The Shoulder

Question 0

For Scapulohumeral rhythm, which joints are involved?

Answer 0

All four joints involved

Question 1

What is the Scapulohumeral Rhythm?

Answer 1

The combined motions of glenohumeral joint abduction/flexion and scapulothoracic upward rotation.

Question 2

What is the movement ratio of Scapulohumeral rhythm?

Answer 2

Overall 2:1 GH to ST

GH = 120 degrees, ST= 60 degrees

Question 3

What is the Scapulohumeral rhythm for Scapulocervical joint?

Answer 3

Retraction 15 degrees
Elevation 25 degrees
Posterior 25 degrees

Question 4

What is the Scapulohumeral rhythm of the acromioclavicular joint?

Answer 4

Upward rotation 35 degrees
Posterior rotation 20 degrees
External rotation 10 degrees

Question 5

What is the Scapulohumeral rhythm of the scapulothoracic joint?

Answer 5

Upward rotation 60 degrees

Question 6

What is the Scapulohumeral rhythm of the glenohumeral joint?

Answer 6

Abduction 120 degrees

External rotation 45 degrees

Question 7

What are the critical motions for smooth Scapulohumeral rhythm?

Answer 7

Superior roll and compression of the humeral head
Upward rotation of the scapula
ER of the humerus

Question 8

At what degree of elevation of phase one and What are eight aspects that occur in phase one of the Scapulohumeral joint

Answer 8

First 90 degrees of elevation
Upper and lower trapezius and serratus anterior upwardly rotate the scapula
Scapula rotation occurs because of clavicle elevation
Clavicle elevation stops at 25 degrees due to costoclavicular ligament taut.
The AC joint does not contribute due to tension in coracoclavicular ligament
Supraspinatus rolls the humeral head superiorly and compresses into fossa
Deltoid elevates humeral head
Infraspinatus, subscapularis and teres minor exert downward translational force to counter excessive superior rotation
Infraspinatus and teres minor begin to ER the humerus

Question 9

What are the degrees of the first phase of Scapulohumeral rhythm?

Answer 9

First 90 degrees of elevation
60 degrees of GH joint elevation
30 degrees of ST upward rotation (axis of rotation at base of spine of the scapula)
Total of 90 degrees of shoulder elevation

Question 10

What are the 4 aspects of the second phase and what are the degrees of elevation?

Answer 10

Second 90 degrees of elevation
SC joint can no longer elevate
Clavicle now rotates posteriorly
Scapula rotates another 30 degrees due to the posterior rotation of the clavicle with the axis through AC
Muscles of the ST and GH joints continue to the same forces as noted during the first 90 degrees

Question 11

What are the degrees during the second phase of Scapulohumeral rhythm?

Answer 11

60 degrees more of GH joint elevation
30 degrees more of ST upward rotation
Total of 180 degree shoulder elevation

Question 12

What occurs when the Deltoid acts alone to elevate the humerus?

Answer 12

The head of the humerus will be pulled into the acromion
This is known as impingement
The rotator cuff muscles act to steer the humeral head from the acromion during humeral elevation

Question 13

What are the rotary cuff muscles

Answer 13

Supraspinatus
Infraspinatus
Teres minor
Subscapularis

Question 14

What occurs during upward rotation of the scapula?

Answer 14

The upper/lower trapezius and serratus anterior are working concentrically

Question 15

What do the rhomboids and middle trapezius do?

Answer 15

Control the strong protraction force of serratus anterior with much of these fibers working eccentrically

Question 16

What are the combined Scapulohumeral motions?

Answer 16

Distributes the motion between the GH and ST joints, permitting a large ROM with less compromise of stability
Maintains the glenoid fossa in an optimal position to receive the head of the humerus, increasing joint congruency
Allow muscles to maintain a good length tension relationship