Osteoperosis Flashcards
What are osteoprogenitor cells?
Stem cell population, gives rise to osteoblasts.
What are osteoblasts?
Responsible for bone formation, cover the surface of bone.
What are osteocytes?
Mature bone cells - embedded in lacunae, relatively inactive. Maintain bone matrix through cell-to-cell communication and influence bone remodelling. Mechanosensing
What are osteoclasts?
Multinucleated, derived from haematopoietic cells. In response to mechanical stresses and physiological demands they resorb bone matrix by demineralization.
How many people does osteoporosis affect?
- 1in3women
* 1in12men
What does osteoporosis do to bone structure?
Decreased size of osteons Thinning of trabeculae
Enlargement of Haversian and marrow spaces
What are the two classifications of osteoporosis?
Type 1 - Post menopausal
Type 2 - Age related in those over 75 years
Discuss Type 1 osteoporosis
- Affects mainly cancellous bone
- Vertebral and distal radius fracture is common
- Related to loss of oestrogen
- F:M = 6:1
Discuss Type 2 osteoporosis
- Affects cancellous and cortical bone
- is related to poor calcium absorption
- Hip and pelvic fractures common
- F:M=2:1
What is disuse osteoporosis?
Conditions resulting in prolonged immobilisation, typically in neurological or muscle disease
Also astronauts
What are the clinical consequences of osteoporosis?
Increase in bone fragility Susceptibility to fracture:
micro- or fragility fracture
Fragility fracture
– “Low energy” trauma
– Mechanical forces that would not ordinarily cause fracture – WHO: ≈ “fall from a standing height or less”
Discuss the consequences of hip fractures
- Fatal in 20-30% of cases
- Only 30% fully recover
- Permanently disables 50%
Where are the common sites of osteoporotic fractures
Proximal humerus, distal radius, spine, femoral neck, vertebral body
What can you use to assess patient risk for osteoporosis?
FRAX - the who fracture risk assessment tool
What are the risk factors for osteoporosis?
Genetic/biological sex Lifestyle/nutritional
Medical conditions Medications
Previous fragility fracture
Discuss race and ethnicity in osteoporosis
– Prevalence ~50% lower in black Americans than white
– Rates of fragility fractures in the UK 4.7x greater in
white compared to black women
– In US, black women less likely to receive treatment or be screened, plus associated with worse outcomes following fracture
– Latin Americans at highest risk of fractures in US, and less likely to take preventative steps
– Chinese women have lower BMD, but lower rates of hip and spine fractures
Discuss trans patients and osteoporosis
– Adherence to gender-affirming hormone replacement therapy (GAHT) may protect BMD of both trans women and trans men
– Trans women tend to have lower BMD prior to initiation of GAHT
– Sparse data on impact of GAHT on fracture risk in both trans women and men
– Currently unclear what impact puberty blockers have on bone mass and fracture risk
What lifestyle/nutritional factors may impact osteoporosis?
Smoking
Excess alcohol
Sedentary
Prolonged immobilisation
What medical conditions may impact osteoporosis?
A ton really
Anorexia nervosa Rheumatoid arthritis Early menopause <45 years of age Primary hypogonadism Secondary amenorrhoea for more than 1 year Hyperthyroidism Primary hyperparathyroidism Multiple myeloma Transplantation Chronic renal, pulmonary or gastrointestinal disease Cushing’s disease/syndrome
What drugs may impact osteoporosis?
Chronic corticosteroid therapy (can increase risk of fracture by 2-3x)
Excessive thyroid therapy
Gonadotrophin releasing hormone agonist or antagonist Anticoagulants
Anticonvulsants
Chemotherapy
Is the risk of another fracture after a previous fragility fracture greater than that of the initial fracture?
Ye
A previous wrist fracture:
Doubles the risk of a future hip fracture Triples the risk of future vertebral fracture
What investigations should one complete for suspected osteoporosis?
Blood tests, FBC, serum biochemistry, bone profile
Thyroid function tests
Testosterone and gonadotrophin levels in men
X-ray of lumbar and thoracic spine
• >30 % of bone loss required to be visible
Bone mineral density measurement
What is a DEXA?
Dual-energy x-ray absorptiometry scan
Low-dose x-rays with two distinct energy peaks (one absorbed by soft tissue and the other by bone)
How do you calculate a patients bone mineral density (BMD) form a DEXA?
Low-dose x-rays with two distinct energy peaks (one absorbed by soft tissue and the other by bone)
Subtracting one from the other gives a patient’s bone mineral density (BMD)
Discuss DEXA scores
T score
Comparison with a young adult of the same sex with peak bone mass:
T-Score : Classification
> -1 : Normal
-1 to -2.5 : Osteopenia (bone thinning)
< -2.5 : Osteoporosis
Z score
Comparison of the patient’s BMD with data from same age/sex/size.
Discuss treatment of osteoporosis
Bisphosphonates
• e.g. alendronate, risedronate
• disrupt the activity of osteoclasts
• potential side effects – oesophagitis, mandibular necrosis
Anabolic agents
• e.g. intermittent PTH, strontium ranelate
Ca++ supplements
Hormone replacement therapy
• carries an increased risk of breast cancer
Increase exercise
