MSK basic sciences (pathology, biochemistry and histology) Flashcards
what is the commonest benign tumour of bone
osteochondroma
what is an osteochondroma
a bony outgrowth on the external surface of bone, covered with a cartilaginous cap
where do osteochondromas typically occur
around the epiphysis of long bones
especially around the knee
symptoms associated with osteochondroma
usually asymptomatic but may cause localised pain
what is an enchondroma
an intramedullary and usually metaphyseal cartilaginous tumour
enchondroma may undergo mineralisation and become patchy and sclerotic in appearance
true/false
true
complications of enchondroma
may weaken the bone causing pathologic fracture
where do enchondromas calssically occur
small tubular bones of the hands and feet
what is a simple bone cyst
solitary unicystic fluid-filled neoplasm located in a bone
most common locations of simple bone cysts
metaphyses of long bones (esp proximal femur and humerus)
talus/calcanues also
complication of simple bone cyst
weakness of bone leading to pathologic fracture
treatment of simple bone cyst
curettage and bone grafting +/- stabilisation
what is an aneurysmal bone cyst
a cyst with many chambers which are filled with blood or serum
where do aneurysmal bone cysts occur
metaphyses of long bones, flat bones and vertebral bodies
symptoms of aneurysmal bone cyst
pain
locally aggressive causing cortical expansion and destruction
risk of pathological fracture
treatment of aneurysmal bone cyst
curettage and grafting or bone cement
what is fibrous dysplasia
diseaseof a bone usually occurring in adolescence where a genetic mutation results in lesions of fibrous tissue and immature bone
monostotic vs polyostotic
monostotic affects one bone
polyostotic affect multiple bones
the most frequent sites of fibrous dysplasia
head and neck
what genetic cause is responsible for fibrous dysplasia
a mutation causing an abnormality in G protein signalling
fibrous dysplasia is often associated with endocrine disorders
true/false
true
effect of fibrous dysplasia on bones
angular growth deformity
wider bone with thinned cortices
what deformity is produced by excessive involvement of the proximal femur in fibrous dysplasia
shepherd’s crook deformity
how does fibrous dysplasia appear on a bone scan
intense increase in uptake during development but the lesion usually becomes inactive
treatment of fibrous dysplasia
bisphosphonates may reduce pain
patholigc fractures should be stabilised with internal fixation and cortical bone grafts
which part of bones do giant cell tumours tend to occur
metaphyseal region (can involve the epiphysis)
can extend to the subchondral bone adjacent to the joint
which bones/joints does giant cell tumour tend to affect
around the knee
distal radius
(other long bones, pelvis and spine)
giant cell tumours are completely benign
true/false
false
they tend to be locally aggressive and destroy the adjacent cortex
giant cell tumour presenation
pain
pathologic fracture
how do giant cell tumours appear on xray
‘soap bubble’
where can giant cell tumours metastasize to
lung
treatment of giant cell tumour
intralesional excision with use of phenol, bone cement or liquid nitrogen to destroy remaining tumour material and reduce risk of recurrence
what is an osteoid osteoma
a small nidus of immature bone surrounded by an intense sclerotic halo
common sites of osteoid osteoma
proximal femur
diaphysis of long bones
vertebrae
symptoms of osteoid osteoma
intense constant pain, worse at night
management of osteoid osteoma
NSAIDs
may resolve spontaneously
may require CT guided radiofrequenct ablation
diagnosis of osteiod osteoma
bone scan (intense local uptake)
CT
malignant bony lesions are cnot uncommon in older age groups but are normally a result of
metastases
red flags for bone cancer
constant pain that’s worse at night
systemic symptoms
unexplained skeletal pain
primary bone malignancy is more likely to occur in which age group
young people
a substantial ill-defined bony swelling may be
primary bone cancer - INVESTIGATE
signs of primary bone tumour on xray
cortical destruction
periosteal reaction
new bone formation (sclerosis/lysis)
extension into surrounding soft tissue
the most common primary bone tumour is
osteosarcoma
which gene is most commonly associated with osteosarcoma
tumour suppressor retinoblastoma gene
osteosarcoma most commonly affects bones surrounding which joint
the knee
common sites of osteosarcoma
knee
proximal femur
proximal humerus
pelvis
which type of metastasis is common in osteosarcoma
blood metastases
NOT LYMPH
treatment of osteosarcoma
adujavant chemotherapy to prolong survival
what is chondrosarcoma
cartilage producing primary bone tumour
characteristics of chondrosarcoma
(aggressive? age group? mets?)
