Basic Sciences 2022, Nov, 28 | 12:00 am

Elbow - Dislocation

Facts
  • Posterior dislocation is most common, often due to a fall on an outstretched hand
  • The result of either valgus posterolateral rotatory force, varus posteromedial rotatory force or direct blow to a flexed elbow
  • Approximately 50% of acute elbow dislocations are sports related
     
  • Proximal ulna has two articulations: the greater sigmoid notch (trochlea) and the lesser sigmoid notch (radial head)
  • Radial head is an important secondary stabilizer of the elbow to valgus stress and posterior translation
  • Coronoid process acts as an anterior buttress and is vital to stability of the elbow
    • Sublime tubercle (medial coronoid): is the insertion of the anterior bundle of the medial collateral ligament (MCL)
    • Fractures of the coronoid involving the anteromedial facet result from varus posteromedial rotation during axial loading
      • Associated with LCL injury and instability
  • Supinator crest (lateral ulna): insertion of the lateral ulnar collateral ligament (LUCL)
  • Lateral aspect of the radial head is not covered by cartilage because it does not articulate with anything
  • Lateral collateral ligament (LCL) consists of the radial collateral ligament, the LUCL and the annular ligament
    • Provides varus and posterolateral rotatory stability
    • LUCL is most important
  • MCL consists of the anterior and posterior bundle as well as the transverse ligament
    • Provides valgus and posteromedial rotatory stability
    • Anterior bundle most important and is the last structure ruptured
  • ROM: 0°-150° flexion, 85° supination, 80° pronation
    • Functional motion: 20°-120° of flexion, 70° of pronation and supination
  • Terrible triad: posterior dislocation with radial head and coronoid fracture
    • Associated with high risk of elbow instability
    • LCL is almost always avulsed from the distal humerus leaving a "bare spot"
  • Patients present with elbow pain and deformity
  • Assess NV status and identify associated injuries, particularly elbow fractures
    • NV injury is rare
      • Median and ulnar nerves are most commonly injured
      • Brachial artery is most common vascular injury
      • If perfusion remains poor after reduction, vascular compromise should be suspected and angiography performed
  • Compartment syndrome: sustained increase in compartment pressure due to inflammation and edema in forearm compartments leading to vascular compromise and muscle death
    • Signs include pain out of proportion to injury, tense forearm compartments, pain with passive extension or flexion of the digits, diminished pulses
    • Severe antecubital swelling may indicate impending forearm compartment syndrome
    • Elevate arm and avoid hyperflexion of elbow
    • Serial NV checks for at risk arms
    • Compartment pressure > 30 mmHg or within 30 mmHg of diastolic blood pressure warrants urgent fasciotomy of the volar and dorsal compartments to release pressure and avoid muscle death

 

Imaging
Normal AP elbow
Normal lateral elbow

Radiographs

  • AP, lateral radiographs of the elbow adequately define simple dislocation
    • Identify associated fractures including radial head and coronoid
  • CT: useful for evaluating morphology of coronoid or radial head fractures
    • Particularly important for preoperative planning in terrible triad injuries

 

Classification
Regan and Morrey classification
  • Description:
    Simple or complex (associated with fracture)
    Open or closed
    Direction: posterorlateral (> 90%), posteromedial, anterior, lateral, medial, divergent
     
  • Associated Fractures:
    • Radial head (10%): by definition, Mason type IV
    • Medial/lateral epicondyle (25%): may become incarcerated in reduction
    • Coronoid (7%): avulsion of brachialis, common with posterior dislocation
  • Regan and Morrey: based on coronoid fracture size
    Type I: avulsion of the tip
    Type II: < 50% of the coronoid by height
    Type III: > 50% of the coronoid by height
O'Driscoll classification
  • O'Driscoll: based on olecranon fracture morphology
    Type 1: tip
    1.1: < 2 mm
    1.2: > 2 mm (associated with terrible triad injuries)
    Type 2: anteromedial
    2.1: anteromedial tip
    2.2: anteromedial and anterior tip
    2.3: medial (sublime tubercle), anteromedial and anterior tip
    Type 3: basal (involves > 50% of the coronoid height)
    3.1: coronoid fracture only
    3.2: olecranon and coronoid fractures
  • OTA: radiohumeral and ulnohumeral (20-A)
    1. Anterior
    2. Posterior
    3. Medial
    4. Lateral
    5. Divergent

