Images in Emergency Medicine: Pelvic Digit

A 48-year-old female with systemic lupus erythematosus and renal failure was admitted to the hospital with pyelonephritis. While in the emergency department (ED), during transfer to a bedside commode, she slipped to the floor and subsequently reported right lateral hip pain. Examination revealed mild tenderness to palpation in that area. Radiographs were obtained and demonstrated a pelvic digit (indicated by arrow). What may be mistakenly interpreted radiographically as a fracture of the pelvic digit is actually a pseudoarticulation, a common finding near the base of the pelvic digit. Also referred to as a pelvic rib or an iliac rib, a pelvic digit is a rare, congenital anomaly that is usually asymptomatic and, therefore, found incidentally by plain radiograph. Pelvic digits are most often associated with the ilium but may also pseudoarticulate with other pelvic bones or the abdominal wall.1 Their wellcorticated appearance without defect facilitates differentiation from post-traumatic myositis ossificans, heterotopic bone formation, ligamentous calcifications and fracture.2 As in the case of our patient, radiographs are often obtained in the ED in the setting of trauma. Consequently, it is important to consider the benign entity of pelvic digit as a possibility and avoid further unnecessary work-up.