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Introduction
  • Epidemiology
    • incidence
      • 1.5-4% of all fractures
      • radial head fractures are among the most common elbow fractures (33%)
  • Pathophysiology
    • mechanism of injury
      • fall on outstretched hand
      • elbow in extension + forearm in pronation
        • most force transmitted from wrist to radial head
  • Associated injuries
    • 35% have associated soft tissue or skeletal injuries including
      • ligamentous injury
        • lateral collateral ligament (LCL) injury
          • most common (up to 80% on MRI)
        • medial collateral ligament (MCL) injury
        • combined LCL/MCL
      • Essex-Lopresti injury
        • distal radioulnar joint (DRUJ) injury
        • interosseous membrane disruption
      • other elbow fractures
        • coronoid fracture
        • olecranon fracture
      • elbow dislocation
        • terrible triad (elbow dislocation, radial head fracture, coronoid fracture)
      • carpal fractures
        • scaphoid fracture
Anatomy
  • Osteology
    • elbow joint contains two articulations
      • ulnohumeral (hinge)
      • radiocapitellar (pivot) 
        • 60% load transfer across elbow joint
    • proximal radius
      • nonarticular portion of the radial head is a ~90 degree arc from radial styloid to Lister's tubercle (safe zone for hardware placement)
  • Ligaments 
    • lateral collateral ligament complex  
      • lateral ulnar collateral ligament (LUCL)
        • primary stabilizer to varus and external rotation stress
        • deficiency results in posterolateral rotatory instability
      • radial collateral ligament (RCL)
      • accessory lateral collateral ligament
      • annular ligament
        • stabilizes proximal radioulnar joint
    • medial (ulnar) collateral ligament (MCL)
      • three bundles
        • anterior bundle
          • primary stabilizer to valgus stress (radial head is second)
        • posterior bundle
        • transverse bundle
  • Biomechanics
    • radial head confers two types of stability to the elbow
      • valgus stability
        • secondary restraint to valgus load at the elbow, important if MCL deficient
      • longitudinal stability
        • restraint to proximal migration of the radius
        • contributions from interosseous membrane and DRUJ
        • load-sharing from wrist to radiocapitellar joint, dependant on radiocapitellar surface area 
        • loss of longitudinal stability occurs when
          • radial head fracture + DRUJ injury + interosseous membrane disruption (Essex-Lopresti) 
            • radial head must be fixed or replaced to restore stability, preventing proximal migration of the radius and ulnocarpal impaction
Classification

Mason Classification (Modified by Hotchkiss and Broberg-Morrey)
Type I Nondisplaced or minimally displaced (<2mm), no mechanical block to rotation
Type II Displaced >2mm or angulated, possible mechanical block to forearm rotation
Type III Comminuted and displaced, mechanical block to motion
Type IV Radial head fracture with associated elbow dislocation

