SAOP1- Patellar Luxation

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  1. What musculature is involved with the anatomy of the patellar mechanism? Describe how they form the patellar mechanism.
    • rectus femoris
    • vastus lateralis, intermedius, and medius
    • all the muscle converge on the patella and continue as the patellar ligament, which inserts on the tibial tuberosity
    • this is an EXTENSOR apparatus
  2. What structures add secondary support to the patellar ligament?
    joint capsule, femoropatellar ligaments
  3. For a stable patella, the extensor apparatus must...
    have all elements (musculature, ligaments) align along the femoral shaft, trochlear grove, and tibial tuberosity
  4. Most patellar luxations are __________, ____________, and __________ and occur due to...
    congenital; bilateral; medial; malalignment of the quadriceps due to anatomical deformation
  5. Describe the etiology of patellar luxation.
    • abnormal femoral neck angle- either coxa vara (decreased femoral neck angle) or coxa valga (increased femoral neck angle)
    • femoral varus/ valgus
    • quadriceps pulls tibial crest medial or lateral
    • trochlear groove doesn't develop or becomes too shallow
  6. Describe the grades of patellar luxation.
    • Grade I: minimal malalignment, patella wants to ride in grove but can be luxated by force, asymptomatic, no txt
    • Grade II: luxation occurs intermittently, patella wants to ride in the grove but luxates easily, often young animals, sx indicated if painful and progressive lameness
    • Grade III: permanent luxation but patella can be reduced into the groove, significant lameness, often young animals, surgery indicated
    • Grade IV: permanent luxation, patella cannot be reduced, trochlear groove not developed, severe gait abnormalities, very young animals (congenital), surgery indicated
  7. What are clinical signs of patellar luxation? (11)
    • may be asymptomatic
    • skipping steps, knee may lock then go back to normal
    • lameness
    • pain
    • abnormal gait
    • abnormal stance
    • mechanical lameness (quads needed for extension)
    • lameness due to pain
    • joint capsule stretching
    • abrasion of articular cartilage
    • concurrent cruciate tear is very common
  8. How is patellar luxation diagnosed? (4)
    • palpation standing- dynamic
    • palpation recumbant- passive
    • internal or external rotation of tibia
    • radiographs- assess DJD
  9. Describe how you palpated  medial versus lateral patellar luxation.
    • Medial: stifle fully extended, internal rotation of tibial, push patella medially
    • Lateral: stifle partially flexed, external rotation of tibia, push patella laterally
  10. For what patellar luxations is surgery indicated?
    • some grade II
    • all grade III and IV
    • when there is pain from bone on bone contact
    • when there is mechanical lameness
  11. Describe methods of stifle joint bone correction. (2)
    • Deepen trochlear groove (trochleoplasty)
    • Realign quadriceps mechanism
  12. Describe trochleoplasty.
    • wedge or block resection
    • chondroplasty
    • abrasion sulcoplasty
    • patellar groove replacement
  13. How is surgical realignment of the quadriceps mechanism achieved?
    • tibial tuberosity transposition
    • anti-rotation suture (tibio-fabellar suture)
  14. Describe the surgical approach to the stifle.
    • standard craniolateral stifle arthrotomy- incision from proximal to the patella to distal to the tibial tuberosity
    • joint exploration- assess cruciates, flip patella over and assess cartilage, assess cartilages of femur
  15. Describe the surgical aspects of trochlear wedge resection.
    • deepen groove until ~50% of the patella is recessed below the trochlear ridges
    • "V-shaped" wedge
  16. What are the pro and con of trochlear wedge resection?
    • Pro- maintains hyaline cartilage
    • Con- can be difficult to deepen the most proximal and distal aspects of the groove
  17. Describe the surgical aspects of trochlear block resection.
    deepen groove as a rectangle instead of a "V-shape"
  18. What are the pros and con of trochlear block resection?
    • Pros- maintains hyaline cartilage, great in large dogs b/c they have more bone, better recession proximal and distal in groove
    • Con- not good in small dogs with small bones
  19. Describe the surgical aspects of trochlear resection and abrasion sulcoplasty.
    • rasp, rongeur, or burr to create the groove
    • defect fills with fibrocartilage and patella fixes to it
  20. What are the pros and con of trochlear resection and abrasion sulcoplasty?
    • Pros- easy to perform, can create custom groovedefect fills in with fibrocartilage
    • Con- removes normal hyaline cartilage
  21. Describe the surgical aspects of chondroplasty.
    • performed in immature animals only (<6 months old), before the cartilage attachment is very strong
    • peel up cartilage
    • remove subchondral bone to deepen groove
    • replace cartilage flap
  22. What is the goal of the tibial tuberosity transposition?
    align quadriceps mechanism
  23. Describe the surgical aspects of tibial tuberosity transposition.
    • cut tibial tuberosity with osteotome, sagittal saw, or bone cutters
    • transpose it laterally for medial luxation or medially for lateral patellar luxation
    • affix tuberosity with K-wires/ pins/ tension band wire- aim K wire parallel to joint, place proximally in widest portion of tuberosity
  24. What is the goal of placing anti-rotational suture?
    rotate tibia laterally (externally) to align the quadriceps
  25. Describe the surgical aspects of anti-rotational suture.
    • suture placed from lateral fabella to tibial crest (same as lateral suture)
    • used in dogs with CCL tear or if the tibial tuberosity transposition is problematic
    • provides ancillary support only!! not a sole correction
    • changes joint configuration
  26. What soft tissue changes occur with correction of patellar luxation?
    soft tissue adapt to position of patella over time- contracts on luxated side, stretched on non-luxated side
  27. What soft tissue release can be done after surgically correcting patellar luxation? (3)
    • incise joint capsule on side of luxation (capsulotomy)
    • release retinaculum on side of luxation- start proximal to tibial attachment of patellar tendon, continue to level of patella as necessary
    • muscle release- quadriceps femoris
  28. Describe soft tissue imbrication after surgical correction of patellar luxation.
    • Remove excess soft tissue on side opposite of luxation (joint capsule, fascia- not too much!)
    • imbrication on side opposite luxation- close capsule with appositional pattern or imbrication with horizontal mattress, retinaculum with mayo-mattress suture pattern
  29. What are complications of surgical correction of patellar luxation? (5)
    • overcorrection
    • undercorrection
    • pin-related issues (too far into soft tissue, pin migration, broken pins)
    • delayed healing of osteotomy or failure of TTT
    • fracture of distal femur, patellar tendon laceration
  30. What is the prognosis with patellar luxation?
    • good to excellent for low-grade luxations
    • fair to good with higher grades
    • warn owners about 10% relaxation rate

Card Set Information

Author:
Mawad
ID:
325457
Filename:
SAOP1- Patellar Luxation
Updated:
2016-11-08 01:04:25
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vetmed SAOP1
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vetmed SAOP1
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