The pelvic digit: A rare bone abnormality

Abstract

The pelvic finger is a rare anatomical abnormality characterized by the development of a bony structure in the soft tissues adjacent to the pelvis. Its origin is still unknown, but the theory suggests an abnormality occurring at the stage of mesenchymal bone growth during the first six weeks of embryogenesis. We present the case of a 40-year old patient, very athletic seeing the doctor for mechanical pain in the right groin that occurred during a training session. The clinical examination revealed a painful right hip mobilization without limitation of the movement. The remainder of the examination showed no somatic abnormalities. Face radiography of the pelvis revealed a bony finger-shaped protrusion articulating with the upper, outer corner of the roof of the right acetabulum (A). Computed tomography showed the pelvic finger, with a well-differentiated cortical bone articulating with the roof of the right acetabulum (B) and extending in the anterior-inferior direction (C). This problem may occur at any level of the pelvic bone, and can even be located entirely within the soft tissues of the abdominal wall. CT is useful in these cases because it helps to establish a differential diagnosis (bone tumors, osteochondroma, myositis ossificans and avulsion fracture of the pelvis). Occasionally the pelvic finger may be bilateral or multiple. It is usually asymptomatic and discovered incidentally. It can sometimes be a source of pain, difficult or functional disability because of its proximity to the articulation. In this case, surgical excision may be necessary.