Hip dysplasia

Question 1

Is it a common dz?

Answer 1

• yes

Question 2

What kind of condition is it? What does this mean?

Answer 2

• it is a developmental condition
• no animal is born with hip dysplasia

Question 3

Type of clinical presentation

Answer 3

• biphasic clinical presentation with signs in the younger and then older animal

Question 4

Management options

Answer 4

• medical and surgical

Question 5

Attempts to reduce incidence

Answer 5

• there have been stringent and moderately successful attempts to reduce its incidence by phenotypic testing and selective breeding

Question 6

Correlation between radiographic and clinical signs

Answer 6

• poor correlation
• therefore assessment of the significance of x-ray changes is always made in light of CS

Question 7

Prevalence in cats?

Answer 7

• it occurs less frequently in the cat but is still a significant cause of lameness in this species

Question 8

Hip dysplasia - aetiology

Answer 8

• genetic predisposition resulting from breeding for ‘desirable’ breed characteristics
• associated with rapid growth
• over supplementation of calcium has also been implicated as a cause
• poor joint conformation results in increased laxity, synovitis and increased synovial fluid
• this in turn results in greater subluxation of the hip and a vicious cycle of pathological changes
• degenerative changes occur within the joint which become more apparent with age
• these changes include radiographic evidence of OA and CS of joint dz
• the latter includes stiffness on rising, pain, poor muscle development and lameness

Question 9

Hip dysplasia - common breeds

Answer 9

• labs
• Grets
• Newfies
• GSD
• CKCS
• cats: larger breeds e.g. Maine Coon

Question 10

Hip dysplasia - age at onset

Answer 10

• 6-12m

Question 11

Hip dysplasia - biphasic presentation

Answer 11

• initial presenting signs at 6-10m with pain on rising etc
• this is due to subluxation of the joint, synovitis and micro-fractures of the acetabular rim
• CS of OA develop in middle age with typical signs of lameness on rising, difficulty mounting stairs, jumping into vehicles etc

Question 12

Hip dysplasia - clinical hx

Answer 12

• pain on rising
• swaggering/swaying gait
• bunny hopping
• occasionally squeal out, particularly on rising
• acute presentations can occasionally occur with micro-fractures of the acetabular rim
• poorly muscled (gluteals)
• pain on manipulation of the hips, particularly on extension
• subluxation maybe detected (the Ortolani sign)
• a clunk as the hip reduces after being subluxated
• as the condition is usually bilateral an obvious lameness may not be present

Question 13

Hip dysplasia - CE

Answer 13

• joint laxity is dependent upon joint capsule thickness, integrity of ligament of femoral head, integrity of dorsal acetabular rim and muscle tension
• Barden’s palpation (hip lift): the hip is lifted from the acetabular by grabbing the diaphysis of the femur
• Barlow’s sign (this is the 1st part of the Ortolani manoeuvre when the hip dorsally subluxates
• Ortolani test (sedation/GA required)

Question 14

Hip dysplasia - Ortolani test

Answer 14

• performed under GA or heavy sedation
• dog in dorsal recumbency
• pressure applied towards the table to sublimate the hip
• abduct the hip till it clunks into the acetabulum (the angle of reduction)
• adduct the hip till it re-luxates (the angle of subluxation)

Question 15

Hip dysplasia - radiographic exam

Answer 15

Standard extended ventrodorsal view of the hips
- the view for the BVA/KC scheme
- hips are inwardly rotated so that the patellas are overlying the trochlea groove of the femurs and hindlimbs extended
- this can result in a reduced degree of subluxation driving the femoral heads into the acetabulae

Question 16

Hip dysplasia - radiographic exam: early signs of hip dysplasia

Answer 16

• subluxation of the joint with poor coverage of the femoral head by the acetabulum
• sclerosis of the cranial acetabular edge

Question 17

Hip dysplasia - radiographic exam: late signs of hip dysplasia

Answer 17

• the hips remain subluxated
• marked remodelling of the femoral heads
• remodelling of the acetabulum with marked sclerosis and new bone on the caudal and cranial edges
• extensive new bone on the femoral neck at the joint capsule attachments

Question 18

Hip dysplasia - radiographic exam: PENN distraction index (the PennHIP test)

Answer 18

• true measurement of the degree of subluxation achievable and hence laxity of the hip
• difficult to achieve without manual handling
• a devise has been produced which allows this to be assessed without manual restraint
• in this technique 2 radiographs are taken
• 1 demonstrates a non-stressed view and the other a distracted view of the hips
• the degree of distraction is then measured and the distraction index is calculated

The distraction index is the DI
- DI = distraction distance (d) / radius of femoral head (r)
- 0 = perfect congruity
- 0.3-0.7 = abnormal
- 1 = complete luxation

This test is more useful in the younger animal when joint instability is at its greatest and gives a good indication of the degree of hip dysplasia.

