We have treated some of these. But first, we have made clear the economic and medical situation to the owner. These require a good three months of rest and repeated SH treatments. If the owner can accept this lay up time, a clinical recovery can be expected in some cases.

Three years ago, our practice relied heavily upon methylprednisolone acetate. Currently we inject five joints with SH for every one with corticosteroid. We're

pleased with the Pharmacia product. It has been effective for us. It is also professionally packaged, presenting very little chance for joint contamination.

In summary, SH represents a significant new form of treatment. Its value is already recognized in the treatment regimen. Excessive and unwarranted use, however, exposes veterinarians to the unsavory reputation of lacking cost consciousness.

DISCUSSION

Hawkins: Dr. Steele, I have heard it said around the track for

years concerning the injection of the coffin joint, that people won't put acid in a coffin joint whereas they would use steroid. They are afraid of a reaction.

Steele: Actually it's just the opposite. SH is the only

medication I will put in the coffin joint. 1 am leary of the steroid situation. Considering the number of coffin joints we are injecting and the potential danger inherent in steroid use, there is too much risk.

Gabel: Dr. Steele, do Swedish trotters, or those owned by

Swedish people, have more coffin joint and fetlock-like problems than American trotters? Students that have come to visit us ask why we in the U.S. see a low incidence

of lameness in the coffin joint and in the fetlock joint?

Steele: I think it is a question of diagnosis rather than

incidence. In the trotting horse there is a lower leg syndrome involving the pastern, ankle and foot that the Swedes diagnose quite readily. These horses may not show it on a jog, but when they get in gear they experience pain so as to get on a line or maybe just not finish their mile properly. This syndrome or condition has been proven to me in working with Swedish veterinarians and trainers. Not that they inject all these horses. They may blister the coffin joints and use local therapy. They will square the toes, use the mushroom shoes and do all those things involved with foot care. These horses do respond clinically. We just don't pursue quite enough or are not aware of this syndrome. Injection of SH in the coffin joint is valuable in this situation.

NOTES ON THE USE OF SODIUM HYALURONATE IN THOROUGHBREDS

By S tephen J a y Selway, D V M

Stephen Jay Selway, DVM, graduated from Washington State University in 1972. He then took an internship in equine medicine and surgery at the University of Pennsylvania, New Bolton Center, folloWed by a residency there. For a year he was Head of Equine Surgery Section at the University of Illinois. Since then he has conducted a race track practice, specializing in arthroscopic surgery.

Address: 7600 NW 3rd Street, Pembroke Pines, FL 33024.

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My experience with SH derives from academia, as well as racetrack practice, and since the time of the clinical trials at a university about thirteen years ago, I've employed hyaluronic acid in many Throughbreds. I, too, still fight the battle as far as lameness diagnosis is concerned. Some of these cases certainly do involve primary and secondary problems. Unless you can determine the primary origin of the horse's pathology, you have little success treating the secondary problem. It can be frustrating at times, not only for you but also for the trainer and owner. Complete physical examination and diagnostic anesthetic injections are often necessary to sort out the w~ole picture.

In the fetlock of the Thoroughbred racehorse, SH is my treatment of choice for so-called green osselets or degenerative joint disease of the ankle. I've also experienced a very positive result with the majority of

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chip fractures to the anterior proximal aspect of PI. Those chips that tend to break off and move to the anterior aspect of the joint have been successfully managed with SH injection in a high percentage of cases. My approach is to cool these joints down, put in SH, walk them 10 to 14 days, and put them back in training usually with very little problem. I do not use any steroid with hyaluronate, and I don' t like to penetrate joints that have had recent corticosteroid injection.

