Orthobiologics… say what?!?!?

If you’ve ever had to deal with lameness issues in your horse, you’ve probably heard us use a buffet of acronyms like IRAP and PRP as we discuss the multitude of intraarticular (ie. in the joint) treatment options available in equine sports medicine today.  Both IRAP (interleukin-1 receptor antagonist protein) and PRP (platelet rich plasma) are considered orthobiologics as these products are harvested from the horse’s own physiologic resources.  Other orthobiologics like stem calls are obtained from bone marrow and adipose tissue (fat).  Regardless of their origin, these products have been well researched in both equine and human athletes and are now being utilized much more regularly in field ambulatory settings.  In this blog, we will review the different types of orthobiologics currently being used in equine medicine and how they compare to the traditional intraarticular steroid therapy. 

IRAP (Interleukin-1 Receptor Antagonist Protein)

IRAP is a protein harvested from the horse’s blood.  It is incubated and processed over an eight-hour period and then reinjected back into the joint at a later date.  It works by permanently binding to the interleukin-1 (IL-1) receptor which in turn, inhibits the inflammatory pathway within the joint environment.  With IRAP permanently bound to the IL-1 receptor, the IL-1 cytokine cannot initiate inflammation in the joint which in turn makes the horse more comfortable and gives the lining of the joint (aka. synovium) the chance to heal.  The more opportunity the synovium has to heal in the absence of inflammation, the lower the risk of subsequent development or perpetuation of arthritis. 

The benefit with IRAP is that it specifically targets the inflammatory pathway within the joint.  It is an extremely specific approach to increasing a horse’s comfort from arthritis, but, it only lasts as long as that deactivated receptor remains intact within the synovium.  Once the body naturally metabolizes and overturns the deactivated IL-1 receptor, a new, active IL-1 receptor becomes present in the joint.  As a result, horses benefiting from IRAP therapy often require more frequent injections to remain comfortable.  Additionally, the initial series of intraarticular IRAP requires two to three injections into the joint, two the three weeks apart.  IRAP is labor intensive compared to other autologous products or steroids, but it is extremely effective in decreasing pain and discomfort associated with arthritis and synovitis in equine joints. 

PRP (Platelet Rich Plasma)

PRP is defined as plasma with a higher concentration of platelets compared to whole blood.  There are a multitude of factors that can impact the quality of the PRP harvested from a patient, the biggest one being the presence of systemic NSIADs.  As a result, we will always ask you to pull your horse off Equioxx/Previcoxx, bute, aspirin or banamine prior to collecting PRP.  Once collected from the patient, the blood that will be used in procuring PRP is spun in a centrifuge and the resulting isolated plasma is collected and injected back into the joint or soft tissue structure at the same appointment as the initial blood draw.  The therapeutic effect of PRP is due to the presence of a wide variety of growth factors and anti-inflammatory cytokines that decrease inflammation and oxidative stress in the synovium.  When used in joints with moderate to severe damage to the cartilage, PRP is thought to help repair the tissue comprising the cartilage to a small extent.  Repeat injections can be performed at 3–4-week intervals but the need for multiple injections is not as necessary as in IRAP.  Whereas IRAP targets a specific inflammatory pathway, PRP provides a generalized collection of positive, beneficial effects on the joint environment with the intent of reducing inflammation and preserving the synovium.  When used in soft tissue injuries, the presence of numerous growth factors in PRP helps to stimulate the development of a stronger matrix for healing as well as the recruitment of proteins for the regeneration of individual cell lines.  In doing so, the goal is to encourage a stronger repair than the scar tissue the body normally uses to fill the lesion in the absence of external influence. 

Prostride

Prostride is essentially a combination of the physiologic effects of IRAP and PRP.  There are a few additional components found within the preparation of Prostride that result in a higher likelihood of joint flares after injection.  As such, this is not a product commonly used in our practice, but it is widely researched and utilized in the equine veterinary community. 

Stem Cells

Stem cells can be harvested from both the fat and bone marrow of a horse.  They are most commonly utilized as part of the therapeutic rehabilitation of soft tissue injuries.  One of the biggest issues currently faced in horses with tendon and ligament injuries is the inability to control or direct the cell-type that the body uses to repair a soft tissue lesion.  As a result, without intervention, horses commonly lay down scar tissue instead of type I collagen, which is the main component of healthy soft tissue structures.  As a result, the repaired structure is usually weaker than the original and prone to a higher rate of reinjury.  The purpose of using stem cells is to specifically direct the body to develop and utilize type I collagen when repairing damage to tendons and ligaments.  The stem cell research as it pertains to equine medicine is still in its early stages of development but every year more is known about the biochemical and physiologic factors that influence soft tissue repair. 

If you have any questions about orthobiologics, as always please reach out to us and we’ll be happy to discuss the options for your horse.

