WASHINGTON — An astute physical examination and the appearance of deep soft tissue swelling on imaging are key to a prompt diagnosis of pediatric acute hematogenous osteomyelitis, John P. Dormans, M.D., said at the annual meeting of the American Academy of Orthopaedic Surgeons.
Soft tissue swelling can be seen on plain radiographs, but MRI—especially advanced MRI—is overall the best diagnostic tool for the infection. “Have the presence of mind to order advanced MRI—it will be very helpful in determining whether there's purulent material that needs to be drained,” said Dr. Dormans, chief of orthopedic surgery at The Children's Hospital of Philadelphia.
In describing his approach to diagnosis—which he said is “still a problem” today, with missed cases of osteomyelitis and with Ewing's sarcoma presumed to be osteomyelitis—Dr. Dormans also emphasized the value of aspiration and excisional biopsies.
Early diagnosis is important because medical treatment alone—not surgery—is now an accepted course of action early on. Studies have shown a 90% response rate to medical management alone when treatment is initiated within the first few days after the onset of symptoms, he said.
“If the diagnosis is made before an abscess [has formed], you can start antibiotics and watch closely and, if the patient is getting better, just continue [with the antibiotic treatment],” he said.
“Unexplained bone pain with fever means osteomyelitis until proven otherwise,” he stressed.
Overall, he advised, “culture everything, go by the rules, don't take short cuts, and you'll do fine.”
Technetium diphosphonate bone scans are “not very accurate [for early diagnosis], since it takes a while for bone to be stimulated,” he said. Gallium citrate tests take 48-72 hours to complete and “we almost always equivocate [over the results],” and CT scans are “really not that helpful,” he said.
Asked about the cost-effectiveness of using advanced MRI, Dr. Dormans acknowledged that he takes “an aggressive approach” but said it's worth it. He warned physicians to “think of zebras”—particularly Ewing's sarcoma in patients with presumed osteomyelitis.
He recalled treating a boy with ankle pain. “The orthopedist encountered pus, started antibiotics, and the symptoms continued … What looked like purulent material ended up being chronic Ewing's sarcoma tissue.
“We all know that patients with Ewing's sarcoma get fevers and elevated white counts,” he said. “That's why I like to do excisional biopsies—we do them in the OR and tend to hand-carry out frozen sections to the pathologist. … I want to establish the diagnosis, and then everyone sleeps better at night.”
Dr. Dormans said that attention to the three stages of pediatric acute hematogenous osteomyelitis—and recognition of the fact that there are “no real bone changes for the first 7-10 days” will “help you differentiate [pediatric osteomyelitis] from tumor or Ewing's sarcoma.”
Stage 1 (within the first 3 days) of pediatric osteomyelitis is characterized by deep soft tissue swelling next to a metaphysis. Swelling of muscles and obliteration of deep soft tissue planes develops later, during stage 2 (3-7 days); purulent material under the periosteum also collects during this time.
Stage 3 (10-14 days) is characterized by the “classical picture” of involucrum and sequestrum, he said.
Symptoms of pediatric acute hematogenous osteomyelitis include swelling, redness, pseudoparalysis, tenderness to palpation, increased warmth, and limited range of motion. Patients with osteomyelitis do not present with joint irritability unless they have concurrent septic arthritis, Dr. Dormans said.
Antibiotic treatment entails 3 weeks of intravenous antibiotics followed by at least 3 weeks of oral therapy.