What is the possible diagnosis for a patient with a history of elbow dislocation 4 months prior, now presenting with a fixed flexion deformity (FFD) of 20 degrees, further flexion up to 60 degrees, increased gap between the radial head and lateral condyle, a healed coronoid fracture with 5mm displacement, and a positive varus stress test?

Chronic Lateral Collateral Ligament Complex Insufficiency with Varus Instability

This patient most likely has chronic lateral collateral ligament (LCL) complex insufficiency with varus instability, resulting from inadequately treated or unrecognized ligamentous injury at the time of the original elbow dislocation. 1

Clinical Reasoning

The constellation of findings points to a specific pattern of chronic instability:

Key Diagnostic Features

• Positive varus stress test indicates lateral collateral ligament complex disruption, which progresses through sequential stages: lateral ulnar collateral ligament transection → complete lateral collateral ligament complex transection → anterior capsule involvement → medial collateral ligament injury 1

• Increased gap between radial head and lateral condyle on radiographs demonstrates lateral joint space widening under stress, a hallmark of lateral ligamentous insufficiency 1

• Healed coronoid fracture with 5mm displacement is significant because coronoid fractures are sequelae of prior elbow dislocation and are commonly associated with soft tissue ligamentous injuries that may have been undertreated 1

• Severe motion restriction (FFD 20° with flexion only to 60°, giving a 40° arc) suggests chronic instability led to capsular contracture and heterotopic ossification 2, 3

Biomechanical Context

The 5mm displaced coronoid fracture is particularly concerning. Research demonstrates that coronoid fragments ≥5mm with concomitant lateral collateral ligament injury cause significant varus instability, and isolated LCL repair without coronoid fixation fails to restore stability in these cases 4. When coronoid loss exceeds 50%, neither LCL repair nor radial head replacement alone provides adequate varus stability 5.

Pattern Recognition: The "Terrible Triad" Variant

This presentation represents a chronic sequela of what may have been an incompletely treated terrible triad injury (posterior elbow dislocation with radial head fracture, coronoid fracture, and LCL complex disruption) 2, 3. The positive varus stress with lateral joint widening indicates the lateral ligamentous structures were never adequately repaired or have failed 1.

Diagnostic Workup

Immediate Next Steps

• MRI without contrast is indicated to assess the current state of the lateral collateral ligament complex, medial collateral ligament, capsule, and any associated tendinous injuries 1

• Stress fluoroscopy can quantify the degree of instability: <10° widening = slight instability, >10° widening = moderate instability, frank redislocation = gross instability, which directly impacts surgical planning 1

Common Pitfall

Do not assume the healed coronoid fracture is clinically insignificant. Even healed coronoid fractures with displacement indicate that the original injury involved substantial ligamentous disruption that likely went unaddressed, leading to the current chronic instability 1, 4.

Clinical Implications

This chronic varus instability pattern typically requires surgical reconstruction including:

• Lateral collateral ligament complex reconstruction
• Possible coronoid reconstruction or augmentation given the 5mm displacement
• Capsular release for the severe contracture
• Consideration of hinged external fixation if instability is severe 2

The severe motion restriction (40° arc) combined with instability portends a challenging reconstruction with guarded prognosis, as patients with moderate instability and prolonged immobilization demonstrate significantly worse Mayo Elbow Performance Scores 1.