The Stifle Flashcards
describe the anatomy of the stifle
see pic on slide
what is the function of the cranial cruciate ligament? (3)
prevent:
1. hyperextension
2. excessive internal rotation
3. cranial tibial translation
note: some internal tibial rotation occurs are you flex your knee, this is called the screw-home mechanism and is normal
describe the anatomy and function of the menisci
- fibrocartilage wedges between the femoral condyles and the tibial plateau
- mostly composed of type I collagen
- alleviate incongruity between a rounded structure and a flat surface
- functions:
-stabilization
-load bearing
-shock absorption
-joint lubrication
-mechanoreceptor
describe the etiology of CrCL disease
- less than 10% due to trauma and hyperextension
- greater than 90% are biological, due to spontaneous degeneration!!
describe traumatic CrCL disease
- may be associated with other damage to the stifle
- typically unilateral, predominantly in COMPLETE tears; can develop easily into a luxation (deranged stifle)
- in puppies is likely associated with an avulsion versus midsubstance tear in the adult
describe degenerative CrCL disease
- spontaneous
- commonly bilateral:
10% bilateral on presentation
-up to 50% will go on to rupture the other side within 1 year
-up to 60% will go on to rupture the other side within their lifetime - tear can be partial of complete, but partial tears usually progress to full tears over time
- risk factors:
-breed: labs, goldens, rotties
-sex: female >male
-altered status: neutered > intact
-dog size: larger >smaller
-obesity: implicated but not proven
-anatomy: increased tibial slope implicated
-other diseases: endocrinopathies (cushing’s)
-age: unknown if true risk factor - smaller dogs (22kgs) present later in life
- larger dogs (>22kgs) present earlier in life
describe meniscal injury
- seen when cruciates are torn due to cranial/caudal instability
- most common location: caudal horn of medial meniscus: 2 giant ligaments tack it down = less mobile in the face of abnormal movement, stuck to tibia, can’t get out of the way of the femur
- lateral: less common, can move with femur in abnormal movement; but can happen so always check during surgery!
describe history and clinical signs of CrCL disease
history:
1. non weight bearing lameness (3-legged lame has CCLR until proven otherwise = hella common!
clinical signs:
1. muscle atrophy of quadriceps
2. medial buttress
3. positive sits test: dogs with stifle ain (CCLR) often sit with the most painful stifle extended out laterally and roll onto the opposite (good) hip or limb bc it is painful to flex the stifle
4. reluctant to have stifle maximally flexed or extended
describe visual observations and palpation of CrCL disease
visual observations:
1. gait:
-look for short stride and/or obvious lameness
-look for atrophy and symmetry
2. sit test
palpation:
1. standing palpationL look for symmetry (weight bearing muscle mass)
2. recumbent palpation: CREPI, cranial drawer, cranial tibial thrust
what is the biggest difference between cranial drawer and cranial tibial thrust
cranial drawer is passive: you are moving it
cranial thrust is active: it mimics what happens when the dog bears weight
-plays a larger role in surgical repair
describe cranial caudal instability with full versus partial tears
- full tears: drawer easy to palpate
- partial tears: mild drawer often present, MUST test in flexion and extension
-caudal lateral (larger band) loos when flexed, taut in extension
-cranial medial (smaller band): taut in both flexion and extension
-test for pain on stifle hyperextension; if pain, likely at least partial tear - base a presumptive diagnosis off of radiographic findings (secondary O)
- or just rest, NSAIDs, recheck in 2-4 weeks and repeat exam bc partial tears will progress to full tears
can you see a cruciate ligament on radiograph?
NOOOOOO; checking for secondary OA and inflammatory signs instead; radiographs DO NOT reveal a torn CCL or a damaged meniscus
if radiographic findings are SOE, with specific location of stifle, most likely radiographic diagnosis is CCLR with secondary OA (EXAM!!!!!!)
what are the 3 categories of surgical options for CrCL disease?
- intracapsular
- corrective tibial osteotomies:
-TPLO
-TTA - extracapsular:
-lateral suture
describe lateral suture
objective: attempting to replace a torn ligament on the outside of the joint to mimic CrCL to neutralize the effects cranial tibial thrust and cranial drawer by replacing the damaged CrCL with the lateral suture
provides: static AND dynamic stabilization
-craniocaudal instability neutralized by extra-capsular support
–short term stability: suture material
–long term stability: suture breaks but replaced by periarticular fibrosis (RUSH to have fibrous tissue laid down, preventing early movement with suture)
clinical concerns and/or benefits:
1. has less evidence for efficacy; instability is still present in most
2. suture will break over time
3. relies on soft tissue healing (may not be as good for animals with slower or impaired healing
describe TPLO
objective: neutralize effect of cranial tibial thrust; redesign the stifle and rotate tibial plateau to be more level (like a human)
-cutting bone, so caudal cruciate MUST be intact!!!!!!!