less aggressive than osteosarcoma
mean age 45
slow to metastasise
where does chondrosarcoma affect
pelvis
proximal femur
treatment of chondrosarcoma
surgery
not radiosensitive or responsive to chemo
what is ewing’s sarcoma
primary bone tumour
which bones does ewing’s sarcoma tend to affect
long bones (esp femur)
how are ewing’s sarcomas radiologically described
onion skin pattern
signs of ewing’s sarcoma
fever
raised inflammatory markers
warm swelling
staging investigations of primary bone cancer
bonce scan
CT
(MRI for involvement of vessels, muscles and nerves)
what margin is reccomended when removing a bone tumour
3-4 cm
how to joint replacements after bone malignancy surgery differ from regular joint replacements
tend to be much bigger to make up for the loss of bone
metastatic bone tumours commonly spread from which types of cancer
breast carcinoma
prostate carcinoma
lung carcinoma
renal cell carcinoma
thyroid carcinoma
breast cancer bony metastases can be blastic (sclerotic) or lytic
true/false
true
prostate cancer produces lytic mets
true/false
false
sclerotic mets
lung cancer usually gives rise to lytic mets
true/false
true
why are renal cell carcinoma mets described as ‘blow out’ lesions
they can bleed tremendously with biopsy or surgery
bones most frequently invovled with mets are
vertebra
pelvis
ribs
skull
humerus
long bones of the lower limb
patients with bony mets may present with
pathological fracture
if a bony lesion is found on xray, how can a primary bone tumour be excluded?
bone scan
occasionally MRI
which blood tests can be done when trying to detect a primary tumour after a bony met has been found?
serum calcium (hypercalcaemia)
LFTs (liver involvement)
plasma protein electrophoresis (myeloma)
FBC
U&Es
what sort of bone lesions are at greater risk of pathologic fracture?
very painful
lesions occupying >50% of the diameter of the bone
cortical thinning
‘at risk’ areas (eg subtrochanteric area of the femur)
managment of bony lesions at risk of patholgical fracture
skeletal stabilisation
joint replacement
bony lesions not at risk of pathologic fracture can be treated with
bisphosphonates and radiotherapy
causes of local soft tissue swelling
inflammatory (bursitis, rheumatoid nodules)
infection (abscess)
cystic lesions (ganglion, meniscal cyst, Baker’s cyst)
benign/malignant neoplasms
what to ask when taking a history of a soft tissue swelling
how long the lump has been present
pain
growing/fluctuating size
solitary or multiple
examination findings of soft tissue swelling
site
size
definition (well-defined, ill-defined)
consistency (cystic, solid, soft, hard)
surface (smooth, irregular)
mobility/fixity
temperature (abscess)
transilluminable
pulsatility
overlying skin changes
local lymphadenopathy
what features would suggest a benign soft tissue neoplasm
smaller size
fluctuation in size
cystic lesions
well-defined lesions
fluid filled lesions
soft/fatty lesions
features that suggest a malignant soft tissue neoplasm
larger lesions (>5 cm)
rapid growth
solid lesions
ill-defined lesions
irregular surface
assocaited lymphadenopathy
systemic upset
extremely rapid growth of a soft tissue neoplasm is suggestive of benign/malignant neoplasm
benign
extremely fast growth is assocaited with a reactive pseudotumour
what structures can benign soft tissue tumours affect
non-bony connective tissues
nerves
vessels
what is a lipoma made of
fat
what is a leiomyoma made of
smooth muscle
what is a chondroma made of
cartilage
what is a rhabdomyoma made of
skeletal muscle
what are neuromas/schwannomas made of
nerves
what are haemangiomas made of
blood vessels
what is the most common type of soft tissue tumour
leiomyoma
they occur as fibroids in the uterus
what is the commonest soft tissue tumour encountered in orthopaedics
lipoma
what is giant cell tumour of tendon sheath
a small firm swelling usually found on the flexor tendon sheath of a finger
what is the macroscopic and microscopic appearance of a giant cell tumour of tendon sheath
macroscopic - pigmented lesion
microscopic - multinucleated giant cells and haemosiderin
what are malignant soft tissue tumours arising from the connective tissues known as?
sarcomas
what is an angiosarcoma
malignant tumour arising from blood vessels
most common cause of angiosarcoma
complication of previous radiotherapy
what is a fibrosarcoma
rare tumour of unknown origin
what is a liposarcoma
malignant tumour arising from fat
where do liposarcomas occur
deep fatty tissue, most often within the abdomen
what is a rhabdomyosarcoma
malignant tumour of skeletal muscle
what age do sarcomas most commonly present
50-70
where are ganglion cysts found
around synovial joints or synovial tendon sheaths
why are ganglion cysts not truly cysts
they do not have an epithelial lining
what is a bursa
a small fluid filled sac lined by synovium around a joint which prevents friction between tendons, bones, muscle and skin
which bursae are often affected by bursitis
pre-patellar
olecranon
1st metatarsal head (bunion)
bursitis can be caused by
infection
gout
repeated pressure
trauma
characteristics of sebaceous cysts
squamous epithelium lining that produces abundant keratin
what is released from a ruptured sebaceous cyst
degenerate keratn (cheesy substance)
what does an abscess consist of
neutrophils
infective and cellular debris
(infection organism)
what can cause an abscess
cellulitis
bursitis
penetrting wound
infected sebaceous cysts
treatment of abscess
incision and drainage
what is a pseudotumour
a tumour that mimics a neoplasm but is a reactive/inflammatory lesion
