MSK Flashcards
Which cells are involved in the formation of bone?
osteoblast
Which cells are responsible for bone resorption?
osteoclasts
Describe osteoblasts
;arge
mononuclear
found on surface on surface of bone
When do osteoblasts become osteocytes?
whenever they become surrounded by osteoid
Describe osteoclastss
large
multinnucleated
How is bone resorption regulated?
complex milia of hormones and local cell mediators
What happens in the immediate aftermath of a fracture?
haematoma formed
acute inflammatory response
What happens within a few days of a fracture?
granulation tissue formed
What is the primary callus response?
differentiation of osteoprogenitor cells into bone-forming cells
What is the external bridging callus stage?
bone formation bridging the gap where the fracture is
What is the remodelling stage in a fractre?
the obvious callus formation on the outside is reduced and streamlines to the shape of what it originally was
Label the arrows
blue: osteoblast
red: osteoid
What is vital in fracture healing?
complete immobilisation
good oxygen supply
good blood supply
What can happen when oxygen supply is poor in distal fractures especially?
cartilage forms instead of bone
What 2 areas do fractures complications fall into?
local
systemic
What are 5 reasons for early local fracture complications?
infection blood loss from haemhorrage dislocation of joint damage to nerves and vessels skin loss and soft tissue injury
What are the 5 reasons for delayed local fracture complications>
damage to epiphyseal plates avascular necrosis of bone secondary osetoarthritis delayed union non-union
What are 8 reasons for systemic complications in fractures?
cardiac shock and circulatory failure fat embolus DVT and pulmonary embolus respiratory distress syndrome pneumonia sepsis bed sores DIC (disseminated intravascular coagulation)
How long after fracturing a major long bone can a fat embolus occur?
24-72 hrs
How long after fracture can a DVT/PE form?
7-10 days if prolonged bed rest
What 11 factors can impair healing?
age malnutrition diabetes cancer radiotherapy soft tissue injury compound fracture large fracture gap poor immobilisation infection ischaemia
What is infection in bones called?
osteomyelitis
What is an infection in a joint called?
septic arthritis
How does acute osteomyelitis present?
septic process high WCC high CRP high ESR temperature toxaemic red/flushed feeling sick vomiting
Who is affected most by acute osteomyelitis?
babies and young children
How long does it take for X-ray changes in acute osteomyelitis?
10 days - too late to make diagnosis
What is the most common organism in acute osteomyelitis?
Staph aureus
In children younger than 4 what is the most common cause of acute osteomyelitis?
H influenzae
What kind of reaction is seen in osteomyelitis?
periosteal reaction
What is seen in this picture?
osteomyelitis
red: neutrophil polymorphs
blue: bone
How do you prevent bone infection in fractures?
urgent and thorough debridement of open fractures in theatre on the same day
strict aseptic technique
appropriate prophylactic antibiotics esp. in metal prosthetic work
Who is mostly affected by chronic osteomyelitis?
adults
How does chronic osteomyelitis present?
smouldering infection causing bone necrosis and new bone formation
this causes marked bone deformity
What is seen in the picture?
chronic myelitis
fibrous tissue with some chronic inflammatory cells
6 complications of osteomyelitis
septicaemia bone deformity secondary arthritis formation of skin sinus squamous carcinoma (Marjolin's ulcer) systemic amyloid
What is bone/joint TB?
occurs secondary to pulmonary TB
Where is bone TB found?
spine
sometimes hips and joints or small bones of hands and feet
What is the name of spinal TB?
Pott’s disease of the spine
What is seen histologically in joint TB?
caseating granulomata
caseous necrosis
Langerhans multinuclear giant cells
cells distributed in horse shoe fashion
What spinal deformities can be caused by joint TB?
ankylosis of joints
loss of joint movement
systemic amyloid
What spinal deformities can be caused by joint TB?
ankylosis of joints
loss of joint movement
systemic amyloid
What is systemic amyloid?
misfolded protein becomes resistant to the body’s catabolic processes and fibrils deposit extracellularly within tissues, leading to organ dysfunction and death
What can be seen in the picture?
caseous necrosis
arrow: giant cells
What are the 3 metabolic bone diseases?
osteoporosis
osteomalacia
Paget’s disease
What is osteoporosis?
reduction in amount of bone and loss of microarchitecture
leading to weakened bone and pathological fracture
What is true about bone mineralisation and osteoblast and clast activity in osteoporosis?
all normal
no increased activity
just smaller amount of bone
7 causes of osteoporosis
idiopathic/senility/post-menopausal Cushing's disease/steroids thyrotoxicosis hypogonadism hyperparathyroidism alcohol abuse scurvy
Who are at risk of osteoporosis due to steroid therapy?
patients with long term asthma
IBD
transplant treatment
How do steroids cause osteoporosis
increased output of glucocorticoids
How can thyroxin cause osteoporosis?
stimulates osteoclasts
How does hypogonadism cause osteoporosis?
lack of sex hormones results in reduced output of oestrogen and testosterone
13 risk factors in osteoporosis
female caucasian/asian early menopause sedentary lifestyle slim body build nulliparity (woman who hasn't given birth) amennhorhoea positive family hx smoking alcohol steroids previous fractures low Ca intake
What can help females in perimenopausal stages for osteoporosis?
HRT
When does the critical zone typically occur in bone structure for females?
65-70
What is osteomalacia?
reduced mineralisation of the bone
What causes osteomalacia?
low serum calcium and phosphate
What are the causes of osteomalacia?
deficient diet (calcium) lack of sun exposure malabsorption chronic liver disease chronic renal disease hypophosphataemia phenytoin therapy
What are symptoms of osteomalacia?
abnormal blood chemistry - low serum calcium or phosphate osteopenia on X-ray pathological fracture bone pain proximal myopathy
