Musculoskeletal Pathology - Osteoporosis Flashcards
(10 cards)
Define ‘osteoporosis’ and describe the classifications of osteoporosis based on severity.
Osteoporosis is a bone disease in which bone mineral density and bone mass decreases. This leads to a decrease in bone strength, that increases risk of fractures.
- Normal BMD
- Osteopenia
- Osteoporosis
- Severe osteoporosis
Describe the characteristics of osteoporotic bone (osseous tissue).
- weak compact bone
- thin and brittle spongey bone
Explain the process of bone remodelling.
Requires the co-ordination of 3 different bone cells:
- osteoclasts (bone resorbing), osteoblasts (bone forming), and osteocytes (detect load applied to bone).
Resting phase
- bone surface covered in a layer of bone cells called lining cells.
Resorption phase
- osteoclasts invade the bone surface
- they erode the bone (dissolve the bone minerals and matrix)
- resorption is complete when a small cavity has been made by the osteoclasts
Formation/repair phase
- osteoblasts arrive at the bone surface
- they deposit minerals and collagen to create new bone
- repair is complete when the cavity has been filled with bone
Explain the process of bone homeostasis.
Blood calcium too high
- thyroid gland detects increase in blood calcium
- thyroid gland releases calcitonin
- calcitonin stimulates osteoblasts to deposit calcium from blood, in bone
- blood calcium returns to normal
Blood calcium too low
- parathyroid gland detects decrease in blood calcium
- parathyroid gland releases parathyroid hormone
- PH stimulates osteoclasts to break down bone to release calcium
- blood calcium returns to normal
Describe the modifiable and non-modifiable risk factors for osteoporosis.
Non-modifiable risk factors:
- Age
- Gender (1 in 2 women, 1 in 5 men)
- Ethnicity
- Rheumatoid arthritis
Modifiable risk factors:
- sex hormones
- diet (low vit D and calcium)
- sedentary lifestyle
- smoking
- GI issues that affect the absorption of micronutrients
Who should be routinely screen for osteoporosis?
All women > 65 years
All men > 70 years
Women aged 50-64 who present risk factors
Anyone taking steroids or taking anti-oestrogen/testosterone treatment.
How is osteoporosis diagnosed?
DEXA scan - measures bone mineral density
T-score
- used in postmenopausal women and older men
- compares pt BMD to BMD of people who have osteoporosis
- used to determine if pt has osteoporosis and requires treatment
Z-score
- used in pre-menopausal women and younger people
- compares pt BMD to BMD of people at similar age with optimal BMD.
Describe the pathogenesis of osteoporosis.
Presence of risk factors = increased loss of bone.
increased loss of bone = poor bone quality and low BMD = skeletal fragility
Skeletal fragility alone = increased risk of fracture
Skeletal fragility + propensity to fall/taking part in activities that cause excessive loading on bones = increased risk of fracture
How can osteoporosis be prevented?
Increased Calcium and Vitamin D in the diet
- Calcium - 1200mg/day
- Vitamin D - goal level of 30-50ug
Calcium and Vitamin D are most effective when supplemented together as Vitamin D compliments the absorption/utilisation of Calcium.
Taking part in weight bearing exercise
- osteocytes detect load placed on bones
- osteoblasts deposit calcium to increase BMD and strength of bone
Stop smoking
Reduce/eliminate risk of falling
Hip protectors
- hip fractures are the most common osteoporotic fracture as huge load applied to a ball and socket joint (not as strong)
Explain the various treatment methods for osteoporosis, including how each prevents risk of fracture.
Biphosphates
- generally the 1st line of treatment
- prevent osteoclast attachment to the bone matrix
- prevents bone resorption
- reduce risk of fracture by 50%
Monoclonal antibodies
- alternative to biphosphates
- prevent the formation of active osteoclasts
- prevents bone resorption
HRT
- was once the preferred treatment for osteoporosis
- blocks cytokine signalling to the osteoclasts
Parathyroid hormone
- stimulates the process of bone remodelling = increased BMD.
