Osteoporosis 1+2 W4 Flashcards
(31 cards)
There are 2 main types of bone (and %)
Cortical bone
- 80%
- compact bone that forms the dense outer supporting structure
Trabecular bone
- 20%
- spongy bone that forms the inner supporting structure
- composed of a lattice or network of branching bone spicules or trabeculae and spaces filled with bone marrow
Bone undergoes…
Constantly undergoes renewal called remodelling where old bone is removed and replaced by new bone
Bone remodelling is a…
Complex interaction between:
- Bone resorbing cells called osteoclasts
- Bone forming cells called osteoblasts
Osteoblasts
▪ Fill in bony cavity with bone matrix
▪ Release cytokines to attract osteoclasts
Osteoclasts
Release proteases which:
▪ dissolve the bone mineral matrix and collagen
▪ clear damaged bone
▪ Release chemicals that attract osteoblasts
Control of Bone Remodelling is under control of
Systemic hormones
Activated vitamin D
Cytokines
External factors
Bone mass is determined by:
Peak bone mass that was attained at around age 30 years
Rate of bone loss that commences in 4th decade
Rate of bone loss is determined by
Genetic factors (approx 75%)
- More likely to have osteoporosis if strong family history
- Possible involvement of several genes investigated: (Vitamin D receptor gene, oestrogen receptor gene, Interleukin (IL)-6 gene)
Osteoporosis is
common
metabolic bone disease
reduction in bone mass per unit volume
Or
A systemic skeletal disease
low bone mass and deterioration of bone tissue with an increase in bone fragility and susceptibility to fracture
T-score
number of standard deviations by which the individual’s BMD (g/cm2) differs from the mean peak BMD for young adults of the same gender
Fracture risk
doubles for every standard deviation below the mean
Normal T-score value
Above -1
Osteopenia t-score value
Low bone mass
Between -1 and -2.5
Osteoporosis t-score value
-2.5 or less
Establish osteoporosis t-score value
-2.5t or less and fracture
How common is osteoporosis
Risk of suffering an osteoporotic fracture in people over 50 years is:
- One in two women
- One in five men
Detection of Osteoporosis
Xray is not capable of detecting bone loss until at least 30% of bone mass is lost
Not sufficiently reliable to diagnose or quantify osteopenia or osteoporosis
Dual Energy X-ray Absorptiometry (DEXA) scan is used
Enables accurate and reproducible measurement of BMD
Primary osteoporosis
Most common form
Diagnosed when the patient has no other disorders known to cause osteoporosis present
Secondary Osteoporosis
Osteoporosis related to Another medical condition:
- IBD
- Cushing’s syndrome, hyperthyroidism
Corticosteroids and osteoporosis (why)
Most common cause of secondary osteoporosis accounting for up to
Steroids:
- Decrease osteoblast activity and active life span
- Decrease calcium absorption from the intestine
- increase renal calcium loss
- Suppress sex hormone production
Fragility fracture
Fracture that occurs as a result of mechanical forces that would not ordinarily cause fracture
- a fall from a standing height or less
Symptoms of fractures from osteoporosis
gradually cause the spine to collapse resulting in height loss, pain and a deformed back
Forward curvature = kyphosis
Most common fracture and least common ones
Most commonly:
- Vertebra
- wrist
- Neck of femur
Less commonly:
- Pelvis
- Distal femur
- Ribs
Prognosis of fractures
- 50% of people with hip fracture lose ability to live independently
- Excess mortality after hip fracture = 20%
- Risk of further fractures
