Common joint dislocations

Shoulder (Glenohumeral) Dislocation

• Epidemiology & Mechanism:
  • Anterior (~95%): Blow to arm in abduction, external rotation, and extension; or FOOSH.
  • Posterior (2–4%): Seizures, electrocution/lightning, or direct anterior shoulder trauma.
  • Inferior (<1%): Hyperabduction force (Luxatio erecta; arm locked overhead).
• Clinical Features:
  • Anterior: Arm held in abduction & external rotation; “squared-off” shoulder with prominent acromion.
  • Posterior: Arm locked in adduction & internal rotation; prominent coracoid, flattened anterior shoulder.
  • NV Exam: Assess axillary nerve (lateral deltoid/“regimental badge” sensation & motor) and distal pulses before and after reduction. c
• Diagnosis:
  • Best Initial Test: XR shoulder trauma series (AP, Scapular ‘Y’, and Axillary lateral view [mandatory to rule out posterior dislocation]).
  • Anterior Lesions:
    • Bankart lesion: Tear of anterior-inferior glenoid labrum ± bony fracture.
    • Hill-Sachs lesion: Compression fracture of posterolateral humeral head.
  • Posterior Lesions:
    • “Lightbulb sign” on AP view (fixed internal rotation).
    • Reverse Hill-Sachs lesion: Anteromedial humeral head impaction.
• Management Hierarchy:
  1. Pre-reduction NV exam: Mandatory documentation of axillary nerve and vascular status.
  2. Closed reduction: Emergent reduction under procedural sedation or intra-articular lidocaine (e.g., traction-countertraction).
  3. Post-reduction NV exam & repeat XR: Confirm joint relocation and rule out iatrogenic fracture.
  4. Immobilization & Rehab:
     • Young pts: Sling for 1–3 weeks followed by PT.
     • Elderly pts (>40 yo): Brief sling use (<1 week) to prevent adhesive capsulitis.
  5. Surgery (Open reduction / Labral repair): Indicated for irreducible dislocation, open injury, neurovascular entrapment, or recurrent instability.

Mnemonic

拍拍肩膀说：嗨H 拍拍屁股说：啊A

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Hip Dislocation

• Patho/Etiology
  • Requires significant force; often from motor vehicle accidents (dashboard injury) or falls from a height.
  • Posterior (>90%): Femoral head is forced posteriorly out of the acetabulum.
  • Anterior (<10%): Usually from forced abduction.
• Clinical Presentation
  • Posterior: The affected limb is shortened, adducted, and internally rotated. This is the classic, high-yield presentation.
  • Anterior: Limb is abducted and externally rotated.
• Diagnosis
  • X-ray (AP pelvis): Confirms diagnosis. In posterior dislocation, the femoral head appears smaller than the contralateral side. A CT scan is often done post-reduction to check for associated fractures.
• Management
  • Orthopedic emergency.
  • Prompt closed reduction under sedation to decrease the risk of avascular necrosis (Allis technique).
  • Open reduction if closed reduction fails or if there are associated fractures.
• Key Complications
  • Avascular necrosis (AVN) of the femoral head: The most serious complication; risk increases with time to reduction.
  • Sciatic nerve injury: Common with posterior dislocations, presenting with foot drop (impaired dorsiflexion).
  • Post-traumatic arthritis: The most common long-term complication.

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Elbow Dislocation

• Patho/Etiology
  • Second most common major joint dislocation in adults; most common in children.
  • Usually caused by a fall on an outstretched hand (FOOSH) with the elbow in extension.
  • Posterior dislocation is the most common type.
• Clinical Presentation
  • Presents with severe pain, swelling, and inability to bend the elbow. The olecranon is prominent posteriorly.
• Diagnosis
  • X-ray (AP and lateral): Confirms dislocation. Important to assess for associated fractures.
  • “Terrible triad” of the elbow: A complex dislocation involving a posterior dislocation, a radial head fracture, and a coronoid process fracture.
• Management
  • Immediate closed reduction after a careful neurovascular exam.
  • Post-reduction, the elbow is splinted in flexion (around 90 degrees). Early range of motion is crucial to prevent stiffness.
• Key Complications
  • Neurovascular injury:
    • Brachial artery injury: Can be limb-threatening. Always check for distal pulses before and after reduction.
    • Median and ulnar nerve injuries are also common.
  • Compartment syndrome: A risk, especially with associated fractures.
  • Contracture/Stiffness: Loss of terminal extension is a very common long-term complication.

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Knee (Tibiofemoral) Dislocation

• Patho/Etiology
  • A rare but limb-threatening orthopedic emergency, often from high-energy trauma (MVA, falls).
  • Can occur with lower energy in morbidly obese individuals.
  • Up to 50% of knee dislocations spontaneously reduce before evaluation, so a high index of suspicion is required.
• Clinical Presentation
  • Gross deformity and instability of the knee. If reduced, may present with significant swelling and multi-ligamentous instability.
• Diagnosis
  • Based on clinical suspicion, even if the joint is reduced.
  • Ankle-brachial index (ABI): A crucial screening tool. An ABI <0.9 warrants further vascular imaging.
  • CT angiography: To rule out vascular injury.
• Management
  • Immediate reduction. Do not delay for imaging if there are signs of vascular compromise.
  • Careful and repeated neurovascular checks are critical.
  • Admission for observation and serial exams is standard.
• Key Complications
  • Popliteal artery injury (up to 40%): High risk of amputation if not recognized and treated promptly (within 8 hours). This is the most feared complication.
  • Common peroneal (fibular) nerve injury: Presents with foot drop and numbness on the dorsum of the foot.
  • Multiple ligament tears (ACL, PCL, etc.): Nearly always present and require surgical reconstruction.