It seems that some people still believe that raising the heels of a laminitic horse will
reduce the pull of the deep digital flexor tendon (DDFT) and thereby prevent rotation. Devices can be bought and fitted that will increase the palmar angle by as much as 18 degrees - that's much the same as the palmar angle in this x-ray - I struggle to believe that anyone can look at that and think it is healthy! Arguments about the effect, if any, of the DDFT in laminitis have raged for years. There is research to support surgically cutting the DDFT, a procedure known as tenotomy, but this research is usually from back in the days when horses with more than 11 or so degrees rotation were considered to have a poor prognosis (that is definitely not the case!), and reference is rarely (never?) made to a correct realigning trim having been carried out before the surgery. And it has to be said that if you look hard enough, you can find research supporting just about anything!
Dr Debra Taylor and Pete and Ivy Ramey address the role of the DDFT in their Hoof Rehabilitation Protocol article: "our therapy of laminitic horses is based on the concept that tension of the deep digital flexor tendon cannot result in stress to the laminae if the toe wall is not allowed to bear weight at impact, stance or during breakover. While tension of the deep digital flexor does exert a rotational force on P3, this force cannot oppose the laminae if the hoof wall remains out of contact with the ground."
Pete Ramey elaborates on p 349 of Care and Rehabilitation of the Equine Foot (2011) - "if the sole at the toe is in ground contact, and the toe wall is out of ground contact"..., "force applied from the DDFT can have little or no effect on lamellar attachment." He reminds us that the sole must be padded, and goes on to say that whilst elevating the heels may temporarily reduce tension in the DDFT while the horse is standing, tension may actually be increased when the horse is moving, and that any relief will be transient anyway as the flexor muscle will quickly adapt. Pete says that in all the presentations he has seen where raising the heel has been advocated, he has never yet seen a hoof restored to health. And finally - sorry to quote you again, Pete, but this is so important (and why IMO anyone involved with laminitis rehab should buy Pete's book!) - "I believe that DDFT tension concerns have held back the veterinary and farrier world, preventing rotation reversal by leading people to stand P3 up on its tip and ultimately destroying the foot."
"There is really no proof anywhere that raising the heel does anything to prevent rotation. The theory of DDFT pull also fails to explain why horses with the most extensive damage sink or how sinkers can have a perfectly aligned bone column with no rotation at all. In fact, some sinkers are more ground parallel than before the laminitis. Raising the heel has negative effects long term by increasing the pressure on the tip of the coffin bone and accelerating bone loss."
We now know thanks to research by Melody de Laat (Insulin-Induced Laminitis - An investigation of the disease mechanism in horses 2011) and others that during endocrine laminitis (~90% of all laminitis cases), the laminar cells stretch, and it is likely that this weakening of the connection between the hoof wall and the coffin/pedal bone leads to laminar failure and rotation and/or sinking, exacerbated by the the horse's weight and perhaps poor foot balance.
Hundreds of horses have been restored to health and returned to work following rotation by following the ECIR group's realigning trim - simply realigning the hoof to the pedal/coffin bone, with a palmar angle of usually no more than 5 degrees - and not a heel wedge in sight.
The Laminitis Site has had the same excellent results in tens of horses - the x-ray above is of Sorrel, who was back in work within 8 months of a correct realigning trim (carried out according to emailed instructions!), after 7 years of laminitis - read her story here.
See more under DDFT.