Summary

The Glenohumeral joint is the most commonly dislocated joint in the body, owing to its inherent mobility ("Golf ball on a tee"). Anterior Dislocation accounts for 95% of cases, typically occurring when the arm is abducted and externally rotated (e.g., throwing/tackling). The resulting pathology typically involves a Bankart Lesion (tear of the anterior labrum) and a Hill-Sachs Lesion (impaction fracture of the humeral head). Management involves urgent reduction and immobilisation. The risk of Recurrence is inversely proportional to age: >90% in teenagers, <10% in patients >40. Conversely, patients >40 have a high risk of concomitant Rotator Cuff Tear. [1,2]

Key Facts

• Direction: Anterior (>95%). Posterior (Seizures/Electric Shock). Luxatio Erecta (Inferior - rare).
• Mechanism: Abduction + External Rotation (Anterior). Adduction + Internal Rotation (Posterior).
• Lesions:
  • Bankart: Labrum tear off the glenoid.
  • Hill-Sachs: Dent in the humeral head.
  • Bony Bankart: Fracture of glenoid rim (Bad prognosis).
• Nerve at Risk: Axillary Nerve (Regimental Badge area).
• Recurrence Rule: "The younger they are, the more likely it is to happen again."

Clinical Pearls

"The Lightbulb Sign": Posterior dislocations are notoriously missed on AP X-rays because the head looks round (like a lightbulb) due to internal rotation. ALWAYS get an Axillary or Y-view. If you can't see the glenoid space, be suspicious.

"The Terrible Triad": In patients >40 years, a dislocation often tears the Rotator Cuff. If they remain weak after reduction, request an MRI. Do not assume it's just a neurapraxia.

"The Epileptic Shoulder": If a patient has a seizure and wakes up with bilateral shoulder pain, assume bilateral POSTERIOR dislocations until proven otherwise.

"Be Gentle": The days of the Hippocratic method (foot in axilla) are gone. Use tension-release methods (Faresh/Cunningham) or sedation/muscle relaxants. Force causes fractures.

The "Golf Ball on a Tee"

The Glenohumeral joint is the most mobile joint in the body, but this comes at the price of stability.

• Bone: The Humeral Head (Golf ball) is 4x larger than the Glenoid Fossa (Tee).
• Labrum: A fibrocartilaginous rim that deepens the socket by 50%.
• Capsule: A loose ligamentous sack.
• Muscles: The Rotator Cuff (SITS) provides dynamic stability, compressing the head into the socket.

The 7-Step Mechanism of Anterior Dislocation (95%)

Step 1: The Vulnerable Position

• The arm is Abducted and Externally Rotated (e.g., throwing a ball, blocking a shot).
• This rotates the Greater Tuberosity away from the Acromion, removing the bony block.

Step 2: The Lever Arm

• A force is applied to the arm (lever), magnifying the torque at the shoulder fulcrum.

Step 3: Anterior Capsule Failure

• The Inferior Glenohumeral Ligament (IGHL) stretches and fails.

Step 4: The Bankart Lesion

• The humeral head pushes anteriorly and inferiorly.
• It tears the Anterior-Inferior Labrum off the glenoid rim.
• Bony Bankart: If it fractures a piece of glenoid bone with it (increases instability risk).

Step 5: The Hill-Sachs Lesion

• As the head dislocates, the posterior-lateral humeral head impales itself on the sharp anterior glenoid rim.
• This creates a Compression Fracture (Hill-Sachs divot).
• Clinical Relevance: If large, it can "engage" with the glenoid, causing recurrent instability.

Step 6: Neurovascular Stretch

• The Axillary Nerve (wrapping around the surgical neck) is stretched like a bowstring.
• Risk of neuropraxia (5-10%).

Step 7: The Locked State

• Spasm of the Pectoralis Major and Latissimus Dorsi pulls the head firmly into the subcoracoid space, locking it in place.

Posterior Dislocation (The "Trap") (4%)

Often missed ("Locked Posterior Dislocation").

• Mechanism: The 3 E's (Epilepsy, Electrocution, ECT).
• Force: Violent internal rotation and adduction. The massive Latissimus/Pec muscles overpower the external rotators.
• Pathology: "Reverse Hill-Sachs" and "Reverse Bankart".

