Orthopaedics: Intro and Developmental Diseases Flashcards
What are the 5 functions of bones?
Skeletal support- movement
Protection
Haematopoiesis
Regulation of mineral haemostasis
Fat storage
What is trabecular and cortical bone?
Trabecular (cancellous) and woven bone-
Location- metaphysis, flat bones- dissipates load
Cortical bone-
dense bone or diaphysis, supports weight, protects organs, provides levers
Describe how bone develops?
Intramembranous ossification
Skull and scapula-
undifferentiated mesenchymal cells into osteoblasts
direct production of bone by osteoblasts
Endochondral ossification-
seen in long bones, formation and replacement of cartilage template by bone, increases length
Physis- key structures responsible for longitudinal bone growth
What is bone modelling?
When does it occur?
Ability of bone to change based on strain put on it in the developing animal
Osteoblasts from bone where there was none before, osteoclasts remove bone to alter shape- work together
Replacement of damaged bone
Fracture repair
Prevent accumulation of fatigue damage - microscopic damage
What is Wolff’s law
Primary regulator of bone remodelling
Adaptable- to life and excercise
Adaption-
Increase/Decrease- size/density
How does bone respond to load?
Bone is anisotropic- mechanical properties depend on- size and shape-
cortical thickness, mineralisation, magnitude, direction, rate
Forces- need to be stopped or bone wont recover-
compression, tension, bending, torsion, shearing
With load bones deform
What are the different types of bone deformation?
Elastic deformation-
with loading and unloading the bone deforms then returns to the original shape
stimulates modelling
Plastic deformation-
with loading and unloading the bone deforms and doesn’t return to original shape-
microcracks, cyclic fatigue, incomplete fractures
What are the practical implications of bone deformation?
Complete bone failure
Weakening of normal bone-
plastic deformation and repetitive loading = stress fractures
abnormal matrix- metabolic, neoplasia
What can cause the failure of a normal bone?
What are stress fractures and where do they commonly occur?
Single supra-physiological load- kick wound, hit by car
Internal truama-
Foot planted and body twists- stuck in hole
Stress fractures- fracture of weakened bone (cannot keep up)
racehorses- MCIII/MTIII condylar fracture, dorsal metacarpal disease
greyhounds- acetabulum, central tarsal bone
What is dorsal metacarpal disease?
- Primary racing force on lateral side
- Primary galloping side on medial side
- Classical training give poor adaption to race- increased bone on medial side
- Modified training gives better density and adaption to race
- Grey hounds race anticlockwise- more weight on left- increased bone
What neoplasia can affect bones?
Osteosarcoma
Haemangiosarcoma
Multiple myeloma
Chondrosarcoma
Bacterial osteomyelitis
What causes metabolic bone disease?
Related to the metabolism of calcium and phosphorus
Controlled by:
vitamin D
PTH
Calcitonin
The mineral content of bone
PTH abnormality
Vit D deficiency
Paraneoplastic
What are developmental orthopaedic diseases?
Group of diseases
Cause musculoskeletal problems- various syndromes, age predisposition
Multifactorial
Disturbance in development- cartilage, bone
What are the different regions in a growth plate?
Resting cartilage
Proliferative cartilage
Hypertrophic cartilage
Calcifying cartilage
Secondary spongiosa
How can disturbances in endochondral ossification lead to developmental orthopaedic disease?
Physeal growth plate-
abnormal deposition of matrix, abnormal mineralisation, poor conversion to bone, retention of cartilage
Result- slow uneven growth
Articular-epiphyseal CC-
abnormal deposition of the matrix, abnormal mineralisation, retention of cartilage
Result- slow growth, uneven growth, cartilage flaps
What does slow, uneven growth from disturbances with endochondral ossification lead to?
ALD- angular limb deformities
FLD- flexural limb deformities
OCD- oestochondritis
Abnormal endochondral ossification- achondroplasia
Associated conditions-
Osteochondrosis- cartilage abnormalities
Osteochondrosis
Subchondral cystic lesions
Describe the pathophysiology of osteochondritis dissecans?
What does it lead to?
What are the clinical signs?
Disruption of blood supply-
Affects the mineralisation of the subchondral bone
Alters biochem and biochemical properties of cartilage and subchondral bone
Affects the ability to adapt and withstand the force- shearing
Shear forces and weight baring-> separation at osteochondral junction -> cartilage flaps and fragmentation -> exposed subchondral bone-> irregular raised cartilage
Clinical signs- fluid swelling, radiography
DIRT- distal intermediate ridge tibia
What is the aetiologies of osteochondrosis/dritis dissecans?
