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)
Do partial rotator cuff tears usually get surgery?
Partial tears >50% often get surgery
What is a “massive” rotator cuff tear?
When there is full-thickness tearing of at least 2 of the 4 rotator cuff tendons
A tear of the ______ is still considered a rotator cuff tear even though it isn’t one of the 4 rotator cuff tendons
Fibrous rotator interval (between the subscapularis and supraspinatus tendons)
Full-thickness rotator cuff tear
Note: You know it is full-thickness because the tendon is replaced with fluid signal and you can see gadolinium in the extra-articular bursa.
Risk factors for adhesive capsulitis in the shoulder
Prior shoulder trauma or surgery
Imaging findings of adhesive capsulitis in the shoulder
- Loss of fat in the rotator interval (between subscapularis and supraspinatus)
- Thickening of the axillary fold of the joint capsule (i.e. the inferior glenohumeral ligament)
Think adhesive capsulitis
Note: The sagittal T2-weighted image demonstrates a thickened coracohumeral ligament (arrow) and soft tissue thickening in the rotator interval (arrowheads). The short arrow indicates the adjacent long head of the biceps tendon.
The coronal T2-weighted fat-suppressed image demonstrates an abnormally thickened inferior glenohumeral ligament (arrow).
Adhesive capsulitis classically affects what location?
The rotator interval (between the supraspinatus and subscapularis tendons)
Think adhesive capsulitis of the shoulder
Note: Replacement of the subcoracoid (rotator interval) fat by intermediate signal soft tissue thickening (asterisk), with synovial and capsular thickening at the anterior inferior aspect of the glenohumeral joint (arrow).
Increased glenohumeral volume is noted during shoulder arthropgraphy…
Think multidirectional instability
Decreased glenohumeral volume noted during shoulder arthrography…
Think adhesive capsulitis (AKA frozen shoulder)
Thickened inferior and posterior capsule…
Think adhesive capsulitis (AKA frozen shoulder)
Enhancement of the rotator cuff interval on post-gadolinium images…
Think adhesive capsulitis (AKA frozen shoulder)
What is a type 4 SLAP tear?
When the SLAP tear extends into the biceps anchor, requiring surgical biceps tenodesis (in addition to the usual debridement for a SLAP tear)
What is the most common mechanism for a SLAP tear?
Overhead motion (classically swimmers)
Are SLAP tears associated with shoulder instability?
Not usually
Sublabral recess
Sublabral recess
If a sublabral recess is longer than ______, you should consider it a SLAP tear
3 mm
Buford complex
Sublabral recess
A normal variant where you have incomplete attachment of the glenoid labrum at the 12 o’clock position (which has the least blood flow and is susceptible to both injury and variants)
Note: This is a SLAP tear mimic.
Sublabral foramen
A normal variant where there is incomplete attachment of the glenoid labrum in the 1 to 3 o’clock position
Note: Unlike a sublabral recess, this is not located at the site of biceps tendon attachment.
What are the common normal variants that look like SLAP tears?
- Sublabral foramen (11% of pts)
- Sublabral recess (70% of pts)
- Buford complex (1% gen pop of pts)
At what point should you consider a sublabral foramen might actually be a labral tear?
If the detachment extends below the equator (below the 3 o’clock position)
Buford complex
A normal variant where there is complete absence of the glenoid labrum from the 1 o’clock to 3 o’clock positions, resulting in compensatory thickening of the middle glenohumeral ligament
Congenital absence of the anterosuperior labrum results in thickening of the…
Middle glenohumeral ligament
Note: This is the Buford complex.
Thickening of the middle glenohumeral ligament (as part of a Buford complex)
Think sublabral foramen
Note: The labrum is detached in the 1 to 3 o’clock position and the middle glenohumeral ligament is not thickened.
Buford complex (absence of the labrum from the 1 to 3 o’clock position with thickening of the middle glenohumeral ligament)
What portion of the glenoid labrum is absent in a Buford complex?
The anterosuperior segment (from the 1 o’clock position to the 3 o’clock position)
What portion of the glenoid labrum is detached in a sublabral foramen?
The anterosuperior segment (from the 1 o’clock position to the 3 o’clock position)
What portion of the glenoid labrum is detached in a sublabral recess?
The superior segment (12 o’clock position) at the site of the biceps anchor
What are the major glenoid injuries that occur at the anteroinferior labrum (commonly associated with a shoulder dislocation)?
- GLAD
- Perthes
- ALPSA
- Bankart (catilaginous and osseous)
GLAD (glenolabral articular disruption)
Note: It’s a mild labral tear with associated articular cartilage damage. This is the most mild form of anteroinferior glenoid injury and is NOT associated with shoulder instability.
Perthes lesion (detachment of the anteroinferior labrum with associated stripping of an INTACT periosteum)
Note: The detached labrum looks like a “P”.
ALPSA (anterior labral periosteal sleeve avulsion)
Cartilaginous Bankart lesion
Osseous Bankart lesion
Are GLAD lesions associated with shoulder instability?
No
Note: “Aren’t you GLAD there’s no shoulder instability.”
GLAD lesion
Glenolabral articular disruption: A superficial anteroinferior labral tear with associated articular cartilage damage
Note: This is the most mild form of anteroinferior glenoid injury and is NOT associated with shoulder instability.