The test is not appropriate in the UK due to the requirement to hand hold unless using a mechanical distraction device is used

Question 19

Hip dysplasia tx - conservative management

Answer 19

• NSAIDs
• physiotherapy to increase gluteal mass resulting in greater joint stability
• nutraceuticals
• cartrophen
• weight control

The majority of dogs presenting win the 1st year of life can be managed conservatively but if this fails there are several surgical options available.

When the hip becomes stable, which it does as a result of increased muscle mass, periarticular fibrosis and new bone formation within the joint, the CS will disappear for several years.

Question 20

Hip dysplasia tx - surgical tx in the young dog

Answer 20

16w or less - pubic symphysideodesis
- fusion of the pubic symphysis with a diathermy probe to cause premature closure of this growth plate
- this results in the pelvis rotating and capturing the femoral heads
- uncommon for a dog to present in time for this

Pectineal myotomy
- straightforward technique and consists of sectioning the pectineal muscle
- it is suggested that this allows the femur to abduct slightly and increase weight bearing on the acetabular surface and reduces tension on the joint capsule both of which reduce pain
- the effects are generally temporary
- can be done in both the young and older animal

12m or less - triple (TPO) or double pelvis osteotomy (DPO)
- in the latter only the ill shaft and pubis are cut, in the former the ischium is cut also
- these isolate the acetabular segment of the pelvis
- it is then rotated to increase the dorsal covering of the femoral head by the acetabulum
- the segment is fixed with a special plate which has set degrees of rotation (20, 30 & 40 degrees)

Salvage procedures
- generally reserved for older dogs but can be done in younger animals
- include femoral head and neck ostectomy and total hip replacement

Question 21

Hip dysplasia tx - surgical management of the older dog

Answer 21

• femoral he’d and neck excision/ostectomy
  – large dogs do less well with this technique
• total hip replacement for the mature dog

Question 22

Hip dysplasia - control measures - the BVA/KC HD scheme

Answer 22

• subject must be >1y/o but doesn’t need to be KC registered
• examination requires GA or heavy sedation
• date, KC reg number, identichip or tattoo number and L/R marker must be present on the radiograph
• 9 parameters are assessed each with a value of 6 except the caudal acetabular edge with a value of 5
• total score 106 (53 for each cup)
• the lower the score, the better the hips
• the score needs to be compared with the breed median
• both hips need to be below the breed median to make the dog a suitable breeding candidate

Parameters examined
- Norberg angle
- degree of subluxation
- cranial acetabular edge
- cranial effective acetabular rim
- dorsal acetabular edge
- femoral head re-contouring
- femoral neck
- acetabular fossa
- caudal acetabular edge
Caudal acetabular edge scores 5, all the rest score 6

The Norberg angle is taken from a line joining the centre of each of the femoral heads. A further line is then drawn to the cranial effective acetabular rim and the constructed angle is measured.
- normal value >105 degrees
- sublimated hips with shallow acetabulum maybe <90

Question 23

Hip dysplasia BVA/KC HD scheme - limitations

Answer 23

• an assessment is being made of the genotype from a phenotypic measurement
• no allowance is made for the age of the dog (older dogs presented to the scheme inevitably have more secondary changes)
• there is no compulsion to have dogs with poor hips scored cf Scandinavian countries
• the breed mean/median is a historical value although now averaged over 5y
• the breed median rather than the mean is used to reduce the effects of outliers
• 1 should only breed from dogs whose worse hip is less than the breed median
• the age of the dog should be taken into consideration when assessing suitability to breed

Question 24

Feline hip dysplasia - signalment

Answer 24

• larger breeds affected particularly the Main Coon, Persian and Himalayan

Question 25

Feline hip dysplasia - CS

Answer 25

- OA develops later than in dogs - difficult to identify in the cat but may include a reluctance to exercise or jump onto work surfaces, reduced grooming

Question 26

Feline hip dysplasia - tx

Answer 26

- most can be managed with conservative tx - femoral head and neck ostectomy or total hip replacement - total hip replacement is prone to complications but has a more consistent outcome than femoral head and neck ostectomy