Bone & Osteoporosis Flashcards
1
Q
What is osteogenesis?
A
Whole process of development of any bone from mesenchyme
2
Q
What is ossification?
A
Selective process of hardening or radiological/histological evidence of bone formation from membrane or cartilage
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
4
Q
Label the diagram
(ADD PIC)
A
5
Q
What is the outermost limit of osteons?
A
Cement lines
6
Q
What is inbetween osteons?
A
Interstitial lamellae
7
Q
Label the diagram
(ADD)
A
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
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
10
Q
Label the diagram
(ADD)
A
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
12
Q
Label the diagram
(ADD)
A
13
Q
Label the diagram
(ADD)
A
14
Q
Label the diagram
(ADD)
A
G= Growth zone H= Hypertrophic zone O= Ossification zone R= Remodelling zone
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
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
- Haematoma formation and fracture healing
- Organisation (hardening of the haematoma)
- Provisional callus formation
- Definitive callus and bony union
25
What are the stages of fracture healing?
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
What is osteoporosis?
* Diminished bone mass
* Disruption of microarchitecture
* Loss of trabeculae
* Diminished bone strength
* Increased susceptibility to insufficiency fractures
27
What is the mechanism behind osteoporosis?
* 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
What are the causes of osteoporosis?
* 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
Risk factors of osteoporosis? & at risk population?
* 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
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)
31
**When to assess in younger age group?**
* \<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
Explain DEXA scores
* 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
What lab investigations would you do for osteoporosis?
* 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
What is superimposed osteomalacia?
* Vit D deficiency
* Ca malabsorption
35
What lifestyle modification and nutrition (prevention) for osteomalacia?
* 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
Pharmacotherapy for osteomalacia
* 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
Complications of osteomalacia
* Daily bisphosphonates- heartburn, dysphagia- weekly better
* Very rare- osteonecrosis of mandible
* IV- flu like symptoms- no long-term side effects
38
Prognosis of osteomalacia
* Untreated- 50% chance of fracture following initiating event
* Treated- 40-70% reduction is spinal fracture and 30-50% reduction in hip fracture
