Patellar Ligament Disease. - Soozoo Canine · PDF file · 2011-09-21Patellar...
Transcript of Patellar Ligament Disease. - Soozoo Canine · PDF file · 2011-09-21Patellar...
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Patellar Ligament Disease.
The patellar ligament disease is a condition of the stifle where the cartilage keeping the
patella in place over knee joint is weakened or damaged. The patella is held in place by
ligaments and slides in a groove in the femur called the trochlea and should be inline as
shown in the picture below on the left.
If the groove is too shallow, the patellar will slip out when the knee bends which is a
patellar luxation (as shown in the picture above on the right). Patellar luxation is usually
an inherited defect, which occurs during the developmental stages of the fetus and is
rarely as a result of trauma. The patella luxates, which causes pain in the limb and the
dog has difficulty in weight bearing on the affected leg.
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The anatomy in patellar luxations revolves around the relationships among the femur,
tibia, pelvis, and hock joint. The relationships among these structures determine the
position of the soft tissues and therefore whether the patella sits within the trochlear
groove or beside it. The medial and lateral femoropatellar ligaments are delicate bands
of loose connective tissue that connect the patella to the fabella on the lateral surface
and the periosteum of the epicondyle of the femur on the medial side A medial patellar
luxation is when the patella slips out going to the inside of the leg (as shown in the
picture above) and is more common in the small breeds (i.e. toy and miniature dog
breeds). The dog may have a gait, which is sometimes normal and sometimes
abnormal, as the patella may slip in and out of place. When it is out, the affected leg is
usually carried with the joint bent and the foot turned inward.
A lateral patella luxation is when the patella slips out going to the outside of the leg (as
shown in the picture above) and is more common in the large breeds (i.e. rottweillers,
1. Patella
2. Femur
3. Patellar ligament
4. Tibial Tuberosity
5. Medial Luxation of Patella
6. Lateral Luxation of Patella
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german shepards etc) and is usually seen in dogs between 5 to 6 months old. The dog
develops a knock-kneed type of stance and the foot often twists outward as weight is
placed on the affected leg.
The examining veterinarian will often make a diagnosis from a physical examination
however, x-rays are needed to determine the degree of arthritis, and deturmine any
malformation of the femur and tibia, the two major bones in the leg, which are joined
together at the knee. The X-ray below shows a severer skeletal abnormality of a medial
patellar luxation in a dog.
There are four grades of patellar luxation based on the severity as follows:
1. Patella can be luxated but returns to normal position when released and the
dog is not lame.
2. Patella luxates with the stifle flexion or on manual manipulation and remains
luxated until the stifle is extended or manually moved into place. The dog will
have intermittent lameness and/or will have occasional skipping gait.
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3. Patella permanently is luxated which can be manually returned to normal
position but spontaneously reluxates. The dog will usually be persistently
lame which will worsen with time.
4. Patella permanently luxated and cannot be manually moved back into
position. The dog will be lame also walks in a crouched position and cannot
fully extend the joint.
Surgical Techniques Trochleoplasty This procedure involves deepening the trochlear grove using a bone rasp, bone burr or
rongeurs which removes the articular cartilage and subchondral bone to achieve 50% of
the patella height. The healing process forms fibrous scar and fidrocartilage in the
groove.
Removing articular cartilage
and bone with a bone rasp,
power burr, or rongeurs to a
depth at which the patella rides
within the new sulcus.
The medial and lateral
trochlear ridges are made
parallel to each other and the
base of the groove
perpendicular to each trochlear
ridge.
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Trochlear Wedge Recession This procedure also deepens the trochlear groove while preserving the articular
cartilage. A ‘V’ shaped cut is made and the wedge of bone is removed, a thin wafer of
bone is removed from both sides of the wedge before it is replaced in to the groove.
This results in the patella sitting deeper in the trochlear groove preventing it from
slipping out.
Trochlear Block Recession
Trochlear block recession deepens the trochlear groove to restrain the patella and
maintain the integrity the patellofemoral articulation. In larger dogs, an oscillating saw is
often used, but in smaller breeds and toy breeds, a fine-toothed, hand-held saw or the
cutting edge of a scalpel blade and mallet may be used to make the cuts in the trochlea
as shown below.
