Swelling of fetlock joint. Horse is reluctant to stand with leg bearing full weight.
Swelling of fetlock joint. Horse is reluctant to stand with leg bearing full weight.

Advanced Diagnostics and Regenerative Medicine

Regenerative Medicine is a relatively new topic that has generated tremendous interest in human and equine medical fields. Stem Cells are probably the first types of treatment that most people think of under this topic, but there are others with equally exciting benefits. In the following article I will delve into these treatments and explain how they are revolutionizing our approach to recovering horses with lameness issues.

As always the best treatment is determined by our ability to arrive at the most specific, accurate diagnosis. When evaluating a lameness case there are multiple components as has been discussed elsewhere on this website. see Lameness Evaluations Once a region has been identified as the cause of a lameness the questions become have we evaluated it thoroughly enough to be sure that it is truly the cause and what can we do now to ensure that the affected area(s) heal quickly with an excellent result? Of course everything can be done correctly and there still could be a less than perfect outcome, but with newer diagnostic and regenerative treatments some injuries that were thought to be career ending are having positive outcomes.

X-ray of horse's hock showing multiple bone fragments. The only means to comment on the cartilage surface of the joint will be through surgery - arthroscopy..
X-ray of horse's hock showing multiple bone fragments. The only means to comment on the cartilage surface of the joint will be through surgery - arthroscopy.

In the past year I have worked on many lame horses and some have injuries that can only be partially evaluated in the field. Examples of these would be a foot or heel lameness that can be clearly localized to that area yet the xrays may be normal and the ultrasound may or may not show a lesion. There are a myriad of treatments for these horses: corrective farriery, medications, joint injections and others, but if there is a soft tissue lesion such as a tendon tear then there will be limited benefits. Fortunately the ultrasound that is used frequently in my practice is very effective at identifying many of these soft tissue injuries. The difficulty is visualizing some of these structures as they course distally into the foot. Sometimes the lesion that I can access down low in the pastern or near the navicular bone is just the start of a deeper lesion that is hidden by the bottom of the foot. So, how do we proceed with cases that are suspect for these type of injuries? MRI is probably the single most helpful diagnostic procedure in the past 25 years.

Bone chip in front of fetlock joint.
Bone chip in front of fetlock joint.

Many of you have undoubtedly heard of using MRI in human medicine and now it is becoming more available on the equine side. The primary role for horses is to evaluate soft tissue, bone and joint structures. Being able to "see" a lesion and comment on the integrity of the affected tissues has been a quantum leap in our diagnostic capabilities. Perhaps I can tell an owner very accurately that there is a chip in the fetlock joint, but I can't clearly tell you if it's having an affect on the joint surface at that point. In addition I can see the disrupted ligament fibers in the ligament, but may not be able to see how the neighboring bone is affected by it.

MRI Images of a Horse's Foot

MRI picture of horse foot from the side
MRI picture of horse foot from the side
MRI image of lame foot with injured tendon.
MRI image of lame foot with injured tendon.
3rd MRI image. In this view we are looking down at the foot and the deep flexot tendon tear can be easily visualized.
3rd MRI image. In this view we are looking down at the foot and the deep flexot tendon tear can be easily visualized.

As you might expect needing these procedures is not routine nor is it inexpensive. Fortunately the average lameness can be resolved without these procedures, but for those that are not resolving and/or seem to have more involved than I can visualize with digital radiography and ultrasound there are options. Equine insurance may be your best friend in these cases as advanced diagnostics along with the regenerative procedures that will be discussed are often covered procedures.

The question that was often heard was "yes I can take my horse for a MRI, but how will it change what we do besides being able to know more about the cause?" Well now I can answer that yes we will undoubtedly know more about the cause, but will also be able to comment on the degree of damage and make predictive statements about prognosis and, most importantly, start some type of treatment that we were unaware of up to this point. Under the broad topic of Regenerative Medicine we can look at these procedures that are designed to help regenerate damaged tissues. A general explanation of what this entails is as follows: regenerative medicine is the process of creating living, functional tissues to repair or replace tissue or organ function lost due to injury, disease, age or congenital defects. This field holds the promise of regenerating damaged tissues and organs in the body by stimulating previously irreparable organs to heal themselves: repair of damaged heart muscle after a heart attack, replacement of skin for burn victims, restoration of movement after spinal cord injury, regeneration of pancreatic tissue to produce insulin for people with diabetes, and so forth. Regenerative medicine can improve the quality of life by supporting and activating the body's natural healing. Of course much of this is specific to human medicine and how we use it in equine medicine at this point primarily involves musculoskeletal issues.

