Chihuahua Vol. 9, No. 1 ■ May 2010

Breeders Are Encouraged to Health Test for Patellar Luxation

lifelong breeder-owner-handler more about patellar luxation and Legg- pain while running and playing. The of Staffordshire Bull Terriers, Calve-Perthes disease. She sought dog pulls the affected hind leg off AKathy Bolin of Foxsong Chihua - breeding advice from Shirley Banderet the ground and begins hobbling on huas was a newcomer to the breed of B-Z-B Chihuahuas in Glendale, Ariz., three legs. After a few minutes, the in 2004 when a puppy she had just and joined her as an advocate for health rear leg drops back to the ground, begun showing was diagnosed with testing for patellar luxation and regis - and the dog resumes a normal gait. luxating patella, a painful, potentially tering the results in the CHIC (Canine “Most commonly owners report crippling genetic disease. Though the Health Information Center) database noticing intermittent lameness char - Chihuahua, named “Seamus,” had maintained by the Orthopedic Foun- acterized by a skipping gait and/or an been giving Bolin hints about having dation for Animals (OFA). extended leg, where the dog sticks the the condition, she hadn’t noticed. A Chihuahua breeder for 56 years, leg out behind,” says James L. Cook, Seamus was reluctant to stack Banderet had years of wisdom and D.V.M., Ph.D., DACVS, director of the squarely, and he occasionally moved experience to share with Bolin. “I Comparative Orthopaedic Laboratory at one of his hind legs just enough so it generally do not breed dogs until they the University of Missouri in Columbia. was no longer parallel with the other are 2 ½ years old,” Banderet says. “Owners also may notice a dog’s inabil - one. Bolin repositioned him each time, “This allows time for multiple health ity to jump, weakness in the hind limbs, unaware that stacking was uncom - evaluations. I usually have dogs checked reluctance to run or exercise, abnor - fortable for the dog. by a veterinarian at 8 weeks of age, mal crouching or standing, abnormal One unforgettable day, while Bolin 4 months and 1 year. After that, dogs appearance of the hind limbs, and was stacking Seamus on the table to are evaluated at annual checkups. bouts of crying out in pain.” be judged at the Toy Dog Breeders “I take health checks seriously. Luxating patella can cause tempo - Association of Southern California Dog After all, we are the caretakers of this rary or permanent pain and lameness, Show, she heard and felt the dog’s toy breed. It is not fair to perpetuate and can occur in one or both rear legs. patella (kneecap) pop. With limited health problems and cause pain for dogs The patella, or the bone known as the experience in the breed, Bolin, of La because of our breeding practices. We kneecap, is part of the stifle joint. In Quinta, Calif., was unsure about what are responsible to the dogs we breed.” normal dogs, the patella moves smooth - had happened. ly up and down a deep groove in the “I wasn’t aware of the knee prob - Sometimes an Intermittent Condition lower end of the thighbone. lems Chihuahuas can have," Bolin says. Many breeders of toy and small In dogs with patellar luxation, the "My veterinarian determined that breeds have learned to recognize alignment of the patella and quadri - Seamus had a bad knee. I then had all signs of luxating patella due to its ceps muscles is “off center,” and the my dogs evaluated. The veterinarian prevalence. The typical scenario is a groove is often too shallow, which referred me to an orthopedic specialist Chihuahua that suddenly yelps in Continued on page 2 with ‘Tiffy,’ who was just 10 months old. The specialist confirmed that Tiffy had a severe case of luxating patella, with How to Take Part in Patellar Luxation Database a Grade 3 luxation in the left stifle (knee) and a Grade 4 luxation in the reeders and owners of Chihuahuas are encouraged to have their dogs right. Radio graphs also showed that Btested for patellar luxation. The condition occurs when the patella Tiffy had Legg-Calve-Perthes disease, (kneecap) pops out of place causing pain and sometimes lameness . a genetic disorder that can lead to Patellar luxation is one of three conditions for which the Chihuahua Club degenerative joint disease, in the of America encourages health testing. The other two are eye disorders and right hip.” congenital heart disease. The parent club also encourages breeders to register Though the news was heartbreaking, health test results with the Canine Health Information Center (CHIC), a central both orthopedic conditions can be database and DNA bank sponsored by the Orthopedic Foundation for Animals managed surgically. Days later, Tiffy and the Canine Health Foundation. underwent surgery on her left patella The benefits of health testing and reporting the results publicly in the and was spayed. Six months later, CHIC database are many. CHIC provides a parent club with recommended surgery was performed on the second health screening protocols and standardizes testing methods. It also pro - patella and the femoral head of the vides a database to archive data, promote more informed breeding decisions, hip joint was removed to alleviate increase awareness of health issues and testing, and promote betterment of the Legg-Calve-Perthes disease. the breed through the pursuit of breeding healthier dogs. The data also can Though the severity of Tiffy’s case be used by researchers who study demographic information across breeds. was rare, the experience didn’t discour - For information about the patellar luxation database, visit the OFA Web age Bolin from breeding Chihuahuas. site at www.offa.org/patluxgeninfo.html . It did, however, motivate her to learn Patellar Luxation position. A dog carries the leg or reduced in a bloodline. Still, it’s never continued from page 1 moves in a crouched position with certain that it will not reappear. the leg flexed. “The dilemma is that while you’re causes the patella to jump sideways, “Interestingly, dogs that are more selecting against patellar luxation, you inside or outside the groove in the lame are often Grade 2, where the may introduce other heritable prob - joint. Most commonly the displace - patella pops in and out on its own, lems,” Roush cautions. “As a result, it ment occurs toward the inside of the rather than Grade 4, where it’s out is important to not cull dogs with joint, known as medial patellar luxation all the time,” says James K. Roush, quality traits because this could result (MPL). Lateral patellar luxation (LPL), D.V.M., DACVS, professor