The vascular angle, which is also called buerger's angle, is the angle to which the leg has to be raised before it becomes pale. In a limb with a normal circulation the toes stay pink, even when the limb is raised by 90 degrees. In an ischaemic leg, elevation to 15 degrees or 30 degrees for 30 to 60 seconds may cause pallor. A vascular angle of less than 20 degrees indicates severe ischaemia.
In arterial disease, on returning the leg from the raised position, and hanging it over the side of the bed, the leg will revert to the pink colour more slowly than normal. Moreover, the affected leg will pass through the normal pink colour to a red-range colour (often known as sunset foot) due to the dilatation of the arterioles in their attempt to remove the metabolic waste that has built up, through the phenomenon of reactive hyperaemia. Finally, the limb will then revert to its normal colour.
- Browse's introduction to the symptoms and signs of surgical disease/4th edtition/International student edtition/Page 175
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