I would like to introduce the following list as procedures considered to have regenerative benefits to horses:

• Stem Cells

• PRP

• IRAP

Stem Cells

The use of stem cells is certainly controversial in human medicine, but for most researchers there are tremendous healing and regenerative benefits that make pursuing this technology worthwhile. There are alternative methods to collect these cells which do not involve embryonic tissue. This discussion will focus on methods to collect equine stem cells, but it is worth keeping in mind that there is considerable overap with what is available on the human side.

Horse being evaluated in a CAT scan machine.
Horse being evaluated in a CAT scan machine.

Not only do we have MRI to call upon for diagnostics, but also CT Scans. CT or Computer Tomography (CAT scan) produces cross sectional and 3-D images of injuries and can further qualify the degree of structural damage to area of concern. This modality can be beneficial in diagnosing hair-line fractures, joint damage, tumors, masses and has many benefits in our lameness options. Anatomical areas such as head and neck distal limbs can be evaluated in significant detail. Because of the ability to visualize the injury on screen in real time 3-dimensionally inta-joint and intra-tendon lesions can be accurately injected while the practitioner is viewing the image. For some patients a combination of these diagnostics will be used.

Images of a horse being injected with stem cells using ultrasound guidance.

By definition, stem cells are immature, vigorous cells that mature into any of the hundreds of various body cell types--nerve, blood, heart, muscle, fat, bone, cartilage, etc. They are what turns an embryo into a fetus into a baby into an adult. They have plasticity, meaning they are adaptable and capable of being manipulated into becoming different types of cells. It's this type of adaptability that is so promising for treating equine tendons, ligaments, joints, and bones. Often, injuries at these sites cannot repair themselves to a stable, pre-injured status. Adult cells are geared toward maintaining the status quo, possessing a limited capacity for replicating normal cells. Often instead of producing new, healthy, normal tissue after an injury, scar tissue is produced, and scar tissue is often a weaker, inferior tissue, making the recently healed site prone to re-injury.

Much of the early work with stem cells and lameness cases was introduced by Dr. Doug Herthel from Alamo Pintado Equine Medical Center in California. Cells harvested from the patient's own bone marrow are showing great promise for several reasons: first, there is no risk of tissue rejection. Second, "many, many studies coming out now are showing that the adult mesenchymal stem cell (from which arises connective tissues of the body, blood vessels, and lymphatic vessels) in the human has tremendous plasticity," says Herthel. "The adult stem cell can become a muscle cell or cardiac cell or tendon cell, etc. It is just as plastic--maybe more so--than embryonic stem cells." Third, blood marrow contains fibronectin (which aids cell migration through the area of injection) and growth factors (which enhance healing). Finally, this therapy could provide very quick pain relief, as was found on the human side when Herthel's group assisted several human orthopedic surgeons in using this procedure for Achilles tendon tears, patellar tendon (tendon that connects the patella to the tibia), quadriceps tendon (tendon that connects the long quadriceps muscle to the patella), and lateral epicondylitis tendonitis.

In 2001, Dr. Herthel published and presented a scientific paper to the American Association Of Equine Practitioners (AAEP) in San Diego." This paper reported the results of 100 suspensory injuries that were not treated with bone marrow stem cells and compared the results to 100 horses that had been treated with bone marrow stem cells. In the untreated group, less than 30% went back to work and stayed sound; in the treated group, 80% went back to work and stayed sound for at least one year.

For the past year I have treated several horses using stem cells collected from a horse's fat located over the rump. In the following images the procedure can be followed.

