http://upload.orthobullets.com/topic/1020/images/coronoid fx.jpg
http://upload.orthobullets.com/topic/1020/images/anteromedial facet fracture 3d ct.jpg
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  • Coronoid fractures are pathognomonic of an episode of elbow instability
    • may be
      • isolated coronoid fracture
        • less common than previously thought
      • coronoid fracture + associated injuries
        • commonly occur with elbow dislocation
          • associated with recurrent instability after dislocation
  • Mechanism
    • traumatic shear injury  
      • typically occurs as distal humerus is driven against coronoid with an episode of severe varus stress or posterior subluxation
      • not an avulsion injury as nothing inserts on tip
  • Pathoanatomy
    • fractures at the coronoid base can amplify elbow instability given that
      • anterior bundle of the medial ulnar collateral ligament attaches to the sublime tubercle 18 mm distal to tip
      • anterior capsule attaches 6 mm distal to the tip of the coronoid
  • Epidemiology
    • incidence
      • 10-15% of elbow injuries
  • Associated conditions
    • posteromedial rotatory instability
      • coronoid anteromedial facet fracture and LCL disruption    
      • results from a varus deforming force
    • posterolateral rotatory instability
      • coronoid tip fracture, radial head fracture, and LCL injury 
    • olecranon fracture-dislocation
      • usually associated with a large coronoid fracture
    • terrible triad of elbow
      • coronoid fracture (transverse fracture pattern), radial head fracture, and elbow dislocation
  • Prognosis
    • complications and reoperation rates are high
  • Coronoid osteology
    • coronoid tip
      • is an intraarticular structure
      • can be visualized during elbow arthroscopy
    • medial facet
      • important for varus stability
      • provides insertion for the medial ulnar collateral ligament
  • Coronoid biomechanics
    • coronoid functions as an anterior buttress of the olecranon greater sigmoid notch
      • important in preventing recurrent posterior subluxation
    • primary resistor of elbow subluxation or dislocation
Regan and Morrey Classification
Type I coronoid process tip fracture

Type II fracture of 50% or less of height
Type III fracture of more than 50% of height
O'Driscoll Classification
  • Subdivides coronoid injuries based on location and number of coronoid fragments
  • Recognizes anteromedial facet fractures caused by varus posteromedial rotatory force  
  • Symptoms
    • elbow deformity & swelling
    • elbow pain
    • forearm or wrist pain may be a sign of associated injuries
  • Physical exam
    • inspection & palpation
      • varus or valgus deformity
      • ecchymosis & swelling
      • diffuse tenderness
    • range of motion & instability
      • document flexion-extension and pronation-supination
        • crepitus should be noted
      • varus/valgus instability stress test
        • challenging but important for an accurate diagnosis
    • neurovascular exam
  • Radiographs
    • recommended views
      • AP and lateral elbow views 
    • findings
      • interpretation may be difficult due to overlapping structures
  • CT scan 
    • useful for high grade injuries and comminuted fractures
  • Nonoperative
    • brief period of immobilization, followed by early range of motion
      • indications
        • Type I, II, and III that are minimally displaced with stable elbow
  • Operative
    • ORIF with medial approach
      • indications
        • Type I, II, and III with persistent elbow instability
        • posteromedial rotatory instability
    • ORIF with posterior approach
      • indications
        • olecranon fracture dislocation
        • terrible triad of elbow
    • hinged external fixation
      • indications
        • large fragments
        • poor bone quality
        • difficult revision cases to help maintain stability
  • ORIF with medial approach
    • approach
      • medial exposure through an interval between two heads of FCU
      • exposure more anteriorly through a split in flexor pronator mass
    • technique
      • cerclage wire or No. 5 suture through ulna drill holes for Type I injuries
      • ORIF with retrograde cannulated screws or plate for Type II or III injuries
      • ORIF with buttress plate fixation or pins and lateral ligament repair for posteromedial rotatory instability 
    • postoperative rehabilitation
      • depends on intraoperative exam following the procedure
      • thermoplastic resting splint
        • applied with elbow at 90° and forearm in neutral
        • restrict terminal 30° extension for 2-4 weeks
      • avoid shoulder abduction for 4-6 weeks
        • to prevent varus moment on arm
      • early active motion
        • dynamic muscle contraction may improve gapping of the ulnohumeral joint after surgical repair
  • ORIF with posterior approach
    • approach
      • posterior
    • technique
      • mobilize olecranon fracture to access coronoid fracture for associated olecranon fracture-dislocations
      • repair coronoid fragment first prior to reducing main ulnar fracture
      • olecranon ORIF with dorsal plate and screws
  • Recurrent elbow instability
    • especially medial-sided
  • Elbow stiffness
  • Posttraumatic arthritis
  • Heterotopic ossification
  • Early failure
    • associated with failure to recognize and repair underlying elbow instability

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