Differential Diagnosis for the Given Scenario

The patient's symptoms and test results suggest a possible infection, but further evaluation is needed to confirm the diagnosis. Here's a differential diagnosis based on the provided information:

• Single most likely diagnosis:
  • Post-surgical infection: The recent surgery and positive three-phase bone scan results in the region of the right femoral epicondyle and tibial plateau suggest a possible post-surgical infection. The mild delayed periosteal uptake in the anterior distal femur also supports this diagnosis.
• Other Likely diagnoses:
  • Osteomyelitis: The positive bone scan and recommendation for further evaluation with a WBC scan and reference bone marrow image suggest osteomyelitis as a possible diagnosis.
  • Septic arthritis: The involvement of the tibial plateau and femoral epicondyle, which are both near joints, raises the possibility of septic arthritis.
  • Soft tissue infection: The patient's symptoms and test results could also be consistent with a soft tissue infection, such as cellulitis or abscess.
• Do Not Miss (ddxs that may not be likely, but would be deadly if missed.):
  • Osteonecrosis: Although less likely, osteonecrosis could present with similar symptoms and test results, and missing this diagnosis could lead to significant morbidity.
  • Bone tumor: A bone tumor, such as osteosarcoma, could also present with similar symptoms and test results, and missing this diagnosis could be devastating.
  • Sepsis: If the patient has a systemic infection, sepsis is a possible diagnosis that should not be missed, as it can be life-threatening.
• Rare diagnoses:
  • Chronic recurrent multifocal osteomyelitis (CRMO): This rare condition presents with recurring episodes of osteomyelitis and could be considered in the differential diagnosis.
  • Sarcoidosis: Although rare, sarcoidosis could present with bone involvement and should be considered in the differential diagnosis, especially if other symptoms are present.
  • Ewing's sarcoma: This rare bone tumor could present with similar symptoms and test results, and although unlikely, should be considered in the differential diagnosis.