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Unit 17 Week 4 > Bone & Osteoporosis > Flashcards

Bone & Osteoporosis Flashcards

1
Q

What is osteogenesis?

A

Whole process of development of any bone from mesenchyme

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2
Q

What is ossification?

A

Selective process of hardening or radiological/histological evidence of bone formation from membrane or cartilage

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3
Q

Types of classifying bone

A
  • 2 modes of classification- anatomical and structural
    • Anatomical- Long, flat
    • Structural- further- macro and microscopic/histological
  • Macroscopic- cortical/compact and cancellous/spongy
  • Histological- lamellar and woven
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4
Q

Label the diagram

(ADD PIC)

A
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5
Q

What is the outermost limit of osteons?

A

Cement lines

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6
Q

What is inbetween osteons?

A

Interstitial lamellae

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7
Q

Label the diagram

(ADD)

A
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8
Q

What is woven bone?

A
  • Not an orderly parallel array
  • Intersecting, crisscross and woven arrangement
  • Irregular thick and thin bundles
  • Seen in foetus
  • Recapitulated in fracture healing
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9
Q

Explain the parts of long bone

A
  • Diaphysis- shaft (primary centre of ossification)
  • Metaphysis- below the growth plate
  • Epiphysis- upon/above the growth plate (secondary centre of ossification)
  • Physis= growth (plate)
  • Nutrient artery- through nutrient foramen- directed away from the growing end- TO THE ELBOW I GO, FROM THE KNEE I FLEE- MILKER’S POSITION
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10
Q

Label the diagram

(ADD)

A
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11
Q

Explain microanatomy of growth plates

A
  • Upper and lower hypertrophic zone
  • Provisional calcification starts in the latter which is the strongest layer of the growth plate compared to the upper hyp zone which is the weakest and usually involved
  • in growth plate injuries
  • Zone of enchondral ossification- intense calcification and in continuity with metaphysis
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12
Q

Label the diagram

(ADD)

A
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13
Q

Label the diagram

(ADD)

A
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14
Q

Label the diagram

(ADD)

A

G= Growth zone H= Hypertrophic zone O= Ossification zone R= Remodelling zone

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15
Q

What happens in longitudinal growth in long bone

A
  • By provisional calcification of cartilage- en(do)chondral ossification-
  • Proliferation (increase in number by mitoses/cell division)
  • Hypertrophy- increase in size
  • Maturation
  • Degeneration
  • Calcification
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16
Q

Explain diametric growth in long bones

A
  • Maintained by periphysis
  • Ring of La Croix- surrounding epiphysis
  • Zone of Ranvier- surrounding metaphysis
17
Q

Factors in bone growth

A
  • Mechanical/Local- space- epiphysiodesis and epiphyseal distraction
  • (Distraction osteosynthesis- Ilizarov)
  • Systemic- Endocrine, Paracrine and Autocrine features
  • PTH-rP (parathyroid hormone related protein)
  • Indian hedgehog Ihh proetin
18
Q

Explain exocrine, endocrine, paracrine and autocrine

A

Exocrine - Exocrine glands secrete enzymes, ions, water, mucins and other substances into the digestive tract (into a duct)

Endocrine - hormones into blood stream (systemic)

Paracrine - a type of cellular communication in which a cell produces a signal to induce changes in nearby cells

Autocrine - a type of cell signaling wherein a cell signal released from the cell binds to the same cell

19
Q

What is membranous ossification?

A
  • Omit the cartilage step
  • Primitive mesenchyme → Osteoprogenitor cells → Osteoblasts
  • Lay down specialized collagen- osteoid
  • Calcify
20
Q

Explain the bone remodelling cycle

A
  • Osteoclasts form a cutting cone resulting in resorption bays destroying bone
  • Osteoblasts follow as closing cone laying new bone
  • Junction visible as a purple blue cement line
  • Constant renewal allows tensile strength to be retained
21
Q

Explain the process of growth

A

NOT proteoblast is Pro-osteoblast

Alkaline phosphatase NOT alkaline phosphate

22
Q

Label the diagram

(ADD)

A
23
Q

What are aetiotypes of fracture

A
  • Traumatic fracture- healthy or brittle bone
  • Stress/fragility fracture- brittle bone with low level or no trauma
  • Pathological fracture- healthy bone involved by a neoplastic pathological process- most commonly secondary metastasis to bone or primary bone tumour- benign or malignant
24
Q

What are the phases of fracture healing?

