February 2019 - Drug Testing in the Horse
Are you looking forward to your first horse show later this year? Or do you have questions regarding what medications can and cannot be used prior to competition? Join us this month as our expert, Dr. Thomas Tobin, answers your concerns regarding equine drug testing.
Click here to read this month's questions and answers.
I have a gelding that had arthroscopy surgery on his right stifle. The lesion was injected with corticosteroids (medial condyle of the right femur) in August of 2015. I took him back to the veterinarian for a reexamination and radiography and nothing had changed. The cysts are still there, the same size and no bone growth. My question is: Would it be possible that this horse could benefit and become sound from intramuscular joint injections in the stifle joints? Or would I be wasting time and money?(View Answer)
There are many treatment options for subchondral bone cysts in the stifle, and to be honest one option has not emerged as the best treatment for every case. The classic treatment for subchondral bone cysts is to debride the cyst arthroscopically, where the entire cyst lining is taken out, as well as any debris that may be in the joint. This treatment option is often recommended for horses with very large cysts and/or suspected damage to the cartilage in the joint. In Thoroughbreds younger than three years old, the surgical debridement of the cyst has a fairly good prognosis for return to training and racing. However, in horses over three years old, often more of the articular cartilage has been damaged and thus the prognosis for return to work is not as good. If there are additional injuries to the stifle, such as a meniscal tear, the chances of the horse becoming sound again are poor.
Another option for treating subchondral bone cysts is the option your horse had performed, injecting the cyst directly with steroids. Usually we use either triamcinolone (Vetalog) or methylprednisolone (Depomedrol) as the steroids of choice. We use either ultrasound, or better yet arthroscopy, which allows direct visualization of the joint and the cyst, to put the steroids directly into the cyst. There have been very good results reported with these injections, and more and more veterinarians are recommending this treatment method for stifle cysts.
We are sorry to hear that even after the intralesional injection and approximately 5 months of rest, your horse did not have any improvement on his recheck radiographs. We would be very curious to know if he had any clinical improvement, i.e. how lame he was before the arthroscopy and how that compares to his current grade of lameness. However, until your horse is sound at a trot, he should not be put back into work, and it sounds like he is not there yet. Depending on how large his cyst was, he may need 3-4 more months in order to restore his soundness and give the defect in the condyle more time to lay down bone. If his cyst was greater than 1.5 cm, it may be difficult to ever make your gelding sound.
In response to your question about joint injections, many veterinarians do inject the stifle joints of these horses with stifle cysts in order to try to medically manage the inflammation, either in lieu of surgery or after surgery. Usually we will use either steroids and hyaluronic acid, or steroids and Adequan. You inquire about “intramuscular” joint injections in the stifle, by this we are assuming you mean putting Adequan directly in the joint? There is an intra-articular preparation of Adequan that can be safely used in joints, and provides building blocks for laying down of fibrocartilage in the joint, as well as lubricating the joint and blocking enzymes that damage the joint. We think this would be a completely reasonable idea to try for your horse if his lameness is mild, perhaps a series of Adequan and steroid injections under the guidance of your veterinarian. If your horse’s lameness is severe, or he has concurrent soft tissue injuries such as a torn meniscus, or he has a significant amount of cartilage damage in the joint, it is possible that the joint injections may not be able to make him sound.
One other point we wanted to make is that if your horse is still lame, it may be helpful to have your veterinarian block your horse’s stifle joint to ensure that all of his pain is coming from his stifle. Sometimes lesions can look bad on radiographs, but not be causing the horse’s clinical lameness. Since it has now been 5-6 months since his surgery, before attempting further treatment it may be worthwhile to make sure all his pain is still coming from that stifle. This may also give you an indication of if the joint can be managed with joint injections—i.e. if the block cannot make your horse sound, then it is unlikely a joint injection would be able to either.
We know you have been working hard along with your veterinarian to try to get your horse sound, and we encourage you to continue working with him or her to develop a plan for further treatment for your gelding. He/she will have the best knowledge of your horse. We wish you the best of luck! Jen Reda, DVM, Aiken, SC and Stephanie Regan, DVM, Lexington, KY
My OTTB has two lacerations on either side of his knee in different locations. The lacerations occurred about a week ago and the cause is unknown. He is currently on IV antibiotics, IV bute and still standing though he seems to be bending the knee less and less. Should he be bending his knee at all or is it better to let him keep it straight? The wound on the right side of the knee is still open and draining, but the inner wound has closed up.(View Answer)
Thank you so much for your question—this is a great question as almost all horse owners will have to deal with lacerations at some point in their lives. To treat a laceration, we usually begin by sedating the horse and then assessing the wound. Generally, radiographs are taken in order to assess whether there is foreign body presence, fractures, possible communication with a synovial space such as a joint or tendon sheath, or presence of gas in the soft tissues extending further than you can see grossly. Sterile lubricant is placed in the wound so that the surrounding area can be clipped, and the hair will not embed in the tissue. The wound is aseptically prepared with chlorhexidine or betadine, and the wound is profusely lavaged with saline. As we assess and probe the wound, we are trying to determine the depth of the wound, any important structures that may be damaged such as tendons, ligaments, or bones, and most importantly whether or not the laceration communicates with a joint.
