Understanding the disease progression of abnormal hoof anatomy, Part 3
Solving the mathematical needs of a Grade IV laminitic foot
Mar 01, 2012
Treatment should be directed at the type of Grade IV laminitis—is it cranial rotation (abnormal increase of the palmar angle), or is it FSS?
In my experience, it is almost always impossible to recover the Grade IV increased palmar angle foot without a deep digital flexor tendon (DDFT) tenotomy. Why? The entire and only reason for performing a DDFT tenotomy is to increase the dorsal palmar mobility, thus allowing you maximum extension of the hoof capsule in order to gain a "0" palmar angle after the surgery. Do not attempt to treat a Grade IV (or any grade of laminitis) by simply cutting the deep flexor tendon and walking away. The DDFT tenotomy is 1 percent of the procedure, and the digital realignment is 99 percent of the procedure. I can't stress this enough.
Please obtain radiographs of the foot before tenotomy, after tenotomy but before digital realignment and after the realignment. You will notice that your interim radiograph shows some relaxation of the P3 within the soft tissue of the hoof capsule following surgery. We consider the post-tenotomy radiograph a necessary feature for proper alignment of the digital structures.
I will not go in-depth here into the entire deep flexor tenotomy procedure since it has been well-described by many authors. But here are a few useful hints:
Figure 6: A subluxation of the DIP joint after a DDFT tenotomy. One more good reason to radiograph the foot after the tenotomy procedure. The use of the tenotomy trailer rail will correct this problem and allow it to heal.
- I perform all tenotomies with the horse standing or in a sling under light sedation.
- I ring block below the carpus.
- I maintain a good sterile environment at all times.
- I use special tenotomy blades.3
- I make my incision mid-cannon.
- I get in and get out (the more you muck around in there, the more scar tissue you will have).
After surgery, we take an interim radiograph and then decide whether we can gain a "0" palmar angle by a simple trim of the hoof wall from the quarters back to the heels or if we need to apply a reverse wedge and tenotomy trailer rail. High level rotation cases will usually subluxate the DIP joint (Figure 6) as all of the supportive structures have been stretched (all DIP lateral collaterals and extensors and possibly other supportive structures of which I am not aware) and will require a tenotomy rail.
Figure 7: A radiograph of the use of a tenotomy trailer rail.
Figures 7 and 8 show two different horses—one shod with a reverse wedge and tenotomy trailer rail and one that was able to be realigned through remodeling of the hoof capsule. Notice that both feet were realigned beyond the normal range of dorsal palmar motion thanks to the tenotomy procedure. Also notice that when a "0" palmar angle is achieved, the originally loaded toe is now floating above the ground surface.
Figure 8: A foot with sufficient hoof mass and sole that allowed the foot to be realigned to a "0" palmar angle without the use of a tenotomy trailer rail. Note that the original loading surface of the toe is now no longer contacting the ground.