Bilateral tibial insufficiency fractures

Case contributed by Dr Bruno Di Muzio

Presentation

12 months after bone marrow transplant due to acute myeloid leukaemia. Long-term graft versus host disease, on steroids. Bilateral knee pain.

Patient Data

Age: 50 years old
X-ray

Knee radiographs

The medial and lateral joint compartments are preserved bilaterally. There are no changes of osteoarthritis, no erosions no loose bony fragment seen within the joint compartments on either side. The patella is normal bilaterally as is the patellofemoral joint. There is no soft tissue abnormality identified. There are no features to suggest avascular necrosis.
Nuclear medicine

Bone Scan/SPECT

A triple-phase bone scan of the knee was performed with delayed SPECT/CT of the knees. Delayed whole body static imaging was also acquired. Dynamic flow and blood pool images show moderate hyperemia in bilateral medial tibial condyles in a bilaterally symmetrical pattern. Delayed static images with SPECT/CT of the knees show symmetrical intense focal uptake in bilateral medial tibial condyle metaphyses, with only subtle sclerotic changes seen on low dose CT. No definite fracture line is identified on low dose CT. The rest of both knee joints show normal activity. Delayed whole body static images show a normal tracer biodistribution in the rest of the skeleton. No other osteoblastic lesion is seen elsewhere.

MRI

MRI both knees (AVN protocol)

Incomplete transverse fracture line is identified within the medial tibial condyle bilaterally, surrounded by bone marrow oedema, and corresponding to the bone scan findings. Bone marrow is otherwise unremarkable. Bilateral joint effusions. No other significant abnormalities within the limitations of this protocol. 

Case Discussion

Insufficiency fractures involving the medial tibial condyles bilaterally showing hyperemia on the nuclear medicine bone scan and SPECT and then confirmed on MRI study.

The primary differential would be avascular necrosis, especially based on the clinical scenario, but the location in the medial tibial condyle, the symmetry, and the intense capitation on the bone scan/SPECT go against this diagnosis. MRI has further shown the fracture lines. 

Insufficiency fractures are a type of stress fracture, which are the result of normal stresses on abnormal bone. This diagnosis was achieved based on the clinical data and imaging appearances. These fractures are usually not identified on conventional radiographs. Radionuclide bone scan, and especially MRI are the modalities of choice when assessing this condition.

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Case information

rID: 46212
Case created: 27th Jun 2016
Last edited: 3rd Jul 2016
Tag: rmh
Inclusion in quiz mode: Included

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