VetInfo Digest       July 2000

 

This Month:

Cranial Cruciate Ligament Injuries

"Tail Jerk" Injuries

The Things That People Say

When I started writing this month's issue of the VetInfo Digest I thought that I would be able to cover three or four of the most common orthopedic problems. As I started to write about cranial cruciate ligament injuries, it became apparent that there would not be enough space to cover more than two. If you have an interest in any particular orthopedic conditions please let me know and I will try to include them in future issues.

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Cranial Cruciate Ligament Injuries

This is a condition that is more common in dogs than it is in cats. In dogs, the condition is usually due to chronic deterioration of the ligament over time and affects middle aged or older dogs. If it occurs in young dogs it is more likely to be due to trauma. In humans, this injury is usually referred to as an anterior cruciate ligament (ACL) injury. While I am not a human orthopedic surgeon, my impression is that in people this injury is usually the result of an acute trauma, at least in young humans. In cats, the injury also appears to occur primarily due to trauma and may be more common than it is diagnosed since the cat's low body weight may allow it to compensate for the injury in a relatively short period of time, which

limits the chance a diagnosis will be made.

The reason that this ligament is not called just "the cruciate ligament" is that there are two ligaments that work together to prevent the femur (the thigh bone) from sliding forward and off of the support provided by the tibia (the shin bone) when the knee moves. These ligaments are able to do this because they cross and tighten against each other, somewhat similar to the added strength a piece of rope gets when another piece is twisted around it. When one of the ligaments ruptures, usually the cranial one, the knee joint doesn't work properly because the femur slides forward in a motion referred to as a drawer movement, and then slides off the tibia. This disrupts weight bearing on the affected leg and the dog carries it. Often these injuries are only acutely painful for a day or two and then the dog seems to be reasonably comfortable but uses three legs instead of four for movement or strongly favors one leg.

From the dog's perspective, the most likely reason for not using the leg is that the dog has learned that it won't bear weight. When the dog tries to use the leg the femur sliding forward produces a weakness that has been referred to as a "trick knee". The knee buckles and dog catches itself with the other leg. Since the dog can't trust the leg to do its job and since dogs can move comfortably using three legs, they just stop depending on the injured leg to bear weight.

When the cranial cruciate ligament ruptures in both knees at the same time, the dog may walk in a crouched position or even drag its rear legs, making it look as if it has a neurologic injury. This is a diagnosis that many veterinary practitioners will miss. I was convinced the first dog we saw with cranial cruciate ligament ruptures in both legs had a spinal disc problem and referred the owners to an orthopedic surgeon, which was still the right thing to do --- but for the wrong reason!

The cranial cruciate ligament will rarely, if ever, heal after it is ruptured. In a small number of cases it is possible to suture the ligament together but this is usually only possible in cases of trauma, since there

is less likely to be ligament deterioration in those cases. Due to the inability to repair the ligament directly, a number of ways of stabilizing the joint through other means have been developed.

The body stabilizes the stifle joint after a cranial cruciate ligament rupture by fibrosis, or thickening, of the joint capsule. As the joint capsule thickens the entire joint becomes less flexible but the inappropriate forward motion of the femur is controlled, allowing the dog to use the joint. This process begins to stabilize the joint within a few weeks of injury, with many small dogs having sufficient strength to use the

leg comfortably within six weeks. Larger dogs take longer to regain use of the limb, often taking several months to show clinical improvement if surgery is not done to provide stability sooner.

Arthritis develops in the stifle joint due to the change in movement. The arthritic process is very persistent and will continue even when stabilization of the joint through surgical means is achieved. In addition, many dogs experience damage to the medial meniscal cartilage, leading to an increase in pain and arthritis formation. This probably also occurs primarily due to inappropriate motion in the joint.

There are a large number of surgical techniques that have been advocated for stabilizing stifle joints after cruciate ligament injuries. This is probably because there isn't a single procedure which has both stabilized the joint and stopped the progression of arthritis in a high enough percentage of patients to make it seem superior to all the other techniques. Recently, a new contender for this goal has been gaining favor, a procedure referred to as tibial plateau leveling osteotomy, or TPLO.

