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Difficulty: MediumOrthopedic Surgery

A 15-year-old boy presents to the orthopedic clinic with a 3-month history of progressively worsening deep pain in his right distal thigh. The pain is persistent, often awakens him at night, and is not relieved by over-the-counter analgesics. Physical examination reveals a palpable, tender, and firm mass over the anterior distal femur. There is no history of preceding trauma, and the patient is afebrile. Arrange the following steps in the most appropriate chronological sequence for the evaluation and definitive management of this patient's suspected primary bone sarcoma.

  1. 1Obtain orthogonal plain radiographs of the right femur
  2. 2Perform a magnetic resonance imaging (MRI) scan of the affected extremity
  3. 3Perform a planned, image-guided core needle biopsy of the mass
  4. 4Initiate a regimen of neoadjuvant systemic chemotherapy
  5. 5Perform definitive limb-salvage surgical resection

Answer

The correct chronological sequence is: 1) Plain radiographs, 2) MRI of the extremity, 3) Core needle biopsy, 4) Neoadjuvant chemotherapy, and 5) Definitive surgical resection.
The management of a suspected primary bone sarcoma follows a strict algorithm to maximize diagnostic accuracy and therapeutic efficacy. Initial evaluation always begins with plain radiographs. Advanced local imaging with an MRI must follow immediately to map the tumor's extent. It is critical that the MRI is performed before any biopsy, as post-biopsy hemorrhage and edema can obscure tumor margins on imaging. Once imaging is complete, a carefully planned biopsy is performed to confirm the histologic diagnosis. For high-grade sarcomas like osteosarcoma, neoadjuvant chemotherapy is then initiated to address micrometastases and shrink the primary lesion, followed finally by definitive surgical resection with wide margins.

Step-by-Step Solution

1
Recognize the clinical presentation of a potential primary bone malignancy.
The patient has a painful, palpable bone mass without trauma, raising high suspicion for a primary bone sarcoma like osteosarcoma.
Identifying the severity of the lesion dictates the rigorous oncologic workup sequence.
2
Determine the first diagnostic step.
Plain radiographs of the femur.
X-rays provide immediate, cost-effective information on bone destruction, matrix type, and periosteal reaction.
3
Determine the next advanced imaging step before intervention.
MRI of the extremity.
MRI determines local extent and soft-tissue involvement. It must precede any invasive procedure to avoid post-procedural artifact.
4
Identify the definitive diagnostic procedure.
Core needle biopsy.
Tissue is required for histologic diagnosis and grading to guide specific oncologic therapy.
5
Determine the sequence of definitive therapies.
Neoadjuvant chemotherapy followed by surgical resection.
Chemotherapy is given first to shrink the tumor and treat micrometastases, followed by limb-salvage surgery to physically remove the primary lesion.

Key Concept

Evaluation and management sequence for primary bone sarcomas requires imaging (radiographs, then MRI) prior to biopsy, followed by neoadjuvant chemotherapy and definitive surgical resection.
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