of clinical in reducing genetic diversity. Dogs or displacement that occurs toward the sciences at Kansas State University that carry this mutation also carry outside of the joint, is less common. College of Veterinary Medicine. other important good genes that Luxation can also result from trauma. In dogs with Grade 4 patella lux - breeders may not want to lose from Experts believe the alignment prob - ation, “we typically see marked bone the breed.” lem occurs during skeletal growth deformities of the femur and/or tibia,” “Ideally, you would not breed pairs and that this can result in a shallow Cook says. “Surgery is recommended, that produce puppies with patellar groove that allows the patella to but it is very involved with multiple luxation, especially if there is a high become displaced. Other causes osteotomies. We typically have to incidence and high severity,” Cook include weak ligaments that fail to cut the femur and tibia in multiple says. “As with everything genetically hold the patella in place, tight liga - places and do internal fixation, which based, you have to consider all factors ments that do not allow for sufficient involves using bone plates to straighten and strike the best balance of desirable flexibility, and a developmental lag out the limb and make the patella and nondesirable traits when breeding.” between the time it takes for a dog’s seat align and track correctly. These As for Tiffy, who is now 5 years old, legs to grow to maturity and cartilage are major surgeries with higher costs she has fared well since her surgeries. to mineralize. All these structures and and complication rates and more Following her veterinarian’s direction, processes are affected at least to guarded prognoses.” Bolin continues to give Tiffy medica - some extent by genetics. A physical examination combined tions that include an anti-inflamma - Treatment for patellar luxation is with radiography helps veterinarians tory, and she tries to make sure Tiffy based on severity and the cause of diagnose patella luxation. “Radiographs is comfortable and pain-free. the condition. Dogs can be affected will only find patellas that are ‘out,’ “Tiffy is a little trooper,” Bolin says. as early as 8 weeks of age; however, as in Grade 3 or 4,” Roush says. “They “Through it all, she has had lots of health test results are not accepted in will miss Grade 1 and 2 luxations spunk. When she feels good, she’ll the patellar luxation database main - because the patella may not be dis - even gallop a little. She is a happy tained by OFA until dogs are 12 months placed at the time of the X-ray. The little dog.” ■ of age. Based on health tests submitted only way a radiograph can find Grade 1 from 1974 to 2009, the Chihuahua or 2 luxation is if secondary osteo ar- breed ranks 22 out of 93 breeds includ - th ritis is detected; however, osteoarthri - Purina appreciates the support of ed in the database. Of the 638 Chihua - tis may not be present or may be due the Chihuahua Club of America hua evaluations entered in the database, to something other than patellar and particularly Beverly Fritzler, 94.5 percent were normal tests and luxation. A physical examination is D.V.M., chairwoman of the CCA 5.5 percent were affected dogs. the diagnostic method of choice.” Health Related Issues Committee, “If a dog is normal at 2 years of Not a condition that improves over in helping to identify topics for age and has had no indication of time, patellar luxation can lead to the Purina Pro Club Chihuahua luxating patella, then it is uncommon lameness and osteoarthritis. Medical Update newsletter. to see clinical problems develop later,” management includes restricted exer - Cook says. cise and nonsteroidal, anti-inflamma - Veterinary orthopedic specialists tory medications for low-grade patella grade a dog’s luxation according to luxation. Surgery, used for more severe, severity, ranging from Grade 0, indi - high-grade cases, consists of returning Want to Reach the Editor? cating a normal state, to Grade 4, the the patella to its proper position to Have comments about Purina Pro Club most severe form. Owner education correct the anatomical abnormality. Update ? Send them to us at: Purina Pro is important to effectively monitor a Dogs with Grades 1 to 3 luxating Club Update , c/o Editor, Nestlé Purina dog’s movements and determine patella generally have a good to excel - PetCare, 2T Checkerboard Square, whether the condition is worsening. lent prognosis, says Roush, noting that St. Louis, MO 63164 or via e-mail at Classifications for each grade based even dogs with Grade 4 luxation can today’[email protected]. on OFA criteria are: have quality lives with careful moni - • Grade 1: The patella is usually in a toring. “The limited factor is the length normal position but can be manu - of time the luxation has occurred and ally pushed out of place. Once the the degree of secondary osteoarthri - Send Us Your Questions patella is displaced, it promptly tis present at the time of surgery,” Have questions about your Purina pops back to the normal position. he says. • Grade 2: The patella can be in a Points or how to redeem weight cir - cles for rewards and rebate checks? normal or luxated position. Frequent Prudent Breeding Recommendations Contact Purina Pro Club at 877-PRO - luxation in some cases becomes Breeding recommendations for CLUB, or 877-776-2582, between more or less permanent. If luxated, dogs diagnosed with luxating patellar 7 a.m. and 5 p.m. Central time Monday the patella can be placed into a should be made cautiously. “Patellar through Friday. You also may visit normal position and will stay there. luxation is most likely a complex www.purinaproclub.com to review If in a normal position, it can be genetic disease involving several and redeem Purina Points . manually luxated and will remain genes,” Roush says. “Breeders can in that position. select against the disease by not • Grade 3: The patella is permanently breeding dogs diagnosed with it, but luxated. Although it can be placed this isn’t complete assurance.” manually into a normal position, it The prevalence of luxating patella will promptly pop back into the in Chihuahuas is not known. Patellar luxated position. luxation may affect some but not all • Grade 4: The patella is always in a puppies in a litter. The more genera - luxated position and cannot be tions bred without the condition, the manually pushed back into a normal stronger the indication the disease is

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