Small animal developmental disease Flashcards
Outline the aetiopathogenesis of hip dysplasia
- Inherited
- Non-genetic factors play role in expression of disease including body size, growth rate, nutrition, exercise, muscle mass
- Grossly normal at birth
- Loss of congruency between articular surfaces of acetabulum and femoral head, leading to osteoarthritis and remodelling
What causes the pain evident in the initial stages of hip dysplasia?
Stretching of the joint capsule and microfractures in the dorsal acetabular rim
Explain why the pain experienced in hip dysplasia appears to subside with age
- Gradual increase in stability to due intra- and peri-articular changes (mainly thickening of joint capsule)
- Secondary changes later in life
- As continues to progress, will get pain again as a result of osteoarthritis
Outline the diagnosis of hip dysplasia
- Joint laxity (degree of subluxation)
- Norberg-Olsson angle
- Signs of osteoarthritis
- NB poor correlation between the severity of radiographic changes and clinical signs
Explain how the Norberg-Olsson angle is used in the diagnosis of hip dysplasia
- Angle between the centre of the femoral head and dorsal edge of the acetabular rim
- Angles smaller than 105˚ are considered abnormal - indicate that femoral head has luxated to some degree out of the acetabulum
Describe the signs of osteoarthritis that are commonly seen in the hip as a result of hip dysplasia
- Change in shape of dorsal acetabular edge
- New bone formation in acetabular fossa, cranial and caudal acetabular edges, femoral head and neck
- Degree of remodelling of the femoral head and neck
List some differentials for hip dysplasia in young dogs
- Patellar luxation
- Cranial cruciate ligament disease
- hock adn stifle osteochondrosis
- Legg-Calve-Perthes disease
- Septic arthritis
- Spinal disorders
- Myasthenia gravis
- Myopathies
List some differential diagnoses for hip dysplasia in mature dogs
- Cranial cruciate ligament disease
- Patellar luxation
- Degenerative lumbosacral disease
- Other spinal disorders
- Achilles tendinopathy
- Septic arthritis
What clinical signs would you expect to see in a young dog with hip dysplasia?
- Variable pelvic limb lameness
- Swaying of pelvis when walking
- Bunny hopping at faster speeds
- Weakness of pelvic limbs
- Reluctance to exercise
- Inability to jump
- Inactivity stiffness
What clinical signs would you expect to see in an adult dog with hip dysplasia?
- Difficulty rising
- Pelvic limb inactivity stiffness
- Exercise intolerance
- Difficulty jumping
- Behavioural changes e.g. aggression around HLs
- Sudden onset lameness (uncommon)
What is the definition of elbow dysplasia in dogs?
Abnormal development of the cubital joint leading to incongruency
What are the 3 main diseases causing elbow dysplasia in dogs?
- Ununited anconeal process (UAP)
- Fragmentation of the medial coronoid process (FCP)
- Osteochondritis dissecans (OCD) of the medial portion of the humeral condyle
Identify uncommon diseases that may be included within elbow dysplasia in dogs
- Joint incongruity
- Incomplete fusion of the medial epicondyle
- Idiopathic osteoarthritis of the medial compartment of the elbow joint
- Angular limb deformity
How may an un-united anconeal process occur?
- Either due to development as a separate centre of ossification
- Or separation secondary to non-traumatic premature closure of the distal ulnar growth plate
Which breed is predisposed to the development of an un-united anconeal process as a result of separate centres of ossification?
GSD
Which breed is predisposed to the development of an un-united anconeal process as a result of non-traumatic premature closure of the distal ulnar growth plate?
Bassett hound
Briefly explain how premature closure of the distal ulnar growth plate leads to an un-united anconeal process
- Ulna does not grow at same rate as the radius, so radius forces heads of humerus caudally
- Puts pressure on anconeal process, preventing fusion
- Radius leads to joint incongruency
What are the consequences of an un-united anconeal process?
- Irritation and instability following separation of the anconeal process causing osteoarthritis
- Often seen in association with FCP
Which breeds are predisposed to elbow dysplasia as a result of an un-united anconeal process?
