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Flashcards in Stifle Deck (81)

Where are the cruciate ligaments?

Understand the basic anatomy

  • Cranial cruciate ligament
    • Arises from medial aspect of lateral femoral condyle
    • Inserts on cranial aspect of the region between the condyles
  • Caudal cruciate ligament
    • Arises from lateral aspect of medial femoral condyle
    • Inserts on caudal aspect of intercondylar region


T/F: The cranial cruciate ligament is named so because the distal portion (insertion) sits cranially on the tibia relative to its proximal portion (the origin)



What is the relationship of the cruciate ligaments to the synovial lining of the joint?

Why is it important?

  • The cruciate ligaments have a thin lining of synovium over them
  • They lie inside the joint capsule but are actually outside the synovial lining of the joint
  • Important because the synovial lining is an effective barrier between the collagen of the ligament and the immunoresponsive mechanisms of the joint
    • When the ligament is damaged, that barrier is disrupted
    • Damaged cruciate ligament is a potent stimulus for ongoing inflammation--> DJD


What is the function of the cranial cruciate ligament?

  • Prevents internal rotation, hyperextension, and tibial thrust
  • Most important: preventing tibial thrust


What is cranial tibial thrust?

When does it occur?

  • Naturally occurs during weight-bearing
  • Wt.-bearing creates compression across the joint
  • Angle between compression and tibial plateau results in shear force--> tibia slides cranially relative to the femur
  • CCL opposes shear


How does cranial tibial thrust relate to cruciate ligament rupture?

  • If the force of tibial thrust > breaking strength of the cruciate ligament --> rupture


T/F: Most cruciate ruptures are a result of abnormally excessive tibial thrust forces


Most cruciate ruptures are a result of normal tibial forces applied to an abnormally weak cruciate ligament


What is the etiology of acute cranial cruciate rupture?

  • Usually traumatic
  • Excessive torsion or extension on a normal, healthy CCL
  • Least common in vet med


What is the etiology of chronic cranial cruciate ligament disease?

  • Chronically weakened CCL
  • Cannot withstand normal forces of wt.-bearing
  • Disease = degenerative process in place before any clinical/radiographic findings
    • Rupture is chronic, progressive process--ligament does not tear all at once


T/F: Chronic cranial cruciate disease is more common than acute cranial cruciate rupture



What factors play a role in the pathogenesis of chronic cranical cruciate ligament disease?

  • Degeneration occurs with age
    • Tends to be worse in larger dogs (> 15kg)
  • Obesity
  • Poor fitness
  • Conformation--straight stifle joint
  • Excessive plateau angle


What is the risk of contralateral disease with chronic cruciate ligament disease?

~50% bilateral disease within 1-2yrs


What is the typical signalment of a dog with CCL disease?

  • Adult
  • Large breeds
    • Rottweiler, Newfie, Staffordshire terrier, lab, mastiff, St. bernard
  • Female > male
  • Neutered > intact (retrospective)


What is the typical history of chronic CCL disease?

  • Variable
  • Intermittent, progressive signs typical
    • Slow degeneration of CCL leads to DJD
    • Fraying of ligament
  • Rupture may present acutely
    • Rupture is acute, disease is chronic
    • DJD on PE and rads confirm chronicity
  • Response to NSAID dependent on DJD
  • Difficulty rising, "bunny hopping"--bilateral


What are the expected PE findings on a dog with cruciate ligament disease?

  • Effusion--infill of parapatellar "divot"
  • Rounding of limb
    • Effusion (acute)
    • Fibrosis and effusion (chronic)
  • Muscle atrophy (disuse)
  • Medial buttress--firm medial fibrosis
  • Crepitus--osteophyte formation
  • Instability
  • Not specific for CCL disease


What are the expected PE findings when testing instability in a patient with cruciate ligament disease?

  • Cranial drawer test--passive constraint
  • Tibial compression test
    • Active constraint
    • Generates tibial thrust
    • AKA "tibial thrust test"


T/F: Sedation is only required for aggressive patients when using the cranial drawer test or the tibial compression test


Sedation is required to definitively test either cranial drawer or tibial compression


What is the significance of "puppy drawer"?

  • Puppies < 6mo


Why is it important to test for instability in both views when evaluating for cruciate ligament disease?

  • Functional divisions in CCL
    • Craniomedial--taut in flexion and extension
    • Craniolateral--taut in extension only
  • If only craniomedial band ruptures--> instability shows only in flexion


How does treatment of a partial tear differ from that of a complete tear?

It doesn't

Dog still experiences discomfort--treat the same


What is the function of the menisci?