provides: dynamic stabilization (work when dog bears weight only)
1. when weight bearing: stifle should be stable (NO craniocaudal instability/thrust)
2. when not weight bearing: cranial drawer may be palpable, but this is not abnormal, just should not have thrust
-partial tear: drawer may or may not be palpable
-full tear: drawer may be palpable but no thrust
key! after surgery, the cranial cruciate is no longer necessary for stifle stabilization under active weight bearing (dynamic procedure)
clinical concerns/benefits
1. has the best evidence for efficacy; dogs use limb quickly after surgery
2. dogs are indistinguishable from normal 6-12 months after surgery
describe TTA
objective: to neutralize the effects of cranial tibial thrust via osteotomy of the tibial tuberosity and advancing it forward/cranial; redesign stifle by placement of patellar tendon perpendicular to tibial plateau
provides dynamic stabilization only in the same way as the TPLO
clinical concerns/benefits
1. less evidence for efficacy than TPLO, results appear similar to a lateral suture
2. studies demonstrated that dogs still not normal 12 months post-op
3. removal of implants if infected can be challenging
what is the function of the caudal cruciate?
- primary stabilizer against caudal drawer (caudal tibial subluxation)
- functions with cranial cruciate ligament to prevent internal rotation and prevent hyperextension
describe the prevalence of caudal cruciate ligament injury (CdCL), breeds, etiology, concurrent injuries
prevalence: rare to see isolated injury
breeds: ANY dog
etiology: trauma; 1–% of cases are attributable to trauma when tibia experiences a traumatic blow to cranial cortex forcing it caudally
concurrent injuries: often combined with medial collateral and/or cranial cruciate ligament injury
describe clinical signs of caudal cruciate ligament injury (3)
- pelvic limb lameness
- pain on palpation
- joint laxity:
-differentiation between cranial drawer can be difficult
-50% of CdCL injury are misdiagnosed as CrCL injuries
describe treatment of caudal cruciate injury
first step: repair concurrent injuries first: often no repair is necessary for CdCL
injury option 1: avulsion fracture
-when ligament tears away from its attachment site and takes a piece of bone
-repair: often difficult to successfully repair; can try to reduce and stabilize the fragments via bone screw, wire suture with bone tunnels, K-wire, etc
injury option 2: mid-substance tear: tear in middle of ligament; usually with no other injuries
repair option: NO surgery, conservative management
what is the purpose of the patella?
complex lever that magnifies the movement arm of the quadriceps mechanism by increasing the leverage that the quadriceps tendon can exert on the femur
describe the dynamic and passive stability mechanisms of the patella (on exam?)
dynamic stability: quadriceps extensor mechanism, quadriceps tendon, patella, patellar tendon
passive stability: trochlear ridges, trochlear sulcus, femoropatellar ligament, adhesion/cohesion of joint fluid, patellar shape
describe common fundings of patella luxation in general
- common in small breeds
- medial luxation is most common in ALL dogs
- lateral luxation is more likely in large dogs
- up to 65% of cases are bilateral
- can occur after other stifle surgeries
- CAN occur in cats
describe etiology and pathology of patella luxation
etiology:
1. underlying cause not entirely understood
- potentially a developmental disorder, the result of bony abnormalities present at birth
-hard tissue abnormalities: result in doft tissue malalignment (extensor mechanism)
-soft tissue abnormalities: result in quadriceps mechanism malalignment - abnormal patella location during growth can also affect bony development (trochlear hypoplasia)
describe history and clinical signs of patellar luxation
history:
1. lameness: intermittent to continuous; mild to moderate weight bearing lameness with occasional carrying of limb (as patella pops in and out)
2. may stretch leg backward to reduce luxation
3. reluctance to jump
medial luxation: bow-legged appearance
lateral luxation: knock-kneed appearance, tend to cause more lameness
describe diagnosis of patellar luxation
- in lateral recumbency, identify the patella by following the patellar ligament from the tibial tuberosity to the patella
- attempt to luxate the patella by pushing the patella medial and lateral while internally and externally rotating the leg
- also elevate the cranial cruciate ligament (cranial drawer); PATELLA MUST BE IN THE GROOVE
describe radiographs to diagnosis patella luxation
- confirm diagnosis
- check for other sources of lameness
- assess for bone malformations/alignment changes
what are the 4 grades of patella luxation
grade 1:
-often incidental finding
-patella in groove
-clinical signs uncommon
-bony abnormalities minimal
-sx intervention generally not required
-it is IN, but can be luxated out
grade 2:
-patella in groove but can be luxated out
-clinical signs are present: non painful skipping, mild intermittent lameness
-mild bony abnormalities
-it is IN, but can be luxated out and has clinical signs
grade 3:
-patella out of groove but can be reduced manually
-clinical signs are present: abnormal crouched gait, more common to see consistent lameness
-moderate bony abnormalities
-out but can be reduced
grade 4:
-patella out of groove but cannot be reduced manually; NON REDUCIBLE
-clinical signs present: abnormal crouched gait, bowlegged, more common to see consistent lameness
-severe bony abnormalities
-out and CANNOT be reduced
what are the 3 most common procedures to correct a patella luxation?
