Terrible Triad Injury of Elbow - Trauma

summary
- Terrible Triad Injury of Elbow is a traumatic injury pattern of the elbow characterized by elbow dislocation, radial head/neck fracture, and a coronoid fracture.
- Diagnosis can be made with plain radiographs of the elbow. CT studies are helpful for surgical planning.
- Treatment is generally ORIF versus radial head arthroplasty, LCL reconstruction, coronoid ORIF, and possible MCL reconstruction.

Etiology
- Characterized by presence of
  - elbow dislocation (often associated with posterolateral dislocation or LCL injury )
  - radial head or neck fracture
  - coronoid fracture
- Pathophysiology
  - mechanism
    
    fall on extended arm that results in a combination of
    
    valgus, axial, and posterolateral rotatory forces
    
    produces posterolateral dislocation
  - pathoanatomy
    
    structures of elbow fail from lateral to medial
    
    LCL disrupted first
    
    anterior capsule injured next
    
    possible MCL disruption

Anatomy
- Radial head
  - a primary restraint to posterolateral rotatory instability (PLRI)
  - secondary valgus stabilizer
  - forearm in neutral rotation, lateral portion of articular margin devoid of cartilage
    
    roughly between radial styloid and listers tubercle
- Coronoid process
  - provides an anterior and varus buttress to ulnohumeral joint
  - resists posterior subluxation beyond 30 deg of flexion
  - fracture fragment typically has some anterior capsule attached
    
    useful in repair
- Medial collateral ligament
  - three components
    
    anterior bundle
    
    most important to stability, restraint to valgus and posteromedial rotatory instability
    
    inserts on sublime tubercle (anteromedial facet of coronoid)
    
    specifically inserts 18.4mm dorsal to tip of coronoid process
    
    posterior bundle
    
    transverse ligament
- Lateral collateral ligament
  - inserts on supinator crest distal to lesser sigmoid notch
  - the primary restraint to posterolateral rotatory instability
  - four components
    
    lateral ulnar collateral ligament (most important for stability)
    
    radial collateral ligament
    
    annular ligament
    
    accessory collateral ligament
  - when injured is usually avulsed off of the lateral epicondyle

Presentation
- Symptoms
  - patients complain of pain, clicking and locking with elbow in extension
- Physical exam
  - possible varus / valgus instability patterns
  - distal radial ulnar joint must be evaluated for possible Essex-Lopresti injury

Imaging
- Radiographs
  - evaluate for concentricity of ulnohumeral and radiocapitellar joints
  - line drawn through center of radial neck should intersect the center of the capitellum regardless of radiographic projection
  - evaluate lateral radiograph for coronoid fracture
  - need prereduction and postredcution films
  - consider PA and lateral films of wrist and forearm when indicated
- CT
  - often utilized for better evaluation of coronoid fracture
  - 3D imaging for determining fracture line propagation

Treatment
- Nonoperative
  - immobilize in 90 deg of flexion for 7-10 days
    
    indications (rare)
    
    ulnohumeral and radiocapitellar joints must be concentrically reduced
    
    radial head fx must not meet surgical indications
    
    coronoid fx must be small
    
    elbow should be sufficiently stable to allow early ROM
    
    technique
    
    one week of immobilization followed by progressive ROM
    
    active motion initiated with resting splint at 90 degrees and forearm pronation, avoiding terminal extension
    
    static progressive extension splinting at night after 4-6 weeks
    
    strengthening protocol after 6 weeks
- Operative
  - ORIF versus radial head arthroplasty, LCL reconstruction, coronoid ORIF, possible MCL reconstruction
    
    indications
    
    terrible triad elbow injury that includes an unstable radial head fracture, a type III coronoid fracture, and an associated elbow dislocation
    
    coronoid fractures involving less than 10% of the coronoid do not confer elbow stability in cadaveric studies and therefore do not require repair
    
    should instability persist after addressing the radial head and the LCL complex in the presence of a small coronoid fracture, the next best step is MCL reconstruction

Techniques
- ORIF vs replacement of radial head, coronoid ORIF, LCL reconstruction, and possible MCL reconstruction
  - approach
    
    posterior skin incision advantageous
    
    allows access to both medial and lateral aspect of elbow
    
    lower risk of injury to cutaneous nerves
    
    more cosmetic
  - technique
    
    radial head ORIF vs. arthroplasty
    
    radial head ORIF indicated if non comminuted fractures that involve < 40% articular surface
    
    1.5, 2.0, or 2.4mm countersunk screws
    
    plate if necessary; 2.0 plates cause minimal loss of motion even when placed on radial neck
    
    plate position should be posterolateral
    
    safe zone: 90-110 arc from radial styloid to Lister's tubercle with arm in neutral rotation
    
    radial head arthroplasty indicated for comminuted radial head fxs (> 3 pieces)
    
    implant should articulate 2mm distal to the tip of the coronoid process
    
    radial head resection without replacement is NOT indicated in presence of Essex-Lopresti lesion or in ligamentously injured elbows
    
    if <25% head damaged or fragments not reconstructable and nonarticulating, can excise fractured portion if elbow stable (rarely indicated)
    
    coronoid ORIF
    
    can be fixed through radial head defect laterally
    
    sutures, suture anchors, screws, or rarely plate fixation.
    
    suture passed through 2 drill holes
    
    posterior to anterior lag screws if fragment large
    
    basal coronoid fxs (rare) fixed with anteromedial or medial plate on proximal ulna
    
    FCU split approach preferred for rare isolated coronoid fractures
    
    LCL repair
    
    usually avulsed from origin on lateral epicondyle
    
    reattach with suture anchors or transosseous sutures
    
    must be reattached at center of capitellar curvature on lateral epicondyle
    
    if MCL is intact, LCL is repaired with forearm in pronation
    
    if MCL injured, LCL is repaired with forearm in supination to avoid medial gapping due to overtightening
    
    repairs are performed with elbow at 90 degrees of flexion
    
    MCL repair
    
    indicated if instability on exam after LCL and fracture fixation, especially with extension beyond 30 degrees
  - postoperative
    
    elbow fixators - hinged or static
    
    consider when instability is noted after complete bone and soft tissue repair
    
    immobilization
    
    can immobilize elbow in flexion with forearm pronation to provide stability against posterior subluxation
    
    if both MCL and LCL were repaired, splint in flexion and neutral rotation
    
    rehabilitation
    
    initiate active ROM exercises 48 hours after surgery to improve functional outcomes

Complications
- Instability
  - more common following type I or II coronoid fractures
- Failure of internal fixation
  - most common following repair of radial neck fractures
    
    poor vascularity leading to osteonecrosis and nonunion
- Post-traumatic stiffness
  - very common complication
  - initiate early ROM to prevent
- Heterotopic ossification
  - consider prophylaxis in pts with head injury or in setting of revision surgery
- Post-traumatic arthritis
  - due to chondral damage at time of injury and/or residual instability

Prognosis
- Historically poor outcomes secondary to
  - persistent instability
  - stiffness
  - arthrosis