Final Exam - Joint Disease of the Hip Flashcards
what is the pathogenesis of canine hip dysplasia?
laxity develops during skeletal growth because the soft tissues supporting the hip are unable to develop & keep pace with rapid bone growth - laxity results in subluxation of the hip joint during weight bearing with repetitive luxation resulting in lameness
what is the 2nd most common cause of pelvic limb lameness?
canine hip dysplasia
why is canine hip dysplasia considered to be developmental & not congenital?
hips are normal at birth
T/F: canine hip dysplasia is typically a bilateral disease
true
what factors have been directly implicated in canine hip dysplasia?
breed - common in large/giant breeds (GSD, st bernards, goldens, labs)
diet - maximizes trait expression in genetically susceptible individuals
body weight - obesity
sterilization - OHE/neuter increases risk
activity level - worsens clinical signs associated with disease
maternal factors - increased relaxin, testosterone, estradiol
what is the one phrase that can be used to describe the underlying pathophysiology of CHD?
excessive joint laxity
what is the source of the lameness in early canine hip dysplasia?
activation of pain fibers within the ligament of the femoral head, joint capsule, & labrum - not osteoarthritis
what has occurred in a dog with CHD that has the resolution of clinical signs by 12-18 months of age?
the body responds to excessive joint laxity & attempts to stabilize the joint through fibrosis of the joint capsule & ligament of the femoral head - the fibrosis can be capable of resolving clinical signs but doesn’t mean the patient is cured
what is the bimodal age distribution for dogs with CHD?
young dogs - display clinical signs because of excessive joint laxity, joint subluxation, & soft tissue pain
mature dogs - display clinical signs because of OA that occurs secondary to previous joint laxity
what is the typical history of a young dog with CHD? what about an old dog?
young - bunny hop gait, acute signs, can be identical to CCL ruptures, normal sit test
mature - pet is ‘getting older’, difficulty rising, insidious/slowly progressive
what is an ortolani sign?
physical exam test used to detect joint laxity - one hand is placed on the dorsal aspect of the pelvis for counter pressure
stifle is flexed 90 degrees & cradled with the other hand, hip is put into a weight bearing position & firm pressure is generated by compression hands together, while maintaining pressure - limb is slowly abducted
during early phases of CHD - a palpable/visible click or pop occurs as the femoral head reduces within the acetabulum
T/F: normal puppies can have a positive ortolani sign until approximately 4-6 months of age
true - if present after 6 months of age, suggestive of CHD
why may a mature dog not have a positive ortolani sign?
as OA develops within the hip, acetabular infilling with new bone occurs resulting in loss of a normal acetabular depth - result is a loss of a deep structurally normal acetabulum to allow for reduction of the femoral head
as the body responds to excessive laxity, periarticular fibrosis develops & may limit the examiner from subluxating the femoral head
why are sedated radiographs necessary for a dog with CHD?
to rule out other causes of lameness, confirm the clinical diagnosis, to provide the owner with recommendations regarding breeding, & to classify or stage the patient’s hips (is the dog in early phases of CHD but no OA? has the dog developed OA? radiographic severity?)
what radiographic techniques are commonly used to evaluate & grade CHD?
OFA-style & pennhip
what are the advantages & disadvantages of using OFA-style rads for CHD?
advantages - excellent for identifying OA & helpful in determining phase/stage of CHD
disadvantages - can miss early cases, if submitting for OFA, can’t be graded until 2 years of age
how are pennhip rads taken?
rads of the hip joints are obtained with the hips in a weight bearing position before & during the simulation of weight bearing - measurements are made creating a distracting index where a DI of 0 indicates zero laxity & a DI of 1 indicates complete luxation
if you have a DI <0.3 on pennhip rads, what does that mean? what about a DI of >0.7?
