Coronoid Fractures - Trauma

Introduction

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

Anatomy

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

Classification

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

Presentation

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

Imaging

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

Treatment

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

Techniques

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

Complications

Recurrent elbow instability
- especially medial-sided
Elbow stiffness
Posttraumatic arthritis
Heterotopic ossification
Early failure
- associated with failure to recognize and repair underlying elbow instability