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Physio in the Ageing > Osteoporosis > Flashcards

Osteoporosis Flashcards

1
Q

What are the 7 important functions of bones?

A
  • Support
  • Protection
  • Movement
  • Mineral and growth factor storage
  • Blood cell formation
  • Triglyceride (fat) storage
  • Hormone production
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2
Q

What are the 2 layers of bone?

A
  • Cortical/compact bone on the outside

- Spongy/cancellous bone in the middle with trabeculae

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3
Q

What are the basic cell types that form different types of bone tissue?

A
  • Osteogenic stem cells: progenitor cells,
    differentiate into osteoblasts
  • Osteoblasts: secrete osteoid
  • Osteocytes: (imbedded osteoblasts) sense stress and strain, communicate with osteoblasts & clasts
  • Bone lining cells: periosteal and endosteal cells, maintain matrix
  • Osteoclasts: resorb bone
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4
Q

What are the organic components of bone?

A
  • Cells & osteoid

- Sacrificial bonds in/between collagen molecules (provide resilience)

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5
Q

What is the osteoid made up of?

A
  • Ground substance (proteoglycans & glycoproteins)
  • Collagen fibres
  • Provides tensile strength & flexibility (1/3 of matrix)
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6
Q

How do sacrificial bonds provide resilience?

A
  • Stretch & break easily on impact to dissipate energy and prevent fracture
  • If no addition trauma, bonds re-form
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7
Q

What are the inorganic components of bone?

A

Hydroxyapatities

  • Mineral salts
  • 65% bone mass
  • Mainly of tiny calcium phosphate crystals in/around collagen fibres
  • Responsible for hardness & resistance to compression
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8
Q

What hormones regulate bone growth?

A
  • Growth hormone: Stimulating epiphyseal plate activity
  • Thyroid hormone: Modulates activity of growth hormone, ensures proper proportions
  • Testosterone & estrogens: Promote adolescent growth spurts, end growth by inducing epiphyseal plate closure
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9
Q

How is bone homeostasis maintained?

A
  • Recycle 5-7% bone mass each week
  • Older bone becomes more brittle (calcium salts crystallise)
  • Bone modelling & repair
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10
Q

What does bone remodelling involve?

A
  • Bone deposit & bone resorption
  • Occurs at surfaces of periosteum & endosteum
  • Remodelling units: Adjacent osteoblasts & clasts
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11
Q

What does bone resorption involve?

A

Osteoclasts

  • Secret lysosomal enzymes that digest matrix & protons
  • Acitdity converts calcium salts to soluble forms
  • Phagocytize demineralized matrix & dead osteocytes
  • Transcytosis allow release into interstitial fluid and then into blood
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12
Q

What happens to osteoclasts once resorption is complete?

A

Undergo apoptosis

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13
Q

What proteins are involved with osteoclast activation?

A

PTH & T cell-secreted proteins

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14
Q

What are the functions of calcium?

A
  • Nerve impulse transmission
  • Muscle contraction
  • Blood coagulation
  • Secretion by glands and nerve cells
  • Cell division
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15
Q

How is calcium stored?

A
  • 1200-1400g, 99% stored as bone minerals
  • Amount in blood tightly regulated
  • Intestinal absorption requires Vitamin D metabolites
  • Dietary intake required
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16
Q

What hormones control blood calcium levels?

A
  • Parathyroid hormone (PTH): Removes calcium from bone regardless of bone integrity
  • Calcitonin: In high doses lowers blood calcium levels temporarily
17
Q

What is involved in the negative feedback mechanism when blood calcium decreases?

A
  • PTH secreted by PTH glands
  • Stimulates clasts, inhibits blasts
  • Blood calcium increases
  • Calcitonin secreted by T gland
  • Stimulates blasts, inhibits clasts
  • Blood calcium decreases
18
Q

What is osteoporosis?

A
  • Reduction of bone mineral density
  • Increase in fracture risk due to bone loss
  • Loss of microarchitecture of bone
19
Q

What bone density levels indicate osteopenia & osteoporosis?

A
  • Normal: BMD 0-1 SD below young healthy adult mean
  • Osteopaenia: < 1-2.5 SD below young adult mean
  • Osteoporosis: < 2.5 SD below young adult mean
  • Measured by T score
20
Q

What does loss of microarchitecture of bone include?

A
  • Total bone mass,
  • Trabecular volume
  • Trabecular connectivity/separation
  • Trabecular plate thickness & number
21
Q

What are the primary risk factors for osteoporosis?