From a practitioner's viewpoint, the limiting factor in success of orthopedic surgeries is often the client's commitment to proper aftercare of the patient. Cruciate ligament repairs are one example of surgery for

which aftercare of the patient can be the difference between success and failure for the surgery. In some of the repair techniques it is necessary to splint or bandage the leg for several weeks post-operatively. This is difficult for many veterinary clients to manage. Enforced restriction from exercise is important in the recovery from all the present surgery techniques and since this can not be explained to the dog, the

responsibility for it falls on the veterinary client. There are definitely times when I am very hesitant to recommend cruciate ligament repairs because I know that the client can not handle the aftercare. After all, a client who is being dragged around my office by their dog's leash is not likely to be able to restrain the dog post-surgically. The ideal repair technique for CCL injuries would involve no aftercare, but that standard has not been reached yet.

My personal opinion is that cruciate ligament repairs should be done by a surgeon who does this procedure very frequently. For this reason, we send most of our cruciate ligament repairs to an orthopedic specialist. In a suburban or city practice it is more likely that the staff surgeons will have enough opportunity to do CCL repairs to develop a technique that works well for them and to be able to modify it for individual patient's needs. For very large dogs it really appears that the TPLO procedure is more

stable at this point and it is probably worth finding a surgeon who can do this procedure. It may take some effort to find a surgeon in your area though, as this technique is relatively new and it requires equipment and training that are patented and have been somewhat limited in availability until recently. At the present time there are no objective studies that I know of that compare this technique with other CCL repair procedures or with conservative care. The anecdotal testimony from orthopedic surgeons

performing the procedure is very good, though.

Due to the cost of repair and the need for aftercare, we have a large number of patients who experience cranial cruciate ligament rupture who do not have surgical repair done. We have even had a large German shepherd rupture both cranial cruciate ligaments within a few days of each other. The owner of this dog refused surgery after referral to an orthopedic surgeon. About a year later this dog walked into our practice without a perceptible limp in either rear leg. I can not recall a single patient whose CCL injury led to permanent inability to use the affected leg. However, there are a number of patients in our practice who have noticeable differences in weight bearing between the leg with the CCL rupture and the unaffected rear leg. Most patients suffer from arthritis after CCL injuries, whether they are repaired or not. Dogs with successful repairs have less arthritis and become comfortable on the leg in less time.

Orthopedic surgeons, including the authors of most texts, almost universally recommend repair of CCL injuries in all dogs, regardless of size. Veterinary practitioners often recommend repair only for patients over 35 lbs, or 50 lbs, or some other weight, based on their experiences. There are two studies to support this approach, both of which failed to show any clinical difference in patients less than 40 lbs. of body weight after six months, whether or not they had surgery. Most practitioners recommend not repairing the ligaments in cats, although it may be worth checking the stifle for cartilage damage and stabilizing it if the cat is not comfortably bearing weight on the limb within six weeks.

This is a common enough injury that your vet may be comfortable doing this surgery but it is a good idea to ask your vet about referral to an orthopedic surgeon. If you sense some relief in their voice or demeanor that you would consider traveling to a specialist, that would be an additional reason to consider going. If your dog is over 100 lbs. or if your dog is not showing good progress towards use of the affected leg within six weeks of a CCL injury, you should also strongly consider surgery, even if you were not initially inclined to pursue this option.

There is mounting evidence in humans that the use of glucosamine and chondroitin compounds limits the degree of osteoarthritis following cruciate ligament injuries. I think that it would be worthwhile to consider the use of these medications in almost any patient with a CCL injury even though there are not currently similar research results published for dogs or cats.

Pain relief medications are beneficial for a few days after the initial injury and after arthritis develops to the point that it becomes painful. Most dogs will develop noticeable arthritis in the stifle as they age if

they have had a CCL injury and most will eventually require anti-inflammatory and analgesic medications to move comfortably. Moderate exercise on a regular basis also seems to help limit the potential for

serious disability. As with almost all orthopedic conditions, weight control is a very important factor in the long term prognosis. Thin dogs do much better than obese dogs, over the long run.

Until the perfect surgery does come along, I think it there will continue to room to decide for or against surgery and to justify either decision. The major benefits of surgery are earlier comfort using the leg and less long term arthritis. I don't think it is has been proven, but many surgeons also feel that repair of a ruptured cruciate ligament helps to preserve the function of the cruciate ligaments in the opposite leg, since it doesn't have to bear as much additional weight if the surgery works well. The disadvantages of surgery include a few patients who get worse (unusual), the need to follow aftercare instructions carefully, anesthetic risk and the cost of the repair.

In the one case we have had in a personal pet, we opted for surgery because we thought the benefits were worth it. However, I only feel like my clients are making a really bad decision when they refuse surgery in obese pets and very large dogs.

