the glenohumeral joint is the most commonly dislocated joint in the body since stability is sacrificed for motion
recurrence rate depends on age of 1st dislocation: <20 yrs = 65-95%; 20-40 yrs = 60-70%; >40 yrs = 2-4%

4 Joints of the Shoulder
glenohumeral acromioclavicular (AC) sternoclavicular (SC) scapulothoracic

Complications

tuberosity fracture, glenoid rim fracture
rotator cuff tear, shoulder stiffness
injury to axillary nerve/artery, brachial plexus injury
recurrent/unreduced dislocation

PEARL

Laxity is a clinical exam finding that refers to the ability to translate the humeral head on the glenoid. Instability is a pathologic condition associated with pain & excessive translation of the joint

Anterior Shoulder Dislocation (>90%)

Mechanism*
abducted and externally rotated arm or blow to posterior shoulder

Clinical Features

pain
arm held in slight abduction, external rotation; internal rotation is blocked (“squared off” shoulder)
+ve apprehension test: apprehension with shoulder abduction and external rotation to 90o since humeral head is pushed anteriorly and recreates feeling of anterior dislocation
+ve relocation test: a posteriorly directed force applied during the apprehension test relieves apprehension since anterior subluxation is prevented
+ve sulcus sign: presence of subacromial indentation with distal traction on humerus indicates inferior shoulder instability
conduct neurovascular exam including
- axillary nerve (sensory patch over deltoid and deltoid contraction)
- musculocutaneous nerve (sensory patch on lateral forearm and biceps contraction)

Investigations

x-rays: AP, trans-scapular, axillary

X-Ray Findings

dislocation
axillary view: humeral head is anterior
trans-scapular view: humeral head is anterior to the centre of the “Mercedes-Benz sign”
± Hill-Sachs lesion: divot in posterior humeral head due to forceful impaction of an anteriorly dislocated humeral head against the glenoid rim
± bony Bankart lesion: avulsion of the anterior glenoid labrum (with attached bone fragments) from the glenoid rim

Treatment

closed reduction with IV sedation and muscle relaxation

Traction-countertraction: assistant stabilizes torso with a folded sheet wrapped across the chest while the MD applies gentle steady traction
Stimson: while patient lies prone with arm hanging over table edge, hang a 5lb weight on wrist for 15-20 min

obtain post-reduction x-rays & check neurovascular status (NVS)
sling x 3 weeks, followed by shoulder rehabilitation
indications for surgery for traumatic shoulder instability
- failed or unstable closed reduction
- soft tissue interposition by the rotator cuff, capsule, or biceps tendon
- greater tuberosity fractures that remain displaced >1 cm after reduction
- large glenoid rim fractures

Posterior Shoulder Dislocations (5%)

often missed due to poor physical exam and radiographs

Mechanism

adducted, internally rotated, flexed arm
FOOSH
3 E’s (epileptic seizure, EtOH, electrocution)
blow to anterior shoulder

Clinical Features

arm is held in adduction and internal rotation; external rotation is blocked
anterior shoulder flattening, prominent coracoid
posterior apprehension (“jerk”) test: with patient supine, flex elbow 90o and adduct, internally rotate the arm while applying a posterior force to the shoulder; patient will “jerk” back with the sensation of subluxation

Investigation

x-rays: AP, trans-scapular, axillary
x-ray findings
- AP view: partial vacancy of glenoid fossa (vacant glenoid sign) and >6 mm space between anterior glenoid rim and humeral head (positive rim sign)
- axillary view: humeral head is posterior
- trans-scapular view: humeral head is posterior to centre of “Mercedes-Benz sign”
- reverse Hill-Sachs lesion: divot in anterior humeral head
- reverse bony Bankart lesion: avulsion of the posterior glenoid labrum from the bony glenoid rim

Treatment

closed reduction: inferior traction on a flexed elbow with pressure on the back of thehumeral head
obtain post-reduction x-rays & check neurovascular status
sling x 3 weeks, followed by shoulder rehabilitation

Superior Labral Anterior and Posterior (SLAP) Lesions

Factors Causing Shoulder Instability
Shallow glenoid Loose capsule Large mobility

tear of the superior labrum that starts posteriorly and extends anteriorly to include the anchor of the long head of the biceps tendon
Mechanism
traumatic injury: superior compression as a result of a FOOSH or forceful traction secondary to a sudden inferior pull
repetitive overhead activity (overhead athletes)

Clinical Features

poorly defined posterior pain exacerbated with overhead activity
symptoms of mechanical pain & dysfunction, rather than instability
instability if tear extends into the anterior ligament
night pain & cuff weakness from associated tears

Snyder classification
– isolated fraying of the superior labrum
II – detachment of the superior labrum & the origin of the long head of the biceps from the glenoid
III – bucket handle tear for the labrum with an intact biceps insertion
IV – bucket handle tear of the labrum that extends into the biceps tendon anchor

Common in practice and exams!
3 major types – Anterior/Posterior/Inferior

Clinical:

History:

Usually a fall onto the outstretched arm but:
Posteriorly directed force to an abducted and externally rotated arm suspect ANTERIOR

3-E’s (epileptic seizure, E=OH, electric shock) suspect POSTERIOR

Physical:

Look for loss of contour, palpate for humeral head.
Check axillary nerve (most commonly injured), but also radial, median and ulnar.
Unable to internally rotate – likely anterior dislocation
Unable to externally rotate – likely posterior dislocation
Abducted – consider inferior dislocation (rare, also called luxation erecta).

X-Ray:

make sure you get adequate films to assess the injury.
An AXILLARY view is great if you can get it (see below) and confirms anterior/posterior position.

Reduction:

Make sure the patient has adequate analgesia/sedation
Do not use the Kocher technique for reduction – it tends to break humeri!
Use one of the methods shown below:

Use a similar technique for posterior dislocation. Inferior dislocation is more difficult and often requires hyperabduction to “unlock” the humeral head.
A fracture of the greater tuberosity is very common with anterior dislocation. Do not be alarmed!! It usually reduces perfectly once the shoulder is reduced.
Immobilize the patient in a good Velpeau. Otherwise the shoulder may slip out during shooting of the post-reduction films!

An axillary view is MANDATORY for evaluation after the reduction.