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Difficulty: MediumOrthopedic Surgery

During a routine sports physical, a 16-year-old adolescent female complains of persistent right lower thigh pain that has progressively worsened over the last two months. She states the pain initially occurred only after running but now throbs at night and regularly disrupts her sleep. She has experienced no fevers, chills, or unintentional weight loss. On examination, the physician palpates a firm, exquisitely tender mass fixed to the underlying bone near the distal right femur. The overlying skin is slightly warm but not erythematous. Plain radiographs of the right lower extremity exhibit a poorly marginated, destructive lytic lesion in the distal femoral metaphysis accompanied by a sunburst pattern of periosteal reaction and a Codman triangle. Which of the following is the most appropriate next step in the management of this patient?

  1. A
    Open incisional biopsy of the femoral mass
  2. B
    Computed tomography scan of the chest
  3. Magnetic resonance imaging of the right femurAnswer
  4. D
    Intravenous administration of broad-spectrum antibiotics
  5. E
    Immobilization in a long-leg cast and non-weight bearing

Answer

The correct answer is magnetic resonance imaging of the right femur.
Magnetic resonance imaging (MRI) of the entire affected bone is the most appropriate next step in the management of a suspected primary bone malignancy. MRI provides the most detailed soft-tissue contrast, allowing accurate assessment of the intraosseous and extraosseous tumor extent, involvement of the adjacent neurovascular structures, and the presence of 'skip' metastases within the same bone. This imaging must be completed before any biopsy is attempted so that the biopsy tract can be carefully planned by the orthopedic oncologist to ensure it can be entirely excised during the definitive tumor resection.

Step-by-Step Solution

1
Analyze the clinical presentation.
A 16-year-old female presents with chronic, worsening bone pain, night pain, and a palpable mass, which strongly suggests a primary malignant bone tumor rather than a benign or infectious process.
Identifying the red flag symptoms (night pain, palpable firm mass) narrows the differential diagnosis to oncologic etiologies.
2
Interpret the radiographic findings.
The presence of a destructive lytic lesion with a 'sunburst' periosteal reaction and a Codman triangle is classically pathognomonic for osteosarcoma.
Radiographic patterns dictate the urgency and type of the subsequent diagnostic algorithm.
3
Determine the proper sequence for oncologic staging and diagnosis.
Before any tissue biopsy is performed, local staging must be completed with an MRI of the entire affected extremity.
An MRI defines the precise anatomic extent of the tumor, assesses for neurovascular bundle involvement, checks for skip lesions within the same bone, and safely guides the surgical approach for the eventual biopsy.

Key Concept

In patients with suspected primary malignant bone tumors (e.g., osteosarcoma), MRI of the entire affected bone is required for local staging prior to performing a biopsy.
Estimated Time:1m 15s
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