Final Exam - Joint Disease of the Stifle Flashcards
what are 3 reasons a dog will have a stable stifle palpation despite suffering from cruciate disease?
- patient pain & excitement - use heavy sedation for a solution
- early, partial rupture
- severe peri-articular fibrosis (buttress) in chronic cases
other than body weight, what clinical factors drive CCL surgical decision making?
activity, purpose level, client compliance, degree of rupture, finances, skeletal conformation, tibial plateau angle, patient history
what are the objectives of CCL surgery?
- elimination of pain/lameness - client’s main concern
- debridement of diseased tissue (CCL & meniscus)
- restoration of function
- slow the progression of OA
what is the grading system used for medial patella luxation?
grades I-IV
what 4 procedures are used for surgical correction of routine medial patellar luxation?
- trochleoplasty - deepen the groove
- tibial tuberosity transposition - re-aligns patella
- medial retinaculum release
- lateral reinforcement - imbrication
when is an extracapsular repair indicated for a dog with a CCL rupture?
sedentary, geriatric dogs, normal BCS, compliant clients, TPA <26-28 degrees, & small to medium breeds
when is an TPLO indicated for a dog with a CCL rupture?
active/high energy working dogs, obese, non-compliant clients, any TPA but > 30-32 degrees, & any size breed
what is the most common cause of pelvic limb lameness in dogs?
cranial cruciate ligament rupture - excluding fractures/joint luxations, CCL rupture until proven otherwise
why are acute CCL ruptures less common than chronic ruptures in dogs?
it involves the sudden mechanical overload of a normal CCL causing failure & instability
90-95% of CCL ruptures involve a chronic, progressive, mechanical, & possibly degenerative breakdown of collagen fibers within the ligament
even when the client describes the primary complaint as acute lameness, why do you suspect chronic?
typically a chronic history of waxing/waning signs until complete failure
T/F: up to 50% of dogs rupture the opposite ligament within one year of the initial injury
true
what breed is most commonly affected by CCL ruptures?
labs
what do you expect to see on physical exam of a dog with a complete CCL rupture?
cranial drawer sign & cranial tibial thrust
pronounced lameness from joint instability from incompetent CCL
why may you not see a drawer sign/tibial thrust in a dog with a partial CCL tear?
some fibers remain intact & functional preventing these signs
T/F: both complete & partial tears of CCL can have meniscal tears
true - more common with complete tears
what is the effect of CCL rupture as far as stability of the joint?
mechanical instability during weight bearing - cranial tibial thrust
causes persistent weight bearing lameness, typically grade 2-3/5
what is the effect of CCL tears on development of OA?
mild to moderate OA present at the time of the injury or that will progress after the ligament rupture
causes insidious waxing/waning lameness that progresses over time
how does a CCL rupture cause meniscal injury?
the tears commonly propagate in a longitudinal manner within the caudal pole of the medial meniscus - bucket handle tear
mild to moderate weight bearing lameness will acutely worsen at the time of meniscal injury
what is the sit test?
tool used to differentiate the source of a pelvic limb lameness in dogs
if positive - lameness is likely due to pathology of the stifle, if not, pathology of the hip
what is a cranial drawer test?
test that evaluates the stability of the stifle joint as assessed by the manipulation of the distal femur & proximal tibia
what is a positive cranial drawer test?
tibia can be moved cranially in relation to the femur more than the normal 2-3mm & the endpoint is indistinct - finding is diagnostic for a CCL tear
what is a positive tibial compression test?
test that mimics the mechanical loading of the stifle during weight bearing - stifle is positioned in a weight bearing position stabilizing the joint with one hand with the index finger of that hand positioned along the patellar tendon with the distal foot grasped & stabilized with the other hand
pressure is placed on the distal most hand while observing the tibial tuberosity for cranial displacement
what is a cranial tibial thrust?
movement of the tibia during a positive tibial compression test that is diagnostic for a CCL rupture
what is a meniscal click?
if concurrent injury to the meniscus occurs, a clicking sound may be heard or felt as the stifle joint is put through its ROM - absence of one doesn’t mean the meniscus is healthy
what is medial buttress?
palpably firm thickening on the medial aspect of the stifle joint that is a common finding in chronic/progressive CCL ruptures
why does medial buttress occur?
thickening is a result of periarticular fibrosis which develops around the stifle joint capsule in response to chronic, low grade instability as the CCL ruptures
why is surgery the treatment of choice for a ruptured CCL?
surgical stabilization is the only treatment that will limit joint instability & restore clinical function of the stifle
it also allows for exploration of the joint to look for other injuries & slows progression of OA
what are the pillars of medical management for a dog with a ruptured CCL?
weight loss, pain control (short dose of steroids followed by NSAIDS), adequan, exercise modification, & joint supplementation
what is the most common technique used in an extracapsular repair?
lateral suture - fabello-tibial suture
what is the goal of an extracapsular repair for a ruptured CCL?
eliminate cranial drawer/tibial thrust by securing a non-absorbable material from the distal femur to the proximal tibia outside the joint capsule in the same orientation as the original CCL
what is the surgical technique of choice for toy/small/medium breed dogs with a ruptured CCL?
extracapsular repair
what are the 2 common slope modifying surgical techniques used for a ruptured CCL?
