Patellar luxation ortho Flashcards
Where does the patella sit normally
In trochlear groove on cranial edge of the femur
What is the purpose of the patella
to give quadriceps a mechanical advantage so it can apply more force
What are common findings anatomically with patella luxation
Coxa vara
Femoral torsion
Distal femoral varus
Shallow trochlear groove
Absent medial trochlear ridge
Internal torsion of food
Medial torsion of tibia causing bow string effect
Epidemiology of patella luxation
More so small and toy breed dogs
More so medial luxation
Occasionally taumatic
What causes the lameness in patella luxation
There is abnormal loading through the stifle causing osteoarthritis, excess wear and wear esp of medial trochlear ridge in medial patellar ligament
- Get both pain and mechanical lameness
Diagnosis of patella luxation
Must do conscious
- Flex and extend stifle feeling patella for crepitus + spontaneous luxation
- Try and push patella out of the groove in extension
Why do we try and luxate patella out of the groove in extension
This is where the ridge is the narrowest
Grading patella luxation
1 = patella can be manually luxated with stifle in extension but then immediately reduces
2 = patella spontaneously luxates when manipulated then reduces when moved again
3 = patella luxated permanently and can be manually reduced
4 = Patella is luxated permanently and cannot be reduced manually
Radiographic views for patella luxation
Mediolateral
Craniocaudal
Can do skyline view to look at the trochlear groove depth
Conservative management of patella luxation
Weight management
Exercise restriction
NSAIDs and analgesia
Joint cupplements
Physiotherapy and hydro
What are some deformities we may try and correct with surery
1) Too shallow femoral trochlear sulcus
2) Malalignment of the quardiceps mechanism
3) Distal femoral varus/femoral torsion
4) Medial tissues too tight
5) Lateral tissues too loose
Suggested approach for patella luxation based on grade
Grade 1 = rarely needs intervention as asymptomatic
Grade 2-4: needs surgery if persistent significant clinical signs
May opt for surgery earlier in young patients to prevent deformities occuring and needing more aggressive surgery
Options for dealing with a shallow femoral trochlear sulcus in patella luxation
Wedge recession trochleoplasty; remove wedge of bone and cartilage
Block recession trochleoplasty which is similar but block shape to allow more proximal section to be removed i.e where luxation more likely
partial parasagittal patellectomy
Artificial trochlear ridge enlargement
Patella groove replacement = salvage procedure to place prosthetic
What must we remember when doing a wedge recession trochleoplasty
Must take cartilage and bone otherwise it won’t heal
How does a trochlear chondroplasty work and when can we do it
Only in very young patients
Elevate flap of cartilage, remove some bone underneath and flap back down
This cartilage can survive in patients <6 months
When might we do a partial parasagittal patellectomy
Where the patella is flat and discoid it may not be able to fit into the block resection
–> Trim the sides off the patella and then it can sit better in the block recession
Done in some cats
What can we do to deal with malalignment of quadriceps mechanism with the patellar groove
Tibial tuberosity transposition; move tibial tuberosity laterally to deal with medial luxation and fix it on to shift patella insertion more towards midline
What surgery can we do where there is distal femoral varus or femoral torsion
Distal femoral osteotomy; closing wedge removat
Where medial tissues are too tight in patella luxation what can we do
release medial quadriceps
NB: done in combination with other things
What are antirotational sutures for with patella luxation
To exert torsional force
But must be done in combination with other things
What can we do where lateral tissues are too loose in patella luxation
Lateral retinacular imbication = closing lateral arthrotomy to overlap muscles tightly
Post-op care for patella luxation
- Crate confinement 6 weeks
- Little and often lead walks; 5 mins 5 times a day
- Avoid high impact activity
- Radiographs after 6-8 weeks to check bone healing etc
- Physiotherapy can be usefu
Prognosis for patella luxation with surgery
Good for grades 2-3
Fair for grade 4 but worse where OA already present, muscle atrophy, severe bone deformities
What must be aware of if an older dog is acutely lame and we notice medial patella luxation
May actually be cranial cruciate ligmanet rupture (and has always had patella luxation)
What else do we do after a tibial tuberosity transposition
Place two pins and tension band wire
to resist tension from quadriceps
