Shoulder Impingement, Biomechanics/Scapular Dyskinesia, Nerve Entrapment and Fractures Flashcards
What are 2 types of shoulder Impingements?
- External Impingement
- Internal Impingement
What is External Impingement?
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.
What causes external impingement?
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.
What are the classic findings of external impingement?
A ‘painful arc’ of motion with greatest pain beyond 90 degrees of abduction
Pain is located along the anterior-lateral side of the shoulder.
What is internal impingement?
Entrapment of soft tissues between the head of the humerus and the glenoid labrum complex
Involves the joint capsule, infraspinatus, and supraspinatus.
Who is most commonly affected by internal impingement?
Overhead athletes
This population is particularly vulnerable due to their range of motion requirements.
What is the mechanism of injury (MOI) for internal impingement?
Abduction and external rotation of the humerus greater than 90 degrees
This position can pinch the posterior joint capsule and/or infraspinatus/supraspinatus.
Where is the pain located in cases of internal impingement?
In the posterior aspect of the shoulder
Pain is greatest towards end-range external rotation.
What is the normal position of the scapula?
- 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°
With the Deltoid and RTC force couple, what happens if the strength ratio of the deltoids are greater than the RTC?
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
What is the role of the Upper Trapezius and Serratus Anterior in shoulder complex elevation?
They create an upward rotation of the scapula
This occurs due to the contractile pull of these scapula-thoracic muscles.
List the four functions of the Upper Trapezius and Serratus Anterior force couple.
- 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.
What is the primary function of the Rotator Cuff (RTC) musculature?
To create stability at the glenohumeral joint throughout a range of motion
The RTC is crucial for maintaining the position of the humeral head.
What does the RTC musculature do to the humeral head during shoulder movement?
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.
Which muscles are part of the anterior and posterior Rotator Cuff?
- Anterior RTC: Subscapularis
- Posterior RTC: Infraspinatus, Teres Minor
These muscles are key in maintaining depression and compression of the humeral head.
True or False: The RTC muscles are primarily inactive during midranges of shoulder elevation.
False
The RTC muscles are primarily active throughout the midranges of shoulder elevation.
How does the RTC contribute to the alignment of the humeral head?
It balances the humeral head in central alignment due to its line of pull
This is essential for maintaining stability during shoulder movements.
What is scapular dyskinesis?
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.
What are the three common patterns of scapular dyskinesis?
- Loss of upward rotation
- Excessive scapular internal rotation
- Excessive scapular anterior tilt
These patterns relate to the dynamic control of the scapula.
What could cause the upper trapezius to become weak?
Excessive scapular internal rotation could be a result of decreased activation of the Serratus Anterior
What could cause decreased activation of the serratus anterior?
Excessive scapular anterior tilt could be a result of a tight pectoralis minor on the same side
“SICK” Scapula is used to describe the presentation of scapular dyskinesis. What does “SICK” stand for?
Scapular Malalignment/Malposition
Inferior-medial border prominence
Coracoid malposition and pain
Kinesis Abnormalities
What is the function of the Suprascapular Nerve? What are its different branches?
- This is a motor nerve to the Supraspinatus and Infraspinatus
Also does sensory to the Posterior GH joint capsule and Acromioclavicular joint