15/04/2011 20:21Medial patellar luxation
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Medial patellar luxation
FIG. 33-136: Trochlear wedge recession. A, Resect an osteochondral wedge from the patellar groove. B, Remove bone from the sides of the incisedgroove to deepen the sulcus. C, Replace the osteochondral wedge.
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Chondroplasty
The hyaline cartilage is lifted from the subchondral bone so that the bone underneath
can be deepened to increase the depth of the groove. The cartilage is then replaced.
Tibial Tubersity Transposition This procedure is carried out if the tibial tuberosity is deviated medially, improving the
alignment of the patella mechanism. It involves sawing through the tuberosity, leaving a
small periosteal attachment distally. The tuberosity is then swiveled until the muscle and
patella are in a straight line. Finally the tibial tuberosity is then pinned in its new position.
Trochlear block recession. A, Use a thin saw blade to make two parallel cuts, axial to both trochlear ridges. B, Use an osteotome from proximal and distal to elevate an osteochondral block from the patellar groove. C, The bone from the bottom is removed from the incised block to deepen the sulcus. D, The osteochondral block is then replaced.
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Medial Desmotomy A desmotomy is simply a release of the medial or lateral retinaculum on the side toward
which the patella was luxated. When the patella luxates medially, retinacular tissues on
that side contract and either prevent reduction of the luxation or provide enough tension
to easily reluxate the patella. The incision is usually left open to prevent tension from
redeveloping.
Lateral Capsular Imbrication
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Tightening the joint capsule, known as imbrication, is
done on the opposite side of the luxation to prevent the
kneecap from having enough slack to pop out of the
trochlear groove. A medial patellar luxation is treated with
a lateral imbrication, and vice-versa also the joint capsule
can be loosened on the side of the luxation, this is called
a release incision. This procedure relieves the tension that
the joint capsule is placing on the patella, allowing it to
ride in the trochlea. In severe cases a synthetic suture is
sometimes necessary to keep the kneecap in place. It is
placed on the side opposite the luxation, and goes from
behind the femur to the patellar tendon. It also prevents
the kneecap from popping over to the other side.
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Corrective Osteotomies A corrective osteotmies is the repositioning of the lateral patellar luxation and is
accomplished by medial and lateral arthrotomy incisions on either side of the patella,
beginning at the tibial tuberosity and extending proximally to above the patella. The
tibial tuberosity is then osteotomized and relocated medially in a new position, which is
aligned properly for the patella to ride in the trochlea.
If the attachment of the patellar ligament to the tibia (this is called the tibial crest) is in
the wrong position, it is repositioned. This is done by creating a cut in the tibial crest
(see picture above) and reattaching the bone in a position so that the patella is
realigned within the trochlear groove. Pins are used to fasten the bone in place, which
will remain in place unless they migrate out of position or a bubble of fluid (seroma)
develops over the end of the pin. The soft tissues along the side of the patella usually
are stretched and are tightened to provide additional support to keep the patella in the
trochlear groove. The femur bone may be twisted in some dogs, which worsens the
condition of the luxating patella.
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Aftercare After consultation with the veterinary surgeon the postoperative patient can have
hydrotherapy but caution in the beginning must be taken. Swimming might be too
strenuous for an unstable joint, especially early after surgery. Some vets consider the
underwater treadmill is a better alternative, because there the dog is allowed to exercise
under better control and quietly in a closed kinetic chain. When the dog enters the
hydrotherapy centre it is important that the dog does not slip on the wet floor and should
remain on a stable surface. Measurements of the limbs chest and waist before the initial
hydrotherapy session, which is repeated after each fifth session to highlight muscle,
gain. The hydrotherapist should also help the dog to enter and leave the pool to also
prevent the dog from slipping / falling when using the ramp. Short swims are to be
conducted at first to build up the muscles, which have been lost post operation. During
each rest period the dogs limb is to be monitored for signs of reduced weight bearing on
the affected limb as it is essential excessive stain is not put on the joint. I also highlight
to the owner the importance that the dog does do any running, jumping or climbing
stairs during recovery period.