The deep and superficial digital flexor tendons run like cables down the back of a horse's leg. | ? Illustrated Atlas of Clinical Equine Anatomy and Common Disorders of the Horse
Nine to 12 months. Your horse has injured one of the major tendons in his leg, and that's how long your veterinarian says he'll be laid up. As you shelve your training and competition plans for the coming year, it sounds more like a prison sentence than a prognosis.
Bringing a horse back from a tendon injury is a long and sometimes frustrating process. There's no guarantee of success?these injuries can end a horse's career. But how you manage your horse's injury can make all the difference in the outcome. In this article, I'll walk you through the steps to recovery and tell you when and how you can help. I'll also point out some of the problems and pitfalls you may encounter. In the box on page 63, you'll find an overview of some new treatments that may help your horse's injury heal better?although, unfortunately, not faster.
It may be cold comfort, but you have lots of company. Injuries are common in the key tendons that run like cables down the back of the lower leg?the deep and superficial digital flexor tendons. The tendons extend from muscles high in the leg to the foot; when the muscles contract, they flex the leg. They also help support the leg, and they come under huge stress when a horse gallops, jumps or does any sort of athletic maneuver.
Although I'll talk mainly about tendons, the steps I'll cover also apply to injuries in ligaments. Tendons and ligaments have different functions?tendons transfer the action of muscles to the skeleton, while ligaments lash bone to bone and keep joints from wobbling. But tendons and ligaments are formed of similar tissue and are injured by similar stresses, and they basically heal in the same way.
Why So Long?
Tendons and ligaments go through the same phases of healing as skin or other body tissues, but the process is much slower because of the way they're built. Both structures are made up largely of an organized network of dense, elastic connective tissue, rich in a tough protein called collagen. Living cells called fibroblasts maintain the network.
Fibers of collagen run lengthwise through tendons. They stretch to take the load when your horse puts his weight on the leg and spring back like rubber bands when the weight comes off. But if he overloads the leg (perhaps by just putting a foot down wrong on uneven ground), the fibers can tear. Damage can be instant, or it can build up over time as repetitive loads outstrip the ability of the fibroblasts to keep up with repairs. There are relatively few of these cells compared to the amount of collagen in a tendon or ligament, and that's one reason why these injuries heal slowly. In addition, tendons and ligaments have poor blood supplies.
A severe tear will take longer to heal than a mild one, and a 20-year-old horse may heal more slowly than a 5-year-old. Typically ligaments heal a bit faster than tendons?but you're still looking at nine to 12 months for all but the mildest of these injuries. And these injuries often heal poorly?instead of long, strong collagen fibers, you get a disorganized tangle of scar tissue that's less elastic and more prone to reinjury.
To get the best outcome, you'll need to follow a management and rehabilitation program that's carefully matched to the progress of healing. Your veterinarian will help you set up a program that fits your horse's injury. Diagnostic ultrasound scans, which many vets can do at intervals with portable equipment, can take much of the guesswork out of managing recovery and improve your odds of success.
Initially, ultrasound will show the extent of the injury. The machine beams ultrasonic waves into the leg and captures their echoes as they bounce off tissues. A tear in a tendon may show up as a gap in what should be a uniform pattern or as an area where echoes are less intense. Repeat exams can show how healing is progressing, letting you adjust your horse's program. Your vet may want to do the exams at 30-, 60- or 90-day intervals, -depending on the severity of the injury, the stage of rehabilitation and the total rest time that's needed for healing.
First Step: Cool Down
When a tendon tears, blood and lymph fluid leak into the injured area, and -enzymes and other body chemicals rush to the site. Inflammation builds, producing heat, pain and swelling. And while it's part of the healing response, it can have harmful effects?it can worsen tissue damage in the injury. So your first steps, while the injury is fresh, are aimed at cooling down the injured leg and reducing inflammation.
- Chill: Cold-water hosing is the simplest way to draw heat out of the injury. Ice water is great, if your horse will stand in it, as are devices like Game Ready? and Ice Horse? that keep cold circulating around the leg. Crushed ice (in ice boots, for example) may be less effective because surface contact between the ice and the leg is often inconsistent.
Sessions should last 20 to 30 minutes?it takes that long to cool the leg, and with cold hosing it may take a little longer. When you can feel that the injured area is cool, you're there. Repeat the treatment twice a day. You can cool more often if the injury is severe, but allow at least 30 minutes between sessions.
- Wrap: Dry the leg after cold therapy and apply a standing wrap (a leg quilt secured with a track bandage) to support the leg and help keep swelling down. You can use a mild poultice with the bandage to help draw out heat, but avoid any agent that could irritate the skin or increase inflammation. Bandage the opposing leg as well, for support. Reset bandages at least once a day.
- Medicate: Your veterinarian may prescribe medication?usually phenylbutazone (bute), flunixin meglumine (Banamine?) or a similar nonsteroidal anti-inflammatory drug during this period. Besides reducing inflammation, these drugs help make your horse more comfortable. A topical nonsteroidal cream (Surpass?) can be used as well.