- GSD primarily
- Large breed dogs e.g. Wolfhound, Rottweiler, St Bernard, Great Dane
Outline the clinical signs of an un-united anconeal process
- Progressive thoracic limb lameness 4-5months of age
- Strange gait with elbow abducted +/- outward rotation of foot
- Palpation/manipulation reveals joint thickening and varying amounts of joint effusion
- Reduced joint movement, pain, maybe crepitus
How is an un-united anconeal process diagnosed?
- Fully flexed lateral radiograph of joint
- Arthroscopy possible for evaluation of remainder of joint for FCP and OCD
What should be avoided when taking a radiograph in a case with a suspected un-united anconeal process?
Superimposition of medial epicondyle on the olecranon
What is the most common cause of elbow lameness in young, rapidly growing dogs of large and giant breeds?
Fragmentation of the medial coronoid process
Which breeds are predisposed to a fragmented medial coronoid process?
- Rottweilers
- Labrador retrievers
- Bernese mountain dog
- GSD
- Golden retriever
- St. Bernard
- Chow chow
- Rhodesian ridgeback
- Newfoundland
What is the main difference between an FCP and a UAP?
There is no separate centre of ossification for the coronoid process - is a result of fracture of this fragment
List the potential causes of a fragmented coronoid process
- Osteochondrosis
- Microfracture/fracture
- Radioulnar incongruity
- Humeroulnar incongruity
- Abnormal pressure on medial coronoid process
Outline the consequences of a fragmented coronoid process
- Fragment may have fractured from inner aspect of medial coronoid process immediately adjacent to the radial head, or from apex of the process
- Fragment may project causing irritation of medial humeral condyle (aka kissing lesion)
Outline the clinical signs of a fragmented coronoid process
- Outward rotation of foot
- Reduced range of flexion and extension
- Painful response to external rotation and hyperextension
- Crepitus in advanced cases
- Pressure on medial coronoid process elicits strong pain response
Outline the diagnosis of a fragmented coronoid process
- Conventional radiography: difficult to see lesion unless large fragment on craniocaudal or craniolateral-caudomedial oblique projections
- CT images better
- Arthroscopy, also for assessment of severity
Outline the development of osteochondrosis of the medial condyle
- Lesion initiates within articular epiphyseal cartilage complex in developing joint
- necrosis of vascular channels leads to development of cartilage flap
- Separates from underlying bone, leading to discomfort
- Usually bilateral, on and on outer edge of central weight bearing region of the articular surface of medial portion of humeral condyle
Which breeds are predisposed to elbow dysplasia due to osteochondrosis of the medial condyle?
Labrador and golden retrievers
Outline the clinical signs of osteochondrosis of the medial condyle
- Similar to FCP
- Outward rotation of foot
- Reduced range of flexion and extension
- Pain on external rotation and hyperextension
- Crepitus in advanced cases
- Pressure on medial coronoid process elicits strong pain response
Outline the diagnosis of osteochondrosis of the medial condyle
- Radiography: flexed lateral radiographs (anconeal process osteoarthritis), craniocaudal or craniolaterla-caudomedial oblique,(defect of subchoondral bone of medial part of humeral condyle)
- CT scans
- Arthroscopy
Outline the appearance of osteochondrosis of the medial condyle on radiography
- Surface not smooth
- Some increased radiodensity where the flap is gone
What is a varus limb deformity?
Medial deviation of distal limb
What is a valgus limb deformity?
Lateral deviation of the distal limb
What is the underlying abnormality that leads to angular limb deformities?
Differing growth rates of the 2 bones of the antebrachium (radius and ulna)
List the potential causes of an angular limb deformity in the dog
- Unilateral: trauma to all or part of an active growth plate in immature dogs
- Abnormal endochondral ossification e.g retained cartilaginous core
- Metaphyseal osteopathy
- Bilateral more likley to be systemic problem e.g. nutrition, growth rate
If the growth plate of the radius is damaged on the medial aspect, in what direction will the limb be deformed?
