Surgical Stabilization of a Medial Patellar Luxation
Dogs are frequently presented to a veterinarian for intermittent or consistent lameness or reluctance to walk or jump. When a small or miniature breed has this symptom, the patella could be in a luxated position and need to undergo surgery.
Where is the patella located?
The patella or “kneecap” is a small bone that protects the knee joint. It is located at the front of the knee where both femur and tibia join together. During the walk, the patella slides up and down within the groove of the femur.
What is a medial patellar luxation?
It is when the patella moves outside of the femoral groove. The term “medial luxation” refers to the patella moving outside the groove towards the inside (median plane) of the knee. The severity of patellar luxation is defined by four grades: grade I, II, III, and IV; “grade four” being the worst. When the patella is in a luxated position (outside the groove) it affects the normal biomechanics of the knee joint.
Who are the candidates for surgical stabilization of patellar luxation?
Any dog showing a constant or intermittent lameness due to patella luxation of a grade equal or superior to two (II). It mainly affects small breeds, in particular: Pomeranians, Yorkshire terriers, chihuahuas, French bulldog, Cavalier King Charles, Pugs, Jack Russel, miniature Poodles, Maltese… not forgetting cats.
Why are small breeds most affected?
Causes for patellar luxation are genetic and include:
- Lack of depth of the femoral groove – while growing up the groove does not develop properly and remains very shallow causing the kneecap to be floating over the surface of the femur.
- Growth bone deformity of femur and tibia – this is also called the “bowed-legged conformation” existing in some breeds of dogs. As the puppy (kitten) grows, the powerful quadriceps muscle of the thigh starts applying forces on the patella towards the inside of the knee. Concurrently the same forces affect the tibial crest which starts to rotate internally, thus aggravating the severity of the patellar luxation.
What are the main objectives of the surgery?
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- Restoring normal biomechanics of the knee joint
- Preventing developments of significant arthritis (largely detrimental to the knee).
- Reducing worsening of limb deformity
- Reducing risk for the development of cranial cruciate injury
What are the surgical steps of patellar luxation surgery?
- Wedge sulcoplasty – this is a procedure where after an approach into the knee joint the surgeon will restore appropriate depth within the femoral groove.
- Tibial crest transposition: this is another very important surgical step. The tibial crest is partially cut using an “osteotome” and repositioned towards the lateral side so that it falls just under the groove of the femur. This way both the groove and a tibial crest become perfectly aligned. At this stage, two small pins are inserted into the bone to fix the tibial crest in position.
- Soft tissue reconstruction: In patients with patellar luxation, the muscles surrounding the knees and the joint capsule itself are very tight, pulling the patella out of place. Therefore, it is necessary to rebalance and re-distribute the forces of these soft tissues during reconstructions. Often the surgeon will also need to create a release incision on the capsule medially.
Figure 1: X-ray showing the “bow-legged syndrome” on a 3-year-old Pomeranian with both patella in luxated position and tibial crests rotated internally.
Figure 2: X-ray of a normal knee showing the patella within the groove and the tibial well aligned with the femur
Figure 3: Post-operative views of a patella re-positioned within the groove (right view) and tibial crest realigned and fixed with two small pins
Prognosis and aftercare
In our experience at Al Barsha Veterinary Clinic, more than 90% of owners are satisfied with the outcome of the surgery with a normal return in function on the operated knee. Post-operative relapses exist but their incidence is low with 10% or less of the operated dogs. Post-operative infection is a rare complication. The outcome on arthritis development is good but operated dogs might need to remain on anti-arthritic food supplements.
After surgery, the doggy will start using his/her leg within two weeks after surgery. Doggy will have to observe an exercise restriction of 4 to 6 weeks which can be followed by a rehabilitation program, but this is often not necessary since the leg function is always better after surgery than before.
Contact our clinic at 04 340 8601 for consultation or for routine surgeries or advanced surgical treatments for your pet in Dubai.
Written by Dr. Mehdi Mzabi, ABVC Partner and Veterinarian