bones and joints

Question 1

inflammatory diseases

Answer 1

CAID

• crystals formation (gout, pseudogout)
• autoimmune (RA)
• infection (septic arthritis/ osteomyelitis)
• degenerative (OA)

Question 2

OA presentation (3) + pathology

Answer 2

presentation:

• generalised OA - post-menopausal
• erosive inflammatory OA - destructive, quick progression
• hypertrophic OA - ostophyte (bone spurs)

pathology

• eburnation** (bone rub bone)
• subchondral bone cyst
• thickened joint
• inflammation of synovium - synovitis
• degeneration of articular cartilage
• bone spurs
• sclerosis

Question 3

what is RA+ who is more susceptible

Answer 3

chronic inflammatory autoimmune disease: CD4+ T cells.
RF and ACPA antibodies produced
-> destructive granulation tissue (pannus) formed + synovial inflammation
bone erosion**
affecting joints - esp proximal (UL)
more common in women

Question 4

RA histology

Answer 4

rheumatoid nodules
fibrinoid necrosis (granuloma) in the centre

Question 5

crystals formation and deposition

• analysis
• location
• 2 types

Answer 5

deposited in joints and soft tissue
gram stain, culture, crystal analysis
- gout + pseudogout

Question 6

gout pathogenesis + risk factors

Answer 6

caused by increased serum uric acid
-> form urate crystals that deposit in the bone

primary: obesity, alcohol, HTN, fatty diet
secondary: anything that causes hyperuricemia

pathogenesis:

• over-production of purines
• catabolism
• kidney failure: uric acid cannot get eliminated

Question 7

gout complications

Answer 7

• deformities, erosion of joints
• gouty tophi
• renal stones/ renal failure

Question 8

gout crystals examintaion

Answer 8

polarised light to examine synovial fluid

birefringent (refractive) needle shaped crystals

Question 9

pseudogout crystals made of what + shape

Answer 9

• calcium pyrophosphate (chondrocalcinosis)

- rhomboid shaped, weakly birefringent

Question 10

inflammation caused by infection - osteomyelitis

• common cause of infection
• way of entering the bone

Answer 10

• staph aureus** (most common)
• E.coli, Group B strep, anaerobes
• direct implantation - trauma
• blood (lung TB)*
• contiguous spread (share a border) - middle ear infection

Question 11

osteomyelitis clinical presentations + where does it happen

Answer 11

tuberculosis
pain, swelling, fever

children: UL/LL
adults: LL, spine

Question 12

osteomyelitis pathogenesis

Answer 12

bacteria and inflammation spread within shaft of the bone, harversian system and periosteum* (similar to osteosarcoma
(periosteum: impair blood supply -> bone necrosis -> sequestrum (bone within bone)
may also spread to synovium -> septic arthritis

Question 13

osteomyelitis complications

Answer 13

• fracture and deformity
• amyloidosis
• distal infection
• malignant transformation

Question 14

TB osteomyelitis

Answer 14

highly destructive - extensive necrosis
chronic inflammation - epithelioid granulomas + caseating necrosis
usually affects the spine

Question 15

TB osteomyelitis complications

Answer 15

• compression fractures
• severe deformities - kyphosis (hunchback)
• compress spinal cord and nerves -> neurological deficits

Question 16

metabolic bone diseases (4)

Answer 16

(POOO)

• osteoporosis (reduced bone mass)
• osteomalacia and rickets (mineralisation defects)
• osteitis fibrosa cystica (excessive bone resorption)
• paget’s disease (uncontrolled resorption + uncoordinated osteoblastic effects - formation of new bone)

Question 17

osteoporosis

• how to measure
• characteristics (serum ca/hormones, mineralisation)

Answer 17

reduced bone mass - BMD <2.5
BMD measurement = X ray absorptiometry at hip/lumbar spine
thinned and reduced trabeculae -> increase risk of fracture
- but normally mineralised!! (osteomalcia has decreased mineralisation)
- normal serum ca/phosphate
- normal ALP (alkaline phosphatase protein: tests liver/bone fn)
- normal PTH hormone

Question 18

causes of osteoporosis (primary + secondary)

+ site

Answer 18

primary: post-menopause cause of estrogen def
estrogen def
-> increase inflammatory cytokines
-> osteoclast recruitment = bone resorption
increase both bone resorption and formation (but resorption more) = overall bone resorption

secondary: decrease in calcium intake/absorption
- GIT/endocrine, drugs

affects spine, fracture of femur/wrist

Question 19

osteomalacia cause

Answer 19

defect in mineralisation (calcification) cause of vit D def

- > weak bone: microfactures/softening of bone
children: bowing of legs, may even distort skull

Question 20

rickets pathogenesis

Answer 20

disturbances of endochondral ossification
-> overgrowth of epiphyseal cartilage - cartilage cells cannot mature

non-calcified, hypertrophied growth plate

Question 21

vit D def causes

Answer 21

• inadequate dietary intake
• lack of sun exposure
• GI problems -> malabsorption (IBD, bowel resection, celiac disease)
• renal disease: vit D cannot be converted to active form