One thing I've obserx, ed over the years is that the time interval f rom injection to re'turn to training is important. We don ' t put them back in training for 10 to 14 days. In almost every case, if you were to do daily fetlock flexion, you'd be out around 9-10-12 days before the horse would not resent manipulation. I 've treated ma~y 'horses that have a history of previous SH injection followed in a relatively short period of t ime- -one or two m o n t h s - - b y a recurrence of lameness caused by the treated joint. Oftentimes rejecting the same product in the samej oint as before, but followed by a full 1.0-14 days ofhandwalking, yields an excellent response and may never have to be injected again. Perhaps, as Dr. Churchill has said, it's the multiple treatments that cause the lasting effect, but 1 attribute the response, at least in part, to allowing the SH time to work and get that joint in a more normal physiologic state before exercise resumes.

One ankle indication where I haven't been nearly as satisfied is the situation of degenerative hooks on the top

and bot tom of the sesamoids. These horses don' t respond as well to the SH.

The carpus is the other common place that we use SH. I do not expect good results in knees where there is significant spur formation, or when a chip fracture i s present. In the more lytic or erosive lesions of the knee, SH seems to be more effective. Many times SH is injected in cases of knee chip fractures in order to keep the animal in training and racing. I haven't had good results doing this. In those that have had multiple SH injections that I've operated on, although the damage is usually not as severe to the entire joint as that with steroids, it's certainly not good for the horse.

I have done some injections of SH into the hocks including the distal joints of the tarsus, initially with Standardbreds in 1973 and later in a fair number of Thoroughbreds. l haven't found the hock injections worthwhile, basically because the SH didn't give a lasting effect. We'd get some benefit, but the duration and degree of response isn't enough to justify its use. In the distal tarsal joints the response to corticosteroids, which I rarely use, is better. I have more succuss with cunean tenotomies or electrostimulation for hock problems.

In conclusion, in the Thoroughbred, I 'm finding SH useful in fetlocks and knees. On rare occasions, the shoulder and stifle (afflicted with minimal OCD changes) have shown favorable response.

DISCUSSION

Gabeh The hock problem is not the same in Thoroughbreds

and Standardbreds. The hindlimb of the Thoroughbred impacts the ground with a large vertical compressive force causing development of a hock osteoarthritis. The Standardbred hock more commonly develops a soft tissue soreness to joint capsule, tendons, and ligaments because the hindlimb does not get very far off the ground and tends to slide into the racetrack, setting up shearing, rather than compressive, forces. This is part of the reason for the poor correlation between radiographic findings on Standardbreds and how sore they are.

Susceptability to sore hocks in Standardbreds varies greatly between horses, and I don' t believe this is related to c o n f o r m a t i o n . I ' ve in jec ted a fa i r a m o u n t of corticosteroid in Standardbreds with hock problems without causing them to get osteoarthritis. I feel that with whatever medication administered we are using the distal hock joints as a route to get the agent to the soft tissues. It is only a route, and not a very perfect one.

Hock soreness is sometimes difficult to demonstrate. We have trouble blocking them so completely that they go lame in the other hind leg. Since I've been using 50 ml Carbocaine and a 6 cc syringe for the hocks; I can make about half of them switchover and get sound, and this dramatic change is important not only for the diagnosis,

Volume 5, Number 4

but to convince the t rainer/owner that we have the diagnosis.

I use a 22 gauge, 1 inch needle placed in each of the distal joints and keep flushing both capsules until I 've emptied the bottle. Initially probably about 10 percent of these joint cavities communicate, but if you inject more that 10 ml you probably open up the pathway. When I inject them about 90 percent communicate. Syringe size is important, too. With the 35 cc syringe such as the anatomists have used, you can't generate enough pressure to open up these communications.

The high pressure, high volume block will diffuse well outside and around the joint. So, I 'm really blocking the whole area. I first saw this extra-articular diffusion by experimentally injecting latex which is certainly much thicker than Carbocaine. So when you want the entire area blocked, you should increase the amount of Carbocaine.

Large amounts of local anesthetic can, however, be a disaster in the shoulder, and I'll never use more than 35cc. The diffusion phenomenon in the shoulder can lead to a brachial paralysis and temporary loss of limb usage. Should the horse become anxious, he may kill himself or someone. With the coffin, I use no more than 5-6 ml and still must consider the effect of diffusion to the navicular bursa and tendon sheath.