Perthes lesion
Detachment of the anteroinferior labrum with associated stripping of an INTACT periosteum
Note: The detached labrum looks like a “P”.
ALPSA injury
Anterior labral periosteal sleeve avulsion: medial displacement of the labroligamentous complex with absence of the glenoid labrum on the rim
Note: The periosteum remains intact.
If the anteroinferior periosteum is disrupted in an injury, what type of lesion is it?
Bankart
Bankart lesion
Disruption of the periosteum at the anteroinferior labrum (from the 3 o’clock to 6 o’clock position)
Bankart lesion (cartilaginous)
Bankart lesion (osseous)
Bankart lesion (osseous)
Reverse Bankart lesion (osseous)
Note: It is the posterior glenoid involved in a reverse Bankart.
Perthes lesion
ALPSA lesion
GLAD lesion
What section of the labrum is involved in a reverse Bankart lesion?
The posteroinferior labrum (6 o’clock to 9 o’clock)
Reverse Bankart lesion (cartilaginous)
POLPSA (posterior labrocapsular poriosteal sleeve avulsion)
Note: This is essentially a reverse Perthes lesion.
POLPSA (posterior labrocapsular poriosteal sleeve avulsion)
Note: This is essentially a reverse Perthes lesion.
Bennett lesion (an extra-articular curvilinear calcification associated with posterior labral tears, such as a POLPSA)
Bennett lesion (an extra-articular curvilinear calcification associated with posterior labral tears, such as a POLPSA)
Kim’s lesion (an incompletely avulsed/flattened/mashed posteroinferior labrum)
Note: The glenoid cartilage and posterior labrum relationship is preserved.
Kim’s lesion (an incompletely avulsed/flattened/mashed posteroinferior labrum)
Note: The glenoid cartilage and posterior labrum relationship is preserved.
Kim’s lesion (an incompletely avulsed/flattened/mashed posteroinferior labrum)
Note: The glenoid cartilage and posterior labrum relationship is preserved.
Red arrow
Abnormal axillary recess due to HAGL (Humeral Avulsion of the inferior Glenohumeral Ligament)
HAGL
Humeral avulsion of the inferior Glenohumeral Ligament
Note: This is often secondary to anterior shoulder dislocation.
HAGL (Humeral Avulsion of the inferior Glenohumeral Ligament)
Note: This is the “J sign” of the inferior glenohumeral recess, which should normally look more like a “U” (see arrow).
The subscapularis attaches to the….
Humeral lesser tuberosity (mainly), but it also sends a few fibers across the bicipital groove (contributing to the transverse ligament) to attach onto the greater tuberosity
What keeps the long head of biceps tendon in the bicipital groove?
The transverse ligament (which is made of fibers from the subscapularis tendon)
A tear of the subscapularis tendon often results in…
Medial dislocation of the long head of biceps tendon from the bicipital groove
Note: Some fibers from the subscapularis tendon contribute to the transverse ligament (which keeps the LHB tendon in the bicipital groove).
Medial dislocation of the long head of biceps tendon from the bicipital groove (implying a subscapularis tear)
Split tear of the long head of biceps tendon
A cyst at the level of the supra scapular notch may result in denervation of the…
Supraspinatus and infraspinatus
A cyst at the level of the spinoglenoid notch may result in denervation of the…
Infraspinatus
Severe fatty atrophy of the supra- and infraspinatus muscles
Note: This is most often due to rotator cuff injury, but could also be due to a cyst at the supra scapular notch.
Where is this cyst located?
Suprascapular notch
Note: This can cause denervation of both the supraspinatus and infraspinatus muscles due to compression of the suprascauplar nerve.
Suprascapular notch
Spinoglenoid notch
Red and Blue circles
Red: Suprascapular notch
Blue: Spinoglenoid notch
Where is this cyst located?
Spinoglenoid notch
Note: This can cause denervation of the infraspinatus muscle due to compression of the suprascapular nerve branches that travel inferior to the spine of the scapula.
What nerve runs through the quadrilateral (AKA quadrangular) space?
The axillary nerve
Isolated atrophy of teres minor, suggestive of quadrilateral space syndrome (due to compression of the axillary nerve)
Note: This is usually due to fibrotic bands.
What are the borders of the quadrilateral space?
- Teres minor
- Teres major
- Triceps (long head)
- Humerus (neck)
Os acromiale
Parsonage-Turner syndrome
Idiopathic neuropathy involving the brachial plexus characterized by sudden, severe pain in the shoulder followed by severe weakness
Note: Think about this if you have muscle edema that spans 2 or more nerve distributions (e.g. axillary and suprascapular nerve muscles).
Edema of the supraspinatus and infraspinatus muscles
Note: This could be due to a supra scapular notch cyst compressing the suprascapular nerve or Parsonage-Turner syndrome affecting the brachial plexus.
Teres minor is innervated by…
The axillary nerve
Infraspinatus is innervated by…
The suprascapular nerve
Supraspinatus is innervated by…
The suprascapular nerve
Subscapularis is innervated by…
The subscapular nerves (branches of the posterior cord of the brachial plexus)
Severe left shoulder pain
Think Parsonage-Turner syndrome (due to idiopathic brachial plexus neuropathy)
Note: Edema in the supraspinatus/infraspinatus (supra scapular nerve) and deltoid (axillary nerve) muscles.
