by Fred Lanting
Fred is the author of the book on HD, and lectures worldwide on orthopedic disorders. His seminar info is available from <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 Wirehaired 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 remodeling), 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 orthopedics files. Thanks. Send them to me
at 3565 Parches Cove Rd., Union Grove AL 35175 8422.