Ch 58 - Pathogenesis, Diagnosis and Control of Canine Hip Dysplasia Flashcards
When are the earliest gross changes of HD visible and what are they?
30 days
- Oedematous ligament of head of the femur with torn fibers and capillary haemorrhage
- Increased volume of ligament and of synovial fluid
When are the first radiographic signs of HD visible and what are they?
7 weeks old
- Subluxation
- Underdevelopment of craniodorsal acetabular rim
- From 60-90d the degree of subluxation increased
What two destructive event accompany subluxation?
- The forces crossing the joint increase as the force of the periarticular muscles increase to attempt stabilisation
- The area over which the forces are transmitted decreased (abnormal forces within the joint)
What muscles help to reduce the femoral head when weight bearing?
- Gluteals
- Adductor magnus et brevis
What is a luxoid hip?
A hip showing the most severe phenotypic characteristics of HD. It is permanently sub-luxated (or luxated) in all the phases of the gait cycle.
What is the neutral stance of the hip?
- 10-15 deg of extension
- 10 deg of abduction
- 0 deg of rotation
Hip joint laxity is at its maximum when at a neutral stance
What is considered a normal Norberg angle?
Over 105°
What did the lifelong Labrador study highlight regarding age of HD?
- Only 55% of those whom would eventually develop HD, showed radiographic evidence by 6yo
What distraction index is considered low chance of developing OA?
- Under 0.3
What hormone may be associated with increased hip laxity?
Relaxin.
- It is elevated in last trimester of pregnancy and also in the milk of lactating bitches
- Last been associated with increased peripheral joint laxity in humans and dogs
- Higher levels found in Labs than Beagles
Gonadal hormones.
Non-neuter male Golden Retrievers are half as likely to develop clinical signs of HD by 4.4yo compared to intact males and those neutered after 12y of age.
- Neutering after 12mo seems to have a protective effect on clinical signs
How does weight effect the development of HD?
- Heaviest male and female GSD puppies at 60d old had highest incidence of HD at maturity
- Overweight dogs develop radiographic OA 6 years earlier than lean counterparts
- Overweight dogs require medication 3 years earlier
- Lean dogs have a higher life expectancy by 1.8yr
What nutritional factors may play a role in HD?
- High dietary Ca and excessive VitD (delayed endochondral ossification ans skeletal remodeling)
- High density anion gap diet (increased osmolality in synovial fluid and increased volume)
How have injectable polysulphated glycosaminglycans been shown to effect development of HD?
Give to puppies from dysplastic parents as twice weekly injections from 6wk to 8mo reduced subluxation scores and reduced histopath evidence of arthritis at 8mo
What are some common DDx for HD?
- Panosteitis
- OCD
- Hypertrophic Osteodystrophy
- CCLR
- LS stenosis
- Neoplasia
What are common findings on the gait exam
- Wide or narrow based stance
- Hips or spinal sway
- Stiff, short-strided
- Bunny-hopping