- Confine: In most cases strict stall rest is best at first. Your horse will come out of his stall for cold-therapy sessions and, if your vet says its OK, you might take him out to hand-graze for short periods. If his injury is mild and he's not lame, you may start brief hand-walking sessions as described in the next section. Otherwise, he should not be exercised or turned out. Adjust his feed accordingly. Plenty of grass hay will help keep him occupied, but he won't need high-energy concentrates.
Cool-down takes anywhere from a couple of days for a mild injury to two weeks or more for a severe tear. You'll find that the leg is no longer hot or painful to finger pressure, and your horse is sound at the walk. He's moving into the next phase of healing.
As the injury cools down, fibroblasts get busy producing new collagen to repair the damage. Their work should show up on ultrasound as thin fibrils of collagen begin to fill in the injury.
This is the point where many ancillary treatments are applied?they tend to be most effective when given after cool-down but early in the healing process. You'll want to use the cool-down time to research these treatments and discuss with your vet whether any might be right for your horse's injury.
Whether you decide to use one of these treatments or not, good management is crucial in early recovery.
- Begin controlled exercise: Lightly loading the injured tendon stimulates collagen formation, and it encourages collagen fibers to align in a way that maximizes strength. But doing too much too soon risks reinjury. With your veterinarian's OK, begin short periods of controlled exercise?just hand-walking for perhaps 10 minutes twice a day at first. Do this on level, smooth footing that's not too deep. If all goes well for two weeks, begin to gradually increase the time. You might add five minutes a day; in another two weeks, five minutes more.
- Medicate as needed: Reinjury is also a risk if your horse is playful when you walk him. If behavior's a problem, talk to your vet about sedative medications to control it. Generally horses should be off anti-inflammatory meds after cool-down. NSAIDs can have long-term side effects, and there's some evidence that they slow healing.
- Stay with stall rest: Horses can do incredibly silly things, even in a small paddock. Keep him on stall rest to avoid reinjury. Continue the standing wraps for three to six weeks, depending on how severe his injury is; then wean him off the support by gradually reducing the time he spends in wraps.
- Repeat the ultrasound: After a month or six weeks, your vet will probably want to repeat the ultrasound exam. The new scan should show more of the injury filling in with collagen. And the fibers, which were a disorganized tangle at first, should be starting to align in ways that will help the tendon withstand stress.
Give Healing a Boost
|A carefully managed rehabilitation program is the tried-and-true formula for recovery from a tendon or ligament injury, but additional treatments may help the process along. Several new therapies make use of a horse's own body cells to encourage healing. In some cases there's little or no formal research on their use in horses, but as more cases are treated, we're getting a better picture of their effectiveness. Whether any of these treatments are right for your horse -depends on the nature of his injury and on your checkbook?some of the more complicated cell-based therapies may run several thousand dollars.|
Platelet-rich plasma. Platelets are small cell fragments that circulate in the blood. They're best known for their role in helping blood clot, but they also have high concentrations of growth factors that encourage healing. Using a horse's own blood, veterinarians can separate platelets and make platelet-rich plasma?basically, platelets concentrated in a little plasma, the liquid portion of blood. Injected into injured areas, the concentrated platelets release growth factors over a period of time, giving healing an extra kick. PRP seems especially helpful in torn ligaments, alone or along with stem-cell therapy as described below.
Fat-derived stem cells. These cells have the ability to transform into different types of tissue; in torn ligaments, they become fibroblasts, cells that make collagen. They also produce growth factors that stimulate healing. Stem cells -occur naturally in various sites in the body, including fat, and your veterinarian can use your horse's own fat-derived stem cells for treatment. The vet collects a small amount of fat from your horse's tail head, under local anesthesia, and ships it express to a commercial service (Vet-Stem). The service concentrates and purifies the stem cells and ships them back within 48 hours for injection into the injured tendon or ligament.
Bone marrow aspirate. Bone marrow contains stem cells along with -serum that's rich in growth factors. With the horse sedated, the veterinarian can collect a sample of the horse's bone marrow (usually from his sternum or hip) with a special needle. This bone marrow aspirate can be injected "as is" at the site of the injury to stimulate healing, or it can first be processed like PRP to concentrate the key cells and serum.
Marrow-derived stem cells. A different process (available through VetCell Bioscience) can expand the number of stem cells from marrow. The aspirate is sent to a lab where the serum is drawn off and the stem cells are cultivated and then recombined with the serum for injection. The process takes two to four weeks, a drawback; but the combination of stem cells and growth factors seems effective.
Extra-cellular matrix. ECM is a scaffold of protein fibers without living cells. An ECM product called ACell Vet, derived from pig bladders, has been used in tendon and ligament injuries. Powdered and suspended in saline solution, it's injected into the injury site. It seems to stimulate healing, although it sometimes produces temporary inflammation.
