bone pathology Flashcards
function of bone
mechanical - support and site for muscle attachment
protective - vital organs and bone marrow
metabolic - calicum reserve
bone composition
65% inorganic
* calcium hydroxyapatite (10Ca 6PO(4) OH2)
* store house for 99% ca
* 85% of phosphorus, 65% of Na and Mg
35% organic - bone and cell matrix
bone georgraphy
outside of bone is lined by the periosteum
then cortex
then medulla
long bone have
* diaphysis (prox)
* epiphysis
* then epipihyseal line and in between is metaphysis (where growth plates are)
describe
XR
in tibia - lytic lesion
2 types of bone
cortical
cancellous
descrive cortical bone
long bones
80% skeleton
appendicular
80-90% calcified
mainly mechanical and protective
describe cancellous bone
vertebrae and pelvis
20% of skeleton
axial
15025% calcified
mainly metabolic
large surface
bone microanatomy
made of many microcolumns
have a canals
concentric lamellae around canals
interstitial lamellae connecting the units
circumferential lamellae surrounding th whole entity
trabecular lamellae deeper inside
cortical bone histology
big pink area is the cortical bone
thick
cancellous bone histology
trabeculae - darker pink
in between - haemopoietic cells and adipose tissue
types of bone cells
osteoblasts - build bone by laying down osteois
osteoclasts - multinucleate cells of macrophage family - resorb or chew bone
osteocytes - osteoblast like cells that sit in the lacunae
histology of bone cells
osteoclast - biggest here, pink, purple nuclei, multinucleated
osteoblast - smaller, single nucleus
osteocyte - small pigmented nuclei
bone remodelling process
controlled by various factors - paracrine
- osteoclast precurser from monocytes.
- osteoblast has osteoprotegrin with RANK-L (when blocked stops transformation of osteoclast precurser into osteoclast)
definition of metabolic bone disease
disordered bone turnover due to imbalance of various chemicals in the body
overall effect -> reduced bone mass (osteopenia) -> fractures with little/no trauma
categories of metabolic bone disease
non-endocrine - age related osteoporosis
related to endocrine abnormality (vit D, parathyroid hormone)
disuse osteopenia
How do you investigate metabolic bone disease - histology
histology - bone biopsy from iliac crest, processed un-decalcified form for histomorphometry
static parameters
* cortical thickness and porosity
* trabecular bone volume
* thickness, number and separation of trabeculae
bone mineralisation studied using osteoid parameters
histodynamic parameters obtained from flurescent tertracycline labelling
tetracycline labelling of normal bone
aetiology of osteoporosis
90% - insufficient Ca intake and post-menopausal oestrogen deficiency
primary - age, post-menopause
secondary - drugs, systemic disease
what is high and low turnover osteoporosis
high turnover - increased bone resorption
low turnover - reduced bone formation
fracture pathogenesis in osteoporosis
low initial bone mass or
accelerated bone loss can reduce bone mass below the fracture threshold
RF for osteoporosis
Advanced age
female
smoking
excess alcohol
early menopause
long term immobility
low BMI
poor diet, low Vit D, low Ca
malabsorption
thyroid disease
low testosterone
chronic renal disease
steroids
how do steroids cause osteoporosis
effect osteoclasts, osteocytes and blasts
decrease bone quality -> osteonecrosis and fracture
presentation of osteoporosis
back pain
fractures:
* colles
* NOF
* intertrochanteric
* pelvis
> 60% vertebral fractures are asx
compression fractures usuallin T11-L2
bone on R has osteoporosis
Ix for osteoporosis
Lab investigations
* serum ca, phos and alk phos - normal
* urinary ca
* collagen break down products
imaging
bone densometry
* T score between 1& 2.5 SD below normal peak bone mass = osteopenia
* T score >2.5 SD below normal peak bone mass = osteoporosis
what organs are effected by PTH, and what do they control collectively
Parathyroid glands
bones
kidneys
proximal small intestine
control calcium metabolism
pathway with hypocalcaemia
reduction in Vit D = increase PTH = increase osteoclast
definition of osteomalacia
defective bone mineralisation
2 types:
* deficiency of vit D
* deficiency of phosphorus
histology in osteomalacia
reduced mineralised bone (Green)
in comparison to the osteoid (orange)
consequences of osteomalacia
bone pain/tenderness
fracture
proximal weaknes
bone deformity
XR in rickets
bowing of femur and tibia
disease around knee
fracture in osteomalacia
horizontal pseudofracture in looser zone
findings in hyperparathyroidism
excess pth -> increase ca and phos excretion in urine
hyperca
hypophos
skeletal changes of osteitis fibrosa cystica
causes of hyperparathyroidism
primary
* parathyroid adenoma
* chief cell hyperplasia
secondary
* chronic renal deficiency
* vit d deficiency
* malabsorption
histology of hyperparathyroidism
multinucleate giant cells - brown cell tumour
background of fibrous stroma
haemorrhage
phases of paget’s disease
disorder of bone turnover
3 phases
1. osteolytic (osteoclasts)
2. osteolytic-osteosclerotic (blasts and clasts - start to get new bone formation)
3. quiescent osteosclerotic (new mosaic of bone forming)
histology of pagets disease
Hand E stain
mosaic lines
large pink cells- osteoclasts
site prediliction for paget’s
Lumbar spine or skull
XR of pagets
bowed
cotton wool appearance
XR of pagets
bowed
cotton wool appearance
macro and micro features of pagets
macro - thickened bone and trabeculae
micro - thickened trabeculae, mosaic pattern
type of fracture
what type of fracture is this
comminuted
stages of fracture repair
organisation of haematoma at fracture site (pro-callus)
formation of fibrocartilaginous callus
mineralisation of fibrocartilaginous callous
remodelling of bone along weight bearing lines
fracture healing
histology of fracture callous
disorganised bone
fibrous background
trabecular
organisms that cause osteomyelitis
mainly staph aureus
histology of osteomyelitis
increase in fibrosis
chronic inflammatory cells - lymphocytes and histocytes
XR changes in osteomyelitis
10days post onset
mottled rarefaction and lifting of periostium
>1wk - irregular sub-periosteal new bone formation called involucrum
later - irregular lytic destruction (10-14days)
some areas of necrotic cortex may become detatched -> sequestra (3-6wks)
macroscopic osteomyelitis image
histology of osteomyelitis
big pink - trabecular bone
fibrosis in the paratrabecular space
granuloma - munltinucleated, langerhans type giant cells (horseshoe nuclei)
lymphocytes
summarise lyme disease
inflammatory arthropathy as part of a complex multisystem illness resulting from tick bite
most prevalent vector bone disease in temperate northern hemisphere
organism - borrelia burgdorferi
tick species - Ixodes dammini
tick bite get skin rash - erythema chronicum migrans
XR of osteoarthritis
Loss of joint space
subchondral sclerosis
bone cysts
osteophytes
identify features of osteoarthritis
wear and tear impact on femoral head
what is this pathology in the femoral head
avascular necrosis
histology of synovium in osteoarthritis
chronically inflammed
plasma cells
lymphocytes
sites that rheumatoid arthritis effects
small joints
hands and feet sparing DIPJ
wrists
elbows
ankles
knees
XR showing features of rheumatoid arthritis
proximal joint involvement
soft tissue swelling
histology of rheumatoid arthritis
proliferative synovitis
* thickening of synovial membranes (villous)
* hyperplasia of surface synoviocytes
* intense inflammatory cell infiltrate - lymphocytes
* fibrin deposition and necrosis
pannus formation with exuberant inflammed synovium overlying the articular surface
gout - needle shaped crystal
summarise gout
affects any joint - big toe in 90%
limited to lwer extremities
needle shaped crystals
tophus is pathopneumonic lesion
macro pathology gout
summarise pseudogout
usual age >50yrs
crystals of calcium pyrophosphate - knees
calcium phsophate (hydroxyapatite) knees and shoulders
