01Approach to the Critical Patient/attcp51

Immediate priorities

›Neurovascular status

›Axillary nerve function pre-reduction

›Lateral deltoid sensation (regimental badge area)

›Deltoid motor strength

›Distal pulses

›Radial pulse

›Brachial pulse

›Hand motor and sensory function

›Median, radial, and ulnar nerve territory

›Alarm features requiring urgent escalation

›Absent distal pulse

›Vascular surgery consultation

›Emergent imaging if reduction fails to restore flow

›Bilateral posterior dislocation

›Pathognomonic for seizure or electrocution

›Concurrent cardiac monitoring and seizure workup

›Electrocution mechanism

›Continuous cardiac monitoring for arrhythmia

›ECG for conduction abnormalities

›Fracture-dislocation pattern

›Urgent orthopedic consultation

›CT prior to reduction attempt

Reduction and monitoring

›Pre-reduction preparation

›Analgesia selection

›Intra-articular lidocaine 1% 10-20 mL as first-line

›Procedural sedation if block insufficient

02History/hx75

Mechanism and presentation

›Classic mechanisms

›Posterior-directed force on flexed, adducted, internally rotated arm

›Most common traumatic mechanism

›Contact sports linemen blocking

›Seizure-related

›34-38% of posterior dislocations

›Tonic-clonic muscular contraction forces

›Electrocution

›Generalized muscle contraction

›Always suspect bilateral dislocation

›High-energy trauma

›Motor vehicle collision

›Fall from height

›Presenting symptoms

›Acute severe shoulder pain

›Sudden onset

›Unable to move arm

›Arm locked in internal rotation

›Cannot externally rotate past neutral

›Hallmark clinical feature

›Inability to abduct

›Variable degree of restriction

Seizure and electrocution history

›Seizure context

›Witnessed convulsive activity

›Tonic-clonic pattern

›Tongue bite or incontinence

03Physical Exam/exam59

Inspection and posture

›Classic posture

›Arm held in adduction and internal rotation

›Unable to externally rotate past neutral

›Hallmark finding

›Flattening of anterior shoulder contour

›Reduced anterior fullness

›Posterior shoulder fullness

›Humeral head palpable posteriorly

›Prominent coracoid process anteriorly

›Anterior shoulder feels empty

Range of motion and palpation

›ROM assessment

›External rotation loss

›Cannot rotate past neutral

›Most specific clinical sign

›Forward flexion restriction

›Variable

›Abduction restriction

›Variable

›Palpation findings

›Posterior humeral head palpable

›Below posterior acromion

›Anterior deltoid region feels empty

›Contrast with normal anterior fullness

›Focal tenderness posterior shoulder

›Posterior capsule and glenoid rim

04Differential Diagnosis/ddx60

Life-threatening and urgent diagnoses

›Immediate concerns

›Fracture-dislocation posterior shoulder

›ICD-10 S43.003A

›Requires CT and surgical planning

›Vascular injury with dislocation

›Axillary artery injury rare but critical

›Absent pulse and expanding hematoma

›Bilateral dislocation from seizure

›Underlying seizure disorder uncontrolled

›Electrocution requiring cardiac monitoring

›Electrocution with cardiac arrhythmia

›Ventricular fibrillation risk

›Prolonged monitoring required

Common mimics and alternatives

›Anterior shoulder dislocation

›ICD-10 S43.013A

›Far more common (90% of dislocations)

