The posterior fat pad sign in association with occult fracture of the elbow in children.

BACKGROUND: An elevated posterior fat pad visible on a lateral radiograph of a child's elbow following trauma is generally considered to be suggestive of an intracapsular fracture about the elbow. However, in previous studies, the prevalence of fracture in elbows with an elevated posterior fat pad and no other radiographic evidence of fracture has ranged from only 6 percent (two of thirty-one) to 29 percent (nine of thirty-one). We are not aware of any prospective studies, limited to children, on the value of an elevated posterior fat pad as an indicator of an occult fracture about the elbow. While it is common practice to manage children who have radiographic evidence of an elevated posterior fat pad as if they have a fracture, scientific evidence for this approach is lacking.

METHODS: Forty-five consecutive children who had an average age of four and a half years, a history of trauma to the elbow, and an elevated posterior fat pad without other radiographic evidence of a fracture were enrolled in the study. At an average of three weeks after the injury, anteroposterior, lateral, and two oblique radiographs were made and evaluated for evidence of fracture-healing. If there was evidence of new-bone formation on any of these four radiographs, it was considered to indicate a fracture of the elbow.

RESULTS: Thirty-four (76 percent) of the forty-five patients had evidence of a fracture. Eighteen (53 percent) of the thirty-four had a supracondylar fracture of the humerus; nine (26 percent), a fracture of the proximal part of the ulna; four (12 percent), a fracture of the lateral condyle; and three (9 percent), a fracture of the radial neck.

CONCLUSIONS: This prospective study demonstrated that the posterior fat pad sign was predictive of an occult fracture of the elbow following trauma in thirty-four (76 percent) of forty-five children who had no other evidence of fracture on anteroposterior, lateral, and oblique radiographs after the injury. This finding is in contrast to those of previous studies, in which the highest prevalence of fracture in elbows with an elevated posterior fat pad and no other radiographic evidence of fracture was 29 percent (nine of thirty-one elbows). Our results support the practice of managing children who have a history of trauma to the elbow, an elevated posterior fat pad, and no other radiographic evidence of fracture as if they have a nondisplaced fracture about the elbow.