  • Primarily act as shock absorbers
  • Fibrocartilage--compressible--act as padding between femur and tibia
  • Reduce stress on cartilage


What is the frequency of meniscal injury?

60-70% of dogs with cruciate rupture will have some amount of meniscal injury


Which meniscus is most commonly damaged?


  • Medial meniscus is most commonly damaged
  • Medial meniscus is attached to the tibia--when the CCL is ruptured and the tibia displaces cranially the meniscus moves with it
    • This predisposes it to crushing injury when there is compression bewteen the tibia and femur 


What are the PE/history findings in a patient with meniscal injury?

  • Increased pain level over uncomplicated CCL disease
  • History: sudden increase in lameness
  • "Meniscal click"--distinct popping sensation as stifle is put through ROM, typically from full flexion to full extension
    • Not completely reliable (present in ~25%)


What is the effect of meniscal damage on the progression of CCL disease?

Meniscal disease significantly increases the wear/tear on the cartilage.

Arthritis will appear sooner and be more severe over time in a stifle with damage to the meniscus


What are the typical radiographic findings with cruciate ligament disease?

  • Rule out other injuries
  • Effusion (displacement of fat pad)
  • Effusion only--early/acute tear
  • Osteophytes--patella, trochlear ridges
  • Subchondral sclerosis--condyles
  • Increased medial soft tissue (medial buttress)
  • Tibial displacement


T/F: None of the typical radiographic findings are truly diagnostic for CCL disease


One can't see the cruciate ligament or meniscus radiographically, so all the changes are simply secondary indicators that would be seen with any long-standing disease


What is being shown in this radiograph?

Cranial tibial thrust

(Very rare to see on rads)


What is the relative value of medical vs. surgical treatment for CL disease?

  • Not recommended
  • 6 wks: confinement, rest, wt. reduction, pain management
  • PT ideal
  • Acceptable fx reported in patients < 10kg


What are the goals of surgical management of CL disease?

  • Explore joint
    • Debride CCL--nidus of inflammation
    • Evaluate/treat meniscus
    • Arthroscopy vs. arthrotomy
    • "Stable" partial tears
  • Stabilize joint


What is the most common type of meniscal tear?

"Bucket handle"


What is the surgical management of meniscal injury?

Generally, damaged portion of meniscus is removed


What is meniscal release? Why might it be done?

  • Cut caudal pole of medial meniscus
  • Allows caudal pole to move caudally
    • Can slide out of the way when tibia slides forward into thrust
  • Can be done on intact or damaged meniscus
  • Done to reduce the likelihood of having a patient develop meniscal injury after surgery


Is meniscal release benign? Why/why not?


  • Release of meniscus alters fx and it can no longer serve the shock-absorbing, wt.-distributing functions it's supposed to
  • This changes the way the wt. is focused on portions of the cartilage and tends to increase development of arthritis


What is the difference between extracapular and osteotomy stabilization?

  • Extracapular
    • Rely on implant to stabilize joint
    • Placed on the outside of joint (hence "extracapular")
    • Implant is oriented in the same direction as the native ligament
  • Osteotomy
    • Rely on a change in forces on the joint to neutralize tibial thrust
    • Cut in the tibia-->induce a change in the way wt. is transferred through the joint
    • Alters forces on the joint so ligament isn't needed


What are the most common stabilization techniques employed for cruciate ligament disease?

  • Intracapsular--historical, research only
  • Extracapsular
    • Lateral suture
    • Tightrope
    • Others (historical)
  • Tibial osteotomies
    • Tibial plateau leveling osteotomy (TPLO)
    • Tibial tuberosity advancement (TTA)


Describe the lateral suture technique for stifle stabilization

  • AKA "extracap", lateral fabellotibial suture (LS)
  • Heavy monofilament nylon placed in orientation similar to the native CCL
  • Nylon mimics function of ligament
  • Around lateral fabella and through hole in tibial tuberosity 
  • Suture tied or crimped
  • Numerous variations in suture material/technique


What are the complications of the lateral suture technique for stifle stabilization?

  • Infection
  • Implant failure
  • Incomplete stabilization 
  • Meniscal injury
  • Peroneal nerve deficit/entrapment
  • Complication rates increased with:
    • Higher body st.
    • Younger age


Why is peroneal nerve damage unique to the lateral suture technique for stifle stabilization?

  • Proximity of the nerve to the fabella
  • Generally the suture is passed around the fabella with a large, curved needle
  • If the fabella is not visualized properly or the bite taken with the needle is too large, it can stretch or even entrap the peroneal nerve


How is the tightrope technique for stifle stabilization different from the lateral suture technique?

