SA developmental disease

Question 1

What is hip dysplasia?

Answer 1

Hip dysplasia is an inherited developmental disease of the hip joint, characterised by hip laxity and the development of osteoarthritis

Question 2

How comon is hip dysplasia?

Answer 2

• Very common disease that usually affects both hips
• May not be devastating disease, with many dogs and cats showing minimal or no clinical signs

Question 3

Who is effected by hip dysplasia?

Answer 3

• Affects all breeds of dog although prevalence is higher in large and giant breeds
• No sex predisposition
• In cats, higher prevalence in Maine Coon, Persian, Devon Rex and Himalayan

Question 4

What can be seen here?

Answer 4

Hip dysplasia

Left: subluxated Right: completely luxated

Both can see femoral neck and acetabular changes

Question 5

What is the causative pathogenesis of hip dysplasia?

Answer 5

Inherited, mechanism of inheritance is consistent with a polygenic trait (the phenotypic expression is influenced by genetic and non-genetic factors)

Variable estimates of heritability ranging from 0.2-0.6 depending on population studied

Non-genetic factors that may play a role in the expression of the disease include

• Body size
• Growth rate
• Nutrition
• Exercise
• Muscle mass

Question 7

What is the aetiopathogenesis of hip dysplasia?

Answer 7

• Grossly normal at birth
• loss of congruency between articular surfaces of the acetabulum and femoral head
• This loss of congruency leads to the development of osteoarthritis and bone remodelling
• Pain in initial stages thought to be the result of stretching of the joint capsule and microfractures in the dorsal acetabular rim
• Pain subsides in many cases following the gradual increase in stability afforded by the intra-and periarticular changes (mainly, thickening of the joint capsule)

Question 8

What can be seen in this image?

Answer 8

Red dots: show that the femoral head has subluxated they aren’t where they should be

Yellow wibbly line: remodelling changes that are trying to stabilise laxity

Yellow arrows: pointing to new bone growth/sclerosis.

Question 9

What are the signs of osteoarthritis in Hip dysplasia?

Answer 9

• Changes in shape of the dorsal acetabular edge
• New bone formation in the acetabular fossa, the cranial and caudal acetabular edges, femoral head and neck
• Degree of remodelling of the femoral head and neck

Question 10

What is the Norberg-Olsson angle?

Answer 10

Angle used to assess hip dysplasia

• Angles smaller than 105 degrees are considered abnormal
• To create mark centre of femoral head and draw straight line between them. Then a line going forwards that touches cranial aspect of acetabular ring and this angle is called the norberg-olsson angle.

Question 11

What is the warning associated with radiographic interpretation of Hip Dysplasia?

Answer 11

• There is poor correlation between the severity of radiographic changes and the clinical signs
• Many dogs (and cats) show radiographic features of hip dysplasia but no clinical signs

Question 12

What are the D/dx for Hip dysplasia in young dogs?

Answer 12

Differential diagnoses in the young dog

• Patellar luxation
• Cranial cruciate ligament disease
• Hock and stifle osteochindrosis
• Legg-Calve-Perthes disease
• Septic arthritis
• Spinal disorders
• Myasthenia gravis
• myopathies

Question 13

What are the D/dx of hip dysplasia in the mature dog?

Answer 13

Differential diagnoses in the mature dog

• Cranial cruciate ligament disease
• Patellar luxation
• Degenerative lumbosacral disease
• Other spinal disorders
• Achilles tendinopathy
• Septic arthritis

Question 14

What are the clinical signs of Hip dysplasia in young animals? (4-10 months of age)

Answer 14

Young dog (4-10 months of age)

• Variable degree of pelvic limb lameness
• Swaying of the pelvis when walking
• ‘Bunny-hopping’ gait at faster speeds
• Weakness of the pelvic limbs
• Reluctance to exercise
• Inability to jump
• Inactivity stiffness

Question 15

What are the clinical signs of Hip Dysplasia in the adult dog (over 12 months of age)?

Answer 15

Adult dog (over 12 months of age)

• Difficulty rising
• Pelvic limb inactivity stiffness (often worse after exercise)
• Exercise intolerance
• Difficulty jumping
• Behavioural changes (e.g. aggression when hindquarters touched)
• Sudden onset lameness (uncommon)

Question 16

Discuss bi-modal hip dysplasia clinical signs?

Answer 16

The clinical signs associated with HD typically have a bimodal age distribution:

1. Although clinical signs can appear at any age, many dogs under 1 year that are affected present with signs related to hip instability and secondary synovitis
2. Older dogs present with signs related to hip osteoarthritis

Be aware that because of the high prevalence amongst dogs, HD tends to be over-diagnosed in both immature and older dogs

Question 17

Strictly define elbow dysplasia?

Answer 17

Elbow dysplasia may be strictly defined as the abnormal development of the cubital joint

Question 18

In dogs, numerous disease processes have been included under the term elbow dysplasia; however, three main diseases predominate, these are?

