lecture 21 - osteoporosis Flashcards
what is osteoporosis?
a disease characterised by low bone structure mass and structural deterioration of bone tissue with a consequent increase in bone fragility and susceptibility to fracture.it is
Asymptomatic - often remains undiagnosed until a fragility fracture occurs
what can osteoporosis lead to ?
Osteoporotic fracture is a fragility fracture occurring as a consequence of osteoporosis. Characteristically, fractures occur in the wrist, spine, and hip, but they can also occur in the arm, pelvis, ribs, and other bones. it defined as a fracture following a fall from standing height or less, although vertebral fractures may occur spontaneously, or as a result of routine activities such as bending or lifting
what is the prevalence on osteoporosis in patients?
Women are at greater risk of osteoporosis due to the decrease in oestrogen production at the menopause, which accelerates bone loss.
The prevalence of osteoporosis increases markedly, from approximately 2% at 50 years of age to almost 50% at 80 years of age
In England and Wales, around 180,000 of the fractures presenting each year are the result of osteoporosis
More than one in three women and one in five men will sustain one or more osteoporotic fractures in their lifetime
White men and women are at increased risk of fragility fracture compared with other ethnic groups
what are causes of osteoporosis ?
The age when osteoporosis becomes apparent depends on:
1. Peak bone mass depends on:
* genetic factors
* levels of nutrition (particularly calcium and vitamin D)
* sex hormone levels (androgens and oestrogens)
* level of physical activity.
- Rate of bone loss, which depends on a number of factors including oestrogen deficiency in women and decreased testosterone in older men and hyperparathyroidism
what is the pathophysiology of osteoporosis ?
Osteoporosis is the end result of an imbalance in the normal process of bone remodelling by osteoclasts and osteoblasts
osteoclasts - cells that degrade bone to initiate normal bone remodelling and mediate bone loss in pathologic conditions by increasing their resorptive activity
osteoblasts - cells that form new bone. They also come from the bone marrow and produce new bone made of bone collagen and other protein. Then they control calcium and mineral deposition, which form the bone multicellular unit.
what happens during normal ageing ?
during normal ageing, bone breakdown by osteoclasts increases and it is not balanced by new bone formation by osteoblasts resulting in a combination of:
- reduced bone mineral density BMDI, which can be measured by dual energy X-ray absorptiometry (DXA) scanning.
- changes in bone composition, architecture, size and geometry
what is the composition of the bone ?
The adult human skeleton is composed of 80% cortical bone and 20% trabecular bone overall. Different bones and skeletal sites within bones have different ratios of cortical to trabecular bone. The vertebra is composed of cortical to trabecular bone in a ratio of 25:75. This ratio is 50:50 in the femoral head and 95:5 in the radial shaft
Cortical bone is dense and solid and surrounds the marrow space, whereas trabecular bone is composed of a honeycomb-like network of trabecular plates and rods interspersed in the bone marrow compartment.
what bones are affected in osteoporosis?
In individuals less than 65 years of age, the largest surface available for bone remodelling is the trabecular bone.
Within this population, trabecular bone – due to its lesser density when compared to cortical bone – provides only about 20% of the skeletal bone mass but responsible for most of the turnover
Bone loss in early osteoporosis is mainly a trabecular bone loss.
With increasing age, the cortical bone becomes more and more porous and, therefore the largest loss of absolute bone mass due to osteoporosis occurs in cortical bone
what are complications associated with osteoporosis ?
Osteoporotic fragility fractures may be asymptomatic: around 50–70% are clinically silent and do not come to clinical attention
Complications of osteoporosis are fragility fractures and their consequences are
hip fracture
- about 50% of people with an osteoporotic fragility fracture of the hip can no longer live independently .
- around 25% of the deaths following hip fractures are related to the fracture, and around 75% to comorbidities
and
Vertebral fracture
- can cause back pain and difficulties in bending, reaching, and other activities of daily living
- Around 30% of deaths following vertebral fractures are related (directly or indirectly) to the fracture, and around 70% to comorbidities
what are the risk factors for fractures?
The risk of getting an osteoporotic fracture depends on the person’s risk of falls, their bone strength (determined by bone mineral density [BMD]), and other risk factors.
Fracture risk increases progressively with decreasing BMD, but BMD is poorly sensitive at predicting fracture risk when used without considering other risk factors.
Factors that reduce BMD include:
- Endocrine disease including Diabetes mellitus, Hyperthyroidism, and hyperparathyroidism.
- Gastrointestinal conditions that cause malabsorption such as Crohn’s disease, Ulcerative colitis, Coeliac disease, and Pancreatitis - chronic.
- Chronic kidney or liver disease.
- Chronic obstructive pulmonary disease.
- Menopause.
- Immobility.
- Body mass index of less than 18.5 kg/m²
what are factors that reduce BMD and risk factors for falls?
Age - risk increases with age and is at least partly independent of BMD.
Oral corticosteroids (dependent on the dose and duration of treatment).
Smoking and smoking
Previous fragility fracture (risk increases with increasing number of fractures). Risk is highest for previous hip fractures and lowest for previous vertebral fractures.
Rheumatological conditions such as rheumatoid arthritis, and other inflammatory arthropathies.
Parental history of hip fracture.
Risk factors for falls include:
Impaired vision.
Neuromuscular weakness and incoordination.
Cognitive impairment.
what does a DEXA scan do?
Measures bone mineral density using central hip and/or spine DEXA scanning and is expressed in the number of standard deviations below peak bone mineral density.
T score- compares bone density to that of a 25 year old. The lower your score, the weaker your bones are:
T-score between -1.0 and -2.5 = low bone density, or osteopenia
T-score of -2.5 or lower = osteoporosis
Sometimes a Z score is used = compares bone density to a normal score for a person of same age and body size.
what are there investigations in testing for osteoporosis ?
Bloods:
FBC, ESR, TSH, U+E’s, bone and LFTs.
Other tests may be used to rule out cancer
what is the role of glucorticoids in osteoporosis?
Modify osteoblastic cell differentiation, number, and function.
Stimulate osteoclastogenesis
Inhibit bone formation - caused by a decrease in the number of osteoblasts
Decrease the function of the remaining osteoblasts directly and indirectly through the inhibition of insulin-like growth factor I expression.
The stimulation of bone resorption is likely responsible for the initial bone loss after glucocorticoid exposure. Eventually causing a decrease in bone remodeling and a continued increased risk of fractures
what is non pharmacological advice for patient with oesteoporosis?
- Diet.
1000 mg Calcium daily intake for postmenopausal women →24 % reduction in hip #
Avoid caffeinated products. Evidence inconclusive. - Regular exercise. Weight bearing exercise > 30 mins/day reduce# rate.
- Stop smoking. Pre-menopause leads to 25 % ↓# rate postmenopausal
- reduce alcohol consumption to recommended intake
