If we start with Xrays, what do we look for:

• On X-ray look initially for increased bone density/ sclerosis.
  
  
• As it progresses fracture, fragmentation and collapse of the sesamoid can occur.
  

• Sesamoid view demonstrates marked sclerosis of the lateral sesamoid (Pink arrow) with a fracture (Green arrow).

   

• Compare the degree of sclerosis of the osteonecrotic lateral sesamoid with the normal density of the medial sesamoid.
  

On CT, what do we look for:

• With osteonecrosis the sesamoid looses its normal lucent central appearance and becomes uniformly hyperdense.

   

• There may or may not be associated fractures which will be seen as lucent lines.
  

• Assess for osteonecrosis on the non fat saturated PD or T1 as it’s the fat signal that’s important.

• The normal sesamoid is full of marrow so it will be high signal on PD/ T1.

• On MRI, Osteonecrosis of the sesamoid will demonstrate loss of the normal high marrow signal on PD/ T1.

• It will be low signal on PD/T1.

• PDFS will be low signal with both normal sesamoid and a sesamoid with osteonecrosis.