Varus deformity
If the growth plate of the radius is damaged on the lateral aspect, in which direction will the limb be deformed?
Valgus deformity
If the distal ulna fuses prematurely, what limb deformity will occur and how?
Ulna stops growing, leg forced out laterally leading to a valgus deformity as radius continues to grow
- Also get external rotation of food and cranial bowing of the radius
Outline the clinical signs of an angular limb deformity of the dog
- Bent leg
- Variable degree of lameness depending on severity
- May be a painful and mechanical lameness
In which region will an angular limb deformity be most painful and why
- Elbow
- Carpal joint impacts on elbow joint
- If ulnar growth plate fuses, radius grows, radial head pushes against condyles of humerus
- Leads to incongruency of elbow joint leading to elbow dysplasia and pain
Outline the diagnosis of an angular limb deformity
- Radiography, orthogonal views of both legs, including antebracium with elbow and carpal joints, and at least proximal 1/2 of metacarpals/tarsals
- Straighten elbow
- Measure and record degree of valgus/varus, length of radius and ulna
- Up to 15˚ of valgus angulation is usually clinically insignificant
What are the potential consequences of premature closure of the distal ulna growth plate
- Elbow incongruity
- Antebrachiocarpal joint incongruity (less common)
- Carpal pain, pad sores etc. due to valgus deformity
List the potential surgical treatment options for premature closure of the distal ulnar growth plate in a young dog with considerable growth potential
- Proximal ulnar osteotomy
- Distal ulnar ostectomy to remove bow-string effect and preserve elbow joint
- Stapling medial side of radius
- Proximal (“dynamic”) ulnar osteotomy
Explain how a proximal ulnar osteotomy works to treat premature closure of the distal ulnar growth plate
- Cut the ulnar proximally
- Allows the radius to continue growing, as the ulna will separate to facilitate this
Explain how an ulnar ostectomy and radial stapling works to treat premature closure of the distal ulnar growth plate
- Ulna has section removed to reduce restriction of growth
- Radius stapled at growth plate to limit radial growth and prevent movement
- Prevents incongruency developing
List the treatment options for premature ulnar distal growth plate closure in animals near skeletal maturity
- Proximal ulnar osteotomy
- Distal ulnar ostectomy
- Radial osteotomy with either one stage correction and stabilisation using linear ex-fix/bone plate OR staged correction using illizarov fixator
What is the main aim of treatment of premature ulnar distal growth plate closure in animals near skeletal maturity
- Elbow and carpal joints parallel to each other and to the ground
- Aim for straight line
- Correction of elbow incongruity is top priority
Outline the process of normal bone development
1: Chondrocytes at centre of growing cartilage enlarge then die as matrix calcifies
2: Newly derived osteoblasts cover shaft of cartilage in thin layer of bone
3: Blood vessels penetrate cartilage, new osteoblasts form primary ossification centre
4: Bone of shaft thickens, cartilage near each epiphysis is replaced by shafts of bone
5: Blood vessels invade epiphyses and osteobalsts form secondary centres of ossification
Outline the signalment for panosteitis
- Young dogs 5-12months usually (reported 2mo-7yrs)
- Large breed dogs (23kg or more, incl. Bassetts)
- M>F
Outline the aetiology of panosteitis
- Unknown
- May have some genetic influence
- Some seasonal and geographical variation in incidence
Outline the presenting signs of panosteitis
- Shift leg lameness
- Pain on deep palpation of long bones, may be multifocal
- Lameness, vocalisation, loss of appetite
- Waxing and waning signs
- Humerus and radius most commonly affected
Outline the diagnosis of panosteitis
- Radiography of multiple long bones
- Signalment
- Clinical history
- Physical examination (lack of joint effusion, no enlarged LNs)
Discuss the use of radiography in the diagnosis of panosteitis
- Normal in early stages (lag for radiographic signs)
- May need to repeat after 2-3 weeks
