Narrow

In narrow hooves when the heels start to grow faster all of the hoof capsule's distortion is focused in the toe area. In mild cases distension (stretching) the laminae is seen only in the toe and the laminae are aligned parallel to each other. In sever cases this type of hoof shape predisposes the distal phalanx to rotation as its only the laminae at the toe which is destroyed.

Round

In round hoof shapes there is no focus for hoof distortion so a greater area of laminae is damaged as the whole hoof distorts outwards. This leads to sinking of the distal phalanx is the more severe cases. 

Asymmetric hoof shapes help to confirm that hoof shape determines how the hoof distorts as an asymmetric hoof shape has one side which is round and one side which is narrow, this causes the laminar distension to be biased towards the side which is rounder in shape. As many hind feet are asymmetric this is mostly seen in hind laminitic feet. This hoof shape predisposes the distal phalanx to sink in one side of the hoof.

Dissipating hoof shape

This pony is not lame at the present time, but shows signs of divergent growth rings at the heels, this would usually cause laminitis in other hoof shapes but the dorsal surface of the hoof is not distorted because the rapid heel growth is not exerting enough of a lifting force onto the dorsal wall to cause pain in the laminae. The rapid heel growth is splaying the heels out laterally. Over time as the heels continue to grow rapidly, the hoof shape will change to a more boxy shape. This modifies the hoof shape into a narrow shape allowing the hoof distortion to now focus in the toe, the laminae will become traumatised and the pony will become laminitic. 

This accounts for why some animals can become laminitic more easily than others.