One way to assess possible communication with a joint is to sterilely insert a needle into the joint space and introduce enough sterile saline to visibly distend the joint. If the saline begins to egress from the laceration site, then communication is confirmed, and the joint is considered contaminated. This will trigger a series of treatment strategies such as intravenous antibiotics, joint lavage, intravenous regional limb perfusions of antibiotics, and intraarticular injections of antibiotics. Synovial fluid originally taken from the joint before beginning distention may be submitted for culture and fluid analysis, which will indicate the number of white blood cells (WBC) and total protein (TP) levels of the fluid. While the cultures usually have low yield, the WBC count will especially guide the treatment protocol. Some combination of the aforementioned therapies will be continued most likely for several days until the veterinarian is sure there is no further risk of infection.
Depending on the location and depth of the wound and if there is any significant pocketing in the tissue, we may need to place a drain, which is a piece of sterile tubing that will be sutured into the wound with a small portion protruding and visible in order to facilitate drainage. Wounds often have dead space underneath the skin in the subcutaneous tissue, and the presence of the drain allows serum and fluid to drain out of the wound without trapping that fluid underneath the skin. Drains usually are removed anywhere from 3-7 days after placement, depending on many factors, including the veterinarian’s preference and the severity of the drainage.
We will often suture the laceration closed so that the wound may heal by first intention. Based on the location, depth, and cleanliness of the wound, such primary closure may not be possible, in which case the lesion will most likely be bandaged and kept clean until the underlying tissue bed can heal with granulation tissue. For superficial wounds, sutures may not be needed. Most veterinarians will use non-absorbable sutures that remain in for 10-14 days (if we are lucky and the horse cooperates)! We will almost always put the horse on antibiotics and pain control such as phenylbutazone (bute), just as you have described with your OTTB.
In response to your question about whether or not your horse should be bending his knee, It would be difficult for anyone to give you a definitive answer without seeing your horse or knowing the exact details of the case. If the wounds were sutured closed it may be preferable for him to keep the leg immobilized (such as with a full limb bandage), so as to not put tension on the sutures. Even if the wounds were not sutured, the less motion and tension that is placed on the wound the better, as this will allow the margins of the wound to heal more quickly. Many veterinarians will recommend stall rest for this purpose while the horse heals. However, if your horse is physically unable to bend his knee because of the pain, or if he has swelling or heat in the knee, or is extremely lame on that leg, this may indicate more serious complications. In any case, your best reference is your local veterinarian, and they can guide you as to the expectations for mobility and return to function. Good luck! Jen Reda, DVM, Aiken, SC and Stephanie Regan, DVM, Lexington, KY
My quarter horse gelding is 15-years-old. About a year and a half ago he bowed his ligament on his front left. He had been ultrasounded 6 months later after stall rest with extensive wrapping treatment and was confirmed that his ligament tissue was at 100%. He was a little stiff after that and this past October I had noticed his "stiffness" was not improving and seemed worse during the winter months. I took him to the veterinarian who took x-rays, which confirmed he had a coffin bone and joint fracture. Not knowing how old this was since he only looked a "little" lame. We saw some calcification on his coffin bone from the x-ray and its my sneaking suspicion that the fracture was a year and a half old. Per my vets recommendation, I put my horse in a bar shoe with 4 clips and a pour in pad (equipack cs). We put him on stall rest for 6 weeks and re x-rayed him and saw healing progress. We continued with the same treatment for 6 more weeks with hand walking every other day for 30 minutes to stimmulate circulation to speed healing. We also started him on Adequan since the x-rays revealed moderate arthritis on his coffin bone. The x-rays revealed healing thus we are doing one more 6 week period of rest and hand walking with the bar shoe. At my next appoitment he said we should consider a joint injection of the coffin joint to slow the arthritis progression. Anything to be concerned with joint injections? I have never had one done and have heard some horrifying stories.(View Answer)
Thank you for your question! Coffin bone fractures are an interesting subject! It is hard to know when the coffin bone fracture would have occurred in that timeline, as it can be due to acute, high impact injury such as kicking a wall, and it can also occur in work, for instance, from training on hard ground. Horses with coffin bone fractures generally present with an acute (sudden), intense lameness, often immediately following exercise or high-impact incident. These fractures are characterized by their location on the bone, whether they involve the joint, and how many fragments are present. They each carry their own prognoses for return to function. Treatment options for the coffin bone fracture itself are the conservative management you mentioned in your question, consisting of a bar shoe with multiple clips and a packing substance to reduce motion as well as long periods of stall rest. Surgical treatment is also a possible option, depending on the characterization of the fracture, and this includes fragment removal or repair with a lag screw. Some coffin joint fractures have a higher propensity than others to develop secondary post-traumatic osteoarthritis (OA), and it sound like your horse has suffered some degree of this.
