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2005 USDF Convention by Jack Snyder, DVM Many horses have lamenesses that block to the foot/navicular region and were previously called “navicular”, but now we know that there is quite a list of potential causes:
In the past, many of these horses had to be nerved for lack of an ability to accurately diagnose and treat these horses, but we have new possibilities available now. Ultrasound of the foot is of limited scope, and can miss many cases, but is not so expensive and is better than what was previously available. MRI is one of the newest tools. The standing version has less resolution, but the advantage that general anesthesia is NOT required. The image quality is generally moe than adequate for diagnosis. The latest technique is CT (CAT) Scan, which has the advantage that it can allow needle localization of lesions at the time of diagnosis for the placement of stem cell treatment (diagnosis and treatment as a single procedure). (MRI cannot, since the magnets do not allow the use of needles). Helical scants allow visualization of the soft tissues. A downside is that general anesthesia is required. In the past, these types of lesions had at best a 40% response with rest on acute cases, and chronic cases rarely recovered. With CT localization and treatment, response rates are 80 – 90% even with longstanding cases. (A horse with a 3 YEAR HISTORY of recurrent lameness and 2 separate lesions within the deep digital flexor tendon in the hoof was shown, treated with stem cell after localization, plus shock wave—the horse had a return to complete and lasting soundness). The mechanism of shockwave therapy has been determined. It apparently increases the level of growth factors in tissues and brings in stem cells from the bone marrow. In a series of 104 horses, mostly with deep flexor tendon and collateral ligament injuries, more than 80% responded in the research study that Dr. Snyder had done. The time course for the healing was 4 to 8 months, with the rehab phase similar to that for suspensory lesions. Only a single Acell treatment was required, with the addition of 3 shockwave treatments given 2 weeks apart. No follow-up CT required—horses are followed clinically. Failures appear to be associated with the presence of concurrent navicular bone disease, and they are currently studying whether the addition of bisphosphonates (which are in the same category as human anti-osteoporosis drugs) can change this. Dr. Snyder thinks this will. Shockwave therapy works best where ligament attaches to bone. For the bone disease itself calcium supplementation plus bisphosphonates is useful. (Either Tildrin or Fosfomax). The collateral ligament is the second most common soft tissue injury in the foot (after the digital flexor tendon). It is hard to get at in the foot, but with the use of CT, can be treated the same as the DFT injuries. Predisposing Factors for Heel Disease:
Note that shoes also change the horse’s ability to adapt to the environment. Delaying shoeing in youngsters is ideal when appropriate, since the development of the digital cushion and cartilage is superior. First shoes after 3, if at all possible, recommended. A new tool for assessing lameness is the DYNAMIC FORCE PLATE which can detect subtleties that the rider may have felt but were not visible to flexions or on the lunge. It can also be useful for blocks. These can be attached to the legs, and measure the force of each leg on landing vs. time and can detect slight delays on “ouch-y” legs that may be hard to spot visually. The “Teckscan System” can also look at breakover points and be used to fine tune shoeing. What options are available for Maintenance and Prevention?
Hyaluronic Acid = Legend
Adequan
Oral
Recommended Dosing Schedules (by Dr. Snyder)
Recommends beginning prevention plan at age 6 – 7 at the manufacturer’s recommended level, and based on the horse’s level of work, progressing to Level III at CDI/FEI level. The last category of drugs are the bisphosphonates, which work by inhibiting bone resorption and altering osteoclastic activity. The most well known drugs are Alendronate Sodium (the human drug Fosfomax), dosed 70 mg sid/month (oral) or Tildren given 0.1 mg/kg IV for 10 days. |
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