›Arm in abduction and external rotation

›Distinguish with axillary view

›Proximal humerus fracture

›ICD-10 S42.209A

›May coexist with dislocation

›Identify on pre-reduction radiograph

›Rotator cuff tear acute massive

›Inability to abduct

›No dislocation on imaging

›Ultrasound or MRI confirms

05Laboratory Tests/lt40

Seizure-related labs

›Metabolic seizure triggers

›Basic metabolic panel

›Sodium for hyponatremia as seizure trigger

›Calcium for hypocalcemia as seizure trigger

›Magnesium for hypomagnesemia as seizure trigger

›Glucose

›Hypoglycemia as seizure precipitant

›Point-of-care glucose immediate

›Antiepileptic drug levels

›If patient on AED therapy

›Subtherapeutic level as etiology

›Toxicology and substance screen

›Blood alcohol level

›Alcohol withdrawal seizure

›Urine drug screen

›Cocaine and sympathomimetic provocation

›Synthetic cannabinoid seizure risk

Electrocution-related labs

›Rhabdomyolysis screen

›Creatine kinase

›Elevated with prolonged seizure or electrocution

›Monitor if CK >1000 U/L

›Myoglobin urine

›Pigmented urine

›Renal injury risk

›Renal function

›Creatinine for rhabdomyolysis-induced AKI

06Diagnostic Tests/dt82

Scoring Systems

›Posterior dislocation instability assessment

›Glenoid bone loss classification

›Less than 20% glenoid loss: arthroscopic repair preferred

›Greater than 20-25% glenoid loss: bone block procedure indicated

›Reverse Hill-Sachs lesion classification

›Small: less than 20% articular involvement

›Medium: 20-40% articular involvement

›Large: greater than 40% articular involvement

›Engaging lesion requires operative intervention

›Engagement determination

›CT-based glenoid track concept applied posteriorly

›Lesion engagement with posterior glenoid during arm positioning

›Seizure risk stratification tools

›SUDEP risk assessment

›Frequency of generalized tonic-clonic seizures

›AED compliance

›Recurrent dislocation risk if seizure uncontrolled

›ACEP Level C recommendation

›Clinical trajectory and orthopedic anatomy guide surgery timing

›Scoring tools adjunctive only

MRI

›MRI shoulder indications

›Soft tissue injury characterization post-reduction

›Posterior labral tear (58% prevalence)

›Reverse Hill-Sachs lesion (86% prevalence)

›Rotator cuff tear (19-20% prevalence)

›Planned as outpatient study in most cases

›Not required acutely after successful reduction

›Consider early MRI in young active patients

›MRI arthrogram for superior labral assessment

›Posterior labrocapsular complex detail

›Biceps anchor evaluation

›MRI findings in posterior dislocation

›Reverse Hill-Sachs (anterior humeral head impaction)

›Best seen on axial sequences

›Quantify percentage of articular surface

›Posterior labral tear

›Reverse Bankart lesion

›Kim lesion variant (incomplete avulsion)

›Posterior capsular stripping

›Capsulolabral complex disruption

›Reverse HAGL lesion rare

CT

›CT shoulder indications

›Pre-reduction in fracture-dislocation

›Proximal humerus fracture-dislocation

›Reverse bony Bankart fracture

›Glenoid bone loss quantification

›Percentage of glenoid surface measurement

›Surgical planning requirement

›Reverse Hill-Sachs lesion sizing

›Percentage of humeral articular surface

›Volume measurement for surgical threshold

›Locked posterior dislocation evaluation

›Chronic missed dislocation

›Define anatomy before any reduction attempt

›CT technique and yield

›CT without contrast for bony anatomy

›3D reconstructions valuable for surgical planning

›Sensitivity for fracture-dislocation

›Superior to plain radiograph

›ACR Appropriateness Criteria 2024 Level 9 (usually appropriate)