A
  • Postmenopausal women: 30% 60-70yrs, 70% by 80yrs
  • Men when older
  • Decreased sex hormone production
22
Q

What are the secondary risk factors for osteoporosis?

A
  • Petite body form
  • Insufficient exercise to stress bones
  • Diet poor in calcium and protein
  • Low Vit D/C
  • Smoking
  • Hormone-related conditions: Hyperthyroidism, low thyroid-stimulating hormone
  • Diabetes mellitus
  • Immobility
  • Males with prostate cancer taking androgen-
    suppressing drugs
  • Genetics
  • Other pathologies
23
Q

What pathologies can be risk factors for osteoporosis?

A
  • Rheumatoid arthritis,
  • Coeliac disease and
  • Chronic lung diseases
  • Chronic renal failure
  • Chronic liver failure
  • *Most involve being on corticosteroid medication (increases loss of bone)
24
Q

How is osteoporosis diagnosed?

A
  • DXA or bone densitometry: Detects bone loss before fracture
  • Previously based on XR, but unable to detect until >30% lost
  • Calcanea US (very inaccurate)
25
Q

What are the sites of BMD measurement?

A
  • Femoral neck (best site for predicting hip fractures)
  • Vertebra (best site for predicting spinal fractures)
  • Radius
26
Q

How does risk increase once a person with osteoporosis has a fracture?

A
  • Women with # spine >4x more likely to have another fracture within a year
  • > 2 osteoporotic fractures = 9x more likely to have another fracture
  • > 3 osteoporotic fractures = 11x more likely to have another fracture
27
Q

How can fractures affect mortality & QOL?

A
  • Osteoporotic hip fractures often result in THR
  • 20-25% will be permanently disabled
  • 50% never regain former independence,
    and will require long-term nursing care
  • 1 in 3 return to activity and independence
  • 12-15% mortality within 6 months
  • 25% mortality at 12 months
28
Q

What are the traditional treatments for osteoporosis?

A
  • Calcium
  • Vitamin D supplements
  • Weight-bearing exercise
  • Hormone replacement therapy
29
Q

What is the function of hormone replacement therapy?

A
  • Slows bone loss but does not reverse it
  • Controversial due to increased risk of heart attack, stroke, and breast cancer
  • Some take estrogenic compounds in soy as substitute
30
Q

What drugs are used for osteoporosis?

A
  • Bisphosphonates: Decrease # risk by 50% (Decrease clast activity/number)
  • Selective estrogen receptor modulators:
    Mimic estrogen without targeting breast & uterus
  • PTH
  • Denosumab: Inhibits clasts, injections every 6 months
31
Q

How can osteoporosis be prevented?

A
  • Maximise peak bone mass (nutrition, milk, limit alcohol, exercise no smoking)
  • Limit gradient of decline
  • Prevent falls & fractures
32
Q

What are the functions of vitamin D?

A
  • Regulation of plasma calcium and bone
    mineralisation
  • Maintains function of NMJs
  • Effects on other systems (immune, oncogenesis)
33
Q

What are the consequences of vitamin D deficiency?

A
  • Increased risk of fracture
  • Independent risk factor for falls in residential facilities
  • More common with increasing age, esp. when limited sun exposure
34
Q

What are the main sources of vitamin D?

A
  • Sunlight acting on the skin

- Also found in some foods (fatty fish, eggs, some low-fat milk)

35
Q

How much sun do you need each day in ACT/NSW?

A
  • June-July: 2-3 hours per week

- Summer: Few minutes on most days

36
Q

What is Wolff’s law for exercise?

A

Bone strength increases and decreases as the functional forces on the bone increase and decrease

37
Q

What exercise is recommended to prevent osteoporosis?

A
  • Weight bearing exercise reduces bone loss,
    maintains muscle strength & proprioception.
  • Walking with stairs, jogging, weights
  • Consider falls, balance, power
38
Q

What are the general principles of exercise for osteoporosis?

A
  • Long-term (forever)
  • Ongoing but changing
  • Site specific
  • Produce tension or force (include partial & NWB)
  • Progressive overload
  • Reversibility
  • Initial values (lower start = more change)
  • Diminished returns
  • Intermittent & dynamic
  • High magnitude, high strain rate
  • Low reps
39
Q

What are examples of weight bearing aerobic exercise?

A
  • Brisk walking, stair climbing (not leisurely walking)
  • Graded exercise
  • Avoid flexion, twisting & asymmetrical loading

Physio in the Ageing (10 decks)

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