Inferior Dislocation (Luxatio Erecta) (<1%)

• Presentation: Arm locked above head (Hand up asking a question).
• Risk: High risk of Axillary Artery injury.

          ACUTE SHOULDER DISLOCATION
                      ↓
    ┌───────────────────────────────────────────┐
    │           IMMEDIATE ASSESSMENT            │
    │  - Neurovascular Check (Axillary Nerve)   │
    │  - X-Rays (Trauma Series)                 │
    │  - Analgesia (Entonox / Morphine)         │
    └───────────────────────────────────────────┘
                      ↓
    ┌───────────────────────────────────────────┐
    │             REDUCTION ATTEMPT             │
    │  1. Cunningham / FARES (Pain free)        │
    │  2. Kocher (Mechanical)                   │
    │  3. Stimson (Gravity)                     │
    │  4. Sedation / MUA (Refractory)           │
    └───────────────────────────────────────────┘
                      ↓
    ┌─────────────────┴─────────────────┐
   SUCCESS                            FAILURE
    ↓                                   ↓
POST-REDUCTION X-RAY                 THEATRE (MUA)
NEURO CHECK
SLING (Broad Arm) 1-3 WEEKS

1. Reduction Techniques (The Art of Medicine)

"Force is failure. Technique is triumph."

A. The Cunningham Technique (Massage)

• Concept: Overcoming muscle spasm allow the shoulder to reduce itself.
• Method:
  1. Sit patient upright.
  2. Ask them to shrug shoulders UP and BACK (retract scapulae).
  3. Massage the Biceps and Trapezius.
  4. Gentle massage creates relaxation. The head slips in.
  5. Success Rate: High, and minimally painful.

B. The FARES Method (Oscillation)

• Concept: Distraction via movement.
• Method:
  1. Patient supine.
  2. Hold hand and gently oscillate (wave) the arm up and down (small amplitude).
  3. Slowly abduct while oscillating.
  4. At 90 degrees abduction, add external rotation.
  5. Clunk.

C. The Kocher Maneuver (The Lever)

• Warning: High risk of spiral fracture if forced.
• Steps (TEAMS):
  1. Traction: Pull in line of humerus.
  2. External Rotation: Rotate arm out (slowly!).
  3. Adduction: Bring elbow across chest.
  4. Medial Rotation: Hand to opposite shoulder.
  5. Stop: If resistance is felt.

D. Stimson's Technique (Gravity)

• Patient lies prone with arm hanging off the bed.
• Strap a 5kg weight to the wrist.
• Wait 20 minutes.
• Gravity tires the muscles. Spasm breaks. Reduction occurs.

2. Surgical Stabilisation

Who needs surgery?

A. Arthroscopic Bankart Repair

"Sewing the rim back on."

• Indication: Soft tissue instability. First-time frequent dislocators (Age <20). Minimal bone loss.
• Technique: Suture anchors placed in glenoid rim. Labrum tied back down.

B. Latarjet Procedure (The "Big Gun")

"Bone block transfer."

• Indication:
  • Glenoid Bone Loss >20%.
  • Off-Track Hill Sachs Lesion.
  • Failed Bankart Repair.
  • Contact Athletes (Rugby).
• Technique: Even if the capsule stretches, the Conjoined Tendon (attached to the transferred coracoid) limits abduction/external rotation. The "Sling Effect".
• Efficacy: Lowest recurrence rate (<1%).

C. Remplissage

"Filling the hole."

• Indication: Large Hill-Sachs lesion.
• Technique: The Infraspinatus tendon is tenodesed (sewn) into the Hill-Sachs defect to fill it and prevent engagement.

The "Diagnostic Trap".

• Mechanism: Electrocution, Seizure, Alcohol withdrawal. (Unbalanced muscle contraction - Internal rotators are stronger than external rotators).
• Signs: Arm locked in Internal Rotation. Cannot externally rotate.
• X-Ray:
  • Lightbulb Sign: Head looks round (symmetrical) because tuberosities are rotated away.
  • Rim Sign: Widened joint space >6mm.
  • Trough Line: Reverse Hill-Sachs.
• Treatment: Traction and gentle external rotation. Often large reverse Hill-Sachs needs filling (McLaughlin procedure).

