2.4 Hindlimb Lameness: Hip and Hock

Question 1

What is hip dysplasia??

Answer 1

a deformity of the hip that occurs during growth; dogs are born normal, but acquire hip laxity from 30 days onward

• the required uniform growth during maturation does not occur
• the result is laxity of the joint, which precipitates subluxation, microfracture, or cartilage erosion, all of which lead to degenerative joint disease (DJD) / osteoarthritis (OA)

the dog’s degree of lameness is dependent on the extent of the arthritic changes and may not be correlated with the appearance of the hip joint on radiographs

Question 2

What signalment is predisposed to hip dysplasia?

Answer 2

• very common in large breed dogs (labs, GSD, golden retrievers), and medium breeds
• rare in giant and small breed dogs and cats
• seen by 6-7 months of age (pelvic swaying, lameness, bunny hopping)
• also seen in older dogs (severe HD and resultant DJD/OA)

hip dysplasia is genetic (30% genetic, 70% other)

• lifestyle changes can steepen the onset and progression of arthritic changes seen in dogs with hip dysplasia

Question 3

What are the key findings on an orthopedic exam for dogs with hip dysplasia?

Answer 3

PAIN on hip EXTENSION (+/- abduction)

• may hear clicking, popping, or clunking
• may present with muscle atrophy from disuse

importantly: if young, more likely to be HD; if older, rule out cruciate rupture first!

Question 4

How do you diagnose hip dysplasia?

Answer 4

(1) radiographs

• VD of extended leg and lateral pelvis
• sedated/anesthitized (painful)
• you MUST see the stifle in the radiograph, as you NEED to insure that the legs are straight (fibellae bisected by the edges of the femur and patella in the middle of the femoral head)

(2) palpation tests

• barlow maneuver: while supporting the dog’s pelvis in lateral recumbency, press the femur toward the hip (with some light adduction); if subluxation occurs, this is a positive barlow test
• ortolani maneuver: after subluxation via the barlow maneuver, attempt to reduce the dislocated hip by abduction of the flexed hip with gentle anterior force - it should “pop” back into place; the angle at which this happens is also significant

(3) other investigations

• Norberg angle
• PennHip distraction index
• % femoral head coverage

barlow (left); ortolani (right)

Question 5

What radiographic changes suggest hip dysplaisa and OA?

Answer 5

ONCE you know that you have a perfect radiograph, then you can look for the hallmarks of hip dysplasia:

• draw a circle over the head of the femur and draw a line at the edge of the acetabular rim: more than 50% of the femoral head should be covered
• early secondary changes in younger animals

in older animls:

• thickening and capsule mineralization
• osteophytes / new bone formation
• flattening of the femoral head: “mushroom”
• flattening of the acetabulium: “dishing”
• subluxation
• completely “luxoid” when severe laxity is displayed, and the femoral head is no longer within the acetabulum

luxoid hips (right): note fibellae/patella NOT pictured here but they MUST be in radiographs detecting HD

Question 6

How do you manage hip dysplasia?

Answer 6

non-surgical management should always be first-line treatment (regardless of age); no need to rush to a decision (are they in pain?)

(1) exercise adjustment:

• regular, SHORT exercise: 10 minutes every 3-4h daily
• increase by 5 minutes every 2 weeks
• rest at home: no free garden access, walk on lead

(2) physical therapies

• hydrotherapy / physiotherapy

(3) diet

• keep lean or lose weight

(4) pain management

• NSAIDs: 4-6 weeks if possible
• “wind-down” pain signalling

Question 7

What surgical treatments are available for hip dysplasia?

Answer 7

(1) prophylactic: done while young to improve conformation

• pelvic osteotomy: cut pelvis to rotate acetabulum (increases coverage of femoral head)
• juvenile pubic symphysodesis: damage growth plate to rotate acetabulum (increases coverage of femoral head)

(2) definitive arthroplasty

• femoral head and neck excision (FHNE): pseudarthrosis (synonymous with femoral head ostectomy [FHO])
• total hip replacement: best outcomes, specialist procedure

Question 8

What is legg calve perthes?

Answer 8

also called avascular necrosis:

Legg-Perthes is a painful condition that affects the hip: poor blood supply to the femoral head causes the collapse of the epiphysis

• leads to a stiff, painful hip joint which causes a limp, and eventually arthritis

Legg-Perthes often develops at around five months old and most commonly affects small breed dogs

• usually only affects one hip; it is rare for both to be affected

moth-eaten or "apple core" appearance of femoral head; in late-stage legg calve perthes a flattening or mottling is seen; re-ossification can occur (along with re-vascularization) which leads to severe malformation of the femoral head and severe OA

Question 9

What is the most common signalment for legg calve perthes?

Answer 9

• small terriers, yorkies, chihuahuas, schnauzers, poodles
• ~4 months old

Question 10

What problems are seen in the tarsus region of dogs?

Answer 10

(1) OCD

• rare in tarsus
• tarsal effusion, upright, stiff hocks
• tarsal thickening
• 5 months - 1 year (labs, rotties, mastiffs)

(2) achilles tendon traumatic rupture

• the Achilles’ tendon or common calcaneal tendon is made up of multiple tendons from several different muscles of the hind limb
• contains the superficial digital flexor muscle and tendon, the gastrocnemius tendon and the combined tendon of the gracilus, semitendinosus and biceps femoris muscles
• dropped hock, claw foot
• swelling/thickening

(3) plantar ligament degeneration and collapse

• progressive lameness

(4) other:

• traumatic metatarsal fracture
• traumatic joint luxations