Question 22

osteitis fibrosa cystica pathogenesis

- serum calcium/phosphate levels

Answer 22

excessive bone resorption by osteoclasts - because of increased PTH hormones

• high serum calcium (cause of the bone resorption), low serum phosphate
• loss of bone mass
• the bone loss replaced by fibrous tissue

Question 23

osteitis fibrosa cystica complications

Answer 23

• formation of brown tumour: cystic solid lesion

developed cause of the osteoclasts

Question 24

Paget’s disease

Answer 24

disorderly bone formation cause of excessive/disorganised bone resorption + formation
-> distorted bone architecture
mosaic pattern of lamellar bone, irregular w/ collagen fibres

Question 25

Paget's disease affects who + sites

Answer 25

- elderly and caucasian | - mainly polyostic - pelvis, spine, skull

Question 26

complication of Paget's disease

Answer 26

- bone overgrowth -> OA - chalkstick fractures (affect long bones that become brittle) - nerve compression - CVS issues cause of hypervascularity of bone - osteosarcoma

Question 27

types of bone tumours

Answer 27

- osteosarcoma - children/young adults** most common malignant - Ewing sarcoma (EWS)/ PNET** - children/ young ^ respond to chemotherapy - chondrosarcoma** - older pts (malignant) - chondroma, osteochondroma (benign) - giant cell tumours - fibrous/ fibro-osseous tumours

Question 28

primary malignant bone tumour presentation

Answer 28

pain, swelling possibly fracture, loss of fn fever, anemia, weight loss, elevated WBC & ESR (cause of inflammation) may metastasise: lungs, bone, bone marrow

Question 29

investigation of bone tumours

Answer 29

- X-ray** first line!! - MRI - relations: nerves/vessels - radionuclide scan: detect metastasis - PET scan: detects spread to see if tumour is malignant - biopsy

Question 30

osteosarcoma | - who it affects more

Answer 30

malignant, high grade produces osteoid from tumour cells - males high proportion - 10-25 yrs

Question 31

osteosarcoma on x-ray

Answer 31

destructive lytic masses permeative margins - arises within medullary cortex -> breaks through cortex & periosteum (like septic arthritis) - tumour: bone formation in soft tissue -> SUNBURST pattern - affects long bones of LL (femur, tibia, humerus) - lots of necrosis & hemorrhage -> fleshy appearance

Question 32

osteosarcoma histology

Answer 32

osteoid** produced by eosinophilic matrix (diagnosis)

Question 33

EWS | - who it affects more

Answer 33

2nd most common malignant bone tumour in children, esp <10yrs affects 5-25yrs, more common in males

Question 34

EWS on x-ray

Answer 34

destructive poorly marginated + permeative layered periosteum -> "onion skinning'

Question 35

EWS on histology

Answer 35

small, round, uniform blue cells arranged around vessels +ve w. CD99 stain** - differentials: lymphomas, rhabdomyosarcoma, metastatic carcinoma, neuroblastoma, small cell osteosarcoma

Question 36

chondrosarcoma

Answer 36

- malignant - produces cartilage - DOES NOT produce osteoid - painful, large

Question 37

chondrosarcoma - who it affects more - sites - reacts to chemo?

Answer 37

males, 30-60yrs (older pts) sites: long bones/ ribs (>8cm) that grow rapidly during adolescence does not respond to chemo

Question 38

macroscopic chondrosarcoma

Answer 38

large lobulated tumour w/ focal calcification | hemorrhagic necrosis present

Question 39

microscopic chondrosarcoma

Answer 39

cartilaginous matrix permeation of bone trabeculae soft tissue and marrow invasion

Question 40

osteochondroma

Answer 40

benign* - most common benign tumour arises from long bones - overgrowth of bone - bone extension containing cortex and periosteum covered by a thin cartilaginous cap

Question 41

types of chondroma

Answer 41

- enchondroma: medullary cavity Ollier's disease; Maffucci syndrome solitary enchondromas: caused by heterozygous mutations of IDH genes - subperiosteal chondroma: surface of bone - soft tissue chondroma: inside soft tissue

Question 42

differences in benign and malignant bone tumour

Answer 42

- permeation of bone trabeculae and marrow | - soft tissue & organ invasion

Question 43

giant cell bone tumour

Answer 43

benign, but locally aggressive (does not metastasise distally) most common skeletal neoplasm

Question 44

giant cell bone tumour - who it affects more - site

Answer 44

``` oriental countries (SEA) affects females more ``` - affects long tubular bones (knee) - epiphyseal-metaphyseal region (growth plate)

Question 45

giant cell tumour characteristics

Answer 45

- NO osteoid formation - NO malignant transformation - abundant giant cell w/ numerous nuclei

Question 46

non-ossifying fibroma - who it affects - site

Answer 46

benign affects children metaphysis of long bones (esp femur) micro: cellular lesions, fibroblasts, activated macrophages, giant cells

Question 47

``` fibrous dysplasia (FD) + 2 polyostotic examples ```

Answer 47

``` benign developmental arrest: does not develop into mature bone structure mutation in GNAS1 gene** - Mazabraud syndrome - McCune-Albright ```

Question 48

FD microscopy

Answer 48

tan-white and gritty (sandy) histo: trabeculae surrounded by fibroblastic proliferation trabeculae is curvilinear