Horse with a hole or core lesion in the superficial digital flexor tendon. See blacker area from fiber disruption in tendon.
Horse with a hole or core lesion in the superficial digital flexor tendon. See blacker area from fiber disruption in tendon.
In this image I have inserted a needle using ultrasound guidance so stem cells can be injected.
In this image I have inserted a needle using ultrasound guidance so stem cells can be injected.
In this third image the brighter white area is where I deposited the stem cells in the torn tendon. .
In this third image the brighter white area is where I deposited the stem cells in the torn tendon. .
Needle being placed on tendon with ultrasound guidance.
Needle being placed on tendon with ultrasound guidance.

To summarize, if we can inject cells into damaged tissue that will allow for regeneration, we have the potential to significantly improve the healing rate, but more importantly, positively affect the integrity of the healed injury.

On the equine side adult stem cells come from one of two sources fat (adipose tissue) or bone marrow. As would be expected in medicine, there are proponents of both methods. Using a relatively simple surgical procedure, stem cells are extracted from the patient's bone marrow. Depending on the clinican's preference the cells can be accessed from a horse's sternum (rib area) or from a hip bone (pelvis). One of the issues with this method may be that the actual number of stem cells may be limited. There are procedures used to cultivate and increase the numbers manifold, but the time interval will be weeks. Other methods involve collecting the cells from bone marrow and concentrating the cells in the fluid portion of the marrow to inject a more concentrated fraction.

The method used by many of us involves collecting fat from a horse's rump through a simple, standing surgical procedure and shipping the fat overnight to a lab in California. Once it arrives at the lab that fat is processed so that the stem cells are concentrated. Following this one day procedure, the small volume of fluid with the stem cells is shipped back for injection on the same day. The quick turnaround and minimally invasive procedure to get stem cells from an equine patient and into a lesion is particularly appealing.

There are obvious advantages with the use of fat-derived regenerative cells rather than regenerative cells derived from bone marrow. First of all it is a minimally invasive, safe procedure that provides a readily available source of stem cells. Secondly the concentration of these cells is more concentrated than what comes directly from bone marrow. Thirdly, the cells are able to differentiate into multiple tissue lineages including: bone, cartilage and muscle.

Of course the bone marrow cells have many of the same potential tissue benefits, but the issue is concentrating these cells to an effective number. Some have argued that the diverse population of cells from fat vs bone marrow has further advantages.

PRP

PRP (Platelet Rich Plasma) refers to the platelet-rich portion of the blood. There are several methods available to concentrate the platelets, which are natural blood components we all have. Once the platelets are acquired they are injected into an equine tendon or ligament injury to help the healing process. In humans, PRP has been used since the mid 1990's. Its use for musculoskeletal injuries especially with atheletes such as Tiger Woods as well as professional football and baseball players, has garnered considerable interst in human and equine sports medicine.

Bone marrow being collected from horse's sternum (rib area).
Bone marrow being collected from horse's sternum (rib area).

At our recent December 2009 American Association of Equine Practitioners (AAEP) convention, held in Las Vegas, Nevada, Dr. Dora Ferris, of the Orthopaedic Research Center at Colorado State University, discussed the use of bone marrow-derived stem cells. She described evaluating treatment success in a variety of musculoskeletal disorders with a mean follow-up of 21 months (range seven to 39 months) on 101 patients. It should be noted there were no control groups in the study for comparing success between treated and nontreated horses; however, Ferris reported that investigators on previously published studies used controls for horses treated with meniscal, tendon, or ligament injuries. The current study reported that 64% of treated horses returned to full work, while 22% returned to work with increased therapy or at a lesser level, but there was a reported 8% re-injury rate. Fourteen percent did not return to work.

All sport horses and 91% of racehorses with superficial digital flexor tendon injuries returned to work following stem cell therapy. Twenty percent of racehorses that returned to racing following stem cell treatment, rest, and rehabilitation re-injured themselves, whereas 66% of horses experienced re-injury when undergoing conservative treatment or rest and rehabilitation. Encouragingly, Ferris noted that 78% of horses treated for chronic suspensory ligament injuries were able to return to work following stem cell treatment after failing to improve with other conventional treatments. These are encouraging numbers especially for soft tissue injuries such as flexor tendon and suspensory ligament injuries. What was particularly exciting was her discussion of meniscal tears and how well they appeared to respond to stem cell treatment.