Several other therapies stimulate tissues around the injury. Extracorporeal shock wave therapy has proponents; it bombards the injury with high-energy pressure waves. It's been shown to encourage bone healing, so it may be especially helpful if a ligament is injured where it attaches to bone. Other options, alone or in combination with any of the treatments listed here, include hyperbaric oxygen therapy (see "Hyper Healing," November 2008) and swim therapy.
As healing progresses, collagen continues to be produced. It also remodels?it becomes denser and better organized in response to the mild stress of carefully controlled exercise. Remodeling makes the tendon stronger and able to bear greater loads, and increasing the loads in step with healing keeps the remodeling process going.
- Tack walk: With your vet's OK, you may be able to replace one of your daily hand-walking sessions with walking under tack. Be sure your horse's feet are properly trimmed and shod, and continue to work on level, smooth footing, in straight lines and large circles.
- Vet check: After six weeks or so, have your vet check your horse's progress. If the ultrasound shows that healing continues to progress, it may be time to ?
- Add trot: The first week, you might add just five minutes of trot to your -exercise sessions. (Walk for a good 15 minutes first to be sure the tendon is warmed up.) After a week or two, if everything's OK, add another five-minute interval, and then a third interval a week or two later. Keep the work easy?big circles are OK, but avoid sharp turns and lateral moves. Don't longe?repetitive circles can be hard on the healing tissues, and as a handler you have little control over your horse's behavior.
- Repeat the ultrasound: If your horse continues to trot sound on circles and straight lines, and his leg shows no sign of heat or swelling, you may be able to gradually increase his work. Get new scans before -major increases in exercise?the first canter, the first jump, the first gallop. Ultrasound should show fibers becoming denser and lining up parallel to each other, which will make the tendon stronger.
- Turnout: When your horse is well along in his exercise program, your vet may tell you it's OK to put him out in a small paddock. He should go out solo, at a quiet time when other horses won't be acting up. Any horse is likely to explode when first out after months in a stall, so talk to your vet about medications to keep him calm at least for a few days. Don't leave him out unwatched, and be ready to bring him in at the first sign that he's going to act up.
If your horse is sore after exercise or if you see a return of heat, swelling or pain at any point, back off the program and contact your veterinarian. A return of soreness and heat isn't always a catastrophe; but your vet may need to see your horse and perhaps do an ultrasound exam to find out what's going on. Here are two possibilities:
Adhesions: Adhesions are strands of fibrous scar tissue that form where they shouldn't and restrict a tendon's ability to stretch and glide. They develop mainly in injuries low in the leg?the area just above, around and below the fetlock. Here, where the tendon passes over the joint, it's encased in a sheath that secretes lubricating synovial fluid. Adhesions can form between the tendon and the sheath or between parts of the sheath; an infection in the sheath makes this more likely. Higher in the leg, adhesions are rare; but in severe injuries (like a tendon laceration) they sometimes form between the superficial and deep flexor tendons.
Adhesions can make a horse very sore, but the fix is to go forward with your restricted exercise program. That will gradually stretch and remodel the adhesions, so they no longer trouble him. Passive manipulation through the normal range of motion?picking up the injured leg and gently flexing the foot, fetlock and knee (or hock)?can also help. You can do it while you're grooming him or at other times during the day.
Reinjury: Doing too much, too soon, is the most likely cause for a setback in healing. When your horse is trotting sound a few months into his rehab, it's easy to think that you're past the danger point?and very tempting to ask him for a little more. In fact, his tendon is still healing. The site of his injury is a weak spot, and it doesn't take much to tear it again.
In this case, forging ahead with exercise will do more damage. And depending on how much damage is done, reinjury can restart the clock on your rehab program, putting you back at the beginning. That's why it's -important to talk to your vet at any sign of soreness. Your vet can compare new and previous ultrasounds to see if there's been a change in the tendon.
When can your horse return to competition? The answer depends on how severe his injury was to begin with, how well it heals and what you want to do with him. After you've brought him through his nine- to 12-month recovery program, if he shows no lameness or heat, swelling or pain in the tendon, and his ultrasound looks good, he may be ready. Unfortunately, reinjury is always a risk in tendons and ligaments because the new tissue that fills in the injury isn't as strong or as elastic as the original?it's basically scar tissue. That weakness means that the old injury may give way under stress.
Researchers are hunting for ways help tendons and ligaments heal "good as new." We're not there yet. Still, many horses with these injuries do successfully return to their previous level of work?given good treatment, the right rehab program and plenty of patience.
Linda Dahlgren, DVM, PhD, is an assistant professor in the Department of Large Animal Clinical Sciences at the Virginia-Maryland Regional College of Veterinary Medicine. Her research interests include tendon biology and healing, wound healing, tissue engineering and adult stem cell biology.
This article originally appeared in the February 2009 issue of Practical Horseman magazine. Read more about the 5 top sporthorse injuries in the October 2011 issue.