What does a sail sign on an elbow X-ray indicate and how is it treated?

Sail Sign on Elbow X-ray: Diagnosis and Management

A sail sign on an elbow X-ray indicates a joint effusion, which is often a sign of an occult fracture even when no fracture line is visible on initial radiographs. 1

What is a Sail Sign?

• A sail sign refers to the elevation of the anterior and/or posterior fat pads on lateral elbow radiographs, creating a triangular or sail-like appearance 1, 2
• Normal fat pads are not visible on radiographs unless displaced by fluid (effusion) within the joint 2
• The posterior fat pad is normally hidden in the olecranon fossa and becomes visible only when displaced by an effusion 1
• The anterior fat pad may be visible normally but becomes elevated (sail sign) when an effusion is present 2

Clinical Significance

• The presence of a sail sign has 85.4% sensitivity for detecting radial head/neck fractures, though specificity is only 50% 2
• Joint effusion identified on radiographs in the context of trauma strongly suggests an occult fracture even when no fracture line is visible 1, 3
• The sail sign is particularly important for detecting occult fractures of the:
  • Radial head (accounts for 50% of elbow fractures) 1
  • Coronoid process 1, 3
  • Olecranon 1, 3

Diagnostic Approach

• Initial imaging should include standard radiographic views: anteroposterior (AP), lateral, and oblique views 1
• The lateral view is most important for visualizing the sail sign 1, 2
• If radiographs show a sail sign but no visible fracture, further imaging is indicated 1
• CT without contrast is the next appropriate study when radiographs are normal or indeterminate but clinical suspicion for fracture remains high 1, 3
• MRI is indicated when soft tissue injury is suspected and radiographs are normal 1

Treatment Approach

For Isolated Joint Effusion with No Visible Fracture:

• Conservative management with:
  • Brief immobilization (1-2 weeks) 1
  • Pain control 1
  • Early range of motion exercises as tolerated 1
  • Follow-up radiographs in 7-10 days to assess for previously occult fractures 1

For Identified Fractures:

• Treatment depends on the specific fracture pattern:
  • Non-displaced fractures: typically managed conservatively with immobilization 4
  • Displaced fractures: often require surgical intervention with open reduction and internal fixation 4, 5
  • Comminuted radial head fractures: may require radial head replacement in some cases 5

For Associated Soft Tissue Injuries:

• Ligament injuries (particularly lateral collateral ligament) may require repair if instability is present 5
• Rehabilitation protocol should be tailored to the specific injury pattern 4

Common Pitfalls to Avoid

• Do not miss evaluating for joint effusion (sail sign), which may be the only radiographic indication of an occult fracture 1
• Remember that not all fractures are visible on initial radiographs; clinical correlation is essential 1, 2
• Avoid overlooking associated injuries in complex elbow trauma, such as the "terrible triad" (posterior dislocation with radial head and coronoid fractures) 5
• Do not dismiss persistent elbow pain after trauma when initial radiographs appear normal, as occult fractures may be present 1, 3