LECTURE 4 DISEASE OF BONE Flashcards
what is CT good for?
imagine bone, soft tissue & blood vessels at the same time- pinpoints injuries with bony structures
what is MRI good for?
imaging soft tissue & showing tissue difference between normal & abnormal
what is good at seeing cortex of bone?
most easily visualised on plain radiographs, MRI of little value in evaluating cortex
what is good at seeing circumference & internal matrix of bone?
CT and MRI
what are 95% of bone radiographs obtained for?
evaluating trauma, arthrities, degenerative conditions or metastases
what is x-ray good for showing?
assessing imaging but not showing any soft tissue injuries
how can bone lesions be diagnosed?
mostly based on history
what are the 2 types of bone disease?
increase & decrease bone density
what is increased bone density known as?
sclerosis
what are the main diseases of sclerosis?
metastatic tumours (diffuse or focal sclerosis), avascular necrosis of bone (focal) , paget disease (focal)
what is the most common type of increased bone density?
metastatic tumours (diffuse or focal sclerosis
what are the characteristics of sclerotic diseases?
increase radio opacity (looks whiter) & loss of visibile structure
what is avascular necrosis of bone?
lack of blood supply to bone- when it dies it collapses & increases in bone density, bone mineral becomes concentrated e.g. scaphoid, head of femur- detected with MRI
what is an example of diffuse metastatic tumours?
metastatic carcinoma (cancer that start is tissue cells) of prostate due to uncontrolled osteoblast activity- travelling cancer
what can focal sclerotic lesions affect?
cortex & medullary cavity- specific regions
what occurs in the cortex due to focal sclerotic lesions?
produce periosteal new bone formation (periosteal reaction) causing thickening of cortex- periosteum is lifted off surface of bone and new bone grows down (sunburst reaction)
what occurs in medulla due to focal sclerotic lesions?
punctuate, amorphous sclerotic lesions surrounded by normal medullary cavity- see holes in medullary cavity (looks white due to more bone mineral)
what are metastatic bone tumours more common than?
primary bone tumours
what is a metastic tumour?
a tumour that has moved from the site where it originally developed e.g. growing in bone but started
what can metastatic tumours be?
both osteoblastic, osteolytic & combination of both
what are examples of osteoblastic tumours?
prostate carcinoma (most common), breast carinoma (can be osteolytic), renal cell carcinoma, thyroid carcinoma
what is a malignant tumour?
have the ability to metastasise- leave point of growth & spread out to distance sites e.g. start is prostate & travels to bone
what is an osteoblastic tumour?
create more bone, more white
what is osteolytic tumor?
break down of bone
what is paget disease?
chronic disease of bone, seen in older men- varyin digress of increased bone resorption & increased bone formation
what diseases occur due to lack of bone density?
osteoporosis, hyperparathyroidism, rickets, osteomalacia
what will the bones look like with decreased bone density?
overall increase in lucency (not as white, more grey), loss of trabeculae, accentuatio of normal cortico-medullary junction (as cancellous bone degrades)- vertebral body cmpression- pathological fracture (occurs where u have bone disease)
what does the cortex and medulla look like with decreased bone density?
cortex is thinner, medulla is more lucent
what is osteoporosis?
systemic (impacts all bones) skeletal disorder, characterised by low bone mineral density
what are the 2 types of osteoporosis?
postmenopaual due to increased bone resorption caused by osteoclastic activity (estrogen inhibits osteoclasts to break down bone) & age related (senile) bone loss aroung 45-55 due to loss of total bone mass
what are the risks factors of osteoporosis?
exogenous steroid administration, cushings disease, estrogen deficiency, inadequate physical activity, alcoholism
what pathological fractures does osteoporosis predisposes one to?
femoral neck, distal radius (colles’ fractures), compression fractures of vertebral bodies
what are risk factors for vertebral and femoral neck fractures?
increases dramatically as BMD levels decrease to less than 1 g/cm2- & can be estimated
are conventional radiographs good to diagnose osteoporosis?
not really, 50% of bone mass must be lost before it is recognised on conventional radiographs
what are the signs of osteoporosis in x-rays?
overall lucency on bone, thinning of cortex, decrease of trabeculae
what is the most accurate scan to diagnose osteoporosis?
