Disorders of bone health including osteoporosis Flashcards
What is osteoporosis?
Progressive skeletal disease characterised by low bone mass and microarchitectual deterioration of bone structure
Which sex gets osteoporosis more commonly?
Women
How does osteoporosis present?
Asymptomatic until fractures
Over which age is osteoporosis frequent?
50
What are the common osteoporotic fracture sites?
Neck of femur
Vertebral body
Distal radius
Humeral neck
What is the domino effect in relation to osteoporosis?
An increasing number of vertebral fractures due to osteoporosis causing progressive curvature of the spine
Where does bone remodelling occur?
Bone remodelling units
Describe bone remodelling
Osteoclasts begin to reabsorb bone at specific sites >
Osteoclasts replaced by osteoblasts which lay down osteoid >
Osteoid undergoes mineralisation to bone >
Resorptive cavity completely filled with new bone
How is bone remodelling altered in osteoporosis?
Reabsorption of bone occurs more than formation
How is osteoporotic bone architecture different from normal bone?
Large spaces and breaks
Weakened
Which factors are important in bone density?
Body weight Genetics Sex hormones Diet Exercise
Which factors contribute to bone density loss?
Lowered sex hormones (menopause) Low body weight Poor genetics Calcium deficient diet Immobility Disease affecting bones Drugs (e.g steroids)
How does bone density change with age?
Bone density increases until around 30
After 40 it begins to decline slowly
During and after menopause bone density loss is rapid and oestrogen deficiency can further perpetuate this
What are the non-modifiable risk factors for fragility fractures?
Age Gender Ethnicity Previous fracture Family history Early menopause (
What are the modifiable risk factors for fragility fractures?
Bone mineral density Alcohol Low weight Inactivity Diet Smoking Pharmacological (steroids)
Which diseases increase the risk factor for an osteoporotic fragility fracture?
Rheumatoid arthritis Hyperthyroidism Chronic liver disease Hypogonadism Diabetes Dementia
Who should be risk assessed?
Patients over 50 with risk factors
Patients under 50 with serious risk factors (steroids, early menopause)
Who should be referred for a dexa bone scan?
High risk patients
How is bone mineral density measured?
DEXA bone scan
Is bone mineral density a dependent or independent risk factor for fragility fractures?
Independent
What is osteopenia?
Low bone density above 1 standard deviation below expected
What is osteoporosis?
Low bone density over 2 and a half standard deviations below expected
What is severe osteoporosis?
Low bone density over 2 and a half standard deviations below expected + fragility fracture
How can osteoporosis be classified in patients younger than 20?
Using the z score
As bone mineral density increases what happens to the risk of fracture?
Decreases
How should suspected osteoporosis be investigated?
U&E LFT Bone biochemistry FBC PV TSH Protein electrophoresis/bence jones proteins (myeloma) Coeliac antibodies Testosterone levels Vitamin D Parathyroid hormone
List some secondary causes of osteoporosis
Hyperthyroidism Hyperparathyroidism Cushing's disease Coeliac IBD Chronic liver disease Chronic pancreatitis Cystic fibrosis COPD Chronic kidney disease
What lifestyle changes can be helpful in the management of osteoporosis (not diet)?
Risk assessment for falls and prevention High intensity strength training Low intensity weight bearing Smoking cessation Avoidance of alcohol excess
What diet changes can be helpful in the management of osteoporosis?
2-3 portions of milk/dairy per day (700g)
3-4 portions of milk/dairy per day (1000g) post menopausal
Non dairy sources (bread, fortified cereal, fish w/ bones, green veg, beans)
When are calcium and/or vitamin D supplements indicated?
Considered as risk reduction of non-vertebral fracture in patients at risk of deficiency due to diet or limited sunlight (housebound, cultural garb)
When should calcium not be taken?
Within two hours of oral biphosphonates
When would vitamin D alone be indicated?
When oral calcium intake is adequate
How do biphosphonates work?
Anti-resorptive agents - analogues of pyrophosphate that get absorbed onto bone and eaten by osteoclasts causing cell death and less reabsorption
Give two examples of biphosphonates
Alendronate
Risedronate
What do biphosphonates reduce the risk of?
Spine and hip fractures
When are biphosphonates indicated?
T score less than -2.5
Existing fragility fracture
How long should biphosphonates be given for?
5 yr +
10 yr + if vertebral fracture
What are the risks of long term biphosphonate use?
Osteonecrosis of the jaw
Oesophageal carcinoma
Atypical fractures
How is zoledronic acid given?
Once yearly IV infusion (5mg in 100ml NaCl) for 5 years
What is a common side effect of zoledronic acid and how can this be treated?
Influenza like symptoms (acute phase reaction)
Paracetamol
How does denosumab work?
Human monoclonal antibody targeting RANKL - inhibiting activation, development of osteoclasts and decreased reabsorption so increased density
How is denosumab administered?
Subcutaneous injections 6 monthly
Which osteoporosis drug can be administered in severe renal failure?
Denosumab
What are the side effects of denosumab?
Hypocalcaemia
Eczema
Cellulitis
What is strontium ranelate?
Antireabsorptive agent
When is strontium ranelate contraindicated?
Thromboembolic disease
Ischaemic heart disease
Peripheral artery disease
Uncontrolled hypertension
When is strontium ranelate indicated?
When there is no other option
What is teriparatide?
Recombinant parathyroid hormone
How does teriparatide work?
Stimulates bone growth
When is teriparatide indicated?
Over 65 with T score -3.5 plus 2 fragility fractures
55-64 with T score
When should patients be treated for osteoporosis?
Anti-resorptive therapy T score 7.5 for 3 months or more OR prevalent fracture and T score
What are the direct and indirect effects of corticosteroids on bone?
Direct - reduced osteoblast activity, suppression of osteoblast growth and reduction in calcium absorption
Indirect - reduced gonadal and adrenal hormones
Are the fracture risks of glucocorticoids dose dependent?
Yes but no safe dose
What is Paget’s disease?
Abnormal osteoclast activity followed by increased osteoblast activity resulting in weakened bone and increased fracture risk
What is the term for paget’s at a single site? What about at multiple sites?
Monostotic
Polystotic
What is the aetiology of Paget’s?
Unknown
Which bones does Paget’s affect?
Long bones
Pelvis
Lumbar spine
Skull
Which age group is affected by Paget’s?
Over 55
How does Paget’s disease present?
Bone pain
Deformity
Deafness
Compression neuropathies
What is a rare complication of Paget’s?
Osteosarcoma
How can Paget’s be investigated?
X-ray
Isotope bone scan
Isolated raise on alkaline phosphate
Normal LFTs
How is Paget’s treated?
Analgesia +/- biphosphonates if not responding
What is osteogenesis imperfecta?
Group of autosomal dominant genetic conditions arising from mutations in type 1 collagen
How many types of osteogenesis imperfecta are there?
8 types
Neonatal lethal - type 2
Very severe - type 3 and 4
Mild - type 1
What is osteogenesis imperfecta associated with?
Blue sclera
Dentinogenesis imperfecta
How do severe forms present?
Childhood fractures
How is osteogenesis imperfecta treated?
Fixation
Surgery for deformity
Biphosphonates
What is osteogenesis imperfecta an important differential of?
Non-accidental injury