  • Tightrope is intended to be placed non-invasively
  • Recovery is more rapid
  • Multifilament nonabsorbable fiber tape implant
  • Fixation with toggle mechanism 


How does altering the angle between the force of weight-bearing and the tibial plateau neutralize tibial thrust?

  • Tibia displaces cranially as a result of shear forces between the femoral condyles and the tibial plateau
  • Generation of this shear force requires an angle between the force of weight-bearing and the tibial plateau
  • By eliminating the angle (making the force of wt.-bearing perpendicular to the plateau), shear is eliminated --> tibial thrust is eliminated


T/F: Osteotomy procedures neutralize both tibial thrust and cranial drawer tests

FALSE--does NOT neutralize cranial drawer

  • Osteotomy procedures stabilize tibial thrust, which occurs naturally during wt.-bearing and is induced artificially by the tibial compression test
  • Cranial drawer test is done by applying direct cranial force to the tibia
    • This never happens during natural wt.-bearing
    • Osteotomies do nothing to prevent translation of the tibia under this direct force


What procedures will neutralize both the tibial thrust AND cranial drawer tests?

Extracapsular procedures

Intended to mimic the negative ligament


What are the potential complications of the osteotomy procedures?

  • Infection 
  • Incomplete stabilization
  • Implant failure
  • Meniscal injury
  • Osteotomy-related
    • Iatrogenic angular limb deformity (TPLO)
    • Iatrogenic patellar luxation (TTA)


What is the importance of post-operative activity?

Osteotomies essentially create a fracture--just as prolonged activity restriction is important for fracture repairs, so too is it important following osteotomies

Most osteotomies are healed in 8-12wks


What is important post-operatively for extracapular procedures?

Physical therapy



What is the prognosis for cruciate ligament disease?

  • Generally good
  • Almost all dogs are improed after surgery no matter the procedure
  • DJD will progress, but will do so far more slowly with surgery than without it


What is the likelihood of the stifle returning to normal following stabilization surgery?

Many studies have shown return of normal function, but just as many have showed otherwise--owners must know that surgery is an essential part of management but there might be limitations following recovery


T/F: TPLO and TTA have a slower return to function than the lateral suture technique for stifle stabilization


TPLO and TTA have a more rapid return than the lateral suture technique


Are TPLO outcomes better than lateral surgery outcomes?

Debatable, but there is some evidence supporting the theory that TPLO outcomes >> lateral surgery outcomes (particularly for large breeds)

Still a HUGE amount of debate


T/F: The tightrope procedure is difficult to compare to other procedures, but the outcome is probably closer to TPLO and TTA than the lateral suture



Which has the better outcome: TPLO or TTA?

TPLO and TTA can be considered largely equivalent in outcome


What is the difference between medial and lateral patellar luxation?

  • MPL is more common than LPL
  • LPL is most common in large breeds
  • Conformational abnormalities
    • Mirror image to MPL
    • Usually more severe


What is the signalment of patellar luxations?

  • Any age/breed dogs, cats
  • Either gender
  • Small and toy breeds most affected
    • 10x more likely in small breeds
  • 98% medial luxations
    • Large breeds higher % LPL (MPL still > LPL)
  • 50% bilateral (often in different grades)


How is patellar luxation named?

Position of the patella


What conformational abnormalities are associated with patellar luxation?

  • Medial malalignment of quadriceps (growth)
  • Result: altered distal femur and proximal tibia
    • Lateral bowing of distal femur (femoral varus)
    • Lateral torsion of femur
    • Medial displacement of tibial tuberosity
    • Medial bowing of proximal tibia (tibial vagus)
    • Abnormal (shallow) trochlear groove
    • Hypoplasia of medial condylar ridge


What does the term "torsion" mean when applied to the femur or tibia in patellar luxation? 

  • Torsion = rotation of a bone around its longitudinal axis
  • Ex: medial luxation
    • Femoral head directed proximomedially (as normal), but as one progresses distally down the bone it twists so that the trochlear groove is actually facing laterally, rather than directed cranially


What do the terms 'valgus' and 'varus' mean when referring to the femur or tibia in patellar luxation?

  • Bowing of the bone
  • Usually refers to distal femur, proximal tibia, or both
  • Usually femur and tibia are bowed in opposite directions
    • Ex: MPL
      • Varus deformation of the distal femur and valgus deformation of proximal tibia


What is the typical history associated with patellar luxation?

