Leaning Cactus
 

I have 2 cacti. One a Saguaro, the other a barrel. Both 20 years old, both
about a foot and a half tall. Both are leaning (like the leaning tower of
Pisa). Other than holding them up with some bamboo rods, what else can I do
to get them to stay straight? There is no evidence that they suffer from
lack of light (enlongation).