- Radiograph other limbs, may show signs if affected 2 weeks ago
- No link between severity of radiographic signs and clinical signs
Describe the radiographic signs seen in panosteitis
Thumbprint lesions typical - areas of increased opacity, which resolve to coarse trabecular pattern +/- smooth periosteal reaction (but often do not)
List differentials for panosteitis
- Elbow dysplasia
- Metaphyseal osteopathy
- IMPA (NB usually older, joint pain rather than bone pain)
- Septic arthritis (NB usually older, joint pain in single joint)
- Bone metastasis
Discuss bone metastases as a differential for panosteitis
- Rare
- Signalment different- mets usually older dogs
- May identify primary neoplastic process elsewhere
- Usually presented for problems caused by primary tumour
Outline the treatment for panosteitis
- Self limiting disease
- Supportive treatment only: rest, analgesia (NSAIDs, opioids if needed, some may need nutritional/fluid support)
- Relapse possible, but excellent prognosis
Outline the signalment for metaphyseal osteopathy
- Usually young dogs, 2-7mo
- Giant breeds
- Weimeraners (inherited)
- M>F
Outline the aetiology of metaphyseal osteopathy
- Aetiology unknown
- Some geographical and seasonal distribution reported
- Considered to a systemic disease, possible causes under investigation (viral, bacterial, nutritional)
Outline the presenting signs of metaphyseal osteopathy
- Severe lameness
- Pyrexia
- Inappetance, GI signs
- Bilaterally symmetrical, painful metaphyseal swellings affecting long bones
- Often affects distal radius, ulna, tibia, but can affect ribs, digits, metacarpal/tarsal bones
Outline the diagnosis of metaphyseal osteopathy
Radiography of both limbs, +/- back limbs, ensure inclusion of joints above and below
Describe the radiographic signs seen with metaphyseal osteopathy
- Can be subtle to severe
- Metaphyseal lucent lines parallel to the physis (double physis appearance), adjacent sclerotic line
What causes the sclerotic line seen adjacent to the radiolucent line in metaphyseal osteopathy?
Collapsed necrotic trabeculae
List the differentials for metaphyseal osteopathy
- Septic physitis
- Septic arthritis
- Inflammatory joint disease
- Hypertrophic osteopathy
Compare hypertrophic osteopathy an metaphyseal osteodystrophy
- Hypertrophic osteopathy usually older animals, underlying cause is mass lesion in chest/abdomen
- Often neoplastic
Outline the treatment of metaphyseal osteopathy
- Self limiting, usually weeks but can be months
- Supportive treatment only: rest, analgesia (NSAIDs, opioids), extreme cases may need fluids/nutritional support
- Relapse possible, long term prognosis more guarded vs panosteitis but usually good
Outline the signalment for craniomandibular osteopathy
- WHWT, but also other breeds and cross breeds
- Young pups 3-8mo
Outline the clinical signs of craniomandibular osteopathy
- Pain (pup miserable)
- Reluctance to eat, dysphagia
- Weight loss
- Salivation
- Signs can wax and wane with periods of growth
Explain the pathology underlying craniomandibular osteopathy
- Excessive and abnormal bone growth affecting mandibles, tympanic bullae, temporomandibular joints, +/- other bones of skull or rarely, long bones
- Pain noted before changes on radiography
Outline the radiographic appearance of craniomandibular osteopathy
- Increased density of mandible
- May look like pillars of bone along ventral aspect of mandible
Discuss the risks associated with radiography in a cases of suspected craniomandibular osteopathy
- May be difficult to intubate as difficult to open jaw
- Increased risks of aspiration under GA due to hypersalivation
- Consider placement of oesophageal feeding tube as same time as puppy may not want to eat
Discuss the prognosis for craniomandibular osteopathy
- Depends on involvement of TMJ
- Episodes of pain resolve by ~12mo
- Some bone remodelling can occur
- Usually left with thick smooth jaws, tongue sticks out a little
What condition may craniomandibular osteopathy be related to?
Calvarian hyperostosis seen in Bull Mastiffs
When does secondary renal hyperparathyroidism occur?