To summarize, if we can inject cells into damaged tissue that will allow for regeneration, we have the potential to significantly improve the healing rate, but more importantly, positively affect the integrity of the healed injury.

Activated patelets in blood.
Activated patelets in blood.

The process by which the platelets improve healing centers around activation. Once this happens platelets release their granular contents into the surrounding environment. The granules are abundant and of particular interest because they contain many of the growth factors responsible for the initiation and maintenance of the healing response. The active secretion of these proteins by platelets begins within 10 minutes after clotting, with more than 95% of the pre-synthesized growth factors secreted within 1 hour. After this initial burst, the platelets synthesize and secrete additional proteins for the balance of their life (5–10 days). The fibrin matrix formed following platelet activation also has a stimulatory effect on wound healing. This matrix traps platelets allowing a slow release of a natural combination of growth factors while providing a provisional matrix that provides a physical framework for wound fibroblast migration and presentation of other biological mediators such as adhesive glycoproteins. All of these methods described here are particularly beneficial with an injury involving fiber damage for tendons and ligaments in horses.

In the past year I have had numerous horses treated with PRP by a clinic in New Hampshire, New England Equine. Fortunately a new kit recently became available that allows for the harvesting of platelets for PRP treatments within 30 minutes of drawing blood from the patient. There have been a number of cases I have successfully treated by this method in the past year. All of the cases involved soft tissue injuries, specifically tendons or ligaments from the proximal flexor tendon of the forelimb down to the distal pastern ligaments. Hind suspensory ligament cases have also been treated. Once the PRP is collected the lesion or teat of the fibers is injected with ultrasound guidance into the affected area. The horses are tranquilized and have the area desensitized before injecting.

Newer treatments are using a combination of PRP with stem cells to improve the healing processes through the use of regenerative cells, fibrin matrix and growth factors.

Large superficial flexor tendon tear - before treatment.
Large superficial flexor tendon tear - before treatment.
Healing tendon 3 months after I injected lesion with PRP.
Healing tendon 3 months after I injected lesion with PRP.

IRAP

IRAP (interleukin-1 receptor antagonist protein) is becoming a more common therapy that again uses the horse's own blood, to produce a product that has a number of potential advantages without the use of outside medications. The most frequent use is in joints that have become inflamed. It may be considered a first line treatment for some of these and for others it is used post joint surgery. I have used it most frequently in the latter situation.

Dr. Jerry Black, a well know equine lameness veterinarian from California, explains the benefits of IRAP as follows: "IRAP, has shown strong promise, it competes with interleukin-1 (IL-1)--an enzyme that is considered to be a major joint inflammatory mediator--for the IL-1 receptor. In this fashion IRAP blocks the effect of IL-1, producing a significant anti-inflammatory effect. IRAP is harvested from the patient's own blood and it is incubated for 24 hours in a syringe filled with chromium-coated beads

IRAP is harvested from the patient's own blood and it is incubated for 24 hours in a syringe filled with chromium-coated beads. The centrifuged and treated product is a concentrated mix of IL-1 antagonist, protein growth factors, and other anti- inflammatory agents described as an "anti- inflammatory soup." As with many treatments reducing inflammation is always beneficial to the return of the tissue to a healthier environment and beyond that, IRAP also provides growth factors which are in stem cells and PRP and aids the healing process.

Many of the horses that are undergoing joint surgery and where the potential for issues concerning joint health is expected to persist post-surgery are excellent IRAP prospects. While the horses are at the hospital for arthroscopic surgery, the blood can be collected and processed so numerous syringes of IRAP can be produced. Once the horses are home and recovering the joint can be injected on a weekly then monthly series for a period of time to maximize the chance of reducing inflammation and restoring joint health.

If we can successfully block some of the major intra-joint inflammation without the chronic use of systemic therapies such as Bute, Banamine, Equioxx and others plus limit the number of steroid injections into a joint then we have imroved the health of the joint and decreased the secondary problems that can develop with the other medications used over a long period of time. Regenerative procedures are at the forefront of sports medicine and all of these exciting procedures are being used at Burlington Equine.