Answer 18

• Un-united anconeal process (UAP)
• Fragmentation of the medial coronoid process (FCP)
• Osteochondritis dissecans (OCD) of the medial portion of the humeral condyle

Question 19

Define Elbow dysplasia?

Answer 19

Elbow dysplasia may be strictly defined as the abnormal development of the cubital joint

Question 20

What is the liklihood of having the conditions that predominate in causing elbow dysplasia?

Un-united anconeal process (UAP)

Fragmentation of the medial coronoid process (FCP)

Osteochondritis dissecans (OCD) of the medial portion of the humeral condyle

Answer 20

• Each condition is usually seen in isolation but any combination of the three is possible
• Having all three conditions at once is unlikely

Question 21

Other diseases implicated in elbow dysplasia are?

Answer 21

• Joint incongruity
• Incomplete fusion of the medial epicondyle
• Idiopathic osteoarthritis of the medial compartment of the elbow joint

Question 22

Do cats get elbow dysplasia?

Answer 22

Elbow dysplasia has not been reported in cats, although there is ever greater recognition of osteoarthritis of the elbow in this species

Question 23

How does the anconeal process usually develop and how does this differ in the GSD?

Answer 23

Normally the anconeal process develops as part of the ulna diaphysis but in certain breeds (e.g. GSD) it develops as a separate centre of ossification

Question 24

How does a UAP occur in a basset hound and other similar breeds?

Answer 24

In certain breeds (e.g. Basset Hound) separation is secondary to non-traumatic premature closure of the distal ulnar growth plate

Question 25

The instability and irritation following separation of the anconeal process causes?

Answer 25

* osteoarthritis * Often seen in association with FCP (diagnosed at arthroscopy)

Question 26

Look at an image of a UAP?

Answer 26

Question 27

What does A mark?

Answer 27

Anconeal process

Question 28

How is a UAP diagnosed?

Answer 28

* One or both elbows * Progressive thoracic limb lameness at about 4-5 months of age * Strange gait with elbow abducted (may have outward rotation of the foot) * Palpation/manipulation will reveal joint thickening and varying amounts of joint effusion * Reduced joint movement, pain, maybe crepitus

Question 29

What breeds is UAP common in?

Answer 29

Predominantly GSD although other large-breed dogs such as Wolfhound, Rottweiler, St. Bernard and Great Dane

Question 30

How is diagnosis of UAP confirmed?

Answer 30

* Diagnosis confirmed by taking a fully flexed lateral radiograph of the joint (avoid superimposition of the medial epicondyle on the olecranon) * Arthroscopy can be performed but is more useful for evaluation of the remainder of the joint for FCP and OCD

Question 31

What is currently the commonest cause of elbow lameness in young, rapidly growing dogs of large and giant breeds •Rottweilers, Labrador retrievers, Bernese mountain dog (also GSD, golden retriever, St. Bernard, chow chow, Rhodesian ridgeback, Newfoundland)?

Answer 31

Fragmentation of the medial coronoid process

Question 32

There is no separate centre of ossification for the coronoid process so why it becomes fragmented is less clear cut but possible causes are?

Answer 32

* osteochondrosis * microfracture/fracture * radioulnar incongruity * humeroulnar incongruity

Question 33

What is the pathology of FCP?

Answer 33

* Currently, one or more fragments of bone may have fractured from either the inner aspect of the medial coronoid process immediately adjacent to the radial head, or from the apex of the process * Fragment/s often remain attached to the annular ligament * The fragment/s may project causing erosion of adjacent medial humeral condyle (kissing lesion)

Question 34

Illustrate where a FCP occurs?

Answer 34

Question 35

Look at this FCP pathology?

Answer 35

Question 36

What are the clinical signs of FCP?

Answer 36

* Outward rotation of pes * Reduced range of flexion and extension * Painful response to external rotation and hyperextension * Crepitus in advanced cases

Question 37

What can be seen on radiography of a FCP?

Answer 37

Difficult to see lesions on conventional radiographs (large fragments might been seen on craniocaudal or craniolateral-caudomedial oblique projections) **CT** scans much better and will allow assessment of congruency as well **Arthroscopy** –Will allow diagnosis of definitive type and severity of elbow dysplasia

Question 38

Show how hard it is to see FCP on radiograph?

Answer 38

Question 39

What is the best imaging modality to diagnose FCP?

Answer 39

Question 40

What might you see on arthroscopy of FCP?

Answer 40

Question 41

What is the aetiology of OCD of medial condyle?

Answer 41

* Aetiology and pathogenesis of OCD of the canine elbow joint is poorly understood * Lesion initiates deep within the articular- epiphyseal cartilage complex in the developing joint * Necrosis of vascular channels lead to development of a cartilage flap (?) * Highest incidence in Labrador and golden retrievers * Commonly, bilateral involvement

Question 42

Where is the OCD lesion usually seen?

Answer 42

* Lesion is usually found near outer edge of the central weightbearing region of the articular surface of the medial part of the humeral condyle * OCD may be identified in conjunction with FCP and medial compartment osteoarthritis

Question 43

Outline where OCD, FCP and UAP can be seen?