TPLO & TTA
what is the goal of TPLO/TTA surgical techniques in repairing a ruptured CCL?
eliminate tibial thrust by redirecting the vectors acting upon the stifle joint through a surgically planned cut followed by rotation of the proximal tibia fragment in the sagittal plane results in the elimination of tibial thrust during weight bearing
after the osteotomy & rotation are done, a bone plate & screws are placed on the proximal & medial aspect of the tibia to stabilize the bone in its new position until healing occurs
T/F: TPLO/TTA techniques eliminate tibial thrust but not the cranial drawer sign
true
when are TPLO/TTA techniques typically used?
dogs of various sizes but usually 20kgs or higher
what is a grade I patellar luxation?
intermittent luxation causing occasional lameness usually associated with heavy exercise
patella is easily luxated manually but returns to the trochlear groove when release - IN OUT IN
what is a grade II patellar luxation?
luxation/lameness occur more often than grade I, but usually intermittent & mild
patella is easily luxated but doesn’t return to the trochlear groove unless the limb is rotated in the direction opposite the luxation - IN OUT OUT
what is a grade III patellar luxation?
continuous luxation causing chronic persistent lameness & an abnormal gait
on palpation, patella is detected in luxated position, can be manually reduced into a shallow trochlea, but reluxates during flexion/extension - OUT IN OUT
tibial tuberosity is markedly deviated & femoral torsion/varus are commonly present
what is a grade IV patellar luxation?
patella is permanently luxated & limb deformities are severe causing chronic lameness, severely affected gait, & in some cases, inability to walk
on palpation, patella is luxated, can’t be manually reduced, & is fixed in the luxated position - OUT OUT OUT
marked distal femoral torsion, femoral varus, tibial valgus, & distal tibial rotation are detected
why is developmental a more appropriate term for patellar luxation?
anatomic deformities in the animal that lead to the luxations are present early in life & cause a subsequent luxation of the patella as the animal grows to mature body size
why should animals with luxating patellas not be bred?
non-traumatic patellar luxations are development/heritable
what direction is most common in patellar luxations?
medial luxation
T/F: there is evidence that suggests that increasing severity of patella luxation predisposes dogs to CCL rupture
true
what is the theory behind the development of patellar luxation?
growth deformity from the hip joint to the distal tibia - external torsional deformity of the distal femur
quadriceps mechanism/patella/patellar tendon are anchored proximally at the pelvis/proximal femur & distally at the tibial tuberosity - they are pulled medially during contraction
external torsion of the distal femur & displacement of the quadriceps mechanism medially causes medial displacement of the tibial tuberosity during bone modeling - the pressure of a normally positioned patella is responsible for the development of a normally shaped trochlear groove
luxation of the patella results in an insufficient trochlear groove development & a groove that is more shallow further predisposing to more luxation
displacement of the patella & altered contractile forces on the quadriceps results in asynchronous loading of distal femoral growth
excessive medial loading results in cessation of growth of the medial aspect of the growth plate
decreased lateral loading allows continued/accelerated on the lateral aspect of this growth plate
end result is some degree of distal femoral varus - bow legged appearance
opposite effects occur on the proximal tibial growth plate (stops laterally & accelerates medially) resulting in distal tibial valgus
what are the clinical consequences of chronic patella luxation?
eburnation (full-thickness wear) of cartilage on articular portion of the patella & femoral trochlea
pain/lameness, & mild stifle joint effusion
increased risk of CCL rupture
what does the gait look like in a dog with medial patellar luxation?
hunched, crab-like gait & difficulty rising
what does the gait look like in a dog with lateral patellar luxation?
cow-hocked appearance with limbs externally rotated so that the hocks are pointed medially & pes are directed laterally
what are the surgical goals when correcting luxating patellas?
realignment of the quadriceps mechanism & stabilization of the patella in the trochlear groove
what are the 4 surgeries used to correct luxating patellas?
- trochleoplasties - most common is recession trochleoplasty to deepen the groove
- tibial tuberosity transposition
- medial or lateral release
- lateral or medial imbrication
how is a wedge recession performed?
v-shaped wedge of bone & cartilage is outlined & removed from the trochlea using a bone saw & deepened
serves to deepen the groove while preserving hyaline cartilage - technically easier to do than a block recession
how is a block recession performed?
rectangular block of bone & cartilage is removed from the groove using a bone saw & osteotome - procedure improves femoropatellar contact & procedure of choice in large breed dogs with patella alta
how is a tibial tuberosity transposition performed for medial luxations? lateral luxations?
medial - tuberosity is transposed laterally
lateral - tuberosity is transposed medially
what is the treatment goal for a grade IV patella luxation?
not a surgical cure as most patients will have dramatic limb deformities - want to reduce severity of luxation to grade I-II & marked improvement in ability to ambulate & function
