Pediatric orthopedic cases 40
CASE 40
The ER requests your consultation on a 3-year-old boy who presented with 5 days
of pain and refusal to bear weight in the right leg for the past day. He also had a fever of 39°C this morning. The ER ordered labs and are requesting your evaluation. The WBC is 8.9 cells/mm3 and the C-reactive protein is 6.4 mg/dL (normal at your hospital is <1 mg/dL). They did not get an ESR. On examination, he looks unhappy but is not septic appearing. You see no evidence of rash. His right lower extremity examination reveals full and painless ROM of the hip, knee, and ankle. He is tender over the distal tibial metaphysis, not tender more distally, and no effusion appreciated in the knee or ankle on examination. You try to get him to walk, but he refuses to put weight on the leg. You confirm with mother that his symptoms began just yesterday—no pain, limp or other complaints prior to that.
You suspect osteomyelitis given the fever, tenderness over distal tibia, refusal to bear weight, and elevated CRP. The lack of elevation of the WBC doesn’t change your thoughts on diagnosis because you know that in only around 25% of patients with osteomyelitis is the WBC elevated. For your next step in evaluation, you order x-rays.
What do you expect to see if your diagnosis is correct?
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Lucency in the tibia
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Periosteal reaction along the tibial cortex
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Moth-eaten appearance throughout the distal tibia
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Normal appearing bone
Discussion
The correct answer is (D). The patient’s symptoms just began a few days ago, so this is a case of acute osteomyelitis. Changes in the bone aren’t seen radiographically usually until 7 to 10 days after the onset of symptoms. Sometimes on early x-rays the soft tissue planes are obscured, but the bone is normal. By 7 to 10 days you can start to see periosteal bone along the cortex and then lucency in the metaphysis.
After reviewing the x-rays, you confirm that they appear normal. There is no evidence of fracture. He is admitted to the hospital for treatment of presumed osteomyelitis. He is started on antibiotics to cover the most common organism responsible for osteomyelitis in children over the age of 1 in the United States.
What organism is that?
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Streptococcus pyogenes
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Group B streptococci
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Kingella kingae
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Salmonella
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Staphylococcus aureus
Discussion
The correct answer is (E). There are a number of pathogens that can cause osteomyelitis in kids (and all of those in the list do), Staphylococcus aureus accounts for 70% to 90% of pediatric acute hematogenous osteomyelitis. Streptococcus pyogenes does cause osteomyelitis in children, but is far less common than S. aureus. Group B strep is the most common in neonates, but this question specifically asked for children older than 1-year old. Salmonella is frequently associated with sickle cell because patients with sickle cell anemia are most at risk of having a Salmonella infection than the general population, but S. aureus is still more common in sickle cell than Salmonella is. Kingella kingae is increasingly the culprit in septic arthritis—in some places surpassing Staph as the primary cause of joint infection in young children. However, Staph aureus continues to be the most common etiologic agent in osteomyelitis and osteaoarticular infections in children when all age groups are considered.
You work with the infectious disease service on this patient’s care and he is put on the appropriate agent for the treatment of S. aureus. Over the next 36 hours he improves clinically and begins to weightbear normally. He is transitioned over to an oral antibiotic which he tolerates well and is ultimately discharged to home. The plan is for him to complete a 4- to 6-week course of antibiotics, per the ID service. They acknowledge that even their literature doesn’t have great data on how long to treat for and even when they should have changed from IV to oral form, but they will monitor his continued response to treatment and respond as needed.
You reflect on the patient and think about how things could have been different if the child had community-acquired MRSA infection. You remember reading about kids that have the MRSA osteomyelitis. All of the following are true about children with multifocal MRSA osteomyelitis, EXCEPT:
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They are less likely to need surgery.
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They are more likely to need surgery.
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They are more likely to need multiple surgeries.
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They are at higher risk of developing DVT and septic pulmonary emboli.
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They are more likely to be in the ICU and have a longer hospital course.
Discussion
The correct answer is (A), because it is NOT true that children with MRSA osteomyelitis are LESS likely to need surgery. Multiple studies have now shown that children with MRSA, when compared to kids with MSSA infections, are more likely to need surgery, they require more surgeries, they have longer hospital stays, they are more likely to require ICU support, and are more likely to develop DVT and septic pulmonary emboli.
Additional Questions
You are working in a remote clinic in an area with limited healthcare resources. A patient comes in, brought by their family, because they have had a problem with their leg for the past year. A year ago, she developed pain in the leg after a trauma. There was a skin wound that got infected, and she was on antibiotics for about a week which improved the infection briefly. They feel it never really went away though and over time, there was continued intermittent drainage, foul smell, and they could see the bone at times—this has worsened over the past 2 months. There is now continued drainage, and she is having difficulty walking. They were not able to access care until now. You are able to obtain an x-ray (Fig. 10–69).
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Figure 10–69
What is the red arrow pointing at?
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Cloaca
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Sequestrum
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Involucrum
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Brodie’s abscess
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Fracture
Discussion
The correct answer is (B). The patient has chronic osteomyelitis of their tibia. In chronic osteomyelitis, there can be increased pressure in the metaphysis where the infection first starts and the fluid can push out through the metaphyseal cortex and into the subperiosteal space. This communication is the cloaca (which ultimately communicates into the soft tissues and sometimes out of the skin). The fluid continues to build up in the subperiosteal space, further stripping the periosteum off the cortex. Both the stripping of the periosteum and the increased pressure from the fluid inside the bone leads to reduced vascular supply to the bone which can lead to necrosis. This necrotic bone is the sequestrum. The body then tries to heal along the periosteum that was lifted off, and this new bone is called the involucrum. On the xray shown in Figure 10–69, the arrow is pointed at the dysvascularized piece of
bone which is the sequestrum. A Brodie’s abscess is seen in subacute and chronic osteomyelitis and is a walled-off area of bone usually in the metaphysis—there is an inner lucency, surrounded by sclerotic bone. E is incorrect because this is simply not a fracture. Treatment of this chronic osteomyelitis will depend on what resources are available. Ultimately, a sequestrectomy will need to be performed to remove the sequestrum since it is a nidus for infection. The timing will depend on surgeon preference and if there is available equipment for stabilization of the involucrum. Because equipment often is not available, many surgeons will wait until the involcrum is in continuity and developed enough to minimize risk of fracture and segmental bone loss.
Objectives: Did you learn...?
Differences in presentation and treatment between acute, subacute, and chronic osteomyelitis?
The most common organisms that cause osteomyelitis in children? The increased risks associated with MRSA osteomyelitis?
The presentation of chronic osteomyelitis?