DEXA scans are most accurate as it measure bone mineral density- measures than compared to mean average
what is normal bone mineral density?
being within 1 standard deviation of yound adult mean
what is osteopenia bone mineral density?
being 1 to 2.5 deviations away from young adult mean
what is osteoporosis bone mineral density?
more than 2.5 SD away from young adult mean
what is hyperparathyroidism caused by?
excessive secretion of parathyroid hormone
what is the role of parathyroid hormone?
stimulates osteoclastic activity- regulates calcium levels in blood by regulating osteoclasts- low calcium, more parathyhoid hormone and breaks down bone to stabilise calcium levels
what are the 3 forms of hyperparathyroidism?
primary, secondary, tertiary
what is primary hyperparathyroidism?
caused by a single adenoma/tumour (80% to 90& of patients- most common)- hypercalcaemia (too much calcium in blood)
what is secondary hyperparathyroidism?
caused by calcium & phosphorous imbalances- chronic renal disease
what is tertiary hyperparathyroidism?
occurs in patients with long standing secondry hyperparathyroidism- autonomous hypersecretion
what is rickets caused by?
disroders afecting vitamin D ingestion, absorption or activation- failure of osteoid to calcify especially at sites of maximal growth in childrens
what population does rickets appear in?
children whose growth plates have not closed
what is osteomalacia?
failure to calcify the osteoid matric of bone in adults, commonly due to renal disease- similar to rickets but in adults- makes bone matrix but doesnt calcify
what is the imaging hallmark of osteomalacia?
pseudofracture (looser line)- occurs at multiple sites at the same time & is associated with nonunion
where are common location of pseudofractures?
medial femoral neck and shaft, pubic and ischial rami, metatarsals, and calcaneus.
how does focal loss of bone density occur?
produced by focal infiltration of bone by cells other than osteocytes
what are the main diseases of focal loss of bone density?
metastatic disease (osteolytic), multiple myeloma, osteomyelitis
what are the common forms of osteolytic metastatic disease?
lung cancer, breast cancer, lymphoma, carcinoid tumours
what occurs in osteolytic metastatic disease?
produces focal destruction of medullary cavity often expanding & destroying cortex
how much reduction in bone mass must occur to observed osteolytic metastatic disease?
50% reduction in bone moss in medullary cavity to be noticeable
how can we diagnose osteolytic metastatic disease?
through MRI- when onl cortex is involved its easier to visualise on plain radiographs
where are osteolytic metastatic disease uncommon?
distal to elbow or the knee- if present here, they are usually widespread & due to lung or breast cancer
what is the best way to observe skeletal metastases?
radionuclide bone scane
what is the most common primary malignancy of bone in adults?
multiple myeloma- originates in the bone
where can multiple myeloma be?
solitary (in spine or pelvis) or disseminated (multiple, lytic lesions throughout axial & proximal appendicular skeleton)- at greater risk of developing fractures e.g. osteoporosis- can impact skull
what is the most common early manisfestations of multiple myeloma?
diffuse & usually severe osteoporosis
how can multiple myeloma be detected?
via plain radiographs
what is osteomyelitis?
focal detruction of bone by bacterial infection (blood borne- haematogenous)- lots of inflammation, destruction of bone
where does osteomyelitis occur in adults & children?
adults (occurs in joint space causing osteomyelitis & septic arthritis/infection of joints )- children (at the metaphysis- growth plates where blood supply is good but slow)
what are the signs of osteomyelitis in plain radiographs?
focal cortical bone destruction, periosteal new bone formation, soft tissue swelling & focal osteoporosis
how is osteomyelitis diagnosed?