what is myositis ossificans
progressive ossification at a site of injury
what is the most common site of AVN
femoral head
AVN is most common in which group of people
chronic alcoholics
what is creeping substitution associated with
AVN
what age group is affected by osteochondritis
children and young adults
what is AVN
ischaemic necrosis of bone
what sites are most prone to AVN
femoral head
femoral condyles
head of humerus
capitellum
proximal pole of scaphoid
proximal talus
how can AVN be caused by fracture
fracture disrupts the blood supply to a portion of bone
causes of AVN
fracture
idiopathic
alcoholism
steroids
hyperlipidaemia
increased coagulability
what type of imaging can detect early changes in AVN
MRI
what type of bone defect is osteoporosis
a quantitave defect
what are the characteristics of osteoporosis
reduced bone mineral density and increased porosity
(normal bone quality, just not enough of it)
complications of osteoporosis
increased risk of fracture
what is the WHO definition of osteoporosis
bone mineral density less than 2.5 standard deviations below the mean peak value of young adults of the same race and sex
what is osteopaenia
an intermediate stagoe of osteoprosis where bone mineral density is 1-2.5 standard deviation below mean peak value
loss of bone density in osteoporosis is due to
gradual slow down of osteoblastic activity
why do females tend to lose more bone density after the menopause
increase in osteoclastic bone resorption with the loss of protective effects of oestrogen
what is type 1 osteoporosis
post menopausal osteoporosis
risk factors for type 1 osteoporosis
smoking
alcohol abuse
lack of exercise
poor diet
what is type 2 osteoporosis
osteoporosis of old age
risk factors for type 2 osteoporosis
chronic disease
inactivity
reduced sunlight exposure
smoking/alcohol
poor diet
what fractures are most common in ype 1 osteoporosis
colles fracture
vertebral insufficiency fractures
fractures associated with type 2 osteoporosis
femoral neck fractures
vertebral fractures
secondary osteoporosis can be caused by
steroid use
alcohol abuse
malnutrition
chronic disease (CKD, malignancy, RA)
endocrine disorders (cushing’s, hyperthyroidism, hyperparathyroidism)
diagnosis of osteoporosis
DEXA scan (measures bone mineral density)
serum calcium and phosphate levels in osteoporosis
normal
treatments for osteoporosis
calcium and vit D supplements
bisphosphonates (reduce osteoclastic resorption)
Desunomab (monoclonal antibody which reduces osteoclast activty)
strontium (increase osteoblast replication and reduces resorption)
risks of HRT for treatment of osteoporosis
increased risk of breast and endometrial cancer and DVT
what sort of defect is osteomalacia
qualitative
what is osteomalacia
abnormal softening of the bone due to deficient mineralisation of osteoid (immature bone) secondary to inadequate amounts of calcium and phosphorus
what is the difference between osteomalacia and ricketts
ricketts affects children
what are the principal causes of osteomalacia
insufficient clacium absorption from the intestine (lack of dietary calcium or a deficiency o or resistance to the action of vitamin D)
phosphate deficiency due to increased renal losses
specific causes of osteomalacia
malnutrition
malabsorption
lack of sunlight
hypophosphataemia
long term anticonvulsant use
CKD
presentation of osteomalacia
bone pain (pelvis, spine, femora)
deformities from soft bones (more ricketts)
pathological fractures
hypocalcaemia (paraesthesiae, muscle cramps, irritability, fatigue, seizures, brittle nails)
serum calcium, phosphate and ALP in osteomalacia
low Ca
low PO4
high ALP
treatment of osteomalacia
vitamin D therapy
phosphate supplementation
what causes primary hyperparathyroidism
benign adenoma
hyperplasia
malignant neoplasia (rare)
what does overproduction of PTH result in
hypercalcaemia
symptoms of hyperparathyroidism
fatigue, depression, bone pain, myalgia, nausea, thirst, polyuria, renal stones, osteoporosis
serum calcium and phosphate in hyperpara
Ca high
PO4 normal/low
what is secondary hyperpara
physiological overproduction of PTH secondary to hypocalcaemia usually casued by vitamin D deficiency or CKD
what are brown tumours
lytic bone lesion caused by hyperpara
treatment of hyperpara
removal of the adenomatous gland
treatment of underlying cause (vit D supplementation)
what is paget’s disease
a chronic disorder which results in thickened, brittle and mis-shapen bones
paget’s disease affects the whole skeleton
true/false
false
it normally affects one or a few bones
what causes the increased bone turnover in paget’s disease
increased osteoclast activity
paget’s pathophysiology
increased osteoclast activity leads to increased bone turnover
osteoblasts become more active to correct excessive resorption
new bone is formed, but fails to remodel sufficiently and the resulting bone is brittle despite its increased thickness and density
which bones are commonly affected by paget’s disease
pelvis
femur
skull
tibia
ear ossicles (conductive deafness)
presentation of paget’s disease
asymptomatic (incidental finding)
arthritis
pathologic fracture
deformity
pain
high output cardiac failure (increased blood flow through pagetic bone)
xray appearance of paget’s disease
enlarged bone with thickened cortices and coarse, thickened trabeculae with mixed areas of lysis and sclerosis
what do bone scans show in paget’s disease
increased uptake in the affected bone(s)
treatment of paget’s disease
bisphosphonates (inhibit osteoclasts)
calcitonin (in extensive lytic disease)
joint replacment
