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| PATELLAR LUXATION SURGERY AT AMERICAN ANIMAL
CARE CENTER |
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Introduction
- The patella (commonly known as the kneecap) normally
rides in a groove at the bottom of the femur at the level
of the knee joint in a groove called the trochlear groove;
Fig 1 and 2 show a front view of the knee joint; Fig 1
demonstrates the patella in the groove, where as Fig 2
demonstrates the knee cap dislocated out out of the groove
(P=patella; F=femoropatellar ligaments which hold the
patella in the groove; PL=patellar ligament; G=trochlear
groove that the patella rides in). Fig 3 demonstrates
a skyline view of the trochlear groove and the patella
- you are looking down the thigh or femur bone toward
the knee joint; take note of the deep groove that is found
in a normal animal.
- Patellar luxation is caused by congenital abnormality
usually at the level of the hip joint and results in abnormal
forces on the kneecap, which cause it to eventually ride
outside of the groove. The groove becomes very shallow
and the attachment of the ligament of the patella may
be malpositioned on the tibia bone. If the patellar luxation
occurs in immature animals, the tibia and femur bones
become twisted.
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Below left is a an illustration
of a normal limb with normal alignment of the femur
bone, tibia bone, quadriceps muscle group (red),
patella (brown) and the attachment of the patellar
ligament (grey) to the tibia. Below right is a dog
that has a deformity of the femur bone which causes
the hind limb to be "bow-legged" and has
resulted in the patellar luxation.
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Clinical signs
- Lameness
- a skipping gait
- pain
- stiffness of the hind limb
- Some pets show only a single sign, whereas others show
many signs of the condition
- Failure to treat the condition could lead progressive
debilitating arthritis of the joint
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| Surgery |
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If the groove
that the patella rides in is shallow or misshapen,
it is surgically deepened; we usually use an advanced
technique to perform this called the block osteotomy
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If the attachment
of the patellar ligament to the tibia, called the
tibial crest, is in the wrong position, it is repositioned
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The capsule of
the knee joint is tightened; this tightens the femoropatellar
ligament
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In some dogs
the femur bone is fairly twisted and needs to be
cut and realigned
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A support bandage
is usually not used after surgery so that physiotherapy
can be started soon after surgery
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Convalescence
- By 10 to 14 days after the surgery your pet should be
touching the toes to the ground at a walk
- By 2 to 3 months after surgery your pet should be using
the limb well
- If your pet does not follow a normal progression of recovery,
the surgeon should be notified
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Prognosis
- Surgery has approximately a 90% success rate. Success
is defined as the return of good function of the limb
- Unfortunately surgery will not remove the arthritis that
may already be present in the knee. As a result, your pet
may have some stiffness of the limb in the mornings or after
laying down for a nap. In addition, your pet may have some
lameness after heavy exercise
- By having the surgery done earlier, the chance of developing
significant arthritis is decreased
- Dogs that have a higher grade of patellar luxation may
have increased risk for reluxation of the patella
- Large breed dogs that have patellar luxation may have
increased risk for reluxation of the patella if a corrective
femoral osteotomy is not performed
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Potential complications
- There is an inherent risk of anesthetic death with any
procedure requiring anesthesia, however, this is very small
- Infection of the surgical site, although not common, can
occur
- If a pin is used for alignment, it may migrate or even
break and may require a second surgery.
- If exercise is not minimized for 8 weeks after the surgery,
breakdown of the repair may occur, thus requiring a second
surgery
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