Coccygeal Vertebral Luxations and Subluxations --- "Tail Jerk" or "Tail Pull" Injuries

Injuries to the tail occur in both dogs and cats, but cats seem to outnumber dogs in this injury by quite a bit. While it is possible to injure the tail in many ways, the injury we see most frequently in cats (other than abscesses) is a condition that is most commonly referred to as a "tail jerk" injury. When a pet's tail stops moving but the pet does not, the tail is pulled or jerked as the pet moves away from it. This happens

when a car tire crosses over the tail, when a bigger dog grabs the tail, when a rocking chair rocks over a tail or any similar situation occurs in which the cat is likely to be running away from a tail that is immobilized by some outside force.

The jerk on the tail causes the vertebrae making up the tail to separate from the vertebrae making up the sacral spine or to separate between tail (coccygeal) vertebrae. In some instances, the separation isn't enough to disrupt the spinal column but still produces bruising or hemorrhage in the spinal canal. In other cases there is complete separation between coccygeal vertebrae or between the coccygeal and sacral vertebrae. This usually damages the nerve roots that have left the spinal cord in the sacral region (the cauda equina) and may produce a limp tail, inability to urinate, weakness of the rear legs or even complete paralysis of the rear limbs.

It is not uncommon for these injuries to occur without any other evidence of trauma and without anyone being aware that a traumatic incident occurred, except the pet, who can't talk about it. For this reason, it is possible to overlook this possibility when examining a cat or dog having difficulty urinating and it is possible to confuse other conditions with this one.

We have seen patients who we really thought had "tail jerk" lesions who actually had spinal tumors, invasion of the vertebrae by non-spinal tumors, caudal lumbar spinal disc disease, and thromboembolisms (blood clots) in the aorta. There are probably other conditions that resemble this problem, as well.

Most of the time it is possible to diagnose this problem by palpation of the coccygeal vertebrae or through X-rays that show a separation between vertebrae. Often there is a wide separation, with several centimeters distance between the injured vertebrae in the tail. In pets showing neurologic signs suggestive of this condition but with normal appearing spinal X-rays, it can be hard to decide if a tail jerk injury is causing the clinical signs.

When there is obvious nerve damage and tail jerk is suspected, it is important to try to figure out if the neurologic signs relate to damage to nerve roots that have exited the spinal column or damage to the spinal cord itself. When the nerve roots are injured the condition is referred to as lower motor neuron (LMN) damage. When the spinal cord is damaged but the lower motor neurons are intact, the condition is referred to as upper motor neuron (UMN) damage. It is possible to have both LMN and UMN damage.

In tail jerk injuries in which the lower motor neurons have been torn away from the spinal cord, the urinary bladder is usually easily expressed by putting pressure on the abdomen. This makes caring for the cat easier, but is a bad prognostic sign because recovery of bladder function is less likely in these pets. When the bladder is enlarged and very difficult to express the lower motor neurons are usually intact and the spinal cord damaged by swelling or bleeding. While this sounds worse and makes short term care more difficult, there is a better chance of the pet recovering normal bladder function in these cases. It is critical whenever one of these injuries is present to evaluate bladder function and to make provisions to keep the bladder as empty as possible. It is sometimes necessary to catheterize the bladder and keep the catheter in place for several days. There are medications that can help a great deal by either relaxing the bladder sphincters (in UMN disorders) or increasing its muscle tone (in LMN disorders). Sometimes it is necessary to use both medications when upper motor neuron damage is present.

The medications that are most helpful for this condition are bethanechol (Urecholine Rx) and phenoxybenzamine (Dibenzyline Rx). Bethanechol causes bladder contractions and it will cause this effect even if the nerves to the bladder are damaged. It is important to be sure that there isn't an obstruction in the urinary tract, such as severe swelling, prior to using this medication. In pets with upper motor neuron signs, it is necessary to give phenoxybenzamine, or some other medication that can relax the bladder sphincters, prior to giving the bethanechol. It can take several days for these medications to work well, so it is necessary in most cases to manually express the bladder or to keep the bladder catheterized until an beneficial effect occurs.

Eventually, owners of pets with nonfunctional bladders have to learn how to express the urine from the bladder and must do this several times a day if they want their dog or cat to have a good chance to recover from this injury. Almost all of our clients who wanted to learn how to do this have been able to successfully express their pet's bladder with instruction. One cat owner in our practice expressed his cat's bladder several times a day for well over a year before moving out of our practice area. I don't know how long he continued to work with his cat but I suspect he did not stop. This kept the cat comfortable and avoided problems with urinary tract infections from urine retention.

