Article

Lameness due to suspensory problems are not uncommon, particularly in show horses. The suspensory ligament is actually a modified muscle that runs from the top of the back of the cannon bone to the front of the pedal (coffin) bone, crossing the leg at the level of the sesamoids in the fetlock directly behind the superficial and deep digital flexor tendon (looking from the back). Its function is to “suspend” the fetlock like an elastic hammock so it can spring back after loading and this way help to propel the horse forward. This important function is compromised when the ligament is damaged resulting in lameness. Although the suspensory ligament can be damaged in the front and hind legs, the athletic outcome is vey different depending if it affects a front leg (better) or a hind end (worse). The ligament can suffer damage in three different regions, either at its origin where it attaches to the back of the cannon bone, its body, half way down the cannon bone or its branches as it splits and crosses over the sesamoids. As a general rule, the lower the lesion the better its outcome. For the purpose of this discussion I will discuss the worse case-scenario, which occurs when damage happens at its origin. I believe that, with the noted exception of some breeds such as the Paso Fino, most horses sustain a suspensory injury due to their athletic pursuits. However there is a possibility that in older horses a degenerative process is at play. Rarely it will be a direct impact or trauma responsible for the damage. As such, horses that load the fetlock excessively (i.e. dressage, thoroughbred racing, jumpers), are predisposed to suffer this injury, particularly if they are older. The injury can go from an extremely severe pull with damage of the ligament and bone to a milder lesion where just a bit of inflammation exists in the ligament with no boney abnormalities.

The diagnosis of this problem can also be challenging and frustrating, particularly in the hind end, requiring diagnostic analgesia (nerve blocks), radiographs, ultrasound and in many occasions a bone scan (scintigraphy). Ideally. the diagnostic process should also include the means to quantify the problem and since all of these techniques are mutually complementary, there is not really a good way to avoid any of them if the objective is to gauge the problem correctly. Although the diagnostic process can be time consuming and expensive, the best way to get a good treatment result is to know what you are treating. Without this important piece of information you may be gambling on possible diagnosis, likely wasting your money and delaying a prompt treatment, which in the end could cost more money and more aggravation. Once the correct diagnosis has been made, there are several options that you may consider depending on finances and future athletic pursuits. With frequency, the treatment of this challenging condition will include one or several of the following:

1. Benign neglect (a.ka. Do nothing): This is hardly a good way to treat these injuries in the hind end. Although some very mild cases may respond to simply turn-out, ideally this is not an optimal option to deal with these problems with the possible exception of front end injuries.
2. Rest and Rehabilitation (aka R&R): This is an integral part of any soft tissue lesion. Appropriate R&R modulates the healing process adapting the loads placed in the area to the healing stage of the tissues. For very mild lesions of the front suspensory, an adequate R & R program is all that is required. In order to follow-up the healing process, several ultrasound evaluations at different time points, usually every 60 days, should be pursued. R&R should be part of any treatment combination. Usually an injury of moderate severity may take 6-8 months to heal.
3. Antiinflammatory therapy (i.e. bute, cold, etc…) In the acute stages, it is paramount to curtail an excessive inflammatory reaction as this in fact may deteriorate the lesion and delay the healing process. The use of cold, particularly in combination with massage (aka. Game ready ) has in my opinion brought a great advancement in the treatment of any acute inflammation. The addition of systemic medications such as phenylbutazone is also another component needed to provide comfort and reduce inflammation.
4. hock wave therapy: Much has been said about shock wave and yet, there is not a study with irrefutable findings about the value of this modality. For the hind end suspensory problems a study showed that return to exercise was increased to about 40 % from the 20 % expected outcome if nothing is done. There still remains unknown what dose and interval are the optimal to treat these lesions. In addition some studies have shown that shock wave therapy tends to numb the area surrounding where it is applied and therefore improvements on lameness may be due to a numbing effect rather than actually improving the lesion. Since this is a controversial area it is best discussed with your veterinarian at the time of treatment.
5. Cell based therapies: These are the “flavor-du-jour” treatment for soft tissue injuries and one wonders if they will stay around for a long time, given that at the moment remain to a certain extent unproven. However their application makes total sense. In order for cells to regenerate new tissue, three components are needed: Cells that are capable of multiplying and becoming the same as the receptor tissue being tendon or ligament(stem cells), growth factors that can recruit more cells and speed up the process (PRP) and a scaffold of tissue where the new cells can grow (A-cell). Although these therapies are offered independently, the future is in making them work together towards a common goal. But we are still a bit far from that point. In the time being, we have seen some very promising results with the use of any of them, but it seems that PRP are becoming more cost-effective at this point in time.
6. Surgical fasciotomy: This is perhaps the best option currently for chronic or recurrent hind end origin of suspensory problems. Reported outcomes are close to 80 % return to exercise when compared to 20 % if you do nothing or 40 % with shock wave therapy. In addition, fasciotomy in the subacute stages has also yielded good results. This technique is based in the findings that the fascia (fibrous tissue) surrounding the suspensory ligament prevents a swollen ligament to expand, thus producing a local compression effect that impairs its repair. The surgery “releases” the fascia and therefore allows the repair process to proceed. This surgery is done in combination with a neurectomy of the deep branch of the lateral plantar nerve. A recent study indicates that the nerve also suffers from a compression syndrome and therefore transecting it would be indicated. In direct controversy, there is a second more recent study that identified neurogenic atrophy of the ligament as a long-term sequelae of cutting the nerve. However no clinical effects were seen associated with this atrophy.

As you can see the jury is still out and case selection is of extreme importance when deciding one treatment. Each horse and each situation is different and the final word should be said by you after appropriate counseling by your veterinarian and/or specialist. Of course an appropriate and accurate diagnosis is the first step to a good treatment selection. We offer every kind of potential treatments at our hospital. For more information, please do not hesitate to contact us at 604 856 3351.