IMAGE OF THE WEEK 2014

IMAGE 6

 

AVASCULAR NECROSIS OF THE FEMORAL HEAD

 

Figure 1: Pelvic xray showing complete destruction of both femoral heads with loss of articular surface between femoral head and acetabulum. Both femoral heads appeared irregular and deformed.

(Click on image to enlarge)

Figure 2: Annotated pelvic xray of Figure 1, showing complete destruction of both femoral heads with loss of articular surface between femoral head and acetabulum. Both femoral heads appeared irregular and deformed. The red ring indicates how the normal femoral head should appeared in relation to the acetabulum

(Click on image to enlarge) 

   

 

 

Avascular necrosis (AVN) is general term used to describe osteonecrosis resulting from an ischaemic injury to subchondral bone.  A wide range of causes may be responsible for the ischaemic event arising from a disrupted blood supply.  Some causes are more common, which are indicated by the mnemonic STARS.

 

S - steriods

T - trauma

A - alcohol excess

R  radiation induced osteonecrosis

S - sickle cell disease

 

Although it can potentially occur in any bone, some sites are more prone to AVN, including the scaphoid, navicular, 2nd metatarsal and femoral head.  Many of these have specific eponymous names, such as Legg-Calve-Perthes disease in the case of the femoral head.

 

In the early stages of the disease plain radiographs may be normal, with MRI being the imaging investigation of choice, with a sensitivity close to 100%.  The double line sign (on T2 weighted sequences) is well documented, which is pathgnomonic for AVN.

 

In the later stages of the disease the bone loses volume, collapses and becomes remodelled, especially in the case of the femoral head (Figure 1 and 2).  The bone appears sclerotic and secondary degenerative changes invariable follow.

 

 

 

 

 
 

Images and text contributed by

Dr Ian Bickle, Department of Radiology,RIPAS Hospital.

All images are copyrighted and property of RIPAS Hospital.

 

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