Review Question - QID 219000

The patient is exhibiting symptoms and persistently elevated lab values suggestive of an additional undiagnosed source of infection. Given the recent diagnosis of osteomyelitis, in this case the source of infection is a subperiosteal abscess, depicted in the MRI in Figure D.

Subperiosteal abscesses in the setting of osteomyelitis develop as a result of the purulence violating the cortical bone and spreading in the underlying subperiosteal space. They can occur in any bone affected by osteomyelitis, with the femur (23-29%) and tibia (19-26%) being the most commonly affected sites. MRI is the best diagnostic modality to detect intraosseous and extraosseous abscesses and guide treatment, and may be repeated in the event of persistent symptoms or elevated inflammatory markers. Technetium bone scan is an alternative imaging modality useful for detecting nonlocalized or multifocal disease; however, its sensitivity and specificity is much lower compared to MRI. Subperiosteal abscesses usually require operative treatment in the form of surgical drainage.

Peltola & Pääkkönen performed a 2014 review of acute osteomyelitis. They review the diagnostic modalities and management details including initial intravenous antibiotics, transition to oral antibiotics, duration of treatment, and the role of surgical intervention. They described a prospective randomized trial demonstrating that a 20-day regimen of high-dose clindamycin or a first-generation cephalosporin performed as well as a 30-day regimen for osteomyelitis caused by MSSA, streptococci, or pneumococci. Due to the lack of data on short-term treatment of MRSA-associated acute osteomyelitis, the authors justify a short (24-48 hours) course of individualized IV antibiotics followed by 4 to 6 weeks of oral medication. Surgical intervention was typically reserved for acute, subacute, or chronic abscesses.

Gornitzky et al. performed a critical analysis review of the current standards of diagnosing and managing pediatric osteomyelitis. They concluded that while ultrasound may be useful as an initial detection tool, MRI is the best diagnostic imaging modality due to its vastly superior sensitivity and specificity. Additionally, while there is insufficient evidence for surgical management of pediatric osteomyelitis, surgical debridement is generally reserved for those with associated abscesses or failure to respond to antibiotic therapy.

Woods et al. consolidated the most up-to-date literature on acute hematogenous osteomyelitis in children and published a clinical practice guideline that was adopted by the Infectious Diseases Society of America (IDSA). In children with suspected AHO requiring further imaging studies to confirm the diagnosis, they recommend MRI over scintigraphy (bone scan), CT, or ultrasound, although this is a conditional recommendation. Additionally, if a child does not respond to medical therapy within 24 to 48 hours or signs and symptoms suggest a potential role for surgical debridement, they recommended that MRI may be performed to better define the location and extent of infection or to evaluate for an alternative diagnosis such as a malignancy.

Figure A is a radiograph of a chondroblastoma. Figure B is a radiograph of a distal femur unicameral bone cyst (UBC) with an associated fracture and fallen leaf sign. Figure C is a coronal MRI slice of osteosarcoma. Figure D is a coronal MRI slice of a subperiosteal abscess affecting the left distal femur. Figure E is a coronal MRI slice of an osteochondritis dissecans (OCD) lesion. Illustration A is a diagram of the anatomical distribution of acute osteomyelitis.

Answer 1: Figure A represents a chondroblastoma, which requires surgical treatment but is not typically associated with osteomyelitis.
Answer 2: Figure B represents a unicameral bone cyst (UBC) with an associated fracture. These are typically treated conservatively with limited weight bearing and are not often associated with osteomyelitis.
Answer 3: Figure C represents malignant osteosarcoma, which requires surgical treatment but is not typically associated with osteomyelitis.
Answer 5: Figure E represents a distal medial femoral condylar osteochondritis dissecans (OCD) lesion. Depending on size, stability, and symptoms, these may be treated either conservatively or surgically. However, these are not typically associated with osteomyelitis.