Stifle Flashcards
Tx options for upward fixation of the patella (UFP)
- Conservative - exercise (hills etc) to develop quadriceps musculature, IA chondroprotection etc
- Injection of counter irritants eg 2% iodine in almond oil andethanolamine oleate
- Medial patella ligament desmoplasty (splitting) - particularly the proximal 1/3 of the ligament
- Medial patella ligament desmotomy
Outcome of MPL desmoplasty (splitting)
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%
Outcome of MPL desmotomy
Variable reports in the literature, 1 reports states 94% success rate but may be assoc. w. high complication rate
Complications of MPL desmotomy
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
5 meniscal ligaments
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

Recumbency and limb position for ASY
Dorsal recumbency
Extension for FPj (cannon roughly vertical)
90° flexion for the femorotibial joints
Cranial cruciate origin and insertion
Origin: caudolateral intercondylar fossa (10 o’clock position in the intercondylar fossa on CC rad
Insertion: Axial aspect of the MICET

Caudal cruciate origin and insertion
Origin: craniomedial intercondylar fossa
Insertion: caudomedial border of the medial tibil condyle
Remember named as per cr/cau insertions on the tibia

Collateral ligament origins and insertions
Medial and lateral femoral epicondyles
Medial inserts on medial tibial condyle extending into metaphyseal region
Lateral inserts on fibular head

Long extensor origin
Extensor fossa of the lateral femoral condyle

Lateral extensor origin
Proximal tibia/head of fibula and lateral collateral insertion

Popliteal tendon origin and insertion
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.
Most common site of FPj OCD
Lateral trochlear ridge - proximal 1/3
Most common patella fracture configuration
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
Standard tx for medial parasagittal patella fractures and size limitations
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
Indications for internal fixation of patella fractures and recommended screw size in adults
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
Method of fixation of transverse patella fractures
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
Grades of congenital patella luxation (from Fubini and Ducharmme)
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
Ddx for patella luxation (F&D)
- Femoral nerve deficits (difficult calving)
- Distal femoral fracture
- Patella fracture
- Femoropatella ligament ruptures (traumatic)
Tx for patella luxations (F&D)
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)
Techniques for sx management of congenital (or traumatic) lateral patella luxation
What is the expected athletic prognosis?
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
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
Compressive stress incr by 25%
Shear stress incr. by 50%
Tensile stress incr by 200%
What effect does an MFC void have on the stresses in the meniscus (Frazer 2019 Vet Surg)
Increases compressive and shear stress by upto 30%. May help to explain the relationship between MFC lesions and medial meniscus damage
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)
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