The other complication in tail jerk cases is that the tail often will not regain feeling or movement. A tail that the pet can not move will eventually cause health problems. Stool sticks to the tail, it gets caught in things (again) and it may even become gangrenous. It is almost always better to amputate the tail if there is not evidence of movement or feeling in the tail within three weeks. In many instances it is necessary to amputate the tail sooner because the involuntary movements associated with normal daily activities are painful to the pet. Once in a while we seem to see "phantom pain" in an amputated tail but most of the time this surgery does not bother the pet at all.

Tail jerk is a common injury. It is often a frightening injury, since paralysis of the rear legs or at least weakness in the legs is very common, along with pain and difficulty urinating. Almost all pets with this

condition will recover function in the legs, most will recover bladder function eventually but many do not recover use of the tail. We have many pet owners who initially strongly favor euthanasia because they just can't believe that recover will occur or believe that the care involved will be too hard. However, many of these pet owners find they are capable of caring for their pet for the time it takes to recover and end up being happy they didn't follow their initial instincts.

Watch out for your pet's tail --- but if your pet experiences a "tail jerk" injury, don't give up without giving your pet at least three weeks or so to recover leg strength and bladder function. Some pets take even longer to recover. I'm not sure this technique works, but this is a true story: my own cat, Gracie, came home with a tail jerk injury and it was very severe. She had lower motor neuron damage, couldn't walk for about a week and didn't urinate on her own for almost two months. Gracie is a horrible patient. She tried to bite every time her bladder was expressed and we were doing it four or five times a day. She didn't like taking the medications for her bladder and we had to chase her around the house to give them. Finally, my wife looked at her one night and said, "Gracie, if you aren't peeing by tomorrow, I'm giving up on you." Gracie used the litter pan on her own the next morning.

The Things People Say...

I was at a meeting last night with a group of architects, including one who just graduated from college and appeared to me to be about 16 years old. As I mulled over asking to see his diploma, I remembered my first encounter with a client who questioned my abilities based on how old she

thought I looked.

It was after work on a particularly busy Saturday. So busy we had forgotten to lock the front door. I was sitting at the reception counter with my feet up on a filing cabinet, finishing the last of the day's records. The door burst open and a large older woman ran into the waiting room. "Good, I'm not too late! Is the doctor in?"

I looked up and said, "I'm Doctor Richards, can I help you?" She looked at me with one eye closed tight and the other about half open, peering through half-glasses perched on the bridge of her nose, her Pomeranian tucked under one arm. "You're too young to PRACTICE on my Princess!" and with that, she left as abruptly as she arrived.

I opened my own practice just short of year a after graduating from veterinary school. It was a necessity because I was so difficult to work with that I was the only one who could stand to do it. I might even have given up the arrangement, but it wasn't an available option. I went to work in a county that had never had a licensed veterinarian even though it was established in 1790. People had a lot of illusions about what a vet should look like, act like and charge for services rendered. I tend to dress casually. My mother thought the best thing about my marriage was getting to see me in a suit and tie. I have some clients who feel that a vet should dress a little more formally. One stood in the middle of the waiting room loudly talking to my receptionist above the din of the crowded room. As I walked by, he said "Is that the vet?". Linda answered in the affirmative. "Well, I'm not taking my pet to any vet who doesn't wear a tie." And he left. People ask me all the time how to evaluate a veterinary practice and I think it is hard to do. Not for that guy, though. His standards were very clear!

Early attempts at price control by county residents included, "You know, Doc, here in the country it's customary for a veterinary to look at the dog for free and only to charge if something can be done for him" and "I never heard tell of anyone charging for a dog that died." In fact, some of this attitude tended to occur in high places in the county. I worked for five days to save the only truly adult dog I can remember having parvovirus. It was an older doberman and was affected by the disease in the initial outbreak in our county in 1981.

Despite hospitalization and medical care based on the best understanding of the disease at that time, the dobie died. The owner refused to pay for the care. We took her to small claims court. After determining that we were owed the money, the judge asked, "Do you want a lien against the dog?" Considering that he clearly understood it was dead, I think he was conveying his attitude towards medical care for pets!

