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Canine Legg-Perthes Disease

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Legg-Perthes Disease or necrosis of the femoral head involves blood supply to the head of the femur in the hip joint being disrupted, causing loss of hip function and secondary arthritic change. It appears to be associated with a recessive gene and is inherited.

LEGG CALVÉ PERTHES DISEASE

By Fred Lanting

Fred is the author of the book on HD, and lectures worldwide on orthopaedic disorders. His seminar info is available from mailto:Mr.GSD@Juno.com.

A disorder sometimes easily mistaken for hip dysplasia is Legg Calvé Perthes disease, perhaps more frequently referred to by the dog fancier as “Legg Perthes”. This is an aseptic (not infected), developmental necrosis (dying of tissue) of the femoral head and neck, found almost entirely in toy or other small breeds. On radiographs, it often looks as if the bone is "rotting away", and lameness is the major or only symptom. Has a history in human medicine, too. As a matter of fact, that's where it was first discovered in 1910 by three researchers working independently. Legg, Calvé, and Perthes saw a flattening of the femoral head (coxa plana) in affected youngsters and thought that trauma was at the heart of its etiology.

Schnelle in the 1930s first saw the disorder in the canine in Wire Haired Fox Terriers, and Moltzen Nielsen in Germany about the same time saw it mostly in the Wires but also in a few other breeds since then, puppies between 3 and 10 months, of many other small, toy, and miniature breeds have been affected.
Radiographic ("X ray"} signs of Legg Perthes are usually gross and discouraging, as many cases are not referred to the vet or the specialist for diagnosis until the dog has been limping for a long time or the disease has progressed to the point that it becomes a more real problem to the owner.

These small dogs put so little weight on their tiny hip joints that they almost can compensate for discomfort by "walking on their forelimbs instead of their four limbs". Many are couch potatoes" or spend much time being carried, but even then, picking up an affected dog in a certain manner can put more pressure on the joint than normal locomotion, so pain at that time is often the stimulus to do something about it. Owners have reported "incredible pain" and constant, progressive discomfort, inability to stay long in any one position, and bone lysis (loss through a process akin to dissolving or consuming) at other areas in the limb distal (further away, the opposite of proximal) to the hip.

The earliest radiographic signs, should you look for them before they change, include an increased radiodensity (opacity as seen on the radiograph) in the lateral part of the epiphysis of the femoral header Lateral means the part away from the mid line or medial; the "outside". Resorption of necrotic (dying, rotting or decomposing) trabecular bone cells is next accompanied by a lysis (dissolving or being consumed) of bone, replacement attempts by the body (similar to the attempt to replace bone that takes place during HD remodelling), and eventually fracture or collapse like a frame house riddled by termites. As HD may or may not be concurrent, the congruity of the ball and socket coxofemoral joint might still be maintained until collapse.

Cause
The most probable cause is a genetic weakness that allows abnormal or inadequate blood supply to the ossifying epiphyses. That's the ends or caps of long bones which are changing from cartilage in the embryo to bone in the adult. Depending upon breed and particular bone portion, all ossification is usually complete by 12 months of age.

Compression/pinching of the blood vessels in that area leads to the necrosis (death) of cartilage and bone tissue. One idea was that some of these little dogs have excess and premature levels of androgen and estrogen (hormones) that influence this process.

Treatment
Various treatments have been suggested but the usual one is excision (surgical removal) of the femoral head and neck, again with a similarity to the operation performed on dogs.

Conservative treatment (as opposed to 'heroic measures such as surgery) has been suggested for those unilaterally limping dogs (lame on only one side and supported well by the other limb) with good congruity and no collapse or deterioration. The dog's worse limb is put into an Ehmer sling for a time, perhaps as much as a couple of months, then the dog is kept in a crate to minimize activity for another few weeks perhaps, during which time the dog is periodically radiographed. If this approach is successful, the resorbed bone is replaced in a normal manner and radiopacity returns, indicating normal bone cells and regained strength. In such an incidence, aseptic necrosis is halted and then reversed by keeping the dog's weight off the limb. Lameness has been reported to cease in perhaps a quarter of dogs treated conservatively, but much of this estimate depends on owners' reports rather than always being followed up by veterinary examination.

A syndicated column called "To Your Good Health" in the Clarksburg (WV) Telegram of June 30, 1994 included a brief discussion by Paul Donohue, M.D., responding to a reader's request for advice. Her 8 year old child had recently been diagnosed with Legg Calvé Perthes disease and she saw no improvement after 3 months in a brace. By the way, human infants with HD are put into slings or casts which keep the legs spread apart until the joint begins to strengthen; did you know that people get HD, too? Anyway, Dr. Donohue told her that the Legg Calve Perthes disorder involved a cutting off of the blood supply to the epiphysis (top part of the femur) and that it might take more than a year for the brace to rest the hip enough so that restoration of blood supply can help restore bone there. If unsuccessful after that long a wait, surgery may be needed. So you see, your dogs aren't the only ones at risk for this problem.

Some cases of Legg-Perthes go unreported or misdiagnosed. To some veterinarians, the radiograph looks like hip dysplasia, and it is not sent in to OFA, GDC, or PennHIP for diagnosis and recording of data. If you come across a case of Legg Perthes in your non toy breed, please get me a copy of the radiograph and medical report, even if only on loan till I can make a copy for my Orthopaedics files. Thanks. Send them to me at 3565 Parches Cove Rd., Union Grove AL 35175 8422.

COPYRIGHT Fred Lanting
Used with permission

Copyright Fred Lanting, All rights reserved, but reprinting allowed after permission. Please read his other articles on http://siriusdog.com/sphider/search.php?query=lanting&search=1 , for example, or e-mail him at: Mr.GSD@netscape.com or Mr.GSD@Juno.com for specific articles.

Editor’s Note: A well-respected and frequent GSD specialty and all-breed judge for many clubs around the world, with KC and other-country credentials, Mr. Lanting since 1966 has lectured on Gait-and-Structure, Canine Orthopedic Disorders, and other topics, and has judged in about 30 countries. He has been described by a former OFA director as the world’s leading non-veterinarian authority on hip dysplasia. He has lectured at numerous veterinary schools in the USA and abroad, and is the author of the following “must read” books for the dog owner (E-mail for curriculum vitae). “Canine HD and Other Orthopedics Disorders” : This expanded revision is a comprehensive (nearly 600-page), amply illustrated, annotated, monumental work that is suitable as a coffee-table book, a reference work for breeders and veterinarians, and a study adjunct for veterinary students. It is equally valuable for the owner of any breed. It covers every aspect of HD and other orthopedic, bone, or spinal disorders, and includes genetics, diagnostic methods, treatment options, and the role of environment. Your autographed copy will be mailed from the USA as soon as the appropriate amount is received and is processed. Pricing: US $68 in the U.S., or ask about mail overseas. Combine orders with “The Total German Shepherd Dog” by the same author ($50 plus $4 postage). 17 of the 20 chapters are suitable for owners of any breed. Order both at once direct from the author, and the postage will be waived.

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The above information is simply informational. It's intent is not to replace the advice of a veterinarian nor to assist you in making a diagnosis of your pet. Please consult with your own veterinarian for confirmation of any diagnosis. Your pets life may depend on it.