We reviewed OA in the previous question, but the information is also applicable here. OA is a disease of moveable joints whose hallmark feature is loss of articular cartilage, along with bone remodeling. Although it can also be from repetitive stress injury over time, in the case of your horse, it developed because of an acute injury, the coffin bone fracture. Medical management of OA has multiple modalities than can be used in numerous combinations, including NSAID administration, such as phenylbutazone, intraarticular injections of steroids, exogenous lubricants, and biologic therapies, such as corticosteroids, hyaluronic acid, and IRAP, respectively. Intramuscular injections of adequan and oral administration of nutraceuticals such as glucosamine and chondroitin sulfate may also be part of a treatment plan. Most of these therapies have published efficacies, some with better results than others, and many of them with significant side effects if not used judiciously. The basic premise is to reduce inflammation, restore lubrication, and mitigate the pro-inflammatory cytokines in the joint. Regardless of origin or management style, OA is a progressive, incurable disease that requires lifelong management.
Since you mention that you have not previously had joints injected on your horse, we thought describing the process of joint injections may help you make the most informed decision on the procedure. Joint injections are very common in the equine world, especially for performance horses. Your veterinarian will often begin by sedating the horse with an IV injection of a fast-acting sedative. Some veterinarians may choose to inject a joint in the front leg without sedating the horse, and this is acceptable as well. The veterinarian or his/her assistant will then perform a thorough scrub of the area to be injected with antiseptic agents such as chlorhexidine or betadine. The site will be wiped clean and then wiped or sprayed with alcohol in order to create the cleanest possible surface. Your veterinarian will most likely inject the joint with a combination of steroids and hyaluronic acid (HA). Some common steroids in use for joint injections are methylprednisolone (Depomedrol), triamcinolone (Vetalog) and betamethasone (Betavet). Every veterinarian creates their joint injection recipe slightly differently, but it is likely he or she will use one of these three steroids. Added to the steroid will be the hyaluronic acid (HA). Ideally, the steroid plus the HA will work together to lubricate the joint and reduce inflammation. The veterinarian will draw these medications up sterilely and then put a single needle into your horse’s coffin joint. Often you will see joint fluid dripping out of the needle, and the consistency of this fluid can give your vet some clues about the health of the horse’s joint. The vet will then inject their steroid/HA combination into the joint in a matter of seconds and then withdraw the needle. The foot is usually then bandaged, and the horse is often given some form of pain relief such as Bute or Equioxx. Your horse’s exercise will then be restricted for the next 3 days, and he will likely be on a pain reliever for those 3 days as well (these protocols will vary slightly from vet to vet).
While joint injections are performed daily in many many veterinary practices (including ours) and are often considered “routine maintenance” for many show horses, they are not without risk. The major risk of joint injections would be a joint infection. Joint infections are rare but they can occur. Veterinarians take many steps to prevent these infections by scrubbing the skin very well, wearing sterile gloves, and drawing up the medications with sterile technique. Many veterinarians will often put a small amount of an antibiotic such as amikacin in with the joint injection as an extra measure to try to prevent any potential infection. As long as you are aware of the rare but potential complication of joint infection, joint injections can be an incredibly useful tool to prolong your horse’s athletic career.