Joint Injections: The what, when and why of intraarticular medications

Photo Courtesy nikki_tate on Flickr

Arthritis is one of the most common joint diseases found in the equine industry.  It is the leading factor of decreased performance and chronic lameness in our equine partners and is the source of much frustration and consternation.  The insidious nature of the process means that we as horseman don’t always catch it in the early stages, and instead, are left dealing with the disease in more moderate to advanced situations.  In a previous blog we’ve focused on how to prolong the onset of arthritis by using systemic nutraceutical or injectable products like Cosequin and Adequan (you can find that post here).  This article will focus on the options available to us when these initial attempts against arthritis are no longer efficacious.

What happens during a joint injection?

Once our systemic therapies like Adequan and Legend have no longer proven to be effective in reducing joint pain associated with arthritis, we turn to localized treatment directly within the damaged joint.  Prior to injecting any joints, your veterinarian will perform a thorough lameness exam to isolate the joint(s) from which the lameness is originating.  From there, we as veterinarians prefer to obtain radiographs of the joint in question.  This provides us both a baseline for future assessments as well as a better opportunity to understand any changes to the diseased joint that may alter our approach to needle placement.  The information obtained from the radiograph enables us to give our clients a more accurate prognosis for both post-injection soundness and duration of efficacy of the injection.

Preventing joint infection

Once you and your veterinarian have agreed to inject a joint(s), your veterinarian will then display an odd set of behaviors in which they tirelessly seek out the ideal location to perform an injection.  The biggest risk associated with a joint injection is infection, so we tend to be pretty picky about when and how we inject.  We avoid all windy situations, including drafts, as it seems just as you place the needle into the joint, a large gust of wind comes along and stirs up dust and debris which could potentially contaminate the joint.  We also avoid injecting horses with wet mud/manure directly over and surrounding the site of injection.  Clean, dry legs are necessary. We avoid areas of high traffic, as all it takes is an unknowing rider or the sneeze of a horse to contaminate our sterile site.

The ideal environment for a joint injection is one that has clean, dry footing (rubber mats or concrete work best), that is enclosed to restrict

Image Courtesy USMC via Flickr

or prevent airflow.  Fewer birds in the overhead peanut gallery is also preferred!  If these requirements cannot be found, don’t be surprised if your vet chooses to reschedule for a calmer/dryer day or you’re asked to relocate to a more ideal location.  At the end of the day, a joint infection can be life altering so we strive to avoid those at all costs!

The injection process itself is also sterile.  We will relocate all sources of potential contamination (tails, lead ropes, etc.) and will usually clip the injection site.  All joint injections are preceded with a 12-minute sterile scrub, and all products used in the injection process are also sterile, including your vet’s gloves!  Most practitioners will also use a small amount of antibiotic within the injection itself to further reduce the risk of infection.

What exactly is injected into the joint? 

As mentioned before, there is a small amount of antibiotic that is included in every injection, but beyond that, there is significant variability.  Larger volume joints (think coffin joints, knees, stifles, fetlocks) usually receive a high molecular weight hyaluronic acid (HA) and possibly steroids.  The steroids work to decrease the pre-existing inflammation within the joint and the HA helps bring healthy components into the area to improve the overall joint environment.  (There is also a mild anti-inflammatory response associated with HA).  Lower volume joints (pastern joints and the lower hocks) usually just receive steroids and antibiotic, forgoing the HA due to the small volume of joint space available to accommodate the injection.  There are several types of steroids available to use and which steroid we use is dependent on a multitude of factors.  These include high vs low motion joints, age of horse, severity of the intraarticular disease process, and metabolic status of the horse.  Steroids are contraindicated in horses with metabolic disorders which then has us reaching for an alternative – autogenous intraarticular therapies also termed “regenerative medicine.”

Regenerative Medicine Therapies

For those horses with metabolic issues or who no longer respond well to intraarticular steroids, we now have a variety of options for use in their place.  IRAP (interleukin-1 receptor antagonist protein), PRP (platelet rich plasma) and Prostride are all newer, autogenous technologies available to the veterinary industry.  While PRP and ProStride have applications in horses with arthritis, IRAP is far and away the most commonly used.

IRAP is processed directly from your horse’s blood and it works to counteract the interleukin-1 (IL-1) inflammatory protein.  The blood is collected into a special tube that is then incubated for several hours.  During the incubation process, the IRAP molecule is amplified within the sample.  After incubation, the sample is spun in a centrifuge which then separates the red blood cells from the IRAP rich plasma.  The plasma is then divided up into small aliquots to be used during the joint injection process.  Unlike steroids, which usually only require one injection to have a beneficial response, IRAP requires 2-3 injections, separated by 2 weeks in order to deliver similar results.  The IRAP injections usually last an average of 6-8 months, but the duration of efficacy is dependent upon a multitude of factors and is different for every horse.

While arthritis can be a difficult condition to overcome, rest assured that we do have a large variety of therapeutic options to pursue.  Please don’t hesitate to reach out with additional questions or concerns the next time you see one of us at your barn.  We’re always happy to help you and your horse!