PATHOLOGY - Bone, Cartilage, Muscles and Tendons Flashcards
List five possible reactions bone can have following injury
Bone remodelling
Altered bone density
Endochondral ossification disruption
Rapid deposition of woven bone
Conversion of periosteum to bone
What is osteitis?
Osteitis is inflammation of the bone
What is periostitis?
Periostitis is inflammation of the periosteum
What is osteomyelitis?
Osteomyelitis is inflammation of the bone medullary cavity
What are sequestrum?
Sequestrum is a fragment of necrotic bone isolated from the blood supply and surrounded by exudate
What is the most common infectious agent that affects bone?
Bacteria
What are the two methods used by infectious agents to enter the bone?
Haematogenous
Direct entry
Why is the metaphyseal region of epiphyseal growth plates predisposed to haematogenous infection?
Branches of the metaphyseal artery form capillary loops at the metaphyseal side of epiphyseal growth plates which provides a large supply of slow flowing blood which encourages the deposition of infectious agents and the establishment of infection
What are the two main causes of a fracture?
Trauma
Pathology
What classifies as a pathological fracture?
A pathological fracture results from the break of a diseased or weak bone
What is a closed fracture?
Fracture where the skin is unbroken
What is an open fracture?
Fracture where the skin is broken
What is a simple fracture?
Clean break of the bone into two pieces
What is a comminuted fracture?
Fracture where the bone is shattered into fragments
What is a greenstick fracture?
Cortex is broken on one side of the bone but bent on the other side
What is a spiral fracture?
A spiral fracture is where the fracture line spirals around the bone due to a twisting or rotational force
What is an infraction?
Fracture of the trabeculae without the involvement of the cortex
What are the consequences of a type I or type II growth plate fracture?
Type I or type II growth plate fractures have few to no complications
What are the consequences of a type III, type IV or type V growth plate fracture?
Type III, type IV or type V growth plate fractures may lead to growth abnormalities as they directly involve the growth plate
What are the four critical factors of fracture healing?
Correct alignment
Lack of movement
Asepsis
Adequate blood supply
How should a stable fracture heal?
A stable fracture has been clinically immobilised at either end and will undergo callus formation
How should an unstable fracture heal?
An unstable fracture will undergo callus formation
How should a rigid fracture heal?
A rigid fracture requires surgical intervention to bring the two ends together and ideally results in healing by surgical fixation
What are the functions of the callus formed during fracture healing?
The callus encircles the fracture site where it bridges the gap between the bone and stabilises the area
What forms in the centre of the callus if the blood supply to the fracture site is inadequate?
Hyaline cartilage
What are the five steps of callus formation?
Haematoma formation
Inflammation
Primary callus formation
Secondary callus formation
Remodelling
Describe briefly the steps of callus formation
- Blood vessels and the periosteum are damaged causing the formation of a haematoma at the fracture site. This haematoma will clot which act as a provisional wound matrix
- Chemotactic agents trigger the recruitment of neutrophils to the injury site. Neutrophils carry out phagocytosis to remove any pathogens and debris
- Fibrous tissue and cartilage are deposited to form a primary callus which bridges the gap between the fracture site
- Osteoblasts produce woven bone which provides temporary stability and support
- Woven bone is gradually replaced by lamellar bone through the activity of osteoclasts and osteoblasts
What are the three main advantages to healing via callus formation?
Natural process
Minimal intervention required
Low cost option
What are the three main disadvantages to healing via callus formation?
Callus may not be able to stabilise the fracture
Callus formation takes time
A large callus may interfere with joint or tendon function
What is healing by surgical fixation?
Healing by surgical fixation brings the ends of the bone closer together which allows for direct osteonal bridging of the fracture site with no callus formation
If a fracture site has a gap less than 1mm in width, which type of bone do osteoblasts deposit?
Lamellar bone
If a fracture site has a gap more than 1mm in width, which type of bone do osteoblasts deposit?
Woven bone
What is the consequence of anoxia during fracture healing?
Anoxia during fracture healing leads to necrosis
What is the consequence of instability to the fracture site during fracture healing?
Instability to the fracture site can lead to pseudoarthrosis (bones do not correctly fuse)
Why should you never use metallic implants that are too large to stabilise a fracture?
Metallic implants that are too large can lead to a lack of mechanical force inflicted onto the bone which could lead to bone atrophy (due to disuse)
What is osteopetrosis?
Osteopetrosis is the deposition of excess bone due to a genetic or infectious defect in bone resorption
What is osteogenesis imperfecta?
Osteogenesis imperfecta is the deposition of too little bone due to a genetic mutation in the type 1 collagen gene
What is chondrodysplasia?
Chondrodysplasia is disproportionate dwarfism caused by a genetic mutation in the cartilage producing genes. This has a resulting effect on endochondral ossification
List three specific examples of chondrodysplasia
Lethal bulldog type bovine chondrodysplasia
Spider lamb syndrome
Texel sheep chondrodysplasia
What causes lethal bulldog type bovine chondrodysplasia?
Mutation in the gene encoding for aggregan proteoglycans
What causes spider lamb syndrome?
Mutation is the gene encoding for fibroblast growth factor receptor 3 (FGFR3) resulting in disorganised centres of ossification leading to abnormally sized, shaped and orientated bones
What causes texel sheep chondrodysplasia?
Autosomal recessive mutation of the SLC13A1 gene encoding for the sodium-sulphate co-transporter resulting in chondrolysis within the articular epiphyseal cartilage complex leaving clefts within the cartilage
What is osteochondrosis?
Osteochondrosis is the failure of endochondral ossification affecting the articular epiphyseal cartilage complex and the physeal growth plates
What are the three forms/stages of osteochondrosis?
Osteochondrosis latens
Osteochondrosis manifesta
Osteochondrosis dissecans
What is osteochondrosis latens?
Osteochondrosis latens is the focal ischaemic necrosis of the epiphyseal growth plates
What is osteochondrosis manifesta?
Osteochondrosis manifesa is the failure of the necrotic epiphyseal cartilage to ossify during endochondral ossification, resulting in the retention of this necrotic cartilage within the subchondral bone
i.e. becomes a focal failure of endochondral ossification
What is osteochondrosis dessicans?
Osteochondrosis dessicans extension of the focal necrosis into the articular cartilage, resulting in dissecting necrosis, cleft formation and articular cartilage flaps
How does physeal osteochondrosis differ from articular-epiphyseal complex osteochondrosis?
Physeal osteochondrosis is the retainment of hypertrophic chondrocytes resulting in a failure of endochondral ossification
Describe the pathogenesis of physeal osteochondrosis
An infraction can interfere with the vascular invasion required for endochondral ossification, leading to the persistence of the hypertrophic chondrocyte zone of the physeal growth plate and thus lead to cartilage retainment
What is cervical stenotic myelopathy (wobblers disease)?
Cervical stenotic myelopathy is osteochondrosis dissecans of the articular facet joints between the vertebrae resulting in intervertebral joint instability
What is osteoporosis?
Osteoporosis is a reduction in bone mass
What are three of the main causes of osteoporosis?
Malnutrition
Low dietary calcium
Androgen deficiency
What is osteomalacia/rickets?
Osteomalacia/rickets is a defect in the mineralisation of bone leading to soft bone formation
What is the main causes of osteomalacia/rickets?
Vitamin D deficiency