Patellar luxation ortho

Question 1

Where does the patella sit normally

Answer 1

In trochlear groove on cranial edge of the femur

Question 2

What is the purpose of the patella

Answer 2

to give quadriceps a mechanical advantage so it can apply more force

Question 3

What are common findings anatomically with patella luxation

Answer 3

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

Question 4

Epidemiology of patella luxation

Answer 4

More so small and toy breed dogs
More so medial luxation
Occasionally taumatic

Question 5

What causes the lameness in patella luxation

Answer 5

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

Question 6

Diagnosis of patella luxation

Answer 6

Must do conscious
- Flex and extend stifle feeling patella for crepitus + spontaneous luxation
- Try and push patella out of the groove in extension

Question 7

Why do we try and luxate patella out of the groove in extension

Answer 7

This is where the ridge is the narrowest

Question 8

Grading patella luxation

Answer 8

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

Question 9

Radiographic views for patella luxation

Answer 9

Mediolateral
Craniocaudal

Can do skyline view to look at the trochlear groove depth

Question 10

Conservative management of patella luxation

Answer 10

Weight management
Exercise restriction
NSAIDs and analgesia
Joint cupplements
Physiotherapy and hydro

Question 11

What are some deformities we may try and correct with surery

Answer 11

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

Question 12

Suggested approach for patella luxation based on grade

Answer 12

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

Question 13

Options for dealing with a shallow femoral trochlear sulcus in patella luxation

Answer 13

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

Question 14

What must we remember when doing a wedge recession trochleoplasty

Answer 14

Must take cartilage and bone otherwise it won’t heal

Question 15

How does a trochlear chondroplasty work and when can we do it

Answer 15

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

Question 16

When might we do a partial parasagittal patellectomy

Answer 16

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

Question 17

What can we do to deal with malalignment of quadriceps mechanism with the patellar groove

Answer 17

Tibial tuberosity transposition; move tibial tuberosity laterally to deal with medial luxation and fix it on to shift patella insertion more towards midline

Question 18

What surgery can we do where there is distal femoral varus or femoral torsion

Answer 18

Distal femoral osteotomy; closing wedge removat

Question 19

Where medial tissues are too tight in patella luxation what can we do

Answer 19

release medial quadriceps
NB: done in combination with other things

Question 20

What are antirotational sutures for with patella luxation

Answer 20

To exert torsional force
But must be done in combination with other things

Question 21

What can we do where lateral tissues are too loose in patella luxation

Answer 21

Lateral retinacular imbication = closing lateral arthrotomy to overlap muscles tightly

Question 22

Post-op care for patella luxation

Answer 22

• 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

Question 23

Prognosis for patella luxation with surgery

Answer 23

Good for grades 2-3
Fair for grade 4 but worse where OA already present, muscle atrophy, severe bone deformities

Question 24

What must be aware of if an older dog is acutely lame and we notice medial patella luxation

Answer 24

May actually be cranial cruciate ligmanet rupture (and has always had patella luxation)

Question 25

What else do we do after a tibial tuberosity transposition

Answer 25

Place two pins and tension band wire
to resist tension from quadriceps