Presentation
  • Symptoms
    • pain and tenderness along lateral aspect of elbow
    • limited elbow or forearm motion, particularly supination/pronation
  • Physical exam
    • range of motion
      • evaluate for mechanical blocks to elbow motion
        • flexion/extension and pronation/supination
        • aspiration of joint hematoma and injection of local anesthesia aids in evaluation of mechanical block
    • stability
      • elbow
        • lateral pivot shift test (tests LUCL)
        • valgus stress test (tests MCL)
      • DRUJ
        • palpate wrist for tenderness
        • translation in sagittal plane > 50% compare to contralateral side is abnormal
          • may be difficult to determine on exam, can get dynamic CT scan in neutral, pronation and supination for subtle injury
      • interosseous membrane
        • palpate along interosseous membrane for tenderness
        • radius pull test
          • >3mm translation concerning for longitudinal forearm instability (Essex-Lopresti)
Imaging
  • Radiographs
    • recommended views
      • AP and lateral elbow
        • check for fat pad sign indicating occult minimally displaced fracture
    • additional views
      • radiocapitellar view (Greenspan view)  
        • oblique lateral view of elbow
        • beam angled 45 degrees cephalad
        • allows visualization of the radial head without coronoid overlap
        • helps detect subtle fractures of the radial head
  • CT
    • further delineate fragments in comminuted fractures
    • identify associated injuries in complex fracture dislocations
Treatment
  • Nonoperative
    • short period of immobilization followed by early ROM  
      • indications
        • isolated minimally displaced fractures with no mechanical blocks (Mason Type I)
      • outcomes
        • elbow stiffness with prolonged immobilization
        • good results in 85% to 95% of patients
  • Operative
    • ORIF   
      • indications
        • Mason Type II with mechanical block
        • Mason Type III where ORIF feasible
        • presence of other complex ipsilateral elbow injuries
      • outcomes
        • # fragments
          • ORIF shown to have worse outcome with 3 or more fragments compared to ORIF with < 3 fragments 
        • isolated vs. complex
          • ORIF isolated radial head fractures versus complex radial head fractures (other associated fracture/dislocation) show no significant difference in outcomes at 4 years
          • isolated fractures trended towards better Patient-Rated Elbow Evaluation score, lower complication rate and lower rate of secondary capsular release
    • fragment excision (partial excision)
      • indications
        • fragments less than 25% of the surface area of the radial head or 25%-33% of capitellar surface area
      • outcomes
        • even small fragment excision may lead to instability
    • radial head arthroplasty 
      • indications
        • comminuted fractures (Mason Type III) with 3 or more fragments where ORIF not feasible and involves greater than 25% of the radial head
        • elbow fracture-dislocations or Essex Lopresti lesions
          • radial head excision will exacerbate elbow/wrist instability and may result in proximal radial migration and ulnocarpal impingement
      • outcomes
        • radial head fractures requiring replacement have shown good clinical outcomes with metallic implants
        • compared to ORIF for fracture-dislocations and Mason Type III fractures, arthroplasty results in greater stability, lower complication rate and higher patient satisfaction
    • radial head resection
      • indications
        • low demand, sedentary patients
        • in a delayed setting for continued pain of an isolated radial head fracture
      • contraindications
        • presence of destabilizing injuries 
        • forearm interosseous ligament injury (>3mm translation with radius pull test)
        • coronoid fracture
        • MCL deficiency
Techniques
  • Approaches to Radial Head 
    • overview
      • PIN crosses the proximal radius from anterior to posterior within the supinator muscle 4cm distal to radial head
      • in both Kocher and Kaplan approaches, the forearm should be pronated to protect PIN 
        • pronation pulls the nerve anterior and away from the surgical field  
    • Kocher approach  
      • interval
        • between ECU (PIN) and anconeus (radial n.) 
      • key steps
        • incise posterior fibers of the supinator 
        • incise capsule in mid-radiocapitellar plane
          • anterior to crista supinatoris to avoid damaging LUCL
      • pros 
        • less risk of PIN injury than Kaplan approach (more posterior)
      • cons 
        • risk of destabilizing elbow if capsule incision is too posterior and LUCL is violated, which lies below the equator of the capitellum
    • Kaplan approach 
      • interval
        • between EDC (PIN) and ECRB (radial n.) 
      • key steps
        • incise mid-fibers of supinator
        • incise capsule anterior to mid-radiopatellar plane (have access)
      • pros 
        • less risk of disrupting LUCL and destabilizing elbow than Kocher approach (more anterior)
        • better visualization of the coronoid
      • cons 
        • greater risk of PIN and radial nerve injury
  • ORIF
    • approach
      • Kocher or Kaplan approach
    • plates 
      • fracture involved head and neck
      • posterolateral plate placement
        • safe zone (nonarticular area) consists of 90-110 degree arc from radial styloid to Lister's tubercle, with arm in neutral rotation to avoid impingement of ulna with forearm rotation
      • bicipital tuberosity is the distal limit of plate placement
        • anything distal to that will endanger PIN
      • countersink implants on articular surface
    • screws
      • headless compression screws (Hebert) if placed in articular surface
      • better elbow range of motion and functional outcome scores at 1 year compared to plate fixation
  • Radial head arthroplasty
    • approach
      • Kocher or Kaplan approach
    • technique
      • metal prostheses
        • loose stemmed prosthesis
          • that acts as a stiff spacer
        • bipolar prosthesis
          • that is cemented into the neck of the radius
      • silicon replacements are no longer used
        • indepedent risk factor for revision surgery
    • complications
      • overstuffing of joint that leads to capitellar wear problems and malalignment instability 
      • overstuffing of joint is best assessed under direct visualization 
  • Radial head resection
    • approach
      • Kocher or Kaplan approach
    • complications after excision of the radial head include
      • muscle weakness
      • wrist pain
      • valgus elbow instability
      • heterotopic ossification
      • arthritis
      • proximal radial migration
      • decreased strength
      • cubitus valgus
Complications
  • Displacement of fracture
    • occurs in less than 5% of fractures; serial radiographs do not change management
  • Posterior interosseous nerve injury (with operative management)
  • Loss of fixation
  • Loss of forearm rotation
  • Elbow stiffness
    • first-line management incluides supervised exercise therapy with static or dynamic progressive elbow splinting over a 6 month period  
  • Radiocapitellar joint arthritis
  • Infection
  • Heterotopic ossification
  • Hardware loosening
  • Complex regional pain syndrome 
 

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