Elephant’s ear sign: a new radiographic finding indicative of acetabular retroversion

Abstract

Acetabular retroversion is a relatively common condition affecting the hip that can result in symptoms in some patients. Diagnosis of acetabular retroversion relies on obtaining a proper anteroposterior radiograph of the pelvis. Cross-over, posterior wall, and ischial spine signs are usually present in patients on the radiographs of patients with acetabular retroversion. In this illustrative case report, we describe an additional radiographic sign, elephant's ear sign, associated with acetabular retroversion that we have seen to be present in patients with acetabular retroversion. A review of 26 acetabular retroversion case series by 2 independent reviewers showed 100% consensus on the presence of elephant's ear sign in patients with evidence of all other radiographic signs of this hip abnormality. This simple and previously unreported radiographic Elephant's ear sign, in which flared iliac wings appear as elephant's ears, highlights the presence of acetabular retroversion.

Acetabular retroversion is prevalent and proportional to the severity of slipped upper femoral epiphysis

“… 14 , 19 , 20 A further radiological sign described as the ‘elephant ear sign’, with flared iliac wings has also been shown to be indicative of acetabular retroversion. 21 CT-based studies have shown scarce reproducibility and important variation in the measurement of retroversion obtained either preoperatively or postoperatively. 11 , 22 Identifying a hip “at risk” for subsequent SUFE might allow for a single surgical procedure for both hips, potentially preventing a more severe slip at secondary presentation.…”