Hoof casts incorporating heel elevation can help horses with acute laminitis, research findings suggest.
The goal of supportive orthopaedic therapy for horses with acute laminitis is to shift the load from the diseased and most painful areas of the hoof to the undamaged areas.
Recently, a study showed that the maximal loading of the toe region in horses with laminitis occurred during the breakover phase of the stride, and that the main shift of the load within the hooves of laminitic horses occurred between the toe and middle hoof regions.
Therefore, easing the breakover phase — the time from heel-off to toe-off — should be considered when treating horses with laminitis to minimize the load on the damaged lamellae in the toe region, Mohamad Al Naem and his colleagues wrote in the journal BMC Veterinary Research.
For their research, the study team from Justus Liebig University in Germany set out to examine the effect of heel elevation on the crucial breakover phase.
Eight horses with acute laminitis who were treated medically as well as with the application of a hoof cast with a heel wedge were included in the study.
Straight after the end of clinical signs of acute laminitis, hoof-related measurements were taken using a proprietary system, firstly with the cast and wedge in place, and then immediately after their removal — that is, in barefoot condition.
The hoof print was divided into three regions: toe, middle hoof, and heel.
Kinetic parameters included vertical force, stance duration, and contact area for all hoof regions during the stance phase, the duration of breakover, vertical force in the toe region at the onset of breakover, and the location of the centre of force.
The study team found that the vertical force and contact area were higher in the heel region (63% and 61%, respectively) and decreased significantly after removal of the wedge and cast (43% and 28% after removal, respectively).
The breakover phase in horses with the cast and wedge in place lasted 2% of the stance phase and was significantly shorter than when the horses were barefoot, when it lasted 6% of the stance phase.
The vertical force at the onset of breakover for the toe region in horses with cast and wedge in place was significantly lower than when barefoot.
The centre of the force was located at the heel region in all horses with the wedge and cast in place, and in the middle hoof region when barefoot.
“Heel elevation in horses with laminitis as examined on a concrete surface significantly shortens breakover phase and decreases the vertical force in the toe region during breakover,” they concluded.
The cast and wedge provided adequate support to the palmar hoof structures by increasing the contact area in the heel region and incorporating the palmar part of frog and sole into weight bearing, they said, thus decreasing the stress on the lamellae.
This indicated that a hoof cast with heel elevation could help horses suffering from acute laminitis.
Discussing their findings, the authors noted that the breakover phase is significantly longer in horses with a long toe, as it acts as a long lever arm.
“Our results can be explained by the fact that heel elevation causes the dorsal hoof wall to be more upright, promoting an earlier breakover.”
Furthermore, the load of the toe region was significantly lower in horses with cast and wedge during the breakover phase when compared with barefoot.
“This is attributed to ease of breakover reducing the time at which the forces acting on the damaged lamellae in the toe region as well as to a palmar shift of the centre of force to the heel region.”
Consequently, the cast and heel wedge have the potential to provide relief from pain caused by the damaged lamellae in horses with laminitis.
They described it as an inexpensive, quick, and easy method to elevate the heel. The plaster bandage can be adapted to any hoof shape and moulded into the frog region, increasing the weight-bearing surface area.
However, they warned that crushed heels, cracks, or displaced bulbs may develop after long-term application of a cast and heel wedge.
“Elevation of the heels may cause hoof contraction in the long term.”
In the study horses, the use of the casts and wedges ranged between 7 and 17 days, with no problems reported.
As such, and depending on clinical observations, their use should be limited to a maximum of two or three weeks.
The study team comprised Al Naem, Lutz-Ferdinand Litzke, Klaus Failing, Johanna Hoffmann and Michael Röcken, all with Justus Liebig University, and Florian Geburek, with the University of Veterinary Medicine Hannover, also in Germany.
Al Naem, M., Litzke, L., Geburek, F. et al. Effect of heel elevation on breakover phase in horses with laminitis. BMC Vet Res 16, 370 (2020). https://doi.org/10.1186/s12917-020-02571-5