Canine Hip Dysplasia Flashcards
What signalment is associated with hip dysplasia? What are the most common signs?
large and giant breeds, presenting as early as 5-12 months
- lameness —> painful to advance limbs
- gait changes —> bunny hopping, wiggling hips
- chronic form is less dramatic
How is the joint manipulated to diagnose hip dysplasia?
Ortolani - place a hand on the spine and drive the stifle up, then abduct —> positive sign is a “clunk feeling when the femoral head slips down into the acetabulum
How are OFA radiographs performed for diagnosing hip dysplasia?
straight VD pelvis with femurs parallel
- triangular femoral head
- decreased coverage of acetabulum
- dorsolateral luxation
What are the 4 most common radiographic signs of hip dysplasia?
- femoral periarticular osteophytosis
- subchondral sclerosis of the craniodorsal acetabulum
- osteophyte formation on the cranial or caudal acetabular margin
- joint remodeling from chronic wear
Hip dysplasia:
- osteophytosis
- absence of acetabulum
Hip dysplasia:
- osteophytosis
- remodeled femoral head
How is femoral head coverage affected by hip dysplasia?
measurement of femoral head displacement from acetabulum, with normal being >50%
decreased coverage with hip dysplasia
- remember, radiographs are static and hip dysplasia is dynamic!
What is the Norberg Angle? How is it affected by hips dysplasia?
line connecting center of femoral heads and to each craniolateral acetabular rim, making an angle normally > 105 degrees, a tight hip
angle on inclination decreases with luxation = laxity!
What 3 views are required for PennHIP’s hip dysplasia diagnosis? What does it require?
- ventrodorsal hip extended - DJD, DI
- compression - congruency of femoral head and acetabulum, acetabular depth, and cartilage thickness
- distraction - passive laxity
general anesthesia, distractor
What information does PennHIP radiographs give?
quantification of femoral head displacement —> greater distraction index (DI) = increased laxity
When can PennHIP be used for hip dysplasia diagnosis? What else can it be used to assess the risk of?
as early as 16 weeks —> dogs with increased DI (looser hips) will develop radiographic and clinical signs sooner than those with lower DI
developing OA later in life
How does distraction index from PennHIP affect likely outcomes and treatment options for patients?
DI < 0.3 = tight hips with low likely hood of OA of CH
DI 0.3-0.7 = mild to moderate laxity at risk for developing OA, should considered pre-emptive surgery or medical plans, not all of these patients will develop DJD
DI > 0.7 = severe laxity where preventative measures are ineffective, OA is expected, recommend THR/FHO
How does PennHIP alter their algorithm based on breeds?
has breed-specific counts, DI, minimums, maximums, and means, where breeds commonly affected by CHD have higher mean DI
What is cavitation seen on PennHIP radiographs? How does it appear?
distraction lowers the intracapsular pressure of the coxofemoral joint, which can cause a void in the formation of synovial fluid due to pressure differential
lucent nitrogen bubbles in the joint space —> no adverse effects to joints, if bilateral repeat in 24 hr
What 2 major surgical procedures are used to save the natural joint when correcting hip dysplasia?
- juvenile pubic symphsiodesis - 12-20 weeks
- triple pelvic osteotomy - 6-12 months
What are the 5 goals to juvenile pubic symphysiodesis?
- cover femoral head with acetabular hyaline cartilage
- achieve and enlarge horizontal weight bearing surface
- greater load distribution
- decreased resultant joint reaction force
- improve joint congruity
When is juvenile pubic symphsiodesis performed? How does it work?
12-20 weeks old
monopolar electrocautery is applied to the symphyseal growth plate, causing thermal destruction of germinal chondrocytes and premature bony fusion (closes symphysis, other plates keep growing) = increased ventroversion of the acetabulum and femoral head coverage
What approach is used for juvenile pubic symphysiodesis? What 3 muscles need to be elevated?
midline over the cranial half of the pelvic symphysis
- gracilis
- adductor
- external obturator
Juvenile pubic symphysiodesis:
- younger doga 12-20 weeks
- closes symphysis to ennhance acetabular coverage ot femoral head
What affects tissue necrosis during electrocautery in juvenile pubic symphysiodesis?
time —> larger dogs need more time
What structures need to be carefully avoided when performing juvenile pubic symphysiodesis?
- urethra
- rectum
What 4 changes are expected with juvenile pubic symphysiodesis?
- shorter, wider pubic rami
- rounder, wider obturator foramen
- more prominent acetabular fossa
- irregular margin of cranial pubis
What objective criteria are used to monitor CT changes following JPS?
- dorsal acetabular rim angle
- acetabular angle
- PennHIP distraction index
What are the major pros for performing JPS to treat hip dysplasia?
- treats both hips
- not technically demanding
- no implants needed
- short recovery and surgery time
- inexpensive
- few complications
- can perform a revision later
What are the 3 major cons to performing JPS to treat hip dysplasia?
- loose or mucoid stool common for 1-3 days
- electrocautery burns
- asymmetrical fusion
What are the 2 requirements for performing a triple pelvic osteotomy to treat hip dysplasia?
- laxity WITHOUT degenerative change (hip is worth saving!)
- 6-12 months old
What 3 cuts are performed during a TPO? What other equipment is used?
- pubic
- ischial
- ilial
pelvic osteotomy plate - 20, 30, 40 degrees available
(pet must be over 30 lbs!)
What is the point of performing a TPO for hip dysplasia?
tilt hip to drive the femur into the acetabulum when load bearing
TPO:
What is important to note about radiographs following a TPO?
the femur will likely still look luxated —> the procedure fixes the luxation upon load bearing (it’s dynamic!)
- post-op laxity on rads normal!
- ensure rads are new
What are the 5 most common complications associated with TPOs?
