Bone Pathology Flashcards
1
Q
What is Osteoporosis
A
Osteoporosis is a health condition that weakens bones, making them fragile and more likely to break. It develops slowly over several years and is often only diagnosed when a fall or sudden impact causes a bone to break (fracture).
- DIminisehd bone mass
- Disruption of microarchitecture
- Loss of trabeculae
- diminished bone strength
- Increased suscpetibility to insufficiency fractures
2
Q
Embryonology of the parts of the bones
A
- Bone -develops from mesoderm (mesenchyme)
- Axial skeleton - from somites
- Appendicular skeleton from lateral mesoderm
- Cranial skeleton - directly from
- Mesenchyma - membranous bones
- Rest - throigj intermediate hyalien cartilage
3
Q
What is osteogenesis and ossification
A
- Osteogenesis = whole process of development of an bone from mesenchyme
- Ossification = selective process of hardenign or radiological/histiological evidence of bone formation from membrane or crtilage
- Membranous ossification, Endochondral ossification, Osteogensis imperfecta.
4
Q
What are the Classifications of bones:
A
- Anatomical - long, flat
- Structural:
- Macroscopic - cortical/comapct and cancellous/spongy
- Hisitiological - lamellar and woven
5
Q
Bone histology:
A
6
Q
A
7
Q
Decsribe Woven Bone
A
- Not an orderly paralll array
- Intersecting, crisscross and woven arrangement
- Iregular thick and thin bundles
- Seen in foetus
- Recapitulated in fracture healing
8
Q
Describe the Parts of a long bone
A
- Diaphysis - shaft (primary centre of ossification)
- Metaphysis - below the growht plate
- Epiphysis - upon/above the growht plate (secondary centre of ossification)
- Physis - growth (plate)
- Nutrient artery = through nutrient foramen - directed away from growing end- ‘to elbow i go, from the knee i flee- Milekrs position)
*
9
Q
Where does provisional calcification start in the growth plate?
A
- Upper and lower hypertrophic zone
- Provisional calcification starts in latter which is storngest layer of growth plate compared to upper hyp zone which is the weakest and usually involved in growth plate injuries
- Zone of endochondral ossification - intense calcification and in continuity with metaphysis 4
10
Q
What are the ones labelled G,H,O,R
A
G = Growth zone
H= hypertorphic zone
0 = ossification zone
R= Remodelling zone
11
Q
What are labelled
A
Osteoid and osteoclasts
12
Q
What is the sequence of longitudinal growth in long bone
A
- By provisional calcification of cartilage - endochondral ossification:
- Proliferation - increase in number by mitoses/cell division
- Hypertrophy - increase in size
- Maturation
- Degeneration
- Calcification
13
Q
Describe Diametric Growth in long bones
A
- Miantained by periphysis
- Ring of La Croix- Surroundig epiphysis
- Zone of Ranvier - surroundign metaphysis.
14
Q
What factors affect bone growth?
A
- Mechanical/Local - s-ace - epiphysiodesis and epiphyseal distarction
- Distractio osteosynthesis - Ilizarov
- Systemic- Endocrine, Paracrine, autocrine
- PTH-rP (parathyroid hormone related protein)
- Indian hedgehog Ihh proetin
15
Q
Membranous ossification - Describe the main steps
A
- (Omit cartilage step)
- Primtiive emsenchyme -> osteoprogenitor cells 0> osteoblasts
- Lay down specialised collageb - osteoid
- Calcify
- Intramembranous ossification is the direct deposition of bone on thin layers ofconnective tissue and is characteristic of the bones on the top of the skull.
16
Q
How do osteoclasts work with osteoblasts in th ebone remodelling cycle
A
- Osteoclasts - form cutting cone reusltign in resorption bays destroying bone
- Osteoblasts follow as closign cone laying new bone
- Junction visible as a purple blue cement line
- Constant renewal allows tensile strength to be retained
17
Q
Pleuripotent mesenchymal stem cells: What can they differentiate into?
A
18
Q
What are the 3 aetiotypes of frctures
A
- Traumatic fracture- healthy or brittle bone
- Stress/frsgility fracture - brittle bone wth low level or no trauma
- Pathological fracture - health bone invovled by neoplastic pahtolgoical process - msot commonly secondary metastasis to bone or primary bone tumour - benign or malignant.
19
Q
What are thr 4 phases of fracture healing:
A
- Haematoma formationa nd fracture healing
- Organisation
- Provisional callus formaiton
- Defintiive callus and bony union
20
Q
Cement lines in bone
A
The cement line, which is the interface between the ‘fibers’ (osteons) and extraosteonal bone matrix, may impart important mechanical properties to compact bone.
