Lame - bone pathology Flashcards
What are the two causes of fracture?
Traumatic - normal bone with excessive force
Pathological - abnormal bone with minimal trauma
What are the 3 locations of bone fractures?
Growth plate
Trabecular bone
Cortical bone
What do fractures that cross/crush the growth plate cause?
Angular limb deformities
What type of fractures of the growth plate are more likely to heal easily?
Fractures that involve only the growth plate and primary bone trabeculae
What type of fractures of the growth plate are more likely to cause irreversible damage?
Fractures crossing growth plate through metaphysis/epyphisis
Crush of growth plate
What is the first step of fracture repair?
Formation of a haematoma around fracture site
What does damage to blood vessels from a fracture cause?
Reduced blood flow
Necrosis of bone fragments
Release of growth factors by macrophages from dying bone
What is formed from the haematoma in fracture repair?
Soft tissue callus/procallus
How is the procallus formed in fracture repair?
Blood vessels proliferate and undifferentiated mesenchymal cells penetrate, forming loose collagenous tissue
What is formed from the procallus in fracture repair? How?
A primary callus - metaplasia of the collagenous tissue into cartilage and woven bone
What is the secondary callus made of? What is it?
Replaces the primary callus over time with lamellar bone
What does the makeup of the primary callus depend on?
Blood an oxygen supply
The poorer the blood and o2 supply, the greater amount of cartilage in a callus - takes bone longer to heal
How does the bone return to its original shape over time?
The portions of callus that dont undergo physical stress are reabsorbed over time
What can complicate bone repair?
Insufficient bone supply
Instability
Infection poor nutrition
What happens when there is instability during bone repair?
Non union - procallus cant mature into bone so forms fibrous tissue instead
Fibrous tissue not strong enough
What can be formed by a non-union of bone due to instability?
Cysts
False joints
Pseudoarthritis
What is common in open fractures?
Septic bone inflammation/infection
Why is it easier for bacteria to invade under the articular epiphyseal cartilage complex?
Capillaries bend sharply to joining veins so there is turbulent blood flow and a discontinuous endothelial lining - easier for bacteria to invade
What pathogens cause osteomyelitis?
Almost always bacterial eg. strep, staph, truperella, E. coli
What causes inflammation during osteomyelitis?
Bacteria invade
Neutrophils recruited to the site causing inflammation
What does inflammation stimulate during osteomyelitis? What does this cause?
Inflammation stimulates osteoclasts to reabsorb bone and enzymes released - bone loss
What does the density of bone cause during osteomyelitis?
Density of bones means exudate cant get out of bone - the increased pressure is very painful, compresses blood vessels
Leads to thrombosis and infarction of intramedullary fat, marrow and bone
What is deposited at the side of osteomyelitis?
Fibrous tissue
What are sequelae?
Complications of osteomyelitis