Radial Head Fractures - Trauma

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 resection (complete excision)
  - 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
- 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
- retrograde titanium nail reduction and stabilization
  - indications
    - not yet considered mainstream treatment as it is in the pediatric population
  - outcomes
    - small powered case studies show good outcomes

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 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
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

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