Q. What is meant by rotation?
A. We generally talk about 2 angles following laminitis:
The palmar angle - in red - is the angle between the solar margin (bottom) of the pedal bone (P3) and the ground.
The dorsal angle or angle/degree of rotation - in yellow - is the angle between the hoof wall at the toe (green) and the dorsal (front) aspect of the pedal bone (blue).
In Care and Rehabilitation of the Equine Foot (p 341) Pete Ramey suggests that what is often called rotation is simply flare, i.e. separation of the hoof wall and the pedal bone. The pedal bone hasn't gone anywhere, it hasn't rotated, but the hoof wall has been displaced (by the stretching of the laminae/laminar wedge). This can be corrected by setting up the pedal bone as it would be if the hoof wall was in the correct place, then growing a new properly connected wall down from the coronary band.
What other measurements might help assess changes after laminitis?
A. In Clinical Outcome of 14 Obese, Laminitic Horses Managed with the Same Rehabilitation Protocol, Debra Taylor et al. measured the degree of rotation and palmar angle (above), and also:
Q. Can rotation always be corrected?
A. In most cases rotation can and should be corrected at the earliest opportunity, it's a case of trimming the hoof capsule back in alignment with the pedal bone.
Sorrel's left fore had a palmar angle of around 21 degrees and a dorsal angle of around 18 degrees, with phalangeal/bony rotation (the bones were out of alignment - purple line) - this rotation was probably long-standing. Within 3 trims her feet had been realigned, and within 8 months she was back in work - see her story here.
On p 350 of Care and Rehabilitation of the Equine Foot, Pete Ramey says that as long as the pedal bone hasn't been significantly remodelled, he is pretty confident that he can rehabilitate 20 degree hoof capsule rotations, most sinkers and even most "sole penetrations".
A. Usually, depending on the individual circumstances. Besides, at some point, talking about the size of an angle of rotation may become rather pointless - what would the angle of rotation be on Cedar's left fore before his realigning trim below (possible position of the pedal bone marked in green)? After 3 months his realigning trim was pretty much complete, and x-rays a month later confirmed this, although there was still distal descent which would hopefully correct with time. See photos of Cedar's rehab here.
The x-rays above are of the same foot taken two months apart. The toes have been brought back slightly but the heels have remained excessively high with a palmar angle of around 17 degrees. After two months there is less sole depth beneath the tip of the pedal bone, and a gas pocket suggesting total separation is now evident. Luckily this horse was kept confined and his feet well supported and made a good recovery, but leaving the heels high could have caused further sinking and rotation.
Following rotation, if the heels are left high and the palmar angle remains large, the live cells of the sole can be compressed underneath the pedal bone, leading to bone loss (osteolysis) and cell death. This in turn can lead to abscessing, penetration of the pedal bone through the sole, or incurable sepsis.
See The circumflex artery and solar corium necrosis.
Left: long-term uncorrected rotation with heels being left too high led to considerable bone loss for this pony.
A. By carrying out a correct realigning trim at the earliest opportunity and supporting the feet.
A. Yes. But it takes dedication.
Read Paige Poss' inspiring story about Druid.
Druid had rotation (around 18 degrees dorsal rotation in one x-ray) which led to penetration of the pedal (coffin) bones in all four feet. He could hardly stand at first, had bed sores, gastric ulcers and weeks of abscessing. However, within 5 months he was able to wander around outside, x-rays at 6 months showed realignment of the feet, and within 10 months he was comfortable on gravel, trotting, and starting to be ridden again.
Blossom, a Clydesdale, recovered from rotation and penetration following laminitis seemingly caused by a liver infection, with a barefoot trim, daily soaks and boots and pads, thanks to Andrew Bowe at www.barehoofcare.com. Andrew also helped Whisky recover from penetration in all four feet. And Jenny Wren.
A. Most cases of laminitis are endocrine, that is they are caused by EMS/PPID. Recent research has shown that with insulin-induced laminitis, the secondary epidermal laminae become longer and narrower - they stretch. Katie Asplin found that there was minimal basement separation in ponies, and Melody de Laat also found less damage to the basement membrane in horses with insulin-induced laminitis than those with SIRS laminitis. So it would appear that there is stretching and weakening of the laminae, but not necessarily complete separation.
The hoof wall growth immediately beneath the coronet is usually connected to and parallel to the pedal bone. A change of angle where the hoof wall flares out is likely to indicate stretching of the laminae and formation of a laminar wedge.
This pony (right) had laminitis in October due to (at that time) undiagnosed PPID. He made a full recovery and was soon back in work. He never had x-rays taken, and had regular "normal" barefoot trims.
Once a correct realigning trim has been carried out and a new hoof grown down from the coronet, even a horse with significant gas pockets should be able to return to work, as was the case with Homer, above.
In Clinical Outcome of 14 Obese, Laminitic Horses Managed with the Same Rehabilitation Protocol, horses were considered to have chronic laminitis (presumably suggesting long-standing damage) if they had hoof rings that were wider at the heel than at the toe, and/or if their pedal bones showed remodelling, e.g. a ski tip, when x-rayed. Horses that had neither of these were considered to have acute laminitis (presumably suggesting recent damage)
On p 341 of Care and Rehabilitation of the Equine Foot, Pete Ramey suggests that it usually takes months to form a laminar wedge that is 2 cm thick at ground level, so when a thick laminar wedge is seen, the rotation is not new, and the original laminitic episode could have happened years ago.
A. This seems quite likely. Melody de Laat recorded that all 4 feet of the heavier horses had laminar damage, but only 3/4 feet in the lightest horse in her 2011 RIRDC report Insulin-Induced Laminitis.
A. Here are a few:
Sophie - All Natural Horse Care
Missy - All Natural Horse Care
Pip - All Natural Horse Care
Oscar - www.barehoofcare.com
Charlie - www.barehoofcare.com
Glynn - www.naturalhorseworld.com
And already mentioned above:
Blossom - www.barehoofcare.com
Whisky - www.barehoofcare.com
Asplin KE, Patterson-Kane JC, Sillence MN, Pollitt CC, Mc Gowan CM
Histopathology of insulin-induced laminitis in ponies
Equine Vet J. 2010 Nov;42(8):700-6 (PubMed)
de Laat M, Sillence M, McGowan C, Pollitt C
Insulin-Induced Laminitis - An investigation of the disease mechanism in horses
RIRDC Dec 2011
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
JEVS published online 05 Feb 2014
Pete Ramey - Care and Rehabilitation of the Equine Foot
Hoof Rehabilitation Protocol - Debra Taylor, Ivy Ramey, Pete Ramey
Taylor D, Sperandeo A, Bell R, Passler T, Ramey I, Ramey P
Hoof Rehabilitation and Restoration of Soundness in Obese Laminitic Horses