- Late stages of CKD
- May occur in juveniles with congenital renal disease
Outline the clinical signs of secondary renal hyperparathyroidism
- Signs of CKD usually predominate
- Increased risk of pathological fracture e.g. in dentals, manual restraint of cats
Explain the elevation in PTH in secondary renal hyperparathyroidism
- Relative hyperphosphataemia (from decreased GFR)
- Relative calcitriol deficiency (decreased production by kidneys)
Describe the radiographic appearance of secondary renal hyperparathyroidism
- May see “floating teeth/rubber jaw”
- Demineralisation of bone more likely in younger animals with congenital renal disease, but possible in older
Discuss the development of secondary nutritional hyperparathyroidism in dogs and cats
- Young dogs and kittens due to increased demand for Ca and minimal reserves
- Related to an inappropriate diet (chronic calcium deficiency, calcium/phosphate imbalance)
- Increased PTH upregulates osteoclasts compared to osteoblasts, leading to Ca resorption
Describe the presenting signs of secondary nutritional hyperparathyroidism
- Bone pain
- Pathological fractures (lameness, spinal cord damage if vertebrae involved, pelvic damage)
- Seizures reported in cats/kittens with severe hypocalcaemia
- Poor radiographic contrast between bone and soft tissues
Outline the treatment of secondary nutritional hyperparathyroidism
- Dietary correction leads to normal mineralisation in 6-8 weeks
- Cats may require O tube feeding
- Rest important
Discuss the prognosis for secondary nutritional hyperparathyroidism
- Good unless fractures have caused long term issues e.g. neurological signs, joint problems, pelvic narrowing leading to constipation
- May look misshapen
What is Legg-Calve-Perthes disease also known as?
Avascular necrosis of the femoral head/ischaemic or aseptic necrosis of the femoral head
Outline the signalment of Legg-Calve-Perthes disease
- Young
- Miniature and small breed dogs
Outline the aetiology of Legg-Calve-Perthes disease
Unknown, likely multifactorial (genetic, trauma)
Outline the cinical signs of Legg-Calve-Perthes disease
- HL lameness (often bilateral)
- Atrophy og quadriceps
- Pain on hip manipulation
Outline the pathophysiology of Legg-Calve-Perthes disease
- Bone infarction leads to collapse of femoral head and neck
- Revascularisation, resorption and remodelling occur
- Chronic osteoarthritis is the end result
Outline the radiographic signs of Legg-Calve-Perthes disease
- Depends on stage of disease
- Irregular bone opacity in femoral head and neck
- Collapse of the femoral neck, rather than abnormal acetabulum
- Fragmentation of bone
- Distortion of femoral head
Compare the diagnosis of LCP vs hip dysplasia
- Breed predisposition should help
- Also less distortion of femoral head and neck in HD
- End stages appears similar
Compare the development of rickets in dogs and cats
- Cats linked to genetic issues, rare
- Dogs: deficiency of vit D, hereditary defect, lack of exposure to sunlight
Describe the appearance of rickets in dogs
- Young
- Stunted
- Bow-legged
- Plantigrade
Describe the radiographic appearance of rickets in dogs
- Bone osteopaenic
- Epiphyseal lines very wide
- Failure to ossify
Outline the treatment and prognosis for rickets in dogs
- Correct diet
- Expose to sunlight
- May be permanent damage to growth plates
- Prognosis guarded for hereditary causes
What is a key differential for rickets in cats?
Nutritional secondary hyperparathyroidism
Outline the clinical signs of rickets in cats
- From 3 mo of age
- Stiffness, reluctance to move, pain
- Signs of hypocalcaemia (tremors, seizures, GI disturbance)
Outline the common findings on physical exam of a cat with rickets
- Stiff joints
- Epiphyseal swelling
- Small stature
- Spinal abnormalities e.g. lordosis, kyphosis
Outline the diagnosis of rickets in cats
- Radiography shows wide physes
- Diagnosis based on blood tests for calcium, phosphate, PTH, vit D
Outline the treatment and prognosis for rickets in cats
- Treatment is supplementation of calcium and vit D
- Prognosis variable