Now that we have discussed different types of coffin bone fractures and the osteoarthritis that may go with them, as well as joint injections, we would encourage you to work with your veterinarian to determine the best course of action for your horse as he progresses through his healing. A coffin joint injection may be very reasonable for your horse before he goes back to work, and your veterinarian will best be able to determine this by the clinical presentation of your horse, his radiographs, and the job you desire him to do. Jen Reda, DVM, Aiken, SC and Stephanie Regan, DVM, Lexington, KY
My 19-year-old Thoroughbred gelding was recently diagnosed with moderate osteoarthritis in his right hind and upon ultrasound, with mild DSLD in both hinds. The number one treatment recommendation is for articular injections. Will these injections resolve the DSLD in any way? Sadly enough, he was also diagnosed with atrial fibrillation (afib) six years ago. I can't help but wonder, are the two diagnosis related?(View Answer)
We are sorry to hear that your Thoroughbred has been diagnosed with these three chronic conditions. A couple points we were unclear on were which joint in the right hind was diagnosed with osteoarthritis (OA) and which two diagnoses you thought might be related. However, we will talk about OA in general, and we assume the link you are questioning is between Degenerative Suspensory Ligament Desmitis (DSLD) and OA.
OA is a disease of moveable joints whose hallmark feature is loss of articular cartilage, along with bone remodeling. This can occur for many reasons, including abnormalities in the subchondral bone underlying this cartilage due to repetitive stress or abnormal forces imposed on the joint due to soft tissue injury. OA can be the result of acute injury such as a fracture or repetitive stress from high impact work. Medical management of OA has multiple modalities that can be used in numerous combinations, including NSAID administration, such as phenylbutazone, intraarticular injections of steroids, exogenous lubricants and biologic therapies, such as corticosteroids, hyaluronic acid, and IRAP, respectively. Intramuscular injections of adequan and oral administration of neutraceuticals such as glucosamine and chondroitin sulfate may also be part of a treatment plan. Most of these therapies have published efficacies, some with better results than others, and many of them with significant side effects if not used judiciously. The basic premise is to reduce inflammation, restore lubrication, and mitigate the pro-inflammatory cytokines in the joint. Regardless of origin or management style, OA is a progressive, incurable disease that requires lifelong management.
Degenerative suspensory ligament desmitis (DSLD) is a difficult disease and one that definitely needs more research. The current best understanding of this disease is that it is likely hereditary, more commonly found in breeds like Paso Finos and Arabians, and less commonly found in Thoroughbreds. It is actually a systemic disease that involves many different connective tissues throughout the body, but often clear manifestations of it are seen in the suspensory ligaments. The current theory on DSLD is that there is an abnormal accumulation of molecules called proteoglycans in between the fibers of the connective tissue. This leads to a decrease in strength of the affected tissues and an irregular fiber pattern, which can be seen on ultrasound. Ultimately, the degeneration can lead to tendon or ligament failure. What can help to differentiate DSLD from a suspensory injury is that it occurs in more than one suspensory ligament at the same time, often in both hind or even in all four ligaments. It is also often diffusely spread throughout the whole ligament, not one focal spot of injury.
Sadly, there is no cure for DSLD either at this time. Intra-articular injections will not treat DSLD, as the problem is not within a joint. Although, potentially the OA is exacerbated by the abnormal biomechanics of the joints due to fetlock drop; it’s hard to say not knowing which joint was diagnosed. Pain management must be considered especially for horses that are currently lame, for this we would look to our nonsteroidal anti-inflammatory drugs such as phenylbutazone (Bute) or firocoxib (Previcox). Previcox can be used for longer periods of time without as great a risk of gastrointestinal side effects, so may be an option if your horse is lame. Your veterinarian may consider supplementing with MSM (methyl sulfonyl methane), which has anecdotally been reported to help restore flexibility to tissues, although to our knowledge this has not been evaluated with a formal research study. One major help to your horse may be shoeing changes; this decision will likely be a result of collaboration between your veterinarian and farrier, and may include either an eggbar or a fish tail bar shoe. Opinions vary on best course of action and will depend on severity of the DSLD and if your horse stays in work. This will provide support to the limb and relieve some of the tension on the suspensory ligament by helping to prevent the fetlock from dropping. You might also consider supportive leg wraps such as sports medicine boots to help support the tendons and ligaments in the lower limb. Most horses with DSLD will eventually not be able to continue an athletic career due to the continued degeneration of the suspensory ligaments, however pasture soundness and comfort could be a realistic goal, especially if his DSLD is mild at this stage.
