Osteoporosis Flashcards
What are the age ranges for bone gain, bone mass stable, and bone loss respectively ?
BONE GAIN: Age 0-25 (Resorption < Formation)
BONE MASS STABLE: Age 25-35 (Resorption = Formation)
BONE LOSS: Age >35 (Resorption > Formation)
What is the proportion of males, and females affected by osteoporosis respectively ?
- 1 in 3 women
* 1 in 12 men
Histologically, what are the features of osteoporosis ?
- Decreased size of osteons
- Thinning of trabeculae
- Enlargement of Haversian and marrow spaces
Define a fragility fracture.
Fragility fracture: any fall from a standing height or less (due to low energy trauma), that results in a fracture (would not occur in someone with normal bone structure)
How are cortical and trabecular bones affected differently by osteoporosis ? Why ?
“Trabecular bone is more vulnerable because it has a higher turnover rate”
What are some risk factors for osteoporosis ? Divide them into modifiable and non-modifiable.
NON-MODIFIABLE: Age Genetic (family history) Biological sex (females more affected) Race Previous fragility fracture (once you've had a fragility fracture, huge increase in risk of getting a new one)
MODIFIABLE: Life style/nutritional (inactivity, vitamin D deficiency, low Calcium, alcohol, smoking, low BMI) Medical conditions (oestrogen deficiency)
Drugs (e.g. Long term steroid therapy) could be classified as both
Explain why age is a risk factor for osteoporosis.
Because over time, osteoblast activity decreases (so less bone deposition)
Explain why genetic/biological sex affects risk of osteoporosis.
Hormonal differences between males and females drives this.
In menopause, this difference is enhanced since changes in hormonal regulation (decreased oestrogen) causes increase in osteoclast activity so rate of absorption far outweighs rate of deposition (resulting in quick bone loss)
Around what age does peak bone mass occur ?
25
What are some lifestyle and nutritional factors which may increase likelihood of osteoporosis ?
Smoking
Excess alcohol
Sedentary lifestyle
Prolonged immobilisation (disuse osteoporosis)
What are some medical conditions which lead to osteoporosis ?
Anorexia nervosa Rheumatoid arthritis Early Menopause (before 45) Primary hypogonadism Hyperthyroidism Chronic renal, pulmonary or gastrointestinal disease
In general, why are some drugs a risk factor for osteoporosis ?
What are some drugs which may increase risk of osteoporosis ?
Because they interfere with hormonal regulation.
- Chronic corticosteroid therapy (can increase risk of
fragility fracture by 2-3x) - Excessive thyroid therapy
- Gonadotrophin releasing hormone agonist or antagonist - Anticoagulants (likely due to effects of vitamin K)
- Anticonvulsants
- Chemotherapy
What is the most common initial fragility fracture ?
Wrist fracture
What is the effect of a wrist fracture on the risk of future hip fracture and future vertebral fracture ?
Doubles the risk of a future hip fracture
Triples the risk of future vertebral fracture
Distinguish between the main types of osteoporosis.
Type 1 - Post menopausal (Loss of hormonal regulation and control)
• Affects mainly cancellous bone
• Vertebral and distal radius fracture is common
• Related to loss of oestrogen (leading to increased osteoclast uptake/activity)
• F:M = 6:1
Type 2 - Age related in those over 75 years
• Affects cancellous and cortical bone
• is related to poor calcium absorption (and loss of osteoblasts)
• Hip and pelvic fractures common
• F:M=2:1
Disuse Osteoporosis
• Due to conditions resulting in prolonged immobilisation,
typically in neurological or muscle disease
What is the main clinical consequence of osteoporosis ?
Increase in bone fragility, leading to increased susceptibility to fracture (micro- or fragility fracture).
Since we get microfractures on a daily basis, why is it that it’s a problem in osteoporosis ?
Because in youth, quite good at fixing microfractures but later in life, not as good at fixing them
What are the most common sites for osteoporotic fractures ?
Proximal humerus Distal radius Spine Femoral neck Vertebral body
What is the risk of the following fragility fractures after age 50:
1) All fractures in females
2) Hip fractures in males
3) Hip fractures in females
1) All fractures in females: 40%
2) Hip fractures in males: 6%
3) Hip fractures in females: 18%
Distinguish the risk of fragility fractures between males and females over time.
Females always have a higher risk of fragility fracture, but this difference with males increases further with age.
How many people in the UK are affected by osteoporosis ?
3 million
What are most of the osteoporosis-related costs to the NHS related to ?
Most costs relate to hip fracture care
What is the fatality rate of hip fractures ?
What is the full recovery rate of hip fractures ?
What is the permanently disabled rate of hip fractures ?
Fatality: 20-30%
Full recovery: 30%
Permanently disabled: 50%
What are the possible investigations for osteoporosis ?
1) Blood tests, FBC, serum biochemistry, bone
profile
2) Thyroid function tests
Testosterone and gonadotrophin levels in men
3) X-ray of lumbar and thoracic spine
• >30 % of bone loss required to be visible
4) Bone mineral density measurement
How is bone mineral density measured ?
Using Dual energy x-ray absorptiometry scan (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)
Identify the main DEXA scores and what the mean.
T SCORE (used more than Z score):
Comparison with a young adult of the same sex with
peak bone mass. (How many standard deviations away from normal value)
Z SCORE:
Comparison of the patient’s BMD with data from same
age/sex/size.
What is a normal and what are abnormal T scores ?
> -1 Normal
-1 to -2.5 Osteopenia (bone thinning)
< -2.5 Osteoporosis
What are treatment options for osteoporosis ? Explain how each option helps, and identify possible side effects.
BIPHOSPHONATES (e.g. alendronate, risedronate)
• disrupt the activity of osteoclasts
• potential side effects – oesophagitis, mandibular necrosis
ANABOLIC AGENTS (e.g. intermittent PTH, strontium ranelate) • Stimulate osteoblast activity (increase bone density)
CALCIUM SUPPLEMENTS
HORMONE REPLACEMENT THERAPY
• Side effect: Increased risk of breast cancer
INCREASED EXERCICE
• Increase bone density
How are biphosphonates administered ? How do they function ? What is the frequency of administration ?
Orally or intraveneously
Bind strongly to bone (due to high Calcium affinity) and disrupt osteoclasts
Some given once a year, others given orally once a day
What is the main problem with the mechanism of action of biphosphonates ?
Halts bone loss, just stop the decline
Do not restore normal balance of turnover of bone
Do not correct microfractures accumulated
Do no help improve quality of bone long term
What is main problem in giving Calcium supplements for osteoporosis, especially in age-related osteoporosis ?
In age related osteoporosis, calcium absorption is reduced so may not help
