Stifle

Question 1

Tx options for upward fixation of the patella (UFP)

Answer 1

1. Conservative - exercise (hills etc) to develop quadriceps musculature, IA chondroprotection etc
2. Injection of counter irritants eg 2% iodine in almond oil andethanolamine oleate
3. Medial patella ligament desmoplasty (splitting) - particularly the proximal 1/3 of the ligament
4. Medial patella ligament desmotomy

Question 2

Outcome of MPL desmoplasty (splitting)

Answer 2

Good px; 17 of 24 (71%) horses returned to work; 3 of 17 (18%) returned at a higher level, 12 of 17 (71%) at same and 2 at lower level Complications: minimal - tx failure (need desmotomy) - recurrence of UFP seen in upt 33%

Question 3

Outcome of MPL desmotomy

Answer 3

Variable reports in the literature, 1 reports states 94% success rate but may be assoc. w. high complication rate

Question 4

Complications of MPL desmotomy

Answer 4

1) femoropatellar joint instability leading to OA,
2) Fragmentation of the apex of the patella
3) distal patellar fibrillation and/or subchondral lysis
4) Femoropatellar synovitis; persistent effusion
5) Medial patellar ligament fibrosis or enthesiopathy
6) Persistent low grade lameness

Question 5

5 meniscal ligaments

Answer 5

Cranial ligament of the medial meniscus

Cranial ligament of lateral meniscus

Caudal ligament of medial meniscus

Caudal ligament of lateral meniscus

Meniscofemoral ligament of the lateral meniscus

Question 6

Recumbency and limb position for ASY

Answer 6

Dorsal recumbency

Extension for FPj (cannon roughly vertical)

90° flexion for the femorotibial joints

Question 7

Cranial cruciate origin and insertion

Answer 7

Origin: caudolateral intercondylar fossa (10 o’clock position in the intercondylar fossa on CC rad

Insertion: Axial aspect of the MICET

Question 8

Caudal cruciate origin and insertion

Answer 8

Origin: craniomedial intercondylar fossa

Insertion: caudomedial border of the medial tibil condyle

Remember named as per cr/cau insertions on the tibia

Question 9

Collateral ligament origins and insertions

Answer 9

Medial and lateral femoral epicondyles

Medial inserts on medial tibial condyle extending into metaphyseal region

Lateral inserts on fibular head

Question 10

Long extensor origin

Answer 10

Extensor fossa of the lateral femoral condyle

Question 11

Lateral extensor origin

Answer 11

Proximal tibia/head of fibula and lateral collateral insertion

Question 12

Popliteal tendon origin and insertion

Answer 12

Origin: Just distal to lat collateral ligament on the lateral epicondyle of the femur

Insertion: ?medial tibia

intra-articular and divides the caudal pouch of the lateral femorotibial joint into proximal and distal compartments within its synovial diverticulum.

Question 13

Most common site of FPj OCD

Answer 13

Lateral trochlear ridge - proximal 1/3

Question 14

Most common patella fracture configuration

Answer 14

Medial parasagittal

Typically occur while the joint is in partial flexion e.g. when jumping over a fixed obstacle hunting or eventing. Patella is fixed against the trochlea in flexion so direct trauma causes contact with the more prominent medial trochlear ridge, hence fracture is medial of midline

Question 15

Standard tx for medial parasagittal patella fractures and size limitations

Answer 15

Fragments lass than 1/3 of the size of the patella are best tx with ASY removal

Need to dissect free from medial patella lig, medial femoropatella lig and parts of the vastus medialis tendon

Question 16

Indications for internal fixation of patella fractures and recommended screw size in adults

Answer 16

Rarely performed

Indications incl. transverse fractures and sagittal fractures exceeding 1/3 the size of the patella

5.5mm cortex screws are recommended in adult horses

Question 17

Method of fixation of transverse patella fractures

Answer 17

Combination of lag screw fixation and cranial tension band with 1.25mm diameter cerclage wire, or screws plus cranial plate

The complete disruption of the quadriceps apparatus is a typical feature of transverse, but not sagittal or parasagittal patellar fractures. Tension band or cranial plate therefore required to oppose the loading in tension that these fractures are subjected to

Question 18

Grades of congenital patella luxation (from Fubini and Ducharmme)

Answer 18

I - intermittent luxation. Can be manually luxated in full stifle extension but readily returns to normal position once released

II - intermittent luxation. Can be manually luxated in full stifle extension, and does NOT readily return to normal position when released

III - Permanent luxation. (permanent crouched posture). Patella can be manually repositioned but reluxates once released

IV - Permanent luxation - can’t be manually repositioned. Trochlear groove is flat and LTR deformed

Question 19

Ddx for patella luxation (F&D)

Answer 19

1. Femoral nerve deficits (difficult calving)
2. Distal femoral fracture
3. Patella fracture
4. Femoropatella ligament ruptures (traumatic)

Question 20

Tx for patella luxations (F&D)

Answer 20

Grades I and II - conservative - can be productive

Grade III - lateral patella release, medial imbrication +/- trochleoplasty

Grade IV - lateral patella release, medial imbrication & trochleoplasty +/- tibial tuberosity repositioning (light/young animals)

Question 21

Techniques for sx management of congenital (or traumatic) lateral patella luxation

What is the expected athletic prognosis?

