Following a previous column in the September 2010 issue of Veterinary Practice News (“Early Surgery Is Only Option for Some Conditions”), we tackle two more conditions that should be treated surgically earlier rather than later.
Let’s review medial patellar luxations and perineal urethrostomies.
They may not seem related in any way, except that we often see patients who have endured months to years of lameness or repeated episodes of urinary blockage.
Medial Patellar Luxation
This radiograph shows an MPL in an 18-month-old husky.
Medial patellar luxation (MPL) may seem like a minor malfunction. Pet owners routinely tell us that when their dogs are limping, they “rub the leg” and make it all better. So it’s no big deal, right?
Actually, it is important to understand that MPL is not merely a mechanical problem. It is a lifelong, slowly deteriorating disease that invariably leads to various degrees of degenerative joint disease (DJD).
Surgery involves three parts in most cases. The first step is a trochleoplasty to deepen the trochlea, which is often too shallow to keep the patella in place. Using a bone rasp to merely “deepen the groove” can be done, but it is certainly not ideal. The whole idea is to save the trochlear cartilage.
The second step is the tibial crest transposition. With an MPL, it is classically rotated medially, thereby allowing the patella to luxate medially (the reasoning is basically the opposite for a lateral patella luxation). The tibial tuberosity is separated with a chisel, displaced laterally and kept in place with pins.
Urethral catheter placement in a blocked 2-year-old cat.
The third step is a lateral imbrication, which aims at shortening the stretched lateral patellar ligament. The synergistic goal of all three steps is to keep the patella in the trochlea.
We seem to deal with two groups of patients: either puppies or young dogs who cannot function, jump on the sofa or leap into the car. These are typically the best candidates for surgery, before cartilage damage is too advanced. Treated early, these canine (or feline) patients typically have an excellent prognosis.
The second group involves middle aged patients who have “bone on bone” contact. The surgery is the same, but with more DJD—which we can’t do much about at that stage. When the patella slides in and out of the femoral trochlea, it damages the cartilage. After a few years of wear and tear, the cartilage of the “lip” of the trochlea may be gone and we end up with “bone on bone” contact. And that’s painful.
This 8-year-old cat has a large bladder and a urethral stone.
At worst, patients with a grade 4 MPL can have severe rotational deformities of the femur and the tibia. It is especially important to recommend early intervention in these patients, or they may need more complicated and costly procedures involving corrective osteotomies of the femur and/or the tibia, which usually require bone plating.
Other possible consequences of not performing early surgery, besides DJD and bowing of the bones, include muscle atrophy, ACL rupture and pain.
In good hands, few complications occur, and in the vast majority of cases, MPL is curable with surgery. An important factor is for early surgery to minimize DJD and ensure optimal quality of life. In any case, joint supplements and an arthritis diet should be recomended.
It is impressive to see how many male cats become blocked. General practices, cat clinics and emergency clinics are all too familiar with feline urethral blockage, an absolute medical emergency. A common scenario is that a middle-aged cat is found vocalizing, straining to urinate, severely painful, as the owner comes back from a hard day’s work. A classic pitfall is when clients mistakenly believe their cats are constipated since they may keep going back and forth to the litter—thereby delaying treatment.
Despite years of research, the etiology of this complex disease is often mysterious, except when tiny bladder stones end up blocking the urethra. Standard initial treatment includes the often challenging urethral catheterization, diuresis, pain management, as well as uremia and hyperkalemia therapy. The fluid of choice may be a buffered solution such as lactated Ringer’s solution (yes, in spite of the small amount of KCl it contains) as opposed to saline. Saline is acidic, so LRS helps reduce acidosis better.
Forceful catheterization can lead to an embarrassing urethral tear. As much as we don’t like this conversation, we must communicate this possibility to the owner during the consultation.
At worst, delayed treatment or aggressive cystocentesis can cause bladder rupture, which increases pain, complicates the clinical picture and increases the final bill.
Once the patient is stable, the dilemma is to decide when the urinary catheter can be safely removed and when the cat can reasonably be sent home. Instructions should include changing the diet, reducing stress and enriching the environment. An excellent website about environment enrichment (now for cats and dogs) is indoorpet.osu.edu created by Dr. Tony Buffington at the Ohio State University.
When a cat experiences multiple obstructions, the topic of definitive surgical treatment should be brought up. Repeated episodes of medical management add up financially, to a point where a cat owner may not be able to afford surgery anymore. This rarely ends up in a happy manner. So again, early surgical intervention may be the best option.
Unfortunately, we don’t have clear data to tell us how many episodes of urinary blockage are “acceptable” before surgery should be performed. That decision may be financial and emotional as much as medical, and it is therefore based on an ongoing conversation with the owner.
It is very important to always take abdominal and pelvic radiographs preoperatively (lateral and ventrodorsal views) for at least two reasons.
First, we need to document whether the patient has bladder stones, which would require a cystotomy. If a cystotomy is performed, current standard of care requires that radiographs should be taken postop to document removal of all bladder stones. Second, the entire urethra should be included in the views to visualize a stone in the distal urethra.
Surgery involves a perineal urethrostomy (P/U). Sure, complications occur, such as urethral stenosis, but in the vast majority of cases, the prognosis is excellent, as long as the urethra is sutured to the skin at the level of the bulbo-urethral glands. The urethra is wide enough at that level, and should ensure life-long urination happiness. And by the way, please don’t call a P/U a “sex change operation.”
Lameness and intermittent urinary blockage seriously decrease our patients’ quality of life. Medical management of these conditions can be unrewarding. Let’s keep in mind that we can make a tremendous difference in the lives of these patients by recommending surgery early in the disease process.
The Four Grades of Medial Patellar Luxation
Grade 1—The patella can be manually luxated and immediately goes back into place when manual pressure stops.
Grade 2—The patella can be physically luxated and remains out of place until it is manually reduced or the patient extends the leg.
Grade 3—The patella is permanently luxated but can be manually reduced when the leg is extended.
Grade 4—The patella is constantly luxated and cannot be manually reduced.
Dr. Phil Zeltzman is a mobile, board-certified surgeon near Allentown, Pa. His website is www.DrPhilZeltzman.com.