Key Studies

1. ISIS Score (Instability Severity Index Score): Scoring system to decide between Bankart (Soft tissue) vs Latarjet (Bone). Points for: Age<20, Contact Sport, Hyperlaxity, Bone Loss. Score >6 needs Latarjet.
2. Kirkley et al. (1999): Arthroscopic stabilisation better than conservative for young athletes.
3. Robinson et al. (2006): Epidemiology of recurrence.

What happened?

The ball of your shoulder popped out of the socket. It tore the rim of cartilage (the seal) that keeps it in place.

Will it heal?

The bone will heal, but the cartilage rim usually heals in the wrong place (like a doorstop that has moved). This makes it easy for the ball to slip out again.

Do I need surgery?

• First time (Young): Often yes, especially if you play rugby/contact sports. Fixing the rim now prevents further damage.
• First time (Older): Usually no. We rest it, then strengthen the muscles.
• Recurrent: Yes. If it keeps coming out, you are damaging the bone. We need to stabilize it.

How long in a sling?

1-3 weeks. No longer, or it will get stiff.

Case 1: The Rugby Player

Scenario: 19-year-old prop forward dislocates shoulder during a scrum. Reduced in ED. X-ray shows small Hill-Sachs. Management:

• High risk of recurrence (90%).
• ISIS Score likely >6 (Age, Contact Sport).
• Plan: Early MRI and Arthroscopic Bankart Repair (or Latarjet if bone loss found).

Case 2: The Electrician

Scenario: 45-year-old man falls from ladder. Shoulder painful, held across chest. X-ray AP looks weirdly "round". Diagnosis: Posterior Dislocation. Clue: The "Lightbulb Sign" on AP. Action: Get an Axillary view. Reduce with traction. Check for Reverse Hill-Sachs.

Case 3: The Grandmother

Scenario: 75-year-old lady trips. Dislocates anteriorly. Reduced easily. 3 weeks later, she cannot lift her arm above 30 degrees. Diagnosis: Massive Rotator Cuff Tear (Terrible Triad). Action: Ultrasound/MRI Shoulder. Likely needs Cuff Repair or Reverse Geometry Replacement if arthritis present.

Q1: What are the static and dynamic stabilizers of the shoulder? A: Static: Labrum, Capsule, Glenohumeral Ligaments (IGHL), Negative intra-articular pressure, Bone geometry. Dynamic: Rotator Cuff (compression), Scapular stabilizers, Biceps (long head).

Q2: Describe the "Bony Bankart"? A: Avulsion fracture of the anterior-inferior glenoid rim. If >20-25% of the glenoid width is lost, the "inverted pear" shape is lost, and soft tissue repair will fail. Needs a Latarjet.

Q3: What is the "Engaging" Hill-Sachs lesion? A: A lesion large enough that when the arm is abducted and externally rotated, the defect drops off the glenoid edge, levering the head out of socket. Calculated using the "Glenoid Track" concept.

Q4: Name 3 complications of Latarjet procedure. A: 1. Non-union of coracoid graft. 2. Screw breakage/irritation. 3. Subscapularis split damage.

Q5: What is the recurrence rate for a 17-year-old male after first dislocation managed conservatively? A: Approx 90-95%.

Phase 1: Protection (Weeks 0-3)

• Sling immobilization.
• Pendulum exercises (gravity assisted).
• Elbow/Wrist/Hand ROM.
• Avoid: External Rotation > 0 degrees.

Phase 2: Motion (Weeks 3-6)

• Wean off sling.
• Active Assisted ROM.
• Regain Forward Flexion.
• Start Isometric Rotator Cuff strengthening.

Phase 3: Strengthening (Weeks 6-12)

• Scapular stabilization.
• Kinetic chain exercises.
• Proprioception (ball on wall).
• Return to Non-Contact Sport at 3 months.
• Return to Contact Sport at 6 months (if strict criteria met).

(End of Topic)