- femoral neck impingement in abduction due to over-rotation (larger plate than needed)
- sciatic or obturator neuropaxia
- dysuria due to a bilateral procedure
- screw loosening - ensure they engage sacrum and use locking screws
- infection
What do TPOs not treat?
- subclinical osteoarthritis can still occur
- DJD
TPO > JPS for altering acetabular coverage
What are the 2 options for replacing the natural joint when treating hip dysplasia?
- femoral head and neck ostectomy
- total hip replacement
What kind of procedure is a FHO? What 4 changes result?
salvage, irreversible
- shortened limb
- significant change in limb biomechanics
- decreased ROM
- muscle atrophy
- pot-op rehab and PT important!
In what patients is an FHO performed?
< 20 kg
immediate and loner post-op rehab needed!
What are the 2 major candidates for FHO?
- clinical signs of lameness and pain not effectively treated with medical management
- TPO or THR surgery not an option due to age, size, or economics
FHO:
FHO:
too much neck left
How is an FHO performed? What post-op management is especially important?
complete incision of the femoral head and neck
- NSAIDs and pain control
- early weight bearing - ilium and femur can fuse
- rehabilitation
Why would a FHO be recommended?
- cheaper
- easier
- faster
- better than nothing
not the best we have to offer!
What are 4 differences between a total hip replacement and other treatments of hip dysplasia?
- quicker recovery
- pain-free
- best function after surgery
- lasts the life time of the patient
What is the goal of total hip replacements? What patients are able to get these?
salvage procedure to replace diseased femoral head and acetabulum —> return to normal function in sporting and working dogs
all sizes (up to 125 kg!), over 6 m/o
What 5 problems are total hip replacements able to solve?
- osteoarthritis - primary, hip dysplasia
- chronic luxation at CFJ - trauma, CFJ dysplasia
- fracture of the femoral head/neck - comminuted, malunion
- avascular necrosis
- revision of failed procedures - FHP, TPO
What patient history and ages are able to receive a total hip replacement?
HX - waxing/waning hindlimb lameness, bunny hopping, weight-bearing lameness
AGE - >6 mo, greater trochanter growth plate closure
What are the 2 major contraindications for total hip replacements? What are some others?
- non-clinical patient
- geriatric patients responsive to medical management - diet, exercise restriction, NSAIDs, intramuscular PSAGAG, glucosamine
- other orthopedic disease, septic arthritis
- dermatitis (pyoderma)
- neurologic disease (IVDD, LS disease)
- myopathy
- neoplasia - histiocytic sarcoma, synovial cell sarcoma
- immune-mediated disease - hyperadrenocorticism causes delaying healing
What are the 3 major systems for total hip replacements?
- cemented - Biomedtrix CFX
- cementless - Biomedtrix BFX, Kyon (Zurich), Helica
- Hybrid - CFX-BFX
Total hip replacement:
What are the 2 components of cemented (CFX) hip replacements?
- FEMORAL - stem, neck, head
- ACETABULAR - cup, polyethylene liner
How are cement implant sizes determined? What do under-sizing and over-preparation lead to?
make a template based off of radiographs
- UNDER-SIZING = decreased iatrogenic fixation
- OVER-PREPARATION = limited to cancellous bone
What is centralization of cemented hip replacements like?
device avoids endosteal contact to avoid femoral fractures
How is the femoral component of a cemented hip replacement aligned?
centrally along the long axis of the femur
- mantel 2mm proximally, 20mm distally
What 2 femoral component initial stabilization interfaces are available for cemented hip replacements?
- bone-cement
- cement-implant
What are the 2 components of cementless hip replacements?
- FEMORAL - stem with collar or porous coating, neck, head
- ACETABULAR - cup of porous coating, polyethylene liner
What kind of fit does cementless hip replacements have?
press fit with the implant in contact with the cortical bone —> stove pipe femur, no isthmus
How are cemented hip replacements placed? What 2 complications are associated?
initial stabilization applies friction
- stress applied at interface (implant-cortical bone) - increases risk of loosening
- stress applied to bone away from implant increases risk of fracture
How are hybrid hip replacements placed?
- CFX (cement) = femoral
- BFX (cementless) = acetabular
What are cemented hip replacements commonly used to correct?
- FHO - low ostectomy at lower trochanter
- THR - isthmus of the femoral neck
What femoral preparation is used for cemented hip replacements?
- drill
- ream
- broach
What are 3 ways of cement preparation and injection? What is commonly added?
- slow vacuum mixing. -decreases porosity, increases fatigue strength
- pressurization - forces cement into irregularities
- retrograde filling - decreases air pockets
antibiotics —> Cefazolin (does not decrease strength)
What is the purpose of reaming the acetabulum?
removal of cartilage for the insertion of an oversized acetabular implant enabling press fit
What are 2 important angles used for proper positioning of cemented hip replacements?
- lateral opening - >60% dorsal covering = more likely to luxate
- version - want a 15-25 degree retroversion to match femoral normoversion-anteversion
How do the sizes of femoral head replacements affect their use? How is external rotation of limbs maintained?
affect neck length
partial tenotomy of the external rotator muscles
Total hip replacement, implant position:
What are 3 important components of post-operative care following a total hip replacement?
- analgesics - NSAIDs for 1-3 weeks due to concurrent DJD exacerbation
- antibiotics - if culture positive, continue for 1-2 months and monitor for radiographic loosening
- exercise restriction - gradual return to activity over 3 months with follow-up radiographs
What should the first 3 months following a total hip replacement look like?
MONTH 1 - “house arrest,” good traction floors, no stairs, running, jumping, or rough play
MONTH 2 - short leash walks several times a day
MONTH 3 - longer leash walks, no running, jumping, or rough play, gradual return to normal