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Steele: What about differences in treating Thoroughbred and

Standardbred hocks?

Churchill: We find a more long-lasting advantage when we inject

the Standardbred hock, from the standpoint of being more effective over a longer period of time. The Thoroughbred hock has the tendency to need injecting more frequently if you a re 'go ing to keep the horse running.

We also f ind c u n e a n t e n e c t o m y m u c h m o r e dramatically effective in the Thoroughbred. Only in a Standardbred that is entirely on t h e toe (and his shoe/foot wear will tell us how he's carrying his weight) do we see an effect with the tenectomy. In the Thoroughbred you can expect a year from the surgery or sometimes less, before the horse starts to sore up again and regress. At that point, you've really nothing else to do but to go back to the SH injections.

In a percentage of the Thoroughbreds you do everything, tenectomy, S H - - a n d still a patent spavin progresses so that after a period of time you can no longer help them.

Gahel: The prognosis for the two breeds is also different. The

Thoroughbred starting to show some hock arthritis is approaching the end, so that over a period of a couple of years it will no longer be a useful horse. These animals are best managed by minimizing hard work, use of non- steroidal anti-inflammatories, and so forth.

The SH ought to theoretically be of some help, although you know it is not going to cure them because it is a progressive disease. You are looking to get a little more use out of them.

In the Standardbred, it is a matter of strengthening the soft tissues around the hock joints. With a good track surface, fiat steel shoes--if they can wear them--and lots of slow, long work, you can really train them out of the problem and make them sound horses. You are making a lot of adjustments, and it takes care, discipline and good judgement as to how much training is enough.

The other situation is when these young trotters are up on their toes and dragging their toes on impact. This brakes their feet more and causes more hock stress and starts up a vicious cycle. You have to put them on a good level of NSAID to try to get them down on their foot again. If that doesn't work, you may have to stop them completely for awhile.

POST S U R G I C A L USE OF S O D I U M H Y A L U R O N A T E

By Stephen J ay Selway, D V M

Although an exact scientific rationale for the post surgical use of sodium hyaluronate (SH) has not been established, I subjectively believe we are providing an important mode of therapy with its use. My interest in using SH goes back to my days at the University of Pennsylvania where we were working with th e drug. At the time, the rationale was that SH prevented large enzyme molecules from getting into articular cartilage, causing destruction.

During the last four-and-a-half years I have been using SH f o l l o w i n g a r t h r o s c o p i c su rge ry . We ' r e j u s t completing the follow-up on Case 500. We've done about 780 arthroscopic surgeries now. When we had reached 246 cases, we had 76 percent where we used SH postoperatively. Since then, I find that in almost every a r throscopy I perform I use SH postoperatively. Fortunately, I am operating on pretty good horses and the added expense is justified. I feel SH is beneficial.

Originally, my criterion for use of SH was that if I had a relatively small spur or a small chip fracture with no underlying long-standing degenerative joint disease 1 did

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not put SH in the joint. If I had a more long-standing degenerative process I used SH post surgically.

Now we are using more SH, partly because I find Iam operating on horses that I would not have previously considered f o r arthroscopic surgery. Improvements in instrumentation and technique have now made these more chronic and degenerative cases operable.

I make a special point to use SH following fetlock chip removal. I am more concerned about putting SH in a joint where there is a lot of soft tissue damage than I am where there is bone damage and remodeling has to be done. One thing that we found in doing the arthroscopic surgery is that the less synovectomy you do the better off you'll be down the road. Now, I will really fight a joint to be able to see to clean up the joinLwithout using the synovial resector. When the synovial villi are removed there is more postoperative inflammation in the joint, and I see more degenerative Change down the road. I have noticed in those horses where I have had occasion to go back into the joint later (up to a year) after having removed the synovium, that it had not grown back. If you

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