MRI & nuclear medicine for early diagnosis as changes occur slowly- holes in skin where pus can escape
what are the characteristics of primary tumours?
most are benign, in young patients they are benign, in older patient most are malignant- male predominance- originate in bone- less common than metastatic
what do we need to know when diagnosing primary tumours?
bone involved, specific site involved (cortex or medulla, epiphysis, diaphysis or metaphysis), tumour margin & contour
what are the characteristics of a benign primary tumour?
localised & well defined- don’t invade structures but grows by expansion (compress structures) vs malignant that throws out roots
what are the characteristics of a malignant tumour?
invasive, ill defined
what is osteosarcoma?
uncontrolled growth of cells- formation of new bone at a rapid rate- occurs in metaphyses of long bone e.g. distal femur- affects under 20 over 60- bone tunour from bone- periosteum lifts off with new bone growing underneath
how does osteosarcoma appear on radiographs?
moth eaten sunburst appearance due to be rapidly growing & invasive
what is chondrosarcoma?
cancer that forms in CT surroundnig the bone- in the metaphysis & diaphysis of long bone e.g. medullary cavity of femur, humerus & pelvis- gives a lucent defect to bone- middle age & older
what is fibrosarcoma?
cancer that effects the fibroblast cells (creates fibrous tissue e.g. tendons)
where does fibrosarcoma occur?
in metaphysis of femur & tibia- lucent lesios with cortical destruction- middle age
what is a fracture?
disruption in continuity of all or part of cortex of a bone
what is a complete fracture?
if cortex is broken on both sides of bone
what is an incomplete fracture?
if only part of cortex is fractured
where do incomplete fractures tend to occur?
in soft bones- children or adults with osteomalacia or paget disease
what is a greenstick fracture?
incomplete fracture seen in children- tends to tear
what is a torus fracture?
incomplete fracture with bulging of the cortex- result from trabeculae compression
what are the signs of a fracture in radiograohs?
fracture lines are more lucent than other lines, tend to be straighter & more acutely angled than naturally occurring lines, edges tend to be jagged & rough
what can fractures be confused with?
sesamoids, accessory ossicles, old ungealed fracture fragments
how can you tell difference between sesamoids & fractures?
sesamoids are usually found on both sides & occur at anatomically predicted site e.g. under tendon
how can you tell difference between accessory ossicle & fractures?
usually found on both sides & anatomically predictable sites- sites that do not fuse with parent bone
how can you tell difference between old fractures & fractures?
white line completely surrounds fragment & edges are usually smooth- might not even see a fracture if there is no visible fracture line (takes a while to develop)
what is a simple fracture?
2 fragments
what is a comminuted fracture?
more than 2 fractures
what is a segmental comminuted fracture?
portion of shaft is isolated
what is a butterfly comminuated fracture?
central fragment has a triangular shape
what directions can fractures occur in?
transverse, oblique, spiral
what is a transverse fracture and how does it occur?
fracture line is perpendicular to long axis of bone- caused by a force directed perpendicular to shaft
what is an oblique fracture & how does it occur?
fracture line is diagonal to long axis of bone- caused by a force applied along same direction as long axis
what is a spiral fracture & how does it occur?
caused by a twisting force- start at one side & comes out the other
what does displacement about a fracture describe?
amount by which the distal fragment is offset, front to back and side to side, from the proximal fragment
what does angulation about a fracture describe?
· the degree to which the distal fragment is deviated from its normal position.
what does shortening about a fracture describe?
how much overlap there is of the ends of the fracture fragments (how much shorter the bone is than its normal length)
what does distraction about a fracture describe?
distance the bone fragments are separated from each other (how much longer the bone is than its normal length)
what does rotation about a fracture describe?
the orientation of the joint at one end of the fractured bone relative to the orientation of the joint at the other end of the same bone.
what is a closed fracture?
no communication between the fracture and the external environment
what is a compound fracture?
there is communication between the fracture and the external environment
what are special types of fracture?
avulsion, epiphyseal, stress
what are avulsion fractures?
fracture fragment (avulsed fragment) is pulled from its parent bone by contraction of a tendon or ligament- any age, can be due to exercise, anatomically predicatable locations
what are epiphyseal fractures?
occurs in epiphyseal plate- 30% of childhood fractures
what are the classifications of epiphyseal fractures?
types i & ii (both heal well), type III (develop arthritic changes or asymmetric growth late fusion), type IV & V (develop early fusion with angular deformities & shortenings)- helps determine treatment & outcomes
what are stress fractures?
occur as a result of numerous microfractures due to repeated forces before remodelling has occured- appear normal
how are stress fractures diagnosed?