›Glenoid retroversion measurement

›Increased retroversion predisposes to posterior dislocation

›ISAKOS 2026 study confirms anatomic risk factor

Ultrasound

›Point-of-care ultrasound for posterior dislocation

›Posterior approach technique

›Probe placed posterior shoulder

›Humeral head position relative to glenoid rim assessed

›Diagnosis when radiographs non-diagnostic

›Posterior humeral head displacement from glenoid

›Dynamic assessment during reduction attempt

›Reduction confirmation in real time

›Concentric reduction confirmed sonographically

›Alternative to post-reduction radiograph in selected cases

›Ultrasound performance

›Emerging evidence base

›Case series support diagnostic utility

›Beck and Chilstrom AJEM 2013 case report

›Operator dependency limitation

›Requires musculoskeletal ultrasound training

›Post-reduction ultrasound

›Rotator cuff integrity gross assessment

›Effusion and hemarthrosis detection

07Disposition/dispo46

Discharge criteria

›Criteria for discharge from ED

›Successful closed reduction confirmed

›Concentric reduction on post-reduction radiograph

›AP plus axillary view post-reduction

›Intact neurovascular exam post-reduction

›Axillary nerve function documented

›Distal pulses present bilaterally

›Adequate pain control achieved

›Tolerable with oral analgesics

›No associated fracture requiring operative fixation

›Review post-reduction films carefully

›Reliable follow-up arranged

›Orthopedic appointment within 1-2 weeks

Admission indications

›Criteria requiring inpatient admission

›Failed closed reduction

›Orthopedic surgery for operative reduction

›General anesthesia for relocation

›Fracture-dislocation

›Operative fixation planning

›Orthopedic surgical consultation

›Neurovascular compromise not resolving

›Vascular surgery involvement

›Serial exams required

›Seizure requiring workup

›New-onset seizure monitoring

›Neurology evaluation

08Treatment/t110

Analgesia and procedural preparation

›Intra-articular lidocaine block

›Technique

›1% lidocaine 10-20 mL

›Posterior approach to glenohumeral joint

›Inject under ultrasound guidance or landmark technique

›Efficacy

›Effective for many patients without procedural sedation

›Onset 5-10 minutes

›Advantage

›Avoids sedation risks

›Faster discharge

›Procedural sedation agents

›Propofol IV

›0.5-1 mg/kg IV induction

›Titrate to procedural sedation depth

›Short duration favorable

›Ketamine IV

›1-1.5 mg/kg IV

›Dissociative analgesia

›Laryngospasm precaution

›Midazolam plus fentanyl

›Midazolam 1-2 mg IV titrated

›Fentanyl 1-2 mcg/kg IV

›Reversal agents available

Closed reduction technique

›Standard closed reduction steps

›Position

›Patient supine

›Arm in adduction

›Step 1: Axial traction

›Apply steady longitudinal traction along arm

›Arm in slight adduction and internal rotation

›Step 2: Anterior-directed pressure

›Apply gentle anterior force to posterior humeral head

›Push humeral head anteriorly over glenoid rim

›Step 3: External rotation

›Slowly externally rotate arm while maintaining traction

›Clunk or reduction sensation indicates success

›Early reduction preferred

›Muscle spasm increases with time

›Reduction easier before spasm develops

›Ultrasound-guided reduction

›Emerging technique

›Real-time confirmation of humeral head position

›Post-reduction confirmation without radiation

Post-reduction care

›Immobilization

›Sling in neutral or slight external rotation

›Neutral rotation sling for 2-4 weeks

›External rotation brace may reduce recurrence risk

›Duration

›2-4 weeks standard

›Longer if associated labral injury

›Analgesia post-reduction

›Acetaminophen

›500-1000 mg PO every 6 hours

›First-line agent

›NSAIDs short course

›Ibuprofen 400-600 mg PO every 6-8 hours with food

›Naproxen 250-500 mg PO every 12 hours

›5-7 day course

›Opioids sparingly

›Reserve for severe pain not controlled with above

›Short course only if required

Physical therapy and rehabilitation

›Rehabilitation phases

›Phase 1: Protection and ROM

›Pendulum exercises within sling

›Gentle passive ROM at 2-4 weeks

›Phase 2: Scapular stabilization

›Scapular retraction and depression exercises

›Periscapular strengthening

›Phase 3: Rotator cuff strengthening

›Internal and external rotator strengthening

›Avoid provocative posterior loading positions initially

›Phase 4: Sport-specific conditioning

›Return to play criteria

›Pain-free symmetric ROM

›3-6 weeks for uncomplicated cases in athletes

Operative management

›Indications for surgery

›Failed closed reduction

›Open reduction under general anesthesia

›Locked posterior dislocation

›Large engaging reverse Hill-Sachs lesion

›Greater than 25-40% of articular surface

›Modified McLaughlin procedure (subscapularis transfer)