A
  1. Haematoma formation and fracture healing
  2. Organisation (hardening of the haematoma)
  3. Provisional callus formation
  4. Definitive callus and bony union
25
Q

What are the stages of fracture healing?

A
  1. Inflammation (t0)- Haematoma and traumatic inflammation
  2. Repair (within 2 weeks)- Fibrous bridging of unopposed surfaces soft/provisional callus/osteoid → hard/definitive callus/spongy bone by mineralization
  3. Remodelling- woven → lamellar bone continues long after clinical healing
26
Q

What is osteoporosis?

A
  • Diminished bone mass
  • Disruption of microarchitecture
  • Loss of trabeculae
  • Diminished bone strength
  • Increased susceptibility to insufficiency fractures
27
Q

What is the mechanism behind osteoporosis?

A
  • Inadequate bone deposition (maintenance), if developmental- osteopenia
  • And/or excessive bone resorption
  • Relative oestrogen deficiency in pre menopause
  • Absolute oestrogen deficiency post-menopause
  • Central role of oestrogen in skeletal homeostasis and bone mineral density
28
Q

What are the causes of osteoporosis?

A
  • Vast majority- idiopathic, age related
  • Selected secondary causes- Frequent, recent, current use of high dose long term systemic glucocorticoids
  • Endocrine blockade therapy for breast and prostate cancers
29
Q

Risk factors of osteoporosis? & at risk population?

A
  • Women > 65
  • Men > 75
  • M 50-74 and F 50-64-
  • History of falls
  • Fragility fracture
  • Very low BMI
  • Family history of hip fracture
  • High alcohol intake ( > 14 weekly units)
  • Long term high dose glucocorticoids
  • Smoking

AT RISK POPULATION

  • Geriatric age group- female dominance
  • Female athletes with amenorrhoea
  • Immobilised patients
  • Breast and prostate cancer on endocrine blockade
  • Rheumatoid arthritis patients on long term steroids
  • Malabsorptive group- coeliac disease, IBD, gastric bypass
  • Childhood cancer survivors
30
Q

How to assess for osteoporosis?

A
  • 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)
31
Q

When to assess in younger age group?

A
  • <50- Steroid use, history of fragility fractures, premature menopause
  • < 40- Steroid use, multiple or major fragility fractures
  • >7.5 mg glucocorticoids/day for > 3 months
32
Q

Explain DEXA scores

A
  • 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-
33
Q

What lab investigations would you do for osteoporosis?

A
  • FBC, serum calcium, phosphorous, magnesium, ALP, creatinine
  • PTH, Vit D, TSH, testosterone
  • Selected clinical scenarios- Myeloma screen, hypercortisolism, malabsorption, 24 hours urinary calcium for malabsorption or idiopathic hypercalciuria,
34
Q

What is superimposed osteomalacia?

A
  • Vit D deficiency
  • Ca malabsorption
35
Q

What lifestyle modification and nutrition (prevention) for osteomalacia?

A
  • Weight and strength training, physiotherapy
  • Smoking cessation and moderation in alcohol consumption
  • Prevention of falls- referral to falls services
  • Vit D- 800-1000IU/day with serum target value of > 30ng/ml Calcium intake- 1000-1200mg – diet +/- supplement
36
Q

Pharmacotherapy for osteomalacia

A
  • Bisphosphonates- oral alendronate, risedronate iv – zolendronic acid, ibandronate
  • Endocrine therapy- Human recombinant parathyroid hormone (teriparatide)- amino terminal of human PTH that binds to PTH 1 receptor and recruits osteoblasts
  • Oestrogen replacement therapy
37
Q

Complications of osteomalacia

A
  • Daily bisphosphonates- heartburn, dysphagia- weekly better
  • Very rare- osteonecrosis of mandible
  • IV- flu like symptoms- no long-term side effects
38
Q

Prognosis of osteomalacia

A
  • Untreated- 50% chance of fracture following initiating event
  • Treated- 40-70% reduction is spinal fracture and 30-50% reduction in hip fracture

Unit 17 Week 4 (2 decks)

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