I can't count the number of times that people have looked at me after getting an estimate for the care of their dog and said something like, "Well, that's sure a lot more than a .22 shell." Some of these people actually leave at this point. At least three or four times a year someone asks us, in total seriousness,

"Do you use anesthesia when you spay (or neuter) a dog?". There may be some basis for this question where we live because there are still a couple of the original "animal doctors" who worked our area prior to the arrival of licensed vets and sometimes continue to do so. I know for absolute certain that one of them actually did spay procedures without anesthesia. I can't even begin to imagine that, but a friend of mine did the humane investigation for that case and I spoke with two of the pet owners who allowed their pets to be spayed by this man. Still, I don't know why anyone would think so little of me as to imagine that I would routinely inflict that kind of pain on my patients.

Michal's favorite statement is still probably, "Yes, my dog needs a distemper shot. He has a really bad temper!"

I have a technician who has worked with me for the entire twenty years I have been in practice. This has entailed riding along on farm calls, being in the exam room for almost all the office visits and sometimes working the front desk at the practice. I have a wife, Moe, who I have been married to for twenty-four years, too. She stayed at home much of the time to raise our kids until our youngest was two years old and then she went to veterinary school five hours away for several years. She worked at another veterinary hospital for a brief time but for the last few years we have worked together. Many of my clients know that my wife and I work together but have not quite figured out who is who in the office and assume I am married to Sonja. One of these clients asked Moe if my wife was around. She replied, "I am Mrs. Richards." To which the client said, "No you're not, I know Dr. Richards' wife and you're not her." Moe, a little dumfounded, answered, "Well, when I roll over at night, he's the man I bump into!"

Moe's favorite client quote was "Oh, you're Doctor Richards, too? Is it fun working with your father?"

I did a preceptorship rotation at the Henry Doorley Zoo, in Omaha, Nebraska. At that time, the zoo was a mixture of very old and very new zoo ideas, with some cages left over from the zoo's origin decades earlier and some natural exhibits. At one of the older exhibits, a red howler monkey with about an eight foot arm span was housed in a circular cage with a rail to keep the zoo patrons about 3 feet away. Anytime she wanted, this monkey could grab someone. She wasn't inclined to do this, but it was a definite possibility. She didn't like to have her space invaded much, though. One day, as the head primate keeper and I approached this monkey's cage we noticed a woman leaning far over the railing and pressing a young child against the cage bars. The keeper immediately picked up speed and reached the cage quickly. "Keep that child behind the railing!", she said crisply, followed by "all monkeys will bite if you push them." The woman looked at her calmly and said, "It's OK, its not my kid".

I like philosophy. Sometimes I don't understand client's philosophical choices, though. I had a client tell me, absolutely seriously, that it was against her personal beliefs to spend more than a hundred dollars on her dog when there were people starving in Africa. I didn't get the connection but I might have thought the philosophy legitimate except that the woman was wearing several thousand dollars worth of jewelry and drove up in a Mercedes Benz convertible.

I have a client, Payton, whose cat has had a kidney transplant. This procedure costs about $10,000 over the course of the first year, for the workups, surgery and aftercare involved. As this client was explaining the adaptations they had made in their household to accommodate their cat, another client leaned over and said "Don't you think it is silly to spend that much money on a cat?" I have always liked the reply from Payton, who said, "I know a lot of people who have found far more selfish ways to spend $10,000, without feeling the least bit guilty."

My personal favorite client line comes when I tell a pet owner that their female dog is pregnant when they are sure she can't be, because: "The only male she is with is her son and he wouldn't breed his mama!"

Quick Notes

We had our first case of maggot infestation this week. Usually this occurs when a patient develops diarrhea which gets caught up in their hair or has a skin infection that weeps serum and attracts flys. It only takes four to six hours for flies to lay eggs and for maggots to appear. It is critically important to keep patients with diarrhea clean and preferably inside when it is fly season. Skin disease, especially when mats are present that trap skin exudates, is also attractive to flies. Keep hair clipped around hot spots and use medications to keep these sores dry. It is important to treat maggots quickly when they are found in order to limit damage to the skin and secondary bacterial infections.

Please pay careful attention to the packaging when applying flea control products to cats. So far this summer we have treated three cats for poisoning from "one spot" flea control products containing permethrin. These products are only approved for dogs and they do have warning labels stating they should not be used on cats but it is easy to get confused when dealing with multiple pets and some people just miss the label warnings. If you do accidentally apply a product like Defend (tm), Bio-Spot (tm) or Control (tm) for dogs on your cat, wash it off as soon as you realize the mistake was made. Do this even if your cat is already showing signs of toxicity or it has been a day or two since applying the product.

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                                  The opinions expressed in this newsletter are those of
                                                     Michael Richards, DVM., author.

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