Gull Wing (Seagull) Appearance | Radiology Signs

Answer:

The gullwing appearance is caused by erosive changes in the distal interphalangeal (DIP) joints characterized by central erosions with surrounding subchondral sclerosis and marginal osteophyte formation. This is a hallmark radiographic feature of erosive osteoarthritis, an inflammatory subtype of osteoarthritis affecting the DIP joints, producing pain, stiffness, and joint deformity.

The same appearance is also called the seagull deformity or gull-wing sign: central erosion of the proximal articular surface combined with peripheral bony proliferation, so the concave central defect flanked by upturned marginal spurs resembles a gull in flight. Erosive osteoarthritis is an aggressive inflammatory variant of hand osteoarthritis, typical of postmenopausal women, that affects the distal more than the proximal interphalangeal joints and spares the metacarpophalangeal joints and wrist.

The differential is the point of reporting it. Psoriatic arthritis produces marginal rather than central erosions with adjacent proliferative new bone, fluffy periostitis, the pencil-in-cup deformity and whole-digit involvement with dactylitis and nail disease. Rheumatoid arthritis produces marginal erosions with periarticular osteopenia and uniform joint space loss at the metacarpophalangeal and proximal interphalangeal joints and the ulnar styloid, and characteristically spares the distal interphalangeal joints. Gout produces well-corticated para-articular erosions with overhanging edges, preserved joint space and soft tissue tophi. Erosive osteoarthritis may end in ankylosis of the affected joints, which rarely happens in nodal osteoarthritis, and MRI or ultrasound demonstrate the synovitis that explains the inflammatory clinical presentation.

Why is it called so?

The term “gullwing” derives from the radiographic outline of the joint erosions and osteophytes resembling the wings of a seagull in flight—two symmetrical concave erosions centrally with sclerotic margins on either side, creating a bilobed shape similar to a gull’s wings.

Pathophysiology

The gullwing appearance develops due to an initial central subchondral bone erosion in the DIP joint caused by inflammation and cartilage loss. This central erosion is flanked by new bone formation at the joint margins (osteophytes) and reactive subchondral sclerosis. The combination of central erosions and peripheral bone proliferation leads to the characteristic bilobed radiographic contour.

Alternative names: Seagull erosions, sawtooth appearance

Other associated named signs: None specifically linked to erosive osteoarthritis but other osteoarthritic changes such as joint space narrowing and subchondral cysts may be present.

References

1. Martel W, Stuck KJ, Dworin AM, Hylland RG. Erosive osteoarthritis and psoriatic arthritis: a radiologic comparison in the hand, wrist, and foot. AJR Am J Roentgenol. 1980.