A 13-year-old girl presented with a 2-week history of mild pain in the right knee, can you guess a diagnosis?
Presentation: Pain in the proximal right tibia
Description: A 13-year-old girl presented with a 2-week history of mild pain in the right knee. On examination, we found tenderness in the proximal right tibia with no swelling, ecchymosis, or any deformity. The range of motion of the knee was normal.
Need more information?
She reported no recent injury. x-rays showed a high-density linear abnormality with a periosteal reaction in the proximal right tibia (figure), which medical staff, at the hospital where she was first seen, thought might have been a tumour of the bone.
What is the most likely diagnosis?
- Ewing’s sarcoma
- Occult fracture
- Osteosarcoma
- Osteomyelitis
Answer: Occult fracture
Breakdown: MRI showed a rough hypointense fracture line surrounded by an extensive hyperintense area of bone marrow oedema in the T2-weighted image (figure) clearly indicating a fracture of the tibia. Further, on closer questioning, the patient remembered that she had recently fallen on her knees while walking. After 4 weeks of rest and restricted weight bearing, the patient had no further trouble with pain during daily activity.
An x-ray repeated 4 weeks after the initial presentation showed a healed fracture with obvious bone callus formation (figure); the repeat MRI showed that the bone marrow oedema had receded (figure).
An occult fracture—often known as a bone contusion or bone bruising—is defined as a fracture that cannot be seen on conventional x-ray or radiographically shows subtle abnormalities which are prone to be overlooked or misdiagnosed at initial presentation. The history of a single traumatic event is an important clue in diagnosing an occult fracture and if suspected, MRI or CT can help confirm the diagnosis and assist in the evaluation of the lesion. In most cases the bone marrow oedema will completely disappear after 6–12 weeks. For most occult fractures without severe ligament or articular cartilage injury, conservative therapy is the first-line treatment—including analgesia treatment and weight-bearing restriction.
In children with symptoms of swelling, pain, or redness, and a fracture of the bone—particularly either side of the knee or in the upper arm—the diagnosis must be considered to be a malignancy until proven otherwise.
Source: All content for this “Diagnostic Puzzle” was sourced from The Lancet. Original article is available at:
https://www.thelancet.com/doi/story/10.1016/pic.2020.12.11.108599
and
https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(20)32516-2/fulltext
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