32. Paediatric long bone diseases. Neoplasia of the bones. Aetiology, symptoms and therapy

What are the components of bone structure?

1. Periosteum (outer thin soft layer)

2. Endosteum (cortex, compact bone)

3. Cancellous bone (diaphysis, spongy bone)

4. Bone marrow (medullary cavity).

What are the parts of a long bone?

Proximal epiphysis, proximal metaphysis, diaphysis, distal metaphysis, distal epiphysis

What are examples of paediatric long bone diseases?

1. Panosteitis juvenilis

2. Hypertrophic osteodystrophy

3. Junvenile osteodystrophy/nutritional secondary hyperparathyroidism

4. Legg-Calve Perthes disease (osteochondritis juvenilis)

5. Short radius/ulna

What is panosteitis?

Aseptic inflammation of all structures of long bones. Self-limiting

Which breeds are commonly affected by panosteitis?

Large breeds (German Shepherd, Basset Hound)

At what age does panosteitis typically occur?

Less than 2 years

What is the aetiology of panosteitis juvenilis?

Unknown (idiopathic). Infection, metabolic disease (protein rich diet, excess Ca), endocrine dysfunction, allergy, autoimmune mechanisms, parasitism & hereditary factors

What are the clinical signs of panosteitis?

Acute onset lameness, no trauma, recurrent bouts. Males are more commonly affected.

How is panosteitis diagnosed?

Palpation (pain), X-ray (blurred trabecular patterns at diaphysis), histopathology

What is the treatment for panosteitis?

No specific treatment, NSAIDs/corticosteroids for pain relief

What is hypertrophic osteodystrophy (HOD)?

Syndrome of gross swellings in distal metaphysis of the radius, ulna, and tibia of young dogs.

Which breeds are commonly affected by HOD?

Medium and giant breeds

What is the aetiology of HOD

Unknown, possibly vitamin C deficiency, infectious agents, obesity, inherited

What are the clinical signs of HOD?

Systemic involvement is common (pyrexia, anorexia, pain, arched back, reluctance to move), diarrhoea may be present. Cranial bowing of forelegs & valgus deformity of carpus is common to develop. (characterised by ↓ blood flow → failure of ossification → necrosis → inflammation of spongy bone).

How is HOD diagnosed?

History of acute lameness, fever, increased WBCs

X-ray (double physeal line, secondary extraperiosteal proliferation, calcification along the metaphysis)

What is the treatment for HOD?

Vitamin C, corticosteroids/NSAIDs, antibiotics (sometimes), supportive care (anti-diarrhoeals [loperamide], supportive fluids)

Most dogs recover in 7-10 days, but recurrent bouts are common

What is juvenile osteodystrophy/nutritional secondary hyperparathyroidism?

Nutritional imbalance (high phosphorus, low calcium e.g. red meat) leading to high PTH

What are the radiographic findings in juvenile osteodystrophy?

Thin cortex, wide medullary cavity, decreased bone density

What are the clinical signs of juvenile osteodystrophy?

Painful deformities and fractures

How is juvenile osteodystrophy diagnosed?

Palpation, X-ray, nutrition review

What is the treatment for juvenile osteodystrophy?

Diet change (increase calcium, decrease phosphorus)

What is Legg-Calve Perthes disease?

Non-inflammatory ischemia and deformation of the femoral head and neck

Which breeds are predisposed to Legg-Calve Perthes disease?

Miniature breeds and terriers

At what age does Legg-Calve Perthes disease typically occur?

4-11 months

What is the aetiology of Legg-Calve Perthes disease?

Unknown, ischemia may be from vascular compression and sex hormone activity. Genetic cause (homozygosity of autosomal recessive gene) is proposed

What is the pathogenesis of Legg-Calve Perthes disease?

1. In all cases bone of femoral head & neck undergoes necrosis & deformation, during which animal manifests pain.

2. Fragmentation phase: Articular cartilage cracks as a result of collapse of subchondral bone.

3. Ossification phase: Formation of new bone in the necrotic area as part of the healing process, but femoral head & neck are deformed, with resulting joint incongruity & instability.

4. This condition leads to severe degenerative changes in the entire hip joint & development of marked osteoarthrosis.

What are the clinical signs of Legg-Calve Perthes disease?

Pain (especially on abduction), crepitus, restricted range of motion, limb shortening, irritability, chewing at hip/flank, progressive lameness, stiffness, muscle atrophy (gluteus, quadriceps).

Lameness is gradual (over 6-8 weeks).

How is Legg-Calve Perthes disease diagnosed?

History, clinical signs, X-ray (radiopacity, lysis with apple-core/moth-eaten appearance)

What are the differential diagnoses for Legg-Calve Perthes disease?

Capital physeal trauma, septic physitis, osteomyelitis, neoplasia, CCL rupture, patellar luxation

What are the treatment options for Legg-Calve Perthes disease?

Mild (activity restriction, NSAIDs), severe (femoral head and neck ostectomy/total hip replacement)

What is short radius/short ulna?

Short radius/ulna causing bending in the opposite bone

1. A metabolic disorder affecting bone growth

2. Viral disorders

Which metabolic disorders may cause short radius/ulna?

1. Secondary parathyroidism

2. Rickets

What is secondary hyperparathyroidism?

Hyperphosphatemia (dietary or renal) causing PTH release → bone resorption (Ca and P)

What is rickets?

Lack of phosphorus, vitamin D, or abnormal calcium:phosphorus ratio, leading to failure of bone mineralisation

What are the clinical signs of rickets?

Bent bones, soft/weak bones, thickened growth plates, swollen joints

What is the treatment for rickets?

Vitamin D supplementation

How does canine distemper affect bones?

Necrosis of osteoclasts, osteoblasts, and marrow cells, leading to persistent cancellous bone

How does canine hepatitis affect bones?

Haemorrhagic necrosis of medullary and endosteal elements in the metaphysis

How are appendicular bone tumours classified?

Primary (benign or malignant) and secondary (metastatic or local invasion)

What are characteristics of benign primary bone tumours?

May grow & cause issues, but are non-cancerous, do not metastasise

What are some examples of benign primary bone tumours?

Osteoma, osteochondroma, osteoblastoma, giant cell tumour

What are some examples of malignant bone tumours?

Osteosarcoma, chondrosarcoma, fibrosarcoma

Where do secondary metastatic bone tumours most often arise from?

Mammary gland, lung, prostate, or local tissues (synovial cell sarcoma)

What is the most common bone tumour?

Osteosarcoma

What are the clinical signs of bone tumours?

Lameness (with or without systemic signs), swelling, heat, sensitivity

How are bone tumours definitively diagnosed?

Biopsy

What are the radiographic features of bone tumours?

Soft tissue swelling, cortical destruction, lysis, periosteal reaction (sunburst appearance)

What are the treatment options for bone tumours?

Local resection (if possible), amputation (most common), limb salvage procedures (endoprosthesis, allografts)

What is a likely diagnosis for a young dog with bone pain?

Growing pains

What is an example of an innovative treatment for osteochondrosis?

Stem cells