›Remplissage-type filling procedure

›Associated displaced fracture

›Reverse bony Bankart requiring fixation

›Proximal humerus fracture-dislocation

›Recurrent posterior instability

›Refractory to conservative management

›Arthroscopic posterior capsulolabral repair

›Surgical options by indication

›Arthroscopic posterior capsulolabral repair

›For posterior labral tear with recurrent instability

›Bone anchors for reverse Bankart repair

›Modified McLaughlin procedure

›Subscapularis tendon transfer into Hill-Sachs defect

›Prevents engagement of lesion

›Bone block procedures

›For posterior glenoid bone loss >20-25%

›Iliac crest or allograft

›Total shoulder arthroplasty

›Chronic locked dislocation with arthrosis

›When joint preservation not feasible

Seizure management

›Antiepileptic therapy

›AED initiation after first seizure with dislocation

›Protective effect against recurrent dislocation injury

›Neurology to guide AED selection

›Seizure-freedom protective

›Even partial seizure control reduces dislocation risk

›Langenbruch et al. Seizure 2019

09Special Populations/sp83

Pregnancy

›Pregnancy considerations for posterior shoulder dislocation

›Reduction technique unchanged

›Closed reduction appropriate in all trimesters

›Intra-articular lidocaine preferred over sedation when possible

›Procedural sedation in pregnancy

›Propofol used with obstetric team awareness

›Fetal monitoring if viable gestation during sedation

›Anesthesia consultation for complex cases

›Imaging in pregnancy

›Plain radiographs with lead shielding acceptable

›Diagnostic benefit outweighs radiation risk

›CT shoulder with abdominal shielding if needed

›Focused limb CT with low fetal dose

›MRI preferred over CT for soft tissue in pregnancy

›No ionizing radiation

›First trimester avoid gadolinium contrast

›Analgesia safety in pregnancy

›Acetaminophen first-line

›Safe across all trimesters

›NSAIDs restricted in third trimester

›Premature ductus arteriosus closure risk

›Avoid after 28 weeks

›Opioids with caution

›Neonatal withdrawal risk with prolonged use

›Short-term use with monitoring acceptable

Geriatric

›Geriatric-specific features

›Increased associated fracture risk

›Osteoporosis increases fracture-dislocation incidence

›CT more likely needed for bony assessment

›Fall mechanism more common

›Lower-energy mechanisms cause dislocation in osteoporotic bone

›Coexisting proximal humerus fracture common

›Chronic locked dislocation risk

›Atypical presentation and delayed diagnosis

›Presenting late with limited ROM

›Medication considerations in older adults

›Procedural sedation caution

›Reduced doses of propofol and benzodiazepines

›Prolonged effect of sedatives

›Aspiration risk if NPO status uncertain

›Opioid sensitivity

›Lower starting doses

›Delirium risk with opioids

›NSAID risks in elderly

›Renal impairment risk

›GI bleeding risk

›Prefer acetaminophen where possible

›Seizure in older adults

›New-onset seizure more likely to have structural cause

›Brain imaging required

›Stroke, subdural, neoplasm workup

›Multidrug interactions with AEDs

›Extensive polypharmacy review

›Sodium levels monitoring with enzyme-inducing AEDs

Pediatrics

›Pediatric posterior shoulder dislocation features

›Less common in children than adults

›Physeal fracture often occurs before dislocation

›Physis weaker than capsuloligamentous structures

›Physeal injury must be excluded

›Salter-Harris fracture vs dislocation

›MRI or comparison views may be needed

›Adolescent athletes

›Contact sports mechanism as in adults

›Posterior instability in throwing athletes

›Pediatric analgesia and sedation

›Intra-articular lidocaine for older adolescents

›0.25-0.5 mL/kg of 1% lidocaine up to 20 mL

›Ketamine IV procedural sedation

›1-2 mg/kg IV for procedural sedation

›Preferred in pediatric ED

›Acetaminophen

›15 mg/kg PO or IV every 6 hours

›Maximum 75 mg/kg per day

›Ibuprofen

›10 mg/kg PO every 6-8 hours

›Maximum 40 mg/kg per day

›Rehabilitation in youth

›Growth plate healing confirmation before return to sport

›Age-appropriate sport return timelines

›Typically 4-8 weeks for uncomplicated cases

›Child protection consideration if mechanism unclear

›Non-accidental injury screen

›Bilateral dislocations in non-seizure pediatric patient require investigation

10Background/b81

Epidemiology

›Incidence and frequency

›Posterior dislocation accounts for 2-5% of all shoulder dislocations

›Most sources cite approximately 10% overall

›Prevalence 1.1 per 100,000 population per year

›Most commonly missed orthopedic emergency

›50-79% missed on initial presentation

›Diagnosis delayed by days to years in chronic cases

›Age and sex distribution

›Peak incidence age 20-49 years

›Male predominance

›Etiology distribution

›Seizure-related

›34-38% of posterior dislocations

›Leading non-traumatic cause

›Traumatic

›High-energy mechanism most common

›Contact sports significant contribution

›Electrocution

›Classic but less common

›Always bilateral consideration

›Associated injury prevalence

›Reverse Hill-Sachs lesion

›86% prevalence

›Most common associated injury

›Posterior labral tear

›58% prevalence on MRI

›Rotator cuff tear

›19-20% prevalence

›Risk increases fivefold in absence of Hill-Sachs (OR 4.6)