Rapid growth-
genetic potential, hormone, nutritional
Genetic predisposition
Nutrition-
excess energy and protein, imbalance of Ca:P- excess P
Imbalance of Cu:Zn- Cu collagen crosslinking
Hormone and GHF influence-
testosterone, GHF, hyperinsulinaemia
Trauma
In neck- WOBBLERS DISEASE
What are the radiographic abnormalities of OCD?
Irregular subchonral bone
Osseous densities- mineralised cartilage, osteochondral fragments
Radiograph opposite- may underestimate damage
How does developmental orthopaedic disease manifest in different species?
Equine-
Osteochondritis- OCD and subchondral bone cysts
Physitis
Angular limb deformities
Flexural deformities
Canine-
Osteochrondrosis- united anconeal process, fragmented medial coronoid process
Hypertrophic osteodystrophy
Legg calve perthes
Hip dysplasia
Bovine-
Oestoechrondrosis
Flexural deformities
Porcine-
Oesteochrondrosis
What does developmental orthopaedic disease result in?
Abnormal endochondral ossification-
abnormal maturation of cartilage
Inappropriate relative growth-
bone vs soft tissue
What is the aetiology of subchondral cyst-like lesions?
Abnormal endochondral ossification-
retention of cartilage core
collapse of cartilage
Trauma- articular cartilage and SC bone- pressure from SC bone
What is physitis?
What are the clinical signs?
How does it progress?
Enlargement of the physis- inflammation, disrupted endochondral ossificatoin
Clinical signs-
lameness, stiff gait
Self-limiting
What causes hypertrophic osteodystrophy?
What is the pathogenesis?
What are the clinical signs?
What are the radiographic abnormalities?
Idiopathic
Pathogenesis- necrosis of the capillary loops of the cartilage of the metaphyseal physis, cuff of metaplastic cartilage and bone
Clinical signs- lameness, fever, lethargy, painful bone
primarily long bones, bilateral and symmetrical
Radiographic abnormalities-
Abnormal bone on the diaphyseal side of physis
Decreased radiodensity parallel to physis
Irregular widening of physis
Sub and extra-periosteal new bone
What causes panostetitis?
Describe the pathogenesis?
What are the clinical signs and the radiographic abnormalities?
Idiopathic
Pathogenesis- fibrosis of bone tissue
increased osteoblastic and fibroblastic activity
Disorganised trabecular formation in SCB
Clinical signs-
acute lameness, shifting, lethargy, pain
Radiographic abnormalities
Increased opacity of medullary cavity
Indistinct trabecular pattern
Increased endosteal opacity
What are the different presentations of hip dysplasia in different species?
Hip dysplasia in dogs-
genetic predisposition to laxity of the CF joint
abnormal anatomy of femoral head and acetabulum
Canine elbow dysplasia-
OCD, united anconeal process, fragmented coronoid process
Shetland shoulder syndrome-
Genetic abnormal humeral head and scapular glenoid
What causes Legg-calve Perthes disease?
What is the pathogenesis?
What are the clinical signs?
What are the radiographic abnormalities?
Idiopathic
Pathogenesis-
Avascular necrosis of the femoral head
Bone remains mechanically stable initially
When SCB loses mechanical strength- collapse of articular surface
Clinical signs-
Acute onset lameness
Fracture/collapse of the femoral head
Radiographic abnormalities-
Osteolysis of the femoral head- SCB resorption
Collapsed and thickened femoral neck
Fracture
Treatment- surgical due to severity of arthritis, femoral head and neck extension
What are medial and lateral angular limb deformities?
What are the potential locations in a horse?
What happens in canines?
Valgus- lateral deviation
Valrus- medial deviation
Equine potential locations-
Metaphyseal growth plate, epiphysis, cuboidal bones- carpus, tarsus, metaphysis
Canine-
Asynchronous growth of a pair of bones- shorter acts to create bowing
Radius and ulna > tibia and fibula
Differential growth between bones, after damage to one- trauma to growth plate
What are the flexural deformities equine and bovine?
Pathogenesis
Disproportionate growth
Muscle-tendon unit vs bony skeleton
Bone functionally longer
Congenital- new born foals
Acquired- rapidly growing foals and yearlings, acute or chronic