<0.3 - no laxity/subluxation, unlikely to have CHD
> 0.7 - excessive joint laxity/subluxation, likely to have CHD
what is the use of pennhip rads?
used to predict the likelihood of development of future CHD based on an objective measure of laxity - big tool for breeders wanting to make selections before 2 years of age
what are the treatment goals for CHD?
controlling clinical signs, elimination of excessive laxity, & treatment of existing OA
what are the indications for a juvenile pubic symphysiodesis?
young dogs ideally 16-20 weeks of age with clinical signs of CHD, positive ortolani, & must be free of OA
what is the goal of performing a JPS?
correcting excessive joint laxity by improving dorsal acetabular rim coverage of the femoral head during skeletal growth
how is a JPS performed?
small ventral approach is made to the pubic symphysis where it is cauterized resulting in necrosis/growth arrest of this portion of the pelvis - as the puppy grows, the sacrum widens & the remainder of the pelvis grows resulting in lateral rotation of the dorsal acetabular rim
results in improved coverage of the femoral head, improved hip congruity, resolution of laxity/subluxation, & resolution of clinical signs
why must you spay/neuter a dog when a JPS is done?
there will be no evidence of the surgery once maturity is reached & the animal could pass certification for breeding if left intact
what are the indications for a triple pelvic osteotomy?
young dogs, 6 months to 1.5 years, with clinical signs of CHD, positive ortolani, & must be free of OA
what is the goal of the TPO/DPO surgery?
corrects laxity acutely by rotating the acetabulum laterally to capture the femoral head & eliminating hip subluxation & associated clinical signs
what is the procedure of a TPO?
osteotomies are performed at the pubis, ischium, & ilium - acetabulum is rotated laterally & held in position with a specialized TPO bone plate that is placed on the ilium
plate maintains the new acetabular orientation until bone healing occurs
how is a DPO performed?
same as TPO except ischial cut is omitted which results in a more physiologic rotation of the dorsal acetabular rim & clinically more stable hemipelvis which improves patient comfort & accelerates return to function
why is it recommended to use specialty locking plates when doing a DPO?
the DPO places increased strain on the bone-screw-bone interface
helps maximize success & prevent complications
what are the indications for an FHP?
young dogs with severe CHD & OA that have failed medical management, hip luxation secondary to CHD, mature dogs with moderate to severe OA that have failed medical management, & dogs that could be candidates for THR but have other constraints
what is the goal of an FHO?
source of the lameness is typically the OA & associated bone on bone contact of the femoral head with the acetabulum
FHO addresses the lameness through surgical removal of the femoral head, most of the femoral neck, & occasionally some of the lateral acetabulum
surgical removal of the painful joint eliminates bone on bone contact, OA-mediated pain, & allowing for adequate limb function
how is an FHO performed?
craniolateral approach to the hip followed by the transection of the ligament of the femoral head & isolation of the femoral head & neck
ostectomy is made from the base of the greater trochanter to the base of the lesser trochanter & the head & neck are removed
the joint is not replaced - soft tissues are interposed & sutured between the acetabulum & the femur & a false joint forms over time
what is required for a successful outcome of an FHO?
meticulous surgical technique & early/regular rehabilitation & rechecks during the post-operative period
what are the complications associated with FHOs?
dogs that undergo FHOs will have a slightly shortened leg & abnormal gait post op due to the mechanical effects of the procedures
what are the indications for a total hip replacement?
young dogs with moderate to severe CHD & radiographic OA, owners who expect a high level of function, hip luxations, mature dogs with mild to severe OA, acute femoral head/neck fractures, & malunion acetabular fractures
what is the goal of a THR?
surgical removal of the femoral head & articular portion of the acetabulum & replacing the diseased joint with an artificial joint
the replaced hip eliminates pain & allows completely normal limb function
how is a THR performed?
similar to an FHO with less bone removed from the femoral neck - acetabular reamer is used to remove the articular portion of the acetabulum & an acetabular implant, femoral head & neck implant are placed
what is the gold standard for treating CHD?
THR
what are the 4 complications associated with THR?
- luxation
- infection
- aseptic loosening
- femur fracture
what is the suggested approach for speaking with clients about options for CHD?
evaluate each patient, determine stage of CHD, & offer all relevant treatments giving detailed pros & cons for each
____ & ___ are surgical treatments for young CHD dogs without OA
JPS & DPO
____ & ___ are surgical treatments for mature CHD dogs with moderate to severe OA
THR & FHO
