Bone Pathology Flashcards
What is Osteoporosis
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
Embryonology of the parts of the bones
- 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
What is osteogenesis and ossification
- 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.
What are the Classifications of bones:
- Anatomical - long, flat
- Structural:
- Macroscopic - cortical/comapct and cancellous/spongy
- Hisitiological - lamellar and woven
Bone histology:
Decsribe Woven Bone
- Not an orderly paralll array
- Intersecting, crisscross and woven arrangement
- Iregular thick and thin bundles
- Seen in foetus
- Recapitulated in fracture healing
Describe the Parts of a long bone
- 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)
*
Where does provisional calcification start in the growth plate?
- 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
What are the ones labelled G,H,O,R
G = Growth zone
H= hypertorphic zone
0 = ossification zone
R= Remodelling zone
What are labelled
Osteoid and osteoclasts
What is the sequence of longitudinal growth in long bone
- By provisional calcification of cartilage - endochondral ossification:
- Proliferation - increase in number by mitoses/cell division
- Hypertrophy - increase in size
- Maturation
- Degeneration
- Calcification
Describe Diametric Growth in long bones
- Miantained by periphysis
- Ring of La Croix- Surroundig epiphysis
- Zone of Ranvier - surroundign metaphysis.
What factors affect bone growth?
- 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
Membranous ossification - Describe the main steps
- (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.
How do osteoclasts work with osteoblasts in th ebone remodelling cycle
- 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
Pleuripotent mesenchymal stem cells: What can they differentiate into?
What are the 3 aetiotypes of frctures
- 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.
What are thr 4 phases of fracture healing:
- Haematoma formationa nd fracture healing
- Organisation
- Provisional callus formaiton
- Defintiive callus and bony union
Cement lines in bone
The cement line, which is the interface between the ‘fibers’ (osteons) and extraosteonal bone matrix, may impart important mechanical properties to compact bone.
What are the 3 stages of fracture healing
- 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
What does this image show
Provisional fracture callus, note zonation.
Arche sof bone - periosteal reaction form inner cambium layer - benign
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.
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
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.
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.
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
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
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
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.
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-
Superimposed osteomalacia - what contributes to this
- Vitamin D deficienc and Ca malabsoprtion
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
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
Complications in osteoporosis
- Daily bisphosphonates -heartburn, dysphagia - weekly better
- Very rare- osteonecrosis of mandible
- IV- flu like symptoms - no long term side effects
Prognosis of osteopororsis
- Untreated - 50% chance fracture following intiiating event
- Treated - 40-70% reduction is spinal fracture nd 30-50% reduction in hip fracture
