Acute Posterior Dislocation

 

post shpost shPosterior Shoulder Dislocation CT 1Posterior Shoulder Dislocation CT 2

 

Epidemiology

 

Rare - 2% of acute dislocations

 

Easily missed diagnosis

 

Etiology

 

Usually secondary major trauma

- MVA

- Seizures

- Electrocution

- Alcohol-related injuries

 

Examination

 

Loss of external rotation

- arm held across chest

- limited active and passive ROM

 

AP Xray

  

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Abnormal overlap of humeral head on glenoid

 

LightbulbLightbulbpost sh dis

Light-bulb sign - globular head secondary to internal rotation of the humeral head

 

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Vacant Glenoid Cavity - > 6 mm space between humeral head and anterior rim of glenoid

 

Scapular lateral

 

Center of the humeral head must be centered on the Y / Mercedes sign

 

Y is formed by 

- coracoid anteriorly

- scapular spine posteriorly

- scapula body inferiorly

 

mercedes signMercedes sign

Normal scapular lateral

 

post dislocationposterior shoulder dislocation

Posterior shoulder dislocation

 

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Posterior shoulder dislocations

 

Axillary Xray

 

Diagnostic - humeral head posterior to glenoid with evidence of reverse Hill Sachs

 

ax lateralpost shPosterior Shoulder Dislocation Axillary Lateral

 

CT scan

 

Confirms dislocation

 

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Reverse Hill Sachs

 

Humeral head defect 

- caused by impaction of anterior humeral head on posterior glenoid

- intra-articular

- measured as a percentage of the articular surface

 

Rev HSRev HS

 

CT Chronic Posterior Humeral Head DefectRev HS

 

Lesser tuberosity fractures

 

LT fractureLT fractureLT fracture

 

Posterior glenoid fractures / bony bankart

 

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MRI

 

Posterior Shoulder DislocationPosterior Shoulder Dislocation 2

Acute MRI demonstrating reverse Hill Sachs and posterior labral tear

 

Chronic Posterior Shoulder Dislocation MRI AxialChronic Posterior Shoulder Dislocation MRI Sagittal

Chronic posterior shoulder dislocation with humeral head remodelling and glenoid bony deficiency

 

Management

 

Closed reduction

 

Issues that limit closed reduction

 

Chronic injuries > 2 - 4 weeks old

Locked dislocations - reverse Hills sachs lesion on glenoid rim

Large Hill Sachs defects - recurrent dislocation / instability

 

Technique

 

Conscious sedation

- arm adducted

- arm flexed to 90o

- increasing IR first to unlock head

- traction

 

Place into external rotation brace / gunslinger cast

 

Breg arc bracedonjoy x act

Breg Arc and Donjoy X-ACT shoulder external rotation braces

 

Acute surgical management

 

Indication

 

Failure closed reduction / locked posterior dislocation

Recurrent dislocation - unable to maintain reduction in gunslinger / external rotation brace

Displaced lesser tuberosity fractures

Displaced posterior bony bankart fractures

 

Technique

 

Anterior deltopectoral approach - reduce humeral head

 

Address bony defects

- reverse Hill Sachs / anterior humeral head defect

- posterior bony bankart

 

Humeral head Defect Management

 

Reverse Hills Sachs < 25% Reverse Hills Sachs 25% - 40% Reverse Hills Sachs > 40%

Non operative

Elevate and bone graft if acute

Subscapularis / lesser tuberosity transfer

Subscapularis / lesser tuberosity transfer

Osteochondral allograft

Hemicap

Osteochondral allograft

Arthroplasty

Rev HS CT Chronic Posterior Humeral Head Defect rev hill sachs

 

Subscapularis +/- Lesser tuberosity transfers

 

Indications

 

Defects 25%

 

rev hsrev hsrev HS

 

rev hsrev hsrev hs

 

Options

 

McLaughlin - subscapularis transfer into defect / makes defect extra-articular

Neer modification - lesser tuberosity + subscapularis transfer into defect

 

Technique

 

Vumedi modified McLaughlin video

 

Vumedi modified McLaughlin video 2

 

Results

 

Berk et al JSES Rev 2023

- systematic review of modified McLauglin for locked posterior dislocation

- 9 studies and 97 shoulders

- reverse Hill Sachs 20 - 50%

- 100% union

- complication 1% (screw loosening)

- recurrent instability 2% (epileptic patients)

 

Osteochondral Allograft Reconstruction

 

Indication

 

Reverse Hills Sachs defects 25 - 50%

 

Technique

 

Video J Sports Med 2022 Reverse Hill Sachs Allograft

 

Surgical technique Reverse Hill Sachs Allograft PDF

 

Case 1: Lesser tuberosity osteotomy, removal comminuted articular fragment, insertion osteochondral allograft

 

Rev HSRev HSrev HS

 

Rev HSrev HSrev HS

 

Shoulder McLaughlin APShoulder McLaughlin Lateral

 

Case 2: Osteochondral allograft with anchor repair of subscapularis



rev HSrev HSRev HS

 

Reverse Hill Sachs AllograftReverse Hill Sachs Allograft 2

 

Results

 

Buda et al J Exp Orthop 2024

- systematic review of McLaughlin and humeral head allograft for reverse Hill Sachs

- 14 studies and 150 patients

- no difference in outcomes between 2 groups

- OA: McLaughlin 11%, allograft 21%

 

Lesser tuberosity ORIF

 

LTLTLT

 

Hemiarthroplasty / TSR

 

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