- deepening the groove: trochlea/sulcus procedures
-cut a wedge: maintains any hyaline cartilage present in the groove
-cut a block: maintains any hyaline cartilage present in groove
-sulcoplasty: removes any hyaline cartilage present in the groove (also called abrasion trochleoplasty) - soft-tissue procedures:
-releasing procedures: fascial release
–medial patella luxation: release of contracted tissue on medial side of joint: medial retinaculum, cranial head of sartorius muscle, medial joint capsule
–lateral patella luxation: release of contracted tissue on lateral side of the joint
-imbrication procedures: fascial imbrication: usually performed after all other procedures have been completed, can combine with any other technique; use a modified mayo mattress (vest over pants)
–medial luxation: imbricate the lateral side
–lateral luxation: imbricate medial side
-benefit is if too tight can just cut suture!
- quadriceps realignment procedures: tibial tuberosity transposition:
- cut the tibial tuberosity
- transpose (push or move) laterally or medially
- reattach the tuberosity with K-wires +/- tension band
-medial luxation: transpose laterall
-lateral luxation: transpose medially
describe alignment correction (the 4th, less common surgery)
- for severe distal varus,
- corrective closing wedge osteotomy/distal femoral osteotomy (DFO)
- results in correction of varus and straightening of quadriceps mechanism
describe anti-rotational suture surgical correction
- often a supplemental procedure when there is severe internal torsion at the level of the stifle joint
- young animals: may reduce or correct deformity with continued growth
- mature animals: typically performed as support procedure for definitive bony corrections
- can be used to treat concurrent CCLR
describe post-operative care for patella luxation
- soft padded bandage 10-14 days
- activity restriction 6 weeks
- ROM physical therapy
- prognosis caries with grade
2-3 good, 4 fair to good
what is the function of the collateral ligaments
medial: main medial stabilizer of the knee: taus in extension (stance) and flexion (swing)
lateral: main lateral stabilizer of the knee taut in extension (stance) but LAX in flexion (swing)
describe the etiology, breed, and diagnosis of collateral ligament injury
etiology: trauma! 100% of cases
1. typically the result of excessive force to the distal medial or lateral extremity
- concurrent injuries: frequently associated with concurrent rupture of the cranial cruciate of caudal cruciate ligaments
- can be stretched, avulsed, or torn
breed: any dog!
diagnosis:
1. non weight bearing lameness
2. palpation
3. radiographs to rule out other injuries
describe diagnostic palpation of collateral ligament injuries
medial collateral ligament:
1. valgus stress test: stifle joint in extension, stabilize femur and apply valgus stress to tibia; compare to contralateral or normal stifle
lateral collateral ligament:
1. varus stress test: stifle joint in extension, stabilize femur and apply varus stress to tibia; compare to contralateral or normal stifle
describe surgical repair of collateral ligament injuries
- stretched: imbrication
- avulsion: reattach bone fragment
- rupture: repair and prosthetic reinforcement with screws and suture
describe post op care and prognosis for collateral ligament injury
post-op
1. soft padded bandage or splint in large dog that extends proximally past the knee for 3-4 weeks
2. for giant dogs, consider trans-articular external fixation for 4 weeks
3. 8 weeks exercise restriction- passive ROM
prognosis:
potentially favorable, dependent on owner and dog compliance
describe etiology of stifle OCD
- failure in the process of endochondral ossification (looks like a blister in the cartilage)
- if dissecans then attached or loose cartilage flaps are present and clinical signs are present (typically lameness, can be misdiagnosed as a juvenile cruciate tear)
- common in young large and giant breed dogs 5-9 months old; often bilateral, if you see it on one side you MUST obtain radiographs of the opposite stifle
describe radiographic diagnosis of stifle OCD
- subchondral bone defect: on axial aspect of lateral and/or medial femoral condyle (96% lateral condyle, medial aspect, 4% medial condyle, lateral aspect)
- sclerosis of the subchondral bone adjacent to the defect
- joint effusion
- mineralized free bodies (joint mice)
- osteophytosis
describe treatment (non-surgical and surgical) and prognosis of OCD
non-surgical:
-not often application
-only in cases where OCD lesion is found as incidental finding and there are NO clinical signs
surgical:
1. palliative techniques: provide site with fibrocartilage (will never get back hyaline cartilage); debride lesion to stimulate lesion, vascular ingress, and fibrocartilage formation
- restorative technique: provide site with hyaline cartilage
-transfer of hyaline cartilage plug from healthy area or different joint
prognosis:
palliative: fair to poor
restorative: unknown, not enough data
what are 3 end stage surgical options?
- knee replacement/arthroplasty
- arthrodesis
- amputation
