4

• Occurs near TRANSVERSE PLANE
• Osteokinematics: translates anteriorly and inferiorly
• Arthrokinematics: Concave on Convex (CVS)
  ->Protraction: Lateral clavicle moves anteriorly, medial clavicle rolls and slides anteriorly
  ->Retraction: Lateral clavicle moves posteriorly, medial clavicle rolls and slides posteriorly

Question 5

Osteokinematics and Arthrokinematics of SC Joint (rotation)

Answer 5

• Occurs around longitudinal axis
• Osteokinematics: Long-axis rolling motions of entire clavicle
  -Arthrokinematics: Occurs as a SPIN between the joint surfaces and disc (clavicle rotates primarily posteriorly)

Question 6

Anterior and Posterior Sternoclavicular Ligaments

Answer 6

Connects medial clavicle to manubrium of sternum
Reinforce the capsule
- Limit anterior and posterior translation

Question 7

Costoclavicular Ligament

Answer 7

Connects clavicle to 1st rib
Very strong ligament, composed of 2 bundles
- Both limit clavicle elevation
- Posterior bundle resists medial translation of clavicle
Function axis of rotation
Absorbs & transmits superiorly directed forces applied to clavicle via SCM and sternohyoid muscles
(Anterior bundle more oblique, Posterior bundle runs up and down)

Question 8

Interclavicular Ligament

Answer 8

Connects medial ends of clavicle together
-Limits excess depression of clavicle
-> Protects brachial plexus and subclavian artery
-Limits superior gliding on medial clavicle on manubrium

Question 9

Characteristics of Acromioclavicular (AC) Joint

Answer 9

Connects lateral clavicle and acromion
Incongruent plane,synovial jt- 3 rotational and 3 translational dof
Functions
- Allows scapula to move in 3 dimensions during arm movement
-> increases UE motion
-> positions glenoid beneath humeral head
-> helps maximize scapula contact w/ thorax
- Assists in force transmission from UE to clavicle

Question 10

AC Joint Surface

Answer 10

Relatively vertical orientation of jt surfaces -> more susceptible to shearing forces -> degenerative effects
- Initially, clavicle and acromion have fibrocartilaginous union btwn them
- UE overuse causes joint space
- leaves “me is al homologous” w/in joint

Question 11

Superior Acromioclavicular ligament

Answer 11

Connects acromion and clavicle
- Resists anteriorly directed forces applied to lateral clavicle
- Reinforced by aponeurotic fibers to trap and delt
- Stronger that inferior capsule and ligament

Question 12

Coracoclavicular Ligament (conoid and trapezoid ligament)

Answer 12

Conoid: triangular shaped, vertically oriented fibers
- primary restraint to inferior translation of acromion (inferior=down, don’t want ice cream cone to fall DOWN)
Trapezoid: Quadrilateral shaped, horizontally oriented fibers
- Restraint to posterior translations of lateral clavicle moves anteriorly
Both limit upward rotation of scapula