So, the question you need to ask is why they cut the leg off and transplanted the foot/ankle 180 at the lower femur.

If you think about it, it is because he needed a joint to flex like his old knee.  If they put the foot on forward there would be no knee bend (ie. his knee would have only bent as much  as you can point your foot…….the motion of ankle plantarflexion.  This would have been extremely insufficient in range to move as well as this fella is moving. )

By doing a rotation transplasty and putting the foot on backwards he could take advantage of the large range of ankle dorsiflexion.  They talk about the toes alot in this video but this really has nothing to do with the success of this surgery, functionally anyways. The genius of this surgery was using the ankle as a knee hinge. 

Pretty amazing stuff.  Enjoy the brain-twister in understanding how he is using ankle dorsiflexion to replicate knee flexion.  !!!!

taking Gait to another dimension……… Shawn and Ivo