For all of these separate diagnoses—the osteoarthritis, the DSLD, and the atrial fibrillation, the best advice and recommendations will come from your veterinarian. He or she has seen your horse and diagnosed these conditions. It is likely that he or she will desire follow-up appointments to monitor the progression of the osteoarthritis as well as the DSLD, and may need to perform further radiographs or ultrasounds along the way. We recommend you continue to work with him or her for the best treatment plan for your horse. Best of luck to you, and thank you for your question! Jen Reda, DVM, Aiken, SC and Stephanie Regan, DVM, Lexington, KY
I have a 7-year-old OTTB stallion that came to me with bone chips in his left front fetlock. Prior to his arrival, the horse was still racing and was purchased off the track by a dressage trainer as sound. Apparently, the race owners had been injecting the joint. The dressage trainer did not inject the joint as he did not know about the injury and the horse came up lame within a month of purchase after light riding. The current vet said surgery was the best option at that time. The horse has been on pasture rest for 8 months. On the 9 month mark I started him on light exercise in the round pen and short light hacks in the field. No sign of lameness, pain or swelling afterwards. We will be going back for further radiographs, but what are the chances the bone chips encapsulated during rest? Would putting smb boots on him help or potentially cause more irritation? I want to keep him as comfortable as possible until I can afford the surgery, if needed. Any advice would be appreciated.(View Answer)
Ankle chips, or osteochondral fragments in the fetlock joint, can have different origins. OCD (Osteochondritis dissecans) lesions, such as those commonly removed from thoroughbred yearlings before sale, occur as a result of abnormal development of the bone just underlying the articular cartilage of the joint. Chip fractures, commonly occurring in thoroughbred race horses racing or in training, are a result of the repetitive impact of the opposing bones in a joint, especially at high speed. Regardless of which etiology is correct for your horse, the ultimate consequence of these lesions is that they can continuously shed debris from the exposed bone into the joint. This is a problem; not only does this cause acute inflammation in the joint, which is indicated by heat, swelling – or joint effusion, and lameness, but in the long run, it will lead to irreversible damage of the articular cartilage.
In most cases, horses with osteochondral fragments, when treated promptly with surgery, have excellent prognoses for return to high-level activity. The minimally invasive surgery performed to remove these fragments is called arthroscopy, where the surgeon will make small incisions, or portals, to access the joint. Racing is such a strenuous activity that participating horses with these lesions are obvious. In sport horse disciplines, it is much more possible to mitigate the clinical signs with “joint maintenance,” such as intra-articular injections. However, while medications such as corticosteroids treat the effects of inflammation, they are not preventing debris shedding and ultimately damage to the articular cartilage in the future. At some point, the disease progresses to osteoarthritis, which is no longer reversible with surgery, as the horse cannot regenerate or repair its articular cartilage.
In the case of your OTTB, it is probable that the inflammation in your horse’s joint was being controlled with the joint injections you describe while he was on the track so that he could continue to train and race. The rest period you gave him was a very generous amount of time, and it is encouraging that he is now hacking without showing signs of lameness or any effusion in the joint. You are right in that with periods of rest, the joint will try to isolate the bone chip and surround it with scar tissue to make it smooth and non-irritating. However, it is possible that with increased demands, the joint may begin again to shed debris and become inflamed once again.
So where do we go from here? We definitely recommend those follow-up radiographs with your veterinarian that you mentioned. Those can elucidate not only the location of the bone chips within the joint, but also what degree of arthritis is already present. Option A (under the guidance of your veterinarian) would be the conservative route--start your horse into work and see if he remains sound. If the bone chips are not on the articular surface of the joint, or have encapsulated, and the joint is not inflamed, he may be sound for the job you would like him to do. The lower the impact of his job (examples of high impact jobs would be racing or jumping), the longer he may continue to be sound, but remember that this may be a tradeoff with the longevity of the health of the joint. Lower levels of debris shedding or inflammation, over time, can lead to the same outcome of an osteoarthritic joint as would acutely happen in a racehorse. As you continue legging your horse back up, if at any point he becomes lame again in that fetlock, or begins to get swelling in that joint, it would be time to revisit the issue of the bone chips.
Option B would be to have the chips removed. We know in racehorses that prompt chip removal is a highly successful surgery where >80% of racehorses return to racing. This is a routine elective surgery with a short period of rest post-operatively to ensure best recovery. If the joint has significant arthritic changes or cartilage damage, neither of these is reversible with surgery, however, prevention of further pathology is important.
In terms of your sports medicine boots, we certainly would see no harm in training your horse with them. They will not prevent changes that may be going on within the joint, but they are definitely a good source of outer protection.
We hope that we have provided you with some helpful information about bone chips. As always, work together with your veterinarian to determine the best option that will give you and your horse many good years together! They will have the best knowledge of your horse’s clinical presentation. Best of luck to you! Jen Reda, DVM, Aiken, SC and Stephanie Regan, DVM, Lexington, KY