›Overall 65% of cases have at least one associated injury

Pathophysiology

›Glenohumeral anatomy and vulnerability

›Posterior dislocation mechanism

›Posterior-directed force with arm flexed, adducted, internally rotated

›Posterior capsule and labrum fail

›Seizure and electrocution mechanism

›Tonic-clonic contraction drives humeral head posteriorly

›Internal rotators overpower external rotators

›Subscapularis, pectoralis major, and latissimus dorsi dominance

›Anatomic predisposing factors

›Increased glenoid retroversion reduces posterior stability

›Higher, flatter acromion associated with posterior dislocation

›Associated injury mechanisms

›Reverse Hill-Sachs formation

›Anterior humeral head impacts posterior glenoid rim

›Impaction fracture creates defect

›Engaging lesion catches on glenoid during arm use

›Posterior labral tear

›Capsulolabral avulsion from posterior glenoid

›Reverse Bankart lesion analogous to anterior counterpart

›Chronic locked dislocation

›Delay in diagnosis allows muscle contracture

›Articular cartilage damage from chronic contact

›Arthrosis develops over months to years

Therapeutic Considerations

›Reduction philosophy

›Early reduction superior

›Reduces muscle spasm duration

›Decreases risk of neurovascular compromise

›Intra-articular block vs procedural sedation

›Block preferred to reduce sedation risk

›Procedural sedation reserved for failure of block

›Failed reduction after two attempts

›Orthopedic consultation and operative reduction

›Do not persist with repeated attempts

›Immobilization evidence

›Neutral rotation sling standard

›2-4 weeks duration

›External rotation bracing may reduce recurrence

›Early mobilization evidence

›Too-early mobilization increases re-dislocation risk

›Structured physiotherapy at 2-4 weeks

›Recurrence prevention

›Seizure control critical

›AED therapy reduces recurrent dislocation

›Even partial control protective

›Surgical threshold

›First-time dislocation with large Hill-Sachs: early surgery consideration

›Recurrent instability: operative repair after failed conservative trial

›Recurrence risk stratification

›Age <40: highest recurrence risk

›Seizure etiology: high recurrence if uncontrolled

›Large reverse Hill-Sachs >1.5 cm cubed: surgical planning required

11Patient Discharge Instructions/pdi45

copy discharge instructions

›Posterior shoulder dislocation home care

›Wear sling at all times except bathing for 2-4 weeks

›Keep arm close to body

›Do not reach behind your back

›Ice application

›20 minutes on, 40 minutes off

›Protect skin with cloth between ice and skin

›Elevate arm when possible

›Use pillow under arm when resting

›Pain medication instructions

›Acetaminophen for pain

›500-1000 mg every 6 hours as needed

›Do not exceed 4000 mg per day

›Anti-inflammatory medication if prescribed

›Take with food

›Do not use if kidney problems or stomach ulcer history

›Avoid heavy lifting with the injured arm

›Activity restrictions

›No driving until cleared by your doctor

›Usually at minimum 2-4 weeks

›No contact sports or overhead lifting

›Until cleared by orthopedic specialist

›No reaching across body or behind back

›Return to emergency department immediately for

›Shoulder coming out of place again

›New numbness or tingling in arm or hand

›Hand or fingers turning cold, pale, or blue

12References/r36

Guidelines and key sources

›Society guidelines

›ACR Appropriateness Criteria Acute Shoulder Pain 2024 Update

›Laur O, Ha AS, Bartolotta RJ, et al. JACR. 2025

›American Family Physician acute shoulder injuries adults 2023

›Simon LM, Nguyen V, Ezinwa NM. AFP. 2023

›Team Physician Consensus Statement musculoskeletal injuries 2024

›Herring SA, Kibler WB, Putukian M, et al. Med Sci Sports Exerc. 2024

Key clinical studies

›Epidemiology and recurrence

›Robinson CM, Seah M, Akhtar MA. Epidemiology, risk of recurrence, and functional outcome after acute traumatic posterior shoulder dislocation. JBJS. 2011

›Recurrence rate 17.7% in first year

›Risk factors: age <40, seizure etiology, large Hill-Sachs

›Kelly MJ, Holton AE, Cassar-Gheiti AJ, et al. Aetiology of posterior glenohumeral dislocations: systematic review. Bone Joint J. 2019

›Seizure 34-38% of cases

›50-79% missed on initial presentation

›Associated injuries

›Rouleau DM, Hebert-Davies J. Incidence of associated injury in posterior shoulder dislocation: systematic review. J Orthop Trauma. 2012

›65% have at least one associated injury

›Rotator cuff tear OR 4.6 without Hill-Sachs

›Saupe N, White LM, Bleakney R, et al. Acute traumatic posterior shoulder dislocation: MR findings. Radiology. 2008

›86% reverse Hill-Sachs on MRI

›58% posterior labral tears

›Seizure-related dislocation

›Langenbruch L, Rickert C, Gosheger G, et al. Seizure-induced shoulder dislocations. Seizure. 2019

›AED treatment protective against recurrent dislocation

›Cucchi D, Baumgartner T, Walter SG, et al. Epidemiology of shoulder injuries in epileptic seizures. Arch Orthop Trauma Surg. 2023

Evidence & Review