Answer 43

Question 44

What can be seen here?

Answer 44

OCD of medial condyle

Question 45

How can OCD be diagnosed?

Answer 45

**Clinical signs** * Clinical signs are very similar to FCP **Radiography** * Flexed lateral radiograph will show presence of osteoarthritis on the anconeal process * craniocaudal or craniolateral-caudomedial oblique projections will usually reveal a defect in the subchondral bone of the medial part of the humeral condyle * CT scans will allow for good assessment, etc. **Arthroscopy** * Diagnosis and treatment may be performed through arthroscopy

Question 46

Compare radiographs and CT images of OCD?

Answer 46

Question 47

How does OCD appear on arthroscopy?

Answer 47

Question 48

Define Varus?

Answer 48

Varus = medial deviation of the distal limb

Question 49

Define Valgus?

Answer 49

Valgus= lateral deviation of the distal limb

Question 50

Unilateral angular limb deformities usually occur as a result of?

Answer 50

Usually occurs as a result of **trauma** to all or part of an active growth plate = immature dogs It can also result from: * other conditions involving abnormal endochondral ossification e.g. retained cartilagenous core * other conditions affecting the growth plate e.g. metaphyseal osteopathy

Question 51

Bilateral angular limb deformity usually occurs due to?

Answer 51

a systemic problem eg nutrition, growth rate etc

Question 52

Most severe consequences of angular limb deformity are when?

Answer 52

One of a set of paired bones involved (e.g. radius and ulna, or tibia and fibula)

Question 53

What is happening in each of these images?

Answer 53

**1st image:** growing normally **2nd image:** Varus abnormality as medial half of the radial epiphysis has fused prematurely so ulna has continued to grow causing varus abnormality **3rd image:** Lateral side of radial epiphysis has fused creating a valgus abnromality **4th image:** distal ulna fused prematurely causing valgus abnormality

Question 54

What are the clinical signs of angular limb deformity?

Answer 54

* ‘bent’ leg * variable degree of lameness depending on severity of deformity * most severe problems when animal cannot placed paw ‘flat’ on the ground * lameness more severe when elbow affected * Therefore lameness resulting from an ALD can have both painful and mechanical elements to it.

Question 55

How should radiography be performed for ALD?

Answer 55

* Good quality orthogonal views of both legs * Include all of antebrachium with elbow and carpal joints, and at least proximal ½ of metacarpals / metatarsals * Straight elbow -let rest of leg do it’s own thing * Measure and record degree of valgus / varus * Measure and record length of radius and ulna * Up to 15 degrees valgus angulation is usually clinically insignificant

Question 56

Describe premature closure of the distal ulnar growth plate?

Answer 56

**3D deformity:** * distal limb valgus * external rotation of the foot * cranial bowing of the radius **Can result in:** * elbow incongruity * antebrachiocarpal joint incongruity (less commonly)

Question 57

Compare normal and abnormal limbs?

Answer 57

Question 58

What can be seen here?

Answer 58

Curvature has occurred as a result of early ulna closure causing the radius to curve

Question 59

How is premature closure of the distal ulna GP --\> leading to short ulna managed in the immature animal?

Answer 59

Immature animal: * Main concern is elbow joint incongruity (= elbow pain) and secondary concern is the valgus deformity (= carpal pain/pad sores etc) * Surgical techniques use the remaining growth of the radial growth plate to help correct the angular limb deformity slowly over time

Question 60

How is premature closure of the distal ulna GP --\> leading to short ulna managed in the mature animal?

Answer 60

**Mature animal:** * main concern is elbow joint incongruity (= elbow pain) and secondary concern is the valgus deformity (= carpal pain/pad sores etc) * radius is cut and re-aligned

Question 61

What are the surgical options for ALD before skeletal maturity?

Answer 61

If the dog is young and still has considerable growth potential, consider: * proximal ulnar osteotomy to improve elbow incongruity * distal ulnar ostectomy to remove bow-string effect and preserve elbow joint * stapling the medial side of the radius

Question 62

What surgical procedure has been done here?

Answer 62

Proximal (‘dynamic’) ulnar osteotomy Young dog still capable of growing can see incongruity in left image. Proximal ulna osteotomy has made elbow joint congruent again post op on the right.

Question 63

What has been done here?

Answer 63

Ulnar ostectomy and radial stapling or use screws and wire This aims to slow down the radial growth to discourage joint from moving in the hope dog may grow out of the problem

Question 64

What are the treatment options for near skeletally mature dogs with ALD?

Answer 64

Elbow incongruity remains priority –proximal ulnar osteotomy if necessary Bones have stopped growing, and so will not ‘self- correct’, therefore: * distal ulnar ostectomy, and * radial osteotomy with either: * one stage correction and stabilisation using linear external skeletal fixator or bone plate * ‘staged’ correction using Ilizarov fixator

Question 65

What is going on here?

Answer 65

* Osteotomy & External Skeletal Fixator (one stage / static correction) * This treatment is reserved to dog that is no longer growing