Answer 21

2 main techniques have been described

(i) fascial release with imbrication
(ii) reconstructive surgery with or without release and imbrication techniques

Reconstructive techniques such as trochlear sulcoplasty, are typically reserved for cases where there is an underlying congenital trochlear hypoplasia contributing to the patellar luxation. In cases of traumatic patellar luxation with no underlying congenital trochlear hypoplasia, trochlear sulcoplasty is likely unnecessary, and increases the risk of post-operative complications

Typically, the prognosis for return to athletic function following surgical repair of patellar luxation is guarded to poor

Question 22

According to Frazer et al 2019 vet surg, what happens to compressive, tensile and shear stress with addition of a 2cm3 void in the MFC

Answer 22

Compressive stress incr by 25%

Shear stress incr. by 50%

Tensile stress incr by 200%

Question 23

What effect does an MFC void have on the stresses in the meniscus (Frazer 2019 Vet Surg)

Answer 23

Increases compressive and shear stress by upto 30%. May help to explain the relationship between MFC lesions and medial meniscus damage

Question 24

Return to intended use following stifle ASY in Western performance horses (QH) reported by McCoy et al (VS 2019)

What were negative prognostic factors (4)

Answer 24

40% return to intended use

Less chance of return to intended use in older horses, increased duration AND severity of lameness, partial thickness cartilage lesions

No IA or systemic PO therapies had a demonstrable beneficial effect on outcome

Question 25

According to the finite element model of Frazer et al (VS 2019) which screw position is most beneficial for stimulating new bone formation WRT MFC cysts

Answer 25

PDO - proximodistal oblique screw in lag

Orients the compressive stresses across the SBC thus promoting new bone formation.

Increasing screw compression, load and cyces (steps) per day (steps) likely increases the rate of new bone formation, therefore hand walking exercise should be provided from 2 weeks PO

Question 26

Quadriceps femoris anatomy

Answer 26

4 heads

1) The rectus femoris (RF) origonates on the pelvis (long head)
2) Vastus lateralis (VL) - originates proximally on the lateral aspect of the femur, at the base of the great trochanter. It is covered proximally by the tensor fascia latae and gluteus superficialis muscles and by the fascia latae itself on the rest of the muscle body. The distal part of the VL fuses with the RF muscle
3) Vastus medialis (VM) - originating on the medial aspect of the femur close to the femoral neck. It is connected caudally to the sartorius and adductor muscles
4) Vastus intermedius (VI) - covering the cranial and adjacent aspects of the femur, between the VM and VL muscle. It is separated in two parallel parts: a lateral and a medial, which end with the corresponding vastus muscles

All insert on the base of the patella

Question 27

Overall tx approach for MFC SCL (CAT EVE 2019 O’Brien)

Answer 27

• APPROACH SUMMARY: arthroscopic intralesional corticosteroid injection appears to be the initial treatment of choice in most cases. This procedure enables thorough joint inspection and treatment of co-existing injuries, confirmation of accurate injection, and a rapid return to function.
• Should this treatment fail, lag screwing appears to be the most suitable second line treatment. Since older animals (>3) may respond more poorly to SCL treatment, delays should be avoided.
• Arthroscopic SCL debridement with chondrocyte and IGF-1 implantation is more costly and technically challenging and offers similar success rate to other treatments, so therefore does not seem to be justified for most cases.
• Conservative treatment (rest +/- intralesional corticosteroid injection under ultrasonographic guidance) may be appropriate where there are economic constraints, a rapid return to work is not expected, and lameness is not uncontrollably severe

Question 28

What radiographic view of the stifle should be included if cruciate ligament injury is suspected? (Adrich 2019 VCOT) and why?

Answer 28

Caudo-45°medial craniolateral oblique

Highlights the origin of the cranial cruciate ligament on the caudoaxial aspect of the lateral femoral condyle within the intercondylar fossa

Question 29

Proposed radiographic grading of medial femoral condyle lesions (0-4)

Answer 29

Grade 0 - normal

Grade 1 - flattening of the MFC

Grade 2 - subchonral bone sclerosis +/- defects in the subchondral bone that don’t extend all the way through the SCB plate

Grade 3 - SCB defects that extend all the way through the SCB plate. Can be wide and shallow lucencies

Grade 4 - well defined round or oval radiolucent area in the middle of the MFC that extends to and communicates with the MFT joint

Question 30

Reported sensitivity and specificity of scintigraphy for stifle disorders?

Answer 30

Graham et al 2015 VRU reported sensitivity of 20.8-29.2% (varied w different radiologists) and specificity was 84.5-88.3%.

Ie high false negatives and low false positives

Question 31

Label the diagram

Answer 31

a - parapatella fibrocartilage

b - medial patella ligament

c - medial collateral ligament

d - tibial tuberosity

e - cut stump of biceps femoris

f - middle patella lig

g - lateral patella lig

h - lateral collateral

i & k - medial & lateral tibial condyles

Question 32

Label the diagram

Answer 32

a - FPJ

b - middle patella lig

c - medial patella lig

d - cut end of lateral patella lig

e - long digital extensor mm

f - lateral femoropatella ligament

g - popliteus mm

h - lateral tibial condyle

i - lateral extensor mm