Hip Replacement
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What is total hip replacement?
A total hip replacement is a procedure in which the orthopedic
surgeon replaces a painful or damaged hip joint with an artificial
one. The hip joint is a "ball and socket" joint made of two bones.
These bones are partially removed and a metal and plastic
artificial implant, or "prosthesis," is placed to function like a
normal hip. Removal of the affected hip joint eliminates the source
of pain and lameness, thus allowing the patient to return to a
normal level of activity. The new artificial hip provides a pain
free joint substitute, and as such, limb function and activity
level return to normal.
LEGEND: A) arrows - diseased
femoral head, asterisk - disease acetabulum. B-D) closed arrows -
femoral component of THR, open arrows - bone cement; thin arrows -
acetabular component of THR, asterisk - remaining
acetabulum.
Total hip replacement radiographs (x-rays) A) Pre-op view of an
arthritic hip. B) Post-op view of a completely cemented THR. C)
Post-op view of a completely cementless THR. D) Post-op view of a
hybrid THR, in which a cemented femoral component and cementless
acetabular component were used.
Why is total hip replacement necessary?
The most frequent indication for total hip replacement in dogs
is the relief of pain and lameness caused by severe arthritis
secondary to hip dysplasia, or fractures (breaks) and dislocation
of the bones that make up the hip joint. Many dogs with arthritic
and painful hips function fairly well with pain medication and
exercise restriction, but when a painful joint is removed and
replaced with an artificial hip, there is often a dramatic change
in the patient's activity, lameness, muscle mass, and
personality.
How do I know if my dog needs a total hip replacement?
A complete physical, orthopedic, and neurologic examination will
be performed by an orthopedic surgeon. A complete history of how
and what your dog has been doing at home will be an important part
of the decision making process. Common clues that a total hip
replacement might be needed include hind limb lameness, reluctance
to rise or jump, inability to exercise, pain after exercise,
decreased activity, and loss of muscle mass.
Radiographs (x-rays) of a dog with hip arthritis, secondary to
hip dysplasia, before and after hip replacement.
Are there reasons why my dog shouldn't have a total hip
replacement?
Yes. If your dog suffers from skin, ear, dental, or urinary
infections, or shows evidence of other potential sources of
weakness or lameness, total hip replacement will not be performed.
Other common causes of hind limb problems in dogs include rupture
of the cranial cruciate ligament and neurologic problems such as
intervertebral disk disease. Once these underlying problems are
addressed and resolved, total hip replacement may again be
considered. If a femoral head ostectomy (FHO) has already been
performed, total hip replacement is extremely challenging and the
chances of success are much lower. Finally, your dog must be
finished growing (skeletally mature), so most dogs must be at least
10 months old before a hip replacement can be performed.
How does the total hip replacement procedure work?
Under general anesthesia, the surgeon removes the cartilage and
bone that make up the hip joint. The diseased femoral head (the
ball) is replaced with a metal implant on a stem that fits inside
the femur (thigh bone). The diseased part of the pelvis (socket) is
replaced with a plastic or combination metal and plastic cup. The
new hip is designed to allow the joint to move in an identical
manner to a normal hip. The implants are very durable, and are
anchored in place using either bone cement (cemented hip
replacement) or by the dog's own bone actually growing into the
implants (cementless hip replacement). For more information on
veterinary total hip implants, please visit www.biomedtrix.com .
Biomedtrix cementless (BFX) total hip replacement implants.
Long-term implant stability is achieved as the patient's bone grows
into the porous portion of the implants. Photo courtesy of
Biomedtrix.
Biomedtrix cemented (CFX) total hip replacement implants.
Long-term implant stability is achieved by placing bone cement
inside the bones, then securing the implants into this bed of bone
cement. Photo courtesy of Biomedtrix.
Should I stop all of my dog's medications before surgery?
Medications prescribed to treat systemic problems such as
hypothyroidism should not be stopped. Medications for hip pain
(aspirin or other non-steroidal anti-inflammatories, like Rimadyl®)
should be stopped 3-5 days before the initial exam. If your dog is
taking corticosteroids, or antibiotics, these medications should be
stopped for a minimum of 2 weeks prior to surgery.
Will surgery be performed the same day as the initial
exam?
No. Dogs undergoing evaluation for hip replacement must be
carefully screened. A thorough physical exam, labwork (complete
blood count, serum chemistry, urinalysis and urine culture), and
specialized x-rays must be completed before surgery is considered.
If problems are detected it might indicate that your dog is not a
good candidate for the surgery. If the initial tests reveal no
abnormalities, surgery is usually scheduled for 1-2 days after the
initial exam.
What about my dog's recovery and care after surgery?
Most dogs can stand and walk on the new hip implants the day
after surgery and are able to go home after 3-5 days of total
hospitalization. However, total hip replacement patients must be
confined to a crate and allowed outside only on a leash to
eliminate for 3 months after surgery. While at home, care should be
taken to avoid walking on slippery surfaces, and long flights of
stairs are not allowed. After the first 4 weeks of crate
confinement, SLOW, 5 minute leash walks are started 2-3 times a
day. These leash walks are increased by 5 minutes each week, until
leash walks are 20 minutes long. These 20 minute leash walks are
continued for 4 additional weeks, at which time the dog is returned
to Texas A&M for re-examination and x-rays.
What are the benefits of a total hip replacement?
The main benefit of total hip replacement is the total relief of
a painful hip joint. Dogs are very good at concealing pain, so once
the affected hip joint is replaced, the dog's activity and attitude
improve dramatically. Once the pain and inflammation associated
with surgery resolve, many dogs can discontinue the daily pain
medications that were previously required to control the signs of
hip pain and arthritis. Total hip replacement is the best surgical
option for an arthritic, painful hip, but it does carry some
risk.
An orthopedic surgery team performing a total hip replacement at
Texas A&M University's Veterinary Medical Teaching
Hospital.
What are the risks of total hip replacement?
There are risks associated with any anesthesia and surgery. Your
veterinarian or orthopedic surgeon will discuss these risks with
you. The reported complication rate following total hip replacement
in dogs is between 7 and 12%. With total hip replacement, it is
critical that complications are identified and treated early.
Complications can be minor, such as swelling at the incision site
(seroma) or a low-grade infection of the skin surrounding the
incision. However, there are three major complications that can
lead to failure of the hip replacement and more surgery. These
include:
Dislocation of the implants
(luxation).
Implant luxation occurs in approximately 2-4% of cases and
usually occurs in the first 3 months after surgery. Dislocation of
the implants may be corrected manually under anesthesia, but often
a second surgery is required.
Infection of the implants.
Infection of the new hip is a serious and catastrophic problem.
If the infection is limited to the skin and surgical wound,
long-term antibiotics may control the problem. If the implants
themselves become infected, removal of the entire hip replacement
is required.
Loosening of the implants.
Loosening can occur either due to low-grade infection or due to
"aseptic loosening", a condition in which the dog's own body
decides to reject the implant. Aseptic loosening occurs in 5-15% of
cemented total hip replacements. If aseptic loosening develops, the
hip implants may have to be removed or replaced.
Is total hip replacement permanent?
In most dogs, the replaced hip will last for the dog's life. In
fact, studies have shown that 90-95% of dogs have good to excellent
function with this procedure. Hip replacement provides years of
pain-free activity that would otherwise not have been possible.
With the arrival and use of newer implants such as the cementless
total hip (also known as press-fit or BFX), the future looks
promising for dogs of all ages and sizes that need total hip
replacement.
A PDF document of this information is available for
printing.
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