Bone Disease Flashcards
Define osteoporosis?
Osteoporosis is a skeletal disease in which their is reduced bone mass and micro-architecteral deterioration of the bone.
It is often asymptomatic
What are the complications of osteoporosis?
Fragility (osteoporotic) fractures: are fractures that result from mechanical forces that would not normally result in a fracture
May occur in any bone but commonly occurs in the:
- Wrist (colle’s)
- Neck of femur
- Spine (may present with back pain +/- loss of height)
Clinically how is osteoporosis diagnosed?
Osteopenia (more radiolucent appearance) may be detected on Xray.
It is formally assessed using a DXA (dual energy X-ray absorptiometry) bone scan.
Using this a T value is used to compare the patients score to a young health control. Less than -2.5 is diagnostic for osteoporosis.
Z scores can also be given. (how many SD deviates from aged matched score)
What are the risk factors for developing osteoporosis?
Increasing age Female gender FH Low oestrogen exposure (late menarche/early menopause) RA
Smoking Inactivity Underweight in 1st 20 years of life (anorexia) Caucasian Alcohol (more than 3 units a day) Corticosteroids
How should osteopaenia be managed?
Osteopenia should get lifestyle advice:
- Smoking cessation
- Weight bearing activity
- Reduce alcohol intake
- Increase dietary calcium (consider supplements)
and repeat DEX scan
Post fragility fracture how should osteoporosis be managed?
Lifestyle advice:
Smoking cessation
Weight bearing activity (after # has healed)
Vitamin D and calcium supplementation (Adcal)
Alendronic Acid* (or alternative bisphosphonate treatment)
*Note: poorly absorbed by GI so taken on an empty stomach with water only (often given in a weekly dose)
What are the bisphosphonate treatments?
What are the common side effects?
Alendronic Acid (1st line), Risedronate and Etidronate (2nd line)
SE: Osteonecrosis of the jaw (rare), GI SE (can switch from 1st to 2nd if so)
Why is osteoporosis more common in females?
As the menopause occurs oestrogen stops being produced.
Oestrogen deficiency causes uncoupling of bone reabsorption and bone formation such that more bone is reabsorbed than formed.
In a patient taking corticosteroids at what point should they be given osteoporosis prophylaxis?
Any patient taking oral steroids for 3 months or more should be on calcium supplementation and a bisphosphonate.
How do corticosteroids induce osteoporosis?
Intestinal calcium absorption is decreased and renal calcium excretion increased, leading to secondary hyperparathyroidism and increased bone turnover.
This is combined with inhibition of bone formation due to a direct inhibitory effect on osteoblast activity and stimulation of osteoblast death through apoptosis.
Note: Osteoblasts make bone. Osteoclasts claim bone (reabsorb)
What are the secondary causes of osteoporosis and how should they be investigated?
VITAMIN D
V
Inflammatory conditions
T
A
Metabolic (Cushings, thyrotocicosis, hyperparathyroidism hypogonadism*)
Iatrogenic (Corticosteroids, smoking, alcohol)
Neoplastic (Lymphoma)
Degenerative (Age, Menopause, Vit D/Calcium deficiency)
FBC, CRP, U&E’s; TFT’s, ESR
Serum calcium, Vit D and consider PTH.
In males should check testosterone.
If picture is indicative of neoplasm or endocrine disease investigate appropriately.
Define osteomalacia?
A vitamin D deficiency in adults that results in a shortage/loss of calcium salts, causing bones to become increasingly soft, flexible, brittle and deformed.
It is characterised by defective bone mineralisation, bone pain, increased bone fragility and fractures.
What are the potential underlying causes of osteomalacia?
- Deficiency of Vitamin D (sunlight, diet, malabsorption) or a defect in Vitamin D metabolism (kidney disease)
- Hypophosphotaemia (genetic)
- Iatrogenic (drug induced inhibition of bone mineralisation e.g. antiepileptics)
- Defects in pyrophosphate metabolism (genetic)
How does osteomalacia present?
Insidiously and when mild it may be asymptomatic.
As it progresses may cause bone pain, pathological fractures, general malaise and proximal muscle weakness
What is osteomalacia called in children and how does it present?
Rickets
It has many manifestations such as:
- Bone pain
- Deformity (genu valgus)
- Epiphysis enlargement at the radius (pathopneumonic)
Describe the pathogenesis of Vitamin D deficiency osteomalacia?
Reduced levels of Vitamin D due to inadequate sunlight exposure, dietary deficiency, malabsorption.
This causes there to be reduced intestinal calcium absorption and low serum calcium.
The low serum calcium stimulates PTH secretion leading to secondary hyperparathyroidism.
Secondary hyperparathyroidism causes increased osteoclastic bone reabsorption, reduced renal calcium excretion and increased renal phosphate excretion.
However with the continued Vitamin D deficiency there is progressive loss of both calcium and phosphate from bone and defective mineralisation.
How should you investigate a patient with suspected osteomalacia/rickets?
Patients suspected of having osteomalacia should have a routine biochemical screen:
- U&E’s (kidney function related to Ca levels)
- Serum Ca
- Phosphate
- Albumin
- Alk phosphatase
- Serum 25(OH)D (vitamin D)
- PTH levels.
X-ray if diagnosis unclear/ bone scan
How would you treat a patient with osteomalacia?
PO Vitamin D supplementation if deficient
- High dose 4 weeks then maintenance
- If malabsorption causing then can do IV
If due to chronic renal failure treat with an active metabolite of Vitamin D as it bypasses the metabolic defect.
What biochemical results would suggest a diagnosis of Vitamin D-deficient osteomalacia?
Low/low-normal calcium and phosphate
Low 25(OH)D (vitamin D)
Raised PTH.
Raised alkaline phosphatase
What are the risk factors for developing osteomalacia?
Poor diet (elderly/alcoholics)
Limited sunlight exposure (housebound elderly/darker skinned individuals more common in ladies that where burkas)
What is Paget’s disease?
A common condition characterised by focal areas of increased and disorganised bone remodelling.
This is due to uncontrolled resorption by large abnormal osteoclasts, with the osteoblast response causing distorted bone architecture.
What is the aetiology of Paget’s disease?
It is epigenetic and is thought to have both an environmental and genetic link.
It is a common disease affecting approximately 10% of the population by 85y of age.
How might a patient with Paget’s present?
80% Asymptomatic (incidental finding on Xray or raised ALP)
Bone pain
Bone deformity (more likely in weight bearing bones e.g. tibial bowing)
Pathological fracture
Deafness (new bone causing compression of cranial nn)
Skull enlargement (osteoporosis cirumscripta)
Increased risk of osteogenic sarcoma
Which bones does Paget’s usually affect?
Pelvis, femur, tibia, lumbar spine.
Skull and scapula.
Describe the pathogenