Bone and joint pathology Flashcards
What is the role of osteoclasts?
Bone resorption
What is the role of osteoblasts?
Synthesis and secretion of bone matrix
What does the classification of a fracture depend on?
Anatomical location
Extent of bone damage
Direction of fracture line
Number of fragments
Stability
Define diaphyseal
fracture of the midshaft
Define metaphyseal
Fracture within the metaphyseal region of the bone
Define epiphyseal
fractuce or the epiphyseal plate
Define condylar
fracture through one condyle
Define a complete fracture
Extends all the way through the bone
Define an incomplete fracture
Fracture does not extend full thickness
Define a greenstick fracture
Incomplete fracture in immature bone. Bone bends and fractures through the outside cortex
Describe a fissure fracture
Crack formation but periosteum remains intact
Define a transverse fractuce
Perpendicular to the long axis
Define an oblique fracture
Runs at an angle to the long axis
Define a spiral fracture
Spirals along the long axis
Define a comminuted fracture
Overlapping fracture lines - fragments
Define a stable fracture
not displaced and some weight bearing force can be applied
Define an unstable fractuce
Cannot withstand any force without displacing
Describe an avulsion fracture
Caused by intrinsic pull from muscle contraction
Describe primary bone healing
Occurs when there is anatomical reduction of fracture fragments
Minimal interfragmentary strain
Good blood supply
Fracture gap <1mm
e.g. fissures or surgically fixated fractures (plates)
Describe secondary bone healing
Most common
Fracture gap and/or interfragmentary strain
What happens within the interfragmentary gap (<1mm)
Granulation tissue and angiogenesis
Within days, lamellar bone deposited
Transverse to long axis
In approx. 3 weeks:
Haversian remodeling
New lamellar bone is orientated longitudinally
What are the three stages of secondary/indirect bone healing?
Inflammatory (2 - 3 weeks)
Repair (2 weeks – 12 months)
Regeneration (can be years!)
Describe the inflammatory stage
Periosteum, soft tissue and blood vessels are torn. haematoma
Acute inflammatory cells to migrate to the area (chemotaxis).
Phagocytosis of necrotic debris
Angiogenesis and mesenchymal stem cells migrate
Fibroblasts then create a ‘soft callus’ containing type III collagen.
Describe the repair stage
Mesenchymal cells chondrocytes cartilage
Endochondral ossification
Soft callus is mineralised to woven bone.
Immature bone
Irregularly arranged collagen fibres
First ‘hard’ or ‘primary’ callus
Describe the remodelling phase
Woven bone is remodelled to lamellar bone
Haversian remodelling of cortical bone
Callus reduces so that bone is back to normal shape/size
Can take years!
What complications can occur?
Soft tissue trauma
Introduction of infection
Malunion
Non-union
Viable vs non-viable
Implant failure
Describe osteitis
Osteo-’ relating to bone
‘-itis’ inflammation of
Can be introduced by
Penetrating injury
Spread from surrounding tissues
Extension of suppurative arthritis
Haematogenous spread
Bone loss via necrosis stimulates new bone growth
Bacteria can reside in cavities / areas of necrosis treatment difficult!
Describe panosteitis
‘Growing pains’
Young, growing large breed dogs
German shepherd dogs
Golden retriever
Basset hound
Dobermans
Labrador retriever
What are the clinical signs of panosteitis?
Clinical signs present at around 5 – 18 months of age
Long bone lameness of 2-5 weeks duration
Shifts legs
Recurs
Eventually remodelled and excess bone removed
Describe metaphyseal osteopathy
hypertrophic osteodystrophy’
Young, growing giant breeds
Great Dane
Wolf hound
Unknown aetiology
?Inappropriate supplementation vit/min
?live canine distemper vaccination
What are the clinical signs of metaphyseal osteopathy?
Clinical signs
Lameness
Fever / pyrexia
Swollen, painful metaphyses of long bone
Most animals respond spontaneously
Describe craniomandibular osteopathy
Non-neoplastic
Developmental disease affecting growing terrier breeds
Genetic link
Resorption of bone leads to replacement with immature bone
Targets bones of the skull
Describe the clinical signs of craniomandibular osteopathy?
Clinical signs
4-8 months of age
Swollen mandible
Difficultly in opening mouth
Dysphagia (difficulty eating)
Usually self-limiting at approx. 1 year of age
Slow replacement with mature bone
Pain relief and soft diet
Describe osteoporosis
Condition that leads to reduced bone mass
Combination of factors
Calcium deficiency
Starvation
Reduced activity
Can be reversible in young animals – not adults!
Explain the process of osteoporosis
Cortical and trabecular bone is reduced in thickness
Trabeculae are eventually lost
Bone lacks density
Prone to pathological fractures
Describe rickets and osteolamacia
Rickets – young animals
Osteomalacia – mainly adult animals
Vitamin D or phosphorous deficiency
Dysfunction of mineralisation
Accumulation of unmineralised bone
What are the clinical signs of rickets?
Disease of cartilage undergoing endochondral ossification at the growth plate
Clinical signs
Bone pain and swelling
Stiff gait
Lameness
Bowed limbs
Folding fractures
What are the clinical signs of osteomalacia?
Disease affecting the osteoid
Clinical signs
Failure to thrive
Pathological fractures
Deformities of spine (lordosis, kyphosis etc)
Describe fibrous osteodystrophy
Widespread resorption of bone
Primary hyperparathyroidism – tumours of the parathyroid gland
Secondary hyperparathyroidism – an increase in PTH which is renal or nutritional in origin
Describe nutritional secondary hyper-parathyroid hormone
Young animals
Diet deficient in calcium / excessive in phosphorous PTH secretion
All meat diets in dogs/cats
High bran/grain diet in horses
Increase in osteoclast resorption and proliferation of fibrous tissue
Describe renal secondary hyper-parathyroid hormone
Chronic renal failure
Inability to excrete phosphorous hypocalcaemia PTH secretion
Reduction in the production of vitamin D
Reduction in calcium absorption
What are the clinical signs of fibrous osteodystrophy?
Bone pain
Deformity of mandibular / maxilla
Due to loss of bone and replacement with fibrous tissue
‘Rubber jaw’
Describe neoplasia
Most common is osteosarcoma
‘Away from the elbow – towards the knee’
Present with:
Lameness
++ pain
Swelling
+/- pathological fracture
Describe angular limb deformities (small animal)
Most common in the forelimbs – radius and ulna
Immature animals:
Osteotomy of the ulna
Animals close to skeletal maturity:
Corrective osteotomy of radius and ulna
Realigns the joints
Stabilisation – ECF +/- internal plate.
+/- limb lengthening
Describe how the joint responds to injury
Inflammation leads to a loss of matrix components
Altered pressure and permeability of joint
Reduction of joint lubrication
Disruption of collagen fibres of cartilage
Describe cartilage repair
Limited blood supply
If just articular cartilage damaged:
Chondrocytes do not fill defect
? Some cartilaginous flow when loaded
If subchondral bone involved:
Highly vascularised
Fibrous tissue fills the defect fibrocartilage
Describe pannus
‘Inflammatory granulation tissue’
Occurs in response to injury to synovial membrane
Arises from insertion of membrane
Spreads over articular cartilage
Fibrovascular and histiocytic lysis of cartilage
Describe arthritis
‘Arth’ – relating to the joint
‘-itis’ – inflammation of
Inflammation of the articular structure
Categorised based on
Cause
Duration
Exudate
Describe degenerative joint disease
Osteoarthritis
Destructive disease of articular cartilage
Young or adult animals
Due to:
Abnormal loading e.g due to trauma
Infection
Immune mediated
Developmental
Describe treatment of osteoarthritis
Medical
Weight loss
Controlled exercise
Pain relief
Surgical
Joint replacement
Arthrodesis
Describe bacterial arthritis
More common in farm animals and horses
- Bacteraemia secondary to
Navel ill
Ingestion
Inhalation
- Puncture wounds
Treatment is debridement and flushing of the joint + ABx
Describe rheumatoid arthritis
Chronic, erosive polyarthritis
Immune mediated
Antibodies produced due to unknown stimulus
Immune complex ingested by neutrophils
Produce enzymes that injury surface
Treatment
Pain relief
Steroids
+/- chemotherapy
Describe osteochondrosis
Focal/multifocal areas of failure of endochondral ossification
Involves growth plate and articular / epiphyseal complex
No exact cause known
Nutrition
Excessive growth
Trauma
Describe the process of osteochondrosis
Delay in endochondral ossification
Abnormal vascularisation and mineralisation
Cartilage weakens
Cracks/fissures/flaps form
Flaps can fracture off
Describe treatment for osteochondrosis
Pain relief!
Surgery always recommended
Remove flap and joint mice
Curette subchondral bone
Stimulates fibrocartilage production
