1. When frog support only is used on a laminitic foot, the pedal bone is left unsupported with the potential for (further) rotation, sinking and penetration (the example shows a foot with dorsal and palmar rotation):
On conforming bedding the front of the foot will be supported so the risks of fitting a frog support should be minimized, but the frog support is unlikely to provide any better support than the bedding alone (and may lead to thrush, excess pressure and atrophy of the frog).
The dorsal and palmar rotation should be corrected immediately. The purple dotted line shows the breakover bevel back to the outer edge of the true white line. The heel/bottom of the foot trim to return the palmar angle to 3 to 5 degrees is not shown, but see below *.
Conforming bedding may support the foot adequately and whilst a laminitic horse is on wall to wall deep conforming bedding, extra support may not be needed, but if a horse is not fully comfortable, padding the full solar surface should be tried and the horse assessed to find optimum comfort.
As above, the dorsal and palmar rotation should be corrected immediately.
It is very important that sole support does not adversely affect the already compromised foot, and thought should be given to the material and design used and to ensure that pressure is released during hoof flight. Dr Taylor (see below) suggests using a shallow air space beneath the margin of the pedal bone when the sole is very thin or perforated. However, if used both the position of the air space and the horse's comfort must be checked regularly, as we have seen the use of an air hole allow the pedal bone to penetrate the sole in a foot that hadn't been correctly realigned.
Jonathon Merritt, Helen Davies and Andrew Parks say, in their chapter on the Digital Biomechanics Relevant to Laminitis (in Equine Laminitis edited by Belknap, Wiley, 2017) that the pedal bone may be supported from below by forces transmitted from the solar surface of the hoof, and that "increasing support from the sole may assist in reducing the force on the lamellar junction."
In 2014 Dr Debra Taylor published a paper describing the laminitis rehabilitation protocol that returned 14 out of 14 horses, many with significant rotation and sinking, to their pre-laminitis level of comfort. The hoof care method used the full solar surface to support the pedal bone (P3), protecting the sole during weight bearing by using foam rubber pads and/or dental impression material inside hoof boots (or casts).
See Section 2.3:
Taylor D, Sperandeo A, Schumacher J, Passler T, Wooldridge A, Bell R, Cooner A, Guidry L, Matz-Creel H, Ramey I, Ramey P
Clinical Outcome of 14 Obese, Laminitic Horses Managed with the Same Rehabilitation Protocol
Journal of Equine Veterinary Science Volume 34, Issue 4, Pages 556–564, April 2014 (online 05 Feb 2014)
Robert Bowker Hoof Anatomy Videos
See Recognizing and Treating Rotated Hoof Capsules - Pete Ramey