 

Treatment
  • Neurologic deficits sustained at the time of injury should be observed, those sustained with manipulation should be explored
     
  • Closed reduction: initial management
    • Regional anesthesia (e.g. lidocaine) should be applied through the lateral soft tissue triangle formed by three landmarks: lateral olecranon, lateral epicondyle and the radial head
    • Post-reduction: evaluate neurovascular status, joint stability, antecubital swelling and forearm compartments
    • Posterior splint with elbow at 90°
      • For simple dislocations with stable reductions, maintain splint for 1-2 weeks followed by early gentle passive ROM
      • Unstable reductions require operative treatment
  • Reduction maneuvers:
    Posterior:
    • Closed reduction usually restores stability and allows early motion
    • Forearm supination and elbow extension tends to be the most unstable position
    • Reduction maneuver: elbow flexed to 90° with distal traction and counter traction on arm
      • Often facilitated with patient prone and affected elbow flexed over the edge of the stretcher
      • Entrapment of median nerve can occur during reduction

    Anterior:
    • Triceps avulsion can occur with this injury
    • Reduction maneuver: flex forearm, dorsally directed pressure on volar forearm with anteriorly directed pressure on arm

    Medial/Lateral:
    • Lateral dislocations are associated with greater soft tissue injury and instability
    • Reduction maneuver: straight medial/lateral pressure with counter-pressure on the arm
    • Anconeus interposition may prevent reduction

    Divergent:
    • Very rare
    • Anterior/posterior (more common): ulna posterior, radius anterior
      • Reduction maneuver: as with posterior dislocation with additional pressure on radial head anteriorly
    • Medial/lateral: distal humerus between radius and ulna
      • Reduction maneuver: axial traction with direct pressure to converge ulna and radius
  • Operative: indications include soft-tissue or bony entrapment in which closed reduction fails, unstable dislocations, neurologic deficits resulting from manipulation, displaced Regan-Morrey type II/III coronoid fractures and displaced radial head fractures (terrible triad is considered separately below)

    Unstable simple dislocations: can be treated with collateral ligament repair and/or hinged external fixation

    Dislocation with coronoid fracture: sutures through drill holes or suture anchors can be used through a lateral approach
    • Large Regan-Morrey type III fractures can be fixed with a screw applied through the dorsal ulna
    • O'Driscoll type 2 fractures may require a separate medial approach, LCL repair and possible hinged external fixation for residual instability

    Dislocation with radial head fracture: Mason II and III fractures should be fixed when possible or replaced (see Radial Head Fracture chapter)

    Terrible Triad:
    • Usually requires surgery to restore stability
    • Nonoperative: requires concentric reduction, stability at 30° of flexion or less, minimally displaced radial head fracture (by CT) without block to rotation and Regan-Morrey type I coronoid (by CT)
      • Immobilize in posterior splint or cast with elbow at 90° for 7-10 days followed by early ROM
    • Operative: generally preferred
      • Usually through a posterior incision
      • Fix coronoid fracture with sutures (Type I/II) or screw (Type III)
      • Fix or replace radial head (see Radial Head Fracture chapter)
      • Repair anterior capsule
      • Repair LCL to lateral epicondyle with suture anchors or drill holes
      • MCL may need to be repaired if instability persists after coronoid and lateral repair
      • A hinged external fixator may be required for residual instability
      • Immobilize for 7-10 days followed by early ROM

 

Complications
  • Compartment syndrome: urgent fasciotomies are required to release pressure and avoid muscle death
  • Elbow stiffness: associated with prolonged immobilization (> 3-4 weeks)
  • Heterotopic ossification:
    • Develops between brachialis and capsule or between triceps and capusule
    • Can significantly decrease ROM
    • Risk increases with greater soft tissue trauma or other fractures
    • Consider indomethacin or radiation therapy
  • Persistent instability: associated with terrible triad and injury to secondary restraints (e.g. flexor-pronator mass, common extensor origin, osteochondral fragments)
    • Further imaging and repair of affected anatomy may be required
  • Posttraumatic arthritis: can be due to persistent instability
    • Monitor for subluxation closely after treatment