  • Intermittent wt.-bearing lameness
  • Holds leg in flexed position for few steps
    • "Skipping gait"
    • NWB when patella is luxated
    • Minimal lameness when patella is reduced


Describe grade 1 patellar luxation

  • Patella generally stays in the groove
  • Can be manually luxated but will spontaneously reduce immediately
  • Spontaneous luxation occurs, but is rare
  • Smooth joint ROM
  • Clinical signs are mild
  • "In-in"


Describe a grade 2 patellar luxation

  • Patella more often reduced than luxated
    • Patella luxates easily with manipulation
    • May luxate spontaneously, causing lameness
  • Once luxated, tends to stay luxated
    • Will reduce spontaneously
    • Until manually reduced or stifle is extended
  • "Skipping", intermittent lameness
  • "In-out"


Describe a grade 3 patellar luxation

  • Patellar almost always luxated
  • Patellar can be manually reduced
  • Reluxates when released or with flexion
  • "Crouched" gait of variable severity 
    • Flexed stifle
    • Internally rotated tibia
  • Lameness is mild to severe
  • "Out-in"


Describe a grade 4 patellar luxation

  • Patella is fixed in luxation
  • Manual reduction not possible
  • Anatomic abnormalities severe
    • Tibia may be rotated 80-90 degrees medially
    • Stifle may not be able to fully extend
    • Severe fibrosis and muscular contracture
  • "Out-out"


Here's a pretty chart for grading patellar luxation:


T/F: When presented with bilateral patellar luxation, both sides are usually the same grade



Why are radiographs used with patellar luxation if the diagnosis is made during the PE?

  • Rule out other problems
  • Evaluate deformities
  • Provides pre-surgical baseline


What are the limitations of radiographs with patellar luxation?

Radiographic luxation is variable with low grade


How is imaging used with severe deformity in patellar luxation?

  • Well-positioned--include hip and stifle
  • Measure varus/valgus/torsion
  • CT may be necessary for severe deformity
    • 3D reconstruction
    • Plan for femoral and/or tibial osteotomies



Lateral patellar luxation


T/F: The conformation abnormalities of LPL and MPL are mirror images of each other


Ex: If there is femoral varus in medial luxation, there is femoral valgus in lateral luxation


What are the treatment options for patellar luxation?

Conservative management

Surgical management (soft tissue reconstruction, bone reconstruction/realignment)


What are the indications for conservative management of patellar luxation?

  • Grade I-II with minimal clinical signs
  • Condition tends to progress over time
  • Must monitor and consider surgery in immature dogs


What are the indications for surgical management of patellar luxation?

  • Significant lameness regardless of grade
    • Episodes lasting 2-3wks or longer
    • 3/more episodes in a short time (~1mo)
  • Higher grade (3-4)--associated with RCCL


Describe soft tissue reconstruction for treatment of patellar luxation

  • Lateral imbrication
    • Chronic stretching of lateral joint capsule, fascia
    • Imbrication prevents reluxation
  • Medial release
    • Chronic fibrosis of medial joint capsule, fascia
    • Free up contracted tissues
    • Allows reduction of patella
  • Must be combined with bony reconstruction


Describe bony reconstruction techniques for the treatment of patellar luxation

  • Trochleoplasties
    • Deepen femoral trochlear groove
    • Wedge or block resection
  • Tibial tuberosity transportation (T3)
    • Osteotomy in tibial crest
    • Realign quadriceps
  • Distal femoral osteotomy (DFO)
  • Patellar groove replacement (PGE)


How does a tibial tuberosity transposition procedure address conformational deficits?

  • Tibial tuberosity cut from proximal to distal, leaving periosteum attached distally
  • Tibial tuberosity shifted laterally
  • Tibial tuberosity fixed in place with K-wires
  • Pins and tension band in large breeds


T/F: In severe cases (grade 4, with severe conformation abnormalities), trocheoplasty and tuberosity transposition alone may not be adequate treatment


Especially in large breeds--every case must be considered carefully

In cases such as these, DFO and PGR are usually indicated


What is the post-op care for patellar luxation?

  • Controlled activity, leash-walking for 6wks
  • PT
  • Rads to assess osteotomy healing in 6wks


What is the risk of recurrence in patellar luxation patients?

50% reluxation in 1987 retrospective

8% in 2007 retrospective


What factors increase the risk of complications following patellar luxation injuries (e.g., recurrence)?

Dogs > 20kg

Lower complication risk for treatment with trochleoplasty + T3


What is the prognosis for patellar luxation?

  • Grades I-III
    • Excellent return to function
    • DJD may occur, usually not clinically significant
  • Grade IV
    • Guarded to poor
    • Recurrence/surgical failure common
    • Often requires more extensive reconstruction
    • Often requires multiple procedures