only after periosteal new bone formation occurs- radionuclide bone scans are useful
where are stress fractures commonly found?
proximal femur, proxinal tibia calcaneous & 2nd, 3rd metatarsals
what are the stages of fracture healing?
haematoma formation, procallus, callus, formation of normal bone with replacement of woven bone, remodelling of periosteal & endosteal surfaces
what is haematoma formation?
occurs with vessel damage- fibrin forms initial framework for healing
what is the procallus stage?
fibroblasts, osteoblasts & capillaries move into the wound to produce granulation tissue
what is the callus stage?
osteoblasts deposit disorganised clumps of primitive bone matrix called woven bone (the callus)
what is the final stages of fracture healing?
formation of normal bone with replacement of woven bone & remodelling of periosteal & endosteal surfaces
what are the factors affecting fracture repair?
local blood supply, type of fracture, fixation, age, concurrent infection, disease, nutritional status
how may type of fracture affect repair?
spiral & oblique repair faster than transverse- communited fractures have avascular fragments which may become sequestrated (necrotic tissue)
how may fixation affect fracture repair?
better fixation gives faster healing- movement may lead to non-union- IM pins may disrupt blood suppy
what are signs that a fracture is healed?
continuity of cortex, calcified complete bridging callus, no visible fracture line- takes 6 weeks with adequate fixation
what are complications in fracture repair?
delayed union, non union, malunion
what is delayed union is fracture repair?
failure of bone to unite within expected period of time, healing will eventually occur though- due to motion, infection, old patient, pathological fracture
what is nonunion is fracture repair?
cessation of bone healing due to motion, avascularity, infection
what are signs of nonunion in fracture repair?
smooth sclerotic edges with no callus, sealed medullary cavity, pseudoarthrosis
what is malunion in fracture repair?
union of a fracture with angulatory or rotatory deformity caused by improper reduction, rotation or collapse during healing
what are pathologic fractures?
fractures that occur in bone with a preexisting abnormality- occur with little force
what occurs in pathological fractures?
bone surrounding the fracture will demonstrate abnormal density or architecture with delayed healing- cannot predict if fracture will occur in diseased bone
what are dislocation?
bones that formed the joint are no longer in correct contact
what are subluxations?
bones that formed the joint are in partial contact.
what is arthritis?
affects joint & bones on either side of joint & caused joint space narrowing
how is arthritis diagnose?
conventional radiography (osseous abnormalities & but can’t see soft tissue change)- also MRI to see soft tissue changes
what are the types of arthritis?
hypertrophic, erosive, infectious
what is hypertrophic arthritis?
causes bone formation at site of involved joint- main bone has subchondral sclerosis e.g. osteoarthrities
what is erosive arthrities?
causes marginal, irregularly shaped lytic lesions in or around joint surfaces called erosions- underlying inflammation e.g. rheumatoid arthrities
what is infectious arthritis?
causes joint swelling, osteopaenia & destruction of articular cortex e.g. septic arthrities
what is osteoarthritis?
wear & tear causes degeneration of articular cartilage- mostly weightbearing joints e.g. hips, knees, hands
how do we diagnose osteoarthritis?
marginal osteophyte formation (bony protrusion at end of bone), subchondral sclerosis, subchondral cysts, narrowing of joint space
what is subchondral sclerosis?
bone thickening when protection of cartilage is removed
how does secondary osteoarthritis occur?
due to trauma & damages the articular cartilage
what is erosive arthrities associated with?
inflammation & synovial proliferation (pannus formation)
how do we diagnose erosive arthritis?
lytic lesions in or near joint, articular cartilage & underlying cartilage called erosions
what is rheumatoid arthritis?
form of erosive- bilateral & symmetrical, hereditary autoimmune disease, appears at a young age
what is the diagnoses of RA?
via convential radiographs= soft tissue swelling, osteoporosis, deformities, changes to spine, hands and wrist joints
what is gout?
when calcium urate crystal deposit in joint leading to inflammation- bone changes appear 5 to 7 years after sign- monoarticular- common in maes
what is infectious arthritis caused by?
haematogenous spread (blood borne), penetrating wound, extension from osteomyelitis adjacent to joint
