MSK: Trauma and Overuse, Shoulder Flashcards
What is the most common type of shoulder dislocation?
Anterior (90%)
Hill-Sachs deformity
What is the best radiographic view to see a Hill-Sachs deformity?
Internal rotation view
Hill-Sachs deformity
A posterolateral humeral head depression fracture resulting from a prior anterior shoulder dislocation
Pts with a Hill-Sachs deformity often also have a…
Bankart lesion (injury to the anterior inferior labrum)
Note: Both result from anterior shoulder dislocations.
Humeral greater tuberosity avulsion fracture
Note: These can be seen after an anterior shoulder dislocation (usually pts over 40).
Anterior shoulder dislocation with avulsion fracture of the greater tuberosity
Anterior shoulder dislocation
Posterior shoulder dislocations are often due to…
Seizure or electrocution
Posterior shoulder dislocation
Note: There is a “trough sign” from an anterior humeral head impaction fracture (i.e. reverse Hill-Sachs lesion) due to impaction of the humeral head on the glenoid rim.
Think posterior dislocation of the shoulder
Note: There is a “rim sign” (when there is no overlap between the humeral head and glenoid fossa due to widening of the glenohumeral joint space).
Why does the humeral head appear abnormal on this frontal radiograph?
There is a posterior shoulder dislocation that has locked the humerus in internal rotation
Note: This is the “lightbulb sign”.
Pt is unable to move their arm out of tis position…
Luxatio erecta humeri, indicating an inferior shoulder dislocation
Inferior shoulder dislocations are associated with…
Neurologic injury (60%), usually the axillary nerve
Which of these is a Hill-Sachs deformity?
B
Note: B is at the level of the coracoid process (arrowhead), which is where you see a Hill-Sachs. A is a pseudo Hill-Sachs (normal flattening of the humeral head below the level of the coracoid process).
How can you tell whether there is a Hill-Sachs deformity or just normal flattening of the humeral head on MRI?
Flattening of the humeral head is abnormal at (B) or above the level of the coracoid process (it is normal below the coracoid, A)
What classification system is used for these fractures?
Neer classification (mostly based for how many fracture fragment parts there are)
Treatment for 3 or 4 part proximal humerus fractures
Reverse total shoulder arthroplasty
What are the 4 major types of shoulder surgery?
- Humeral head resurfacing
- Hemi-arthroplasty
- Total shoulder arthroplasty
- Reverse total shoulder arthroplasty
What type of surgery?
Humeral head resurfacing
What type of surgery?
Shoulder hemi-arthroplasty
What type of surgery?
Reverse total shoulder arthroplasty
(Anatomic) total shoulder arthroplasty
Note: There is a glenoid component in addition to the humeral component.
What type of shoulder replacement is best if the glenoid is deficient and the rotator cuff is trashed?
Reverse total shoulder arthroplasty
What factors determine which type of shoulder replacement is best?
- Whether the rotator cuff is intact
- Whether the glenoid is intact or deficient
What type of shoulder replacement is best if the glenoid is deficient, but the rotator cuff is intact?
(Anatomic) total shoulder arthroplasty
What type of shoulder replacement is best if the glenoid is intact, but the rotator cuff is trashed?
Hema-arthroplasty
or
Reverse total shoulder arthroplasty
What type of shoulder replacement is best if both the glenoid and rotator cuff are intact?
Humeral head resurfacing
or
Hemi-arthroplasty
What is the most common complication of an anatomic total shoulder arthroplasty?
Loosening of the glenoid component
What has failed?
The subscapularis muscle
Note: This is called “anterior escape” (anterior superior migration of the humeral head due to subscapularis failure).
Which muscle must be intact for a reverse total shoulder arthroplasty to be successful?
The deltoid
Note: The deltoid takes over most of the stabilizing function of the rotator cuff (which is usually trashed if you’re considering a reverse total shoulder arthroplasty).
What is the most common complication of a reverse total shoulder arthroplasty?
Posterior acromion fracture (due to excessive deltoid tugging)
Note: The deltoid is the main stabilizing muscle in these pts (who have trashed rotator cuffs).
Acromion fracture
Note: Posterior acromion fractures are a common complication of reverse total shoulder arthroplasty (due to excessive deltoid tugging).
