Shoulder Impingement, Biomechanics/Scapular Dyskinesia, Nerve Entrapment

Question 1

What are 2 types of shoulder Impingements?

Answer 1

• External Impingement
• Internal Impingement

Question 2

What is External Impingement?

Answer 2

The common impingement at the glenohumeral joint causing compression of soft tissues between the greater tuberosity and the coraco-acromial arch

Characterized by a decrease in subacromial space and a ‘painful arc’ of motion.

Question 3

What causes external impingement?

Answer 3

A decrease in the amount of subacromial space leading to early contact of the humerus with the coraco-acromial arch

This results in compression of the soft tissues.

Question 4

What are the classic findings of external impingement?

Answer 4

A ‘painful arc’ of motion with greatest pain beyond 90 degrees of abduction

Pain is located along the anterior-lateral side of the shoulder.

Question 5

What is internal impingement?

Answer 5

Entrapment of soft tissues between the head of the humerus and the glenoid labrum complex

Involves the joint capsule, infraspinatus, and supraspinatus.

Question 6

Who is most commonly affected by internal impingement?

Answer 6

Overhead athletes

This population is particularly vulnerable due to their range of motion requirements.

Question 7

What is the mechanism of injury (MOI) for internal impingement?

Answer 7

Abduction and external rotation of the humerus greater than 90 degrees

This position can pinch the posterior joint capsule and/or infraspinatus/supraspinatus.

Question 8

Where is the pain located in cases of internal impingement?

Answer 8

In the posterior aspect of the shoulder

Pain is greatest towards end-range external rotation.

Question 9

What is the normal position of the scapula?

Answer 9

• Lateral border of the scapula is angled anterior 30-45° from the frontal plane
• Upwardly rotated scapula of ~10-20°
• Anterior Tipping of ~10-20°

Question 10

With the Deltoid and RTC force couple, what happens if the strength ratio of the deltoids are greater than the RTC?

Answer 10

It would result in an upward/superior migration of the humeral head during arm movements, thereby causing pathological compression of the greater tuberosity of the humerus into the underside of the coraco-acromial arch

Question 11

What is the role of the Upper Trapezius and Serratus Anterior in shoulder complex elevation?

Answer 11

They create an upward rotation of the scapula

This occurs due to the contractile pull of these scapula-thoracic muscles.

Question 12

List the four functions of the Upper Trapezius and Serratus Anterior force couple.

Answer 12

• Allows rotation of the scapula
• Maintains efficient length-tension relationship for the deltoid
• Prevents impingement of the RTC from the coracoacromial arch
• Stabilizes the scapula during movement

This stabilization allows for the recruitment and action of the scapula-humeral muscles.

Question 13

What is the primary function of the Rotator Cuff (RTC) musculature?

Answer 13

To create stability at the glenohumeral joint throughout a range of motion

The RTC is crucial for maintaining the position of the humeral head.

Question 14

What does the RTC musculature do to the humeral head during shoulder movement?

Answer 14

Depresses the humeral head away from the coracoacromial arch and compresses it into the glenoid fossa

This is important for seating the humeral head within the glenoid labrum.

Question 15

Which muscles are part of the anterior and posterior Rotator Cuff?

Answer 15

• Anterior RTC: Subscapularis
• Posterior RTC: Infraspinatus, Teres Minor

These muscles are key in maintaining depression and compression of the humeral head.

Question 16

True or False: The RTC muscles are primarily inactive during midranges of shoulder elevation.

Answer 16

False

The RTC muscles are primarily active throughout the midranges of shoulder elevation.

Question 17

How does the RTC contribute to the alignment of the humeral head?

Answer 17

It balances the humeral head in central alignment due to its line of pull

This is essential for maintaining stability during shoulder movements.

Question 18

What is scapular dyskinesis?

Answer 18

A change or abnormality in the normal resting position or dynamic movement of the scapula

Scapular dyskinesis may be a specific response to shoulder injury or a non-specific response to other conditions.

Question 19

What are the three common patterns of scapular dyskinesis?

Answer 19

1. Loss of upward rotation
2. Excessive scapular internal rotation
3. Excessive scapular anterior tilt

These patterns relate to the dynamic control of the scapula.

Question 20

What could cause the upper trapezius to become weak?

Answer 20

Excessive scapular internal rotation could be a result of decreased activation of the Serratus Anterior

Question 21

What could cause decreased activation of the serratus anterior?

Answer 21

Excessive scapular anterior tilt could be a result of a tight pectoralis minor on the same side

Question 22

“SICK” Scapula is used to describe the presentation of scapular dyskinesis. What does “SICK” stand for?

Answer 22

Scapular Malalignment/Malposition
Inferior-medial border prominence
Coracoid malposition and pain
Kinesis Abnormalities

Question 23

What is the function of the Suprascapular Nerve? What are its different branches?

Answer 23

• This is a motor nerve to the Supraspinatus and Infraspinatus

Also does sensory to the Posterior GH joint capsule and Acromioclavicular joint

Question 24

How can the Suprascapular Nerve become entrapped?

Answer 24

It can become entrapped as it runs through the spinal notch of the superior aspect of the scapula.
- Any space occupying lesion, cyst or tumor may cause compression of the nerve

Question 25

Clinically will you see the suprascapular nerve compressed or tensioned?

Answer 25

Clinically we will see that the nerve has become tensioned, if there is excessive protraction or repetitive protraction, the nerve can become tensioned and may cause significant pain in the posterior aspect of GH joint

Question 26

With the suprascapular nerve, what would happen if there is tension for long time?

Answer 26

We will see motor loss of the supraspinatus and infraspinatus and pain in the posterior aspect of the GH joint

Question 27

In terms of treatment, how do you treat a nerve that is under too much tension or there is repetitive protraction?

Answer 27

We must keep the scapular in a retracted position, can be used with taping, bracing or postural cue.
- This will put the nerve in more slack

Question 28

What is the function of the Dorsal Scapular Nerve?

Answer 28

A motor nerve to the Rhomboid and Levator Scapulae

Question 29

How can the Dorsal Scapular Nerve get entrapped?

Answer 29

This nerve tends to get entrapped between the scalenes, due to muscle tightness associated with poor posture or just tightness in general.
- Also 1st rib hypomobility may cause muscle tightness leading to entrapment

Question 30

Those patient that have a Dorsal Scapular Nerve Entrapment, they will typically present with what?

Answer 30

Patients will come with a diagnosis of another shoulder dysfunction; impingement syndrome, tendinopathy, bursitis

Question 31

What is common to find objectively with those patients with a Dorsal Scapular Entrapment?

Answer 31

They would have weak levator scapulae, rhomboids and tight scalenes