21
Q
What are the 3 stages of fracture healing
A
- Inflammation (to) - haematoma + traumatic inflammation
- Repair (Within 2 weeks) - fibrous bridging if unopposed -> surfaces soft/provisional calludosteoid -> hard/definitive callus/spongy bone by mineralisation
- Remodelling - woven -> lamellated bone continues long after clinical healing
22
Q
A
23
Q
What does this image show
A
Provisional fracture callus, note zonation.
24
Q
A
Arche sof bone - periosteal reaction form inner cambium layer - benign
25
Fractur ehealing - what type of bone changes are they?
Woven to lamellar bone (recapitulates otogeny ie, foetal boen growth)
CHodnrocytes/cartilage intemrediary involved only in displaced, unreduced fracture or where immobilisation is not fully ahcieved.
26
in fractures - what tp we have to exclude as DDx?
* Boen tumours. dx and D/D related ot anatomical site with respect to bone or speific bone and age (open or fused growth plate- skeletal maturity)
* Osteomyelitis 0 inflammation of bone - acute or chronic - acute emergency
* Nutritional deficiency disorders - Vit D def
* Epiphyseal injuries and disorders, avascular necrosis
* Non and malunion of fractures 0 neck of femur, scaphoid
* Skeletal homeostasis
27
Mechanism of osteoporisis
* Inadequate bone deposition (maintainence), if developmental - osteopenia
* And/or excessive bone resportion
* Relative oestrogen deficiency in pre menopause
* Absoloute oestrogen deficienct post- menopause
* Central role of oestrogen in skeletla homeostasis and bone mineral density.
28
Whata re the causes of osteoporosis
* Vats majority - idiopathic, age related
* Selected secondary causes 0 frequent, recent, current use of high dose long term systemic glucocorticoids
* Endocrine blockage therapy for breast and prostate cancers.
29
When to asses osteoporosis (NICE)
* WOmen \>65
* Men \>75
* M 50-74, and F 50-64
* History of falls
* Fragility fracture
* Very Low BMI
* FH of hip fracture
* High alcohol intake (\>14 weekly units)
* Long term high dose glucocorticoids
* SMoking
30
When do we assess the younger age group for osteoporosis
* \<50 steroid use, hisotry fragility fractures, premature meopause
* \<40 steroid use, multiple or major fragility fractures
* \>7.5mg glucocorticoids/day for ?3m
31
WHo is at risk of osteoporosis
* Geriatric age group -female dominence
* Female athletes with amenorrhoea
* immobialised patients
* Breast + prostate cance ron endocrine blockagde
* Rheumatoid arthritis ptient son long term steroids
* Malabsorptive group - coeliacs, IBD, gastric bypass
* Childhood cancer survivors
32
How to assess for osteoporosis
* FRAX/Q fracture risk algorithm without BMD (bone mineral density) using a DEXA scan- accuracy may be affected by previous vertebral or multiple fractures, high alcohol intake and glucocorticoids use
* If in the intervention threshold- DEXA (dual energy X ray absorptiometry)
* Lab investiagtions:
* FBS, serum calcium, phosphorus, magnesium, ALP, creatinine
* PTH, Vit D, TSH, testosterone
* Selected clinical scenarios -Myeloma screen, hypecortisolism, maalbsroption, 24hours urinary calcium for malabsroption or idiopathic hypercalciuria.
33
What is a DEXA score?
T scores- comparison of SD with young healthy cohort, 65 and M\>75
Z score- compare with age matched healthy cohorts- useful for younger age group-
34
Superimposed osteomalacia - what contributes to this
* Vitamin D deficienc and Ca malabsoprtion
35
How to prevent the risk of osteoorosis
* Weight + strength training, physiotherpy
* Smoking cessation and moderation in alcohol consumption
* Prevention of falls - referral to falls services
* Vit D: 800-1000IU/day with serumt arget value of ?30ng/ml calcium intake. 1000-1200mg - diet +/- supplement
36
Pharacotherapy in Osteoporosis
* Bisphosphontes -oral alendronate, risedronate iv - zolendronic acid, ibandronate
* Endocrine therapy - human recombinant parathyroid homrone (teriparatide) - amino terminal of human PTH that binds to PTH1 receptor and recruits osteoblasts
* Oestrogen replacement therpy
37
Complications in osteoporosis
* Daily bisphosphonates -heartburn, dysphagia - weekly better
* Very rare- osteonecrosis of mandible
* IV- flu like symptoms - no long term side effects
38
Prognosis of osteopororsis
* Untreated - 50% chance fracture following intiiating event
* Treated - 40-70% reduction is spinal fracture nd 30-50% reduction in hip fracture
