Dog Owner's Home Veterinary Handbook.pdf - Mr. Walnuts

among littermates who have one dysplastic parent. Experience shows that
repeatedly using only dogs with normal hips for breeding stock significantly
reduces the incidence of hip dysplasia in susceptible bloodlines.
Information on breed risk is available through the OFA and PennHip. In
breeds in which hip dysplasia is a particular problem, prospective puppy buyers
are advised to check pedigrees for OFA, PennHip, or GDC certifications,
particularly for sires and dams. Ideally, you will also be able to find evaluations
of littermates of the sires and dams, as well as the grandparents.
LEGG-PERTHES DISEASE
Legg-Perthes disease is caused by a vascular necrosis of the femoral head.
Avascular necrosis means death of bone in the head of the femur resulting
from an interruption in the blood supply. It is not clear what causes this, but
genetic factors may be involved.
The disease occurs most often in toy-breed puppies between 4 and 11 months
of age. Large breeds are occasionally affected. Avascular necrosis occurs in both
hips in about 15 percent of cases. Occasionally, it is the result of a traumatically
dislocated hip caused by trauma such as an auto accident or a fall from a height.
Weight bearing causes the dead bone beneath the cartilage of the femoral
head to collapse. This fractures the cartilage and causes a gradual destruction
of the hip joint.
Signs are severe lameness and sometimes the inability to bear weight on
the leg. Muscle wasting is pronounced and the joint loses some range of
motion. The affected leg may be shorter than the opposite normal leg. A standard
X-ray of the hips and pelvis establishes the diagnosis.
Treatment: Medical therapy involves restricting activity and administering
analgesics. Some dogs may improve, but surgery generally produces the
best results. Surgery involves either a femoral head and neck excision arthroplasty
or a total hip replacement, as described in Hip Dysplasia, page 392. It is
difficult to do hip replacement surgery on very small dogs.
The GDC maintains a Legg-Perthes registry, which is now merged with
OFA, for breeds in the Terrier Group. OFA also has a Legg-Perthes registry for
a variety of breeds. The determination can be made from standard hip X-rays.
LUXATING PATELLA (SLIPPING KNEECAP)
THE MUSCULOSKELETAL SYSTEM • 397
The patella, or kneecap, is a small bone that protects the front of the stifle joint
on the rear leg. The patella is anchored in place by ligaments and slides in a
groove in the femur called the trochlea. If the groove is too shallow, the patella
will slip out when the knee bends. When the patella slips out to the inside of
the knee joint, it’s called medial luxation. When it slips out to the outside, it’s
called lateral luxation.