What are the two major types of shoulder impingement?
- External (impingement of the rotator cuff overlying the superficial burial surfaces adjacent to the coracoacromial arch)
- Internal (impingement of the rotator cuff on the deep undersurface adjacent to the glenoid labrum and humeral head)
What are the primary external causes of shoulder impingement?
- Subacromial impingement (e.g. due to a “hooked” type III Bigliani acromion or subacromial osteophyte formation
- Subcoracoid impingement
Note: Primary external causes are due to an abnormal coracoacromial arch.
What are the secondary external causes of shoulder impingement?
- Multidirectional glenohumeral instability
Note: The coracoacromial arch is normal for secondary external causes.
What are the internal causes of shoulder impingement?
- Posterior superior impingement
- Anterior superior impingement
Which Bigliani acromion type is at the highest risk for external shoulder impingement?
Type 3 (hooked)
Supraspinatus tear due to impingement from a subacromial osteophyte
Subacromial impingement (e.g. due to a hooked acromion or subacromial osteophyte) predisposes to tears of the…
Supraspinatus tendon
Subcoracoid impingement predisposes to tears of the…
Subscapularis tendon
Note: The coracoid process is an anterior structure and so is the subscapularis.
Subcoracoid impingement
Note: Reduced coracohumeral distance on axial imaging (double arrow).
Subcoracoid impingement can be congenital or develop after fracture of the…
Coracoid or humeral lesser tuberosity
Note: Look for a decreased coracohumeral distance.
Why can multidirectional glenohumeral instability lead to external shoulder impingement?
Repeated micro-subluxation of the humeral head results in chronic micro-trauma that predisposes to external impingement
Note: This is usually seen in pts with joint laxity and often involves both shoulders.
Posterior superior shoulder impingement is mostly seen in what pts?
Athletes who make overhead movements (pitchers, tennis, swimming)
Posterior superior shoulder impingement predisposes to tears of the…
Posterior superior rotator cuff (the junction of the supra- and infraspinatus tendons)
and
Posterior superior glenoid labrum
Note: This is often simply refered to as “internal impingement” (because it’s more common than anterior superior internal impingement).
In posterior superior shoulder impingement, the supra- and intraspinatus tendons get pinched between…
The glenoid and the humeral greater tuberosity
Posterior superior shoulder impingement is best appreciated on what view?
ABER (abduction and external rotation)
Posterior superior internal shoulder impingement
Note: Posterior fiber supraspinatus tendinosis with intrasubstance delamination and overlying bursal fluid (black arrow). Humeral head cysts underlying the superior insertional fibers of infraspinatus which demonstrate undersurface fraying (white). Significant fraying of the posterosuperior glenoid labrum (grey arrow).
Anterior superior internal shoulder impingement predisposes to tears of the…
Subscapularis tendon
and
Anterior superior glenoid labrum
In anterior superior internal shoulder impingement, the undersurface of the biceps and subscapularis tendons become impinged against…
The anterior superior glenoid rim
Note: The impingement occurs when the arm is in horizontal adduction and internal rotation.
Cystic change in the humeral greater tuberosity is associated with what type of shoulder impingement?
Posterior superior internal shoulder impingement
Note: Look for posterior superior labral tears. Look for damage to the infraspinatus (and posterior supraspinatus) tendons.
What is the most common form of shoulder impingement?
Subacromial impingement
Note: This predisposes to supraspinatus tendon injury.
What are the two different sides of a partial rotator cuff tear?
- Bursal-sided (superficial)
- Articular-sided (undersurface)
Which side of the tendon is more likely to get torn?
The articular side (undersurface) is 3x more likely to tear than the bursal side
What is the most common tendon involved in a rotator cuff tear?
Supraspinatus
Note: Teres minor is the least likely to tear.
What is the most common location for a supraspinatus tear?
The relatively avascular “critical zone” (within 1-2 cm of the tendon footprint on the humeral head)
Note: This is also the most common location for calcium hydroxyapatite deposition in calcific tendonitis.
What 4 tendons make up the rotator cuff?
- Supraspinatus
- Infraspinatus
- Teres minor
- Subscapularis (anterior)