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

Question 13

Scapular Protraction muscles

Answer 13

Serratus anterior
Pectoralis major
Pectoralis minor

Question 14

Scapular retraction muscles

Answer 14

Middle traps
Rhomboids

Question 15

Scapaular elevator muscles

Answer 15

Upper traps
Levator scap
Rhomboids

Question 16

Scapular depression muscles

Answer 16

Lower traps
Lats
Pectoralis minor

Question 17

Scapular downward rotators

Answer 17

Rhomboids
Lats
Levator scap
Pectoralis minor

Question 18

Scapular upward rotators

Answer 18

Upper traps
Serratus anterior
Lower traps

Question 19

What does the Superior GH ligament do

Answer 19

Limits anterior and inferior translations of humeral head WHEN ARM IS AT THE SIDE

Question 20

What does the Middle GH ligament do

Answer 20

Limits anterior humeral translation with arm at side and UP TO 60 DEGREES ABDUCTION

Question 21

What does the Inferior glenohumeral ligament complex (IGHLC) do?

Answer 21

• Major role of jt stabilization w/ ABD greater than 45 degrees or with combined ABD + rotation *
• ABD greater than 45 degrees,
  -> INFERIOR CAPSULE SLACK IS TAKEN UP, and RESISTS INFERIOR HUMERAL HEAD TRANSLATION
• ABD + ER
  -> ANTERIOR BAND of IGHLC fans out anteriorly to provide anterior joint stability, RESISTS ANTERIOR AND INFERIOR HUMERAL HEAD TRANSLATION
• ABD + IR
  -> POSTERIOR BAND of IGHLC fans posteriorly to provide posterior jt stability, RESISTS POSTERIOR AND INFERIOR HUMERAL HEAD TRANSLATION

Question 22

What does the Coracohumeral ligament do?

Answer 22

-Limits inferior translation of humeral head in dependent arm position
-Resists humeral lateral rotation with the arm adducted