Bone Flashcards
which Bone Cells are of the macrophage family?
osteoclasts
what. is the process allowing bone resorption?
osteoblasts with RANK-L bind to RANK on surface of osteoclast precursors
osteoblasts also release macrophage colony-stimulating factor (M-CSF) which binds to MCSF receptor. on surface of osteoclasts p
these 2 together induce activation into osteoclasts
what is the process stopping bone resorption?
stromal cells / osteoblasts release Osteoprotegrin
OPG acts as a “decoy” receptor for RANKL, preventing it from binding the RANK receptor
Consequently, OPG prevents bone resorption by inhibiting osteoclast differentiation.
what is the downstream factor activated by RANK-RANK-L. binding?
NFKB
90% cases of osteoporosis is due to ??
insufficient Ca intake and post-menopausal oestrogen deficiency
what are the mechanisms. of. Glucocorticoid-Induced Bone Disease ?
excess steroids can lead to osteonecrosis and fractures through;
- Osteocytes - increased apoptosis
- Osteoblasts - less made = less bone formed
- Osteoclasts - less made, but temporary increased in bone breakdown
how. does. Osteoporosis typically present?
back pain and #
> 60% vertebral # are asymptomatic
compression sx
what are the 2 types of osteomalacia?
- Deficiency of vitamin D
2. Deficiency of PO4
Looser’s zone fracturesare seen in?
osteomalacia
what are the sx of Hyperparathyroidism?
Stones (Ca oxalate renal stones)
Bones (osteitis fibrosa cystica*, bone resorption)
Abdominal groans (acute pancreatitis)
Psychic moans (psychosis & depression)
- Browns tumours - fibrovascular tissue and giant cells with abundant deposits hemorrhage and hemosiderin.
what does Renal Osteodystrophy involve?
Comprises all the skeletal changes of chronic renal disease
name. a disorder of bone turnover?
Pagets disease
what is the aetiology of Pagets disease?
Familial cases show autosomal pattern of inheritance with incomplete penetrance (mutation 5q35-qter - sequestosome 1 gene)
what is the. presentation of pagets?
pain
microfractures
nerve compression (incl. Spinal N and cord)
+/- haemodynamic changes, cardiac failure
Development of sarcoma in area of involvement 1%
what are the histological features of pagets?
cortex - thickened
trabeculae - coarse, irregular, thick
what are the stages of fracture repair?
- Organisation of haematoma at # site (pro-callus)
- Formation of fibrocartilaginous callus
- Mineralisation of fibrocartilaginous callus
- Remodelling of bone along weight-bearing lines
what are the presenting sx of osteomyelitis?
General - malaise, fever , chills , leucocytosis
Local - pain, swelling and redness
what are. common sites for osteomyelitis?
Vertebrae
Jaw (2º to dental abscess)
Toe (2º to diabetic skin ulcer) (>3mm)
Long bones (usually metaphysis)
how might we ivx osteomyelitis?
60% positive blood cultures
X-ray - mixed picture; eventually lytic
what is the most common organism in osteomyelitis?
Staph Aureus(90%)
name some xray changes for osteomyelitis?
exam purpose only
Usually appear 10 days or so post onset
Mottled rarefaction and lifting of periosteum
>1week - irregular sub-periosteal new bone formation called involucrum
Later - irregular lytic destruction (takes 10-14days)
Some areas of necrotic cortex may become detached called sequestra (takes 3-6 weeks)
psoas abscess and severe skeletal deformity (Pott’s disease) may present in the skeletal manifestation of which condition?
Tuberculosis
TB Osteomyelitis
since osteomyelitis only means infection n inflammation of bone
list some rarer causes of Osteomyelitis?
TB
Syphilis
name the most prevalent vector bone disease
Lyme disease
aetiology of lyme disease?
Inflammatory arthropathy
Organism:-
Borrelia burgdorferi
Tick Species:-
Ixodes dammini
erythema chronicum migrans rash is seen in?
lyme disease
how does lyme disease present?
Characterised by rash (90%)
Often thigh, groin, axilla (earlobe in children)
Early - Disseminated disease:
Affects many organs, musculoskeletal, heart, nervous system.
Late, persistent: Dominated by arthritis
what processes underline osteoarthiritis?
cartilage degeneration
fissuring
abnormal matrix calcification
osteophytes
most common sites affected in osteoarthiritis?
Main sites vertebrae hips and knees
+/-DIPJ PIPJ of the hand
+/- carpometacarpal and metatarsophalangeal joints
what clues can the synovium give us about osteoarthiritis?
Infiltration of mononuclear cells, thickening of the synovial lining layer and production of inflammatory cytokines
the following are found in which condition:
Radial deviation of wrist
Ulnar deviation of fingers
‘Swan neck’ & ‘Boutonniere’ deformity of fingers
‘Z’ shaped thumb
Rheumatoid Arthritis
what would be the histological features of Rheumatoid Arthritis?
Proliferative synovitis with
1. Thickening of synovial membranes ( villous) 2. Hyperplasia of surface synoviocytes 3. Intense inflammatory cell infiltrate 4. Fibrin deposition and necrosis
Pannus formation with exuberant inflamed synovium
overlying the articular surface
what are Grimley-Sokoloff cells?
synovial giant cells found in Rheumatoid Arthritis
what is the commonest malignant bone tumour ?
metastatic bone cancer
list some Primary Bone Tumours - Malignant? most common?
Osteosarcoma - most common
Chondrosarcoma
Ewing’s sarcoma
epidemiology of Osteosarcoma?
peak in adolescence
what would be the histological n X-ray features of osteosarcoma?
malignant mesenchymal cells +/- bone and cartilage formation
xray: elevated periosteum (Codman’s Triangle)
the following are consitent with which condition:
X-ray: lytic with fluffy calcification
Histo: malignant chondrocytes +/- chondroid matrix may dedifferentiate to high grade sarcoma
chondrosarcoma
because it is a cartilage producing tumour
the following are consitent with which condition:
X-ray: onion skinning of periosteum, lytic +/- sclerosis
Histo: sheets of small round cells
Ewing’s Sarcoma/PPNET
- 80% -> reciprocal rearrangement of t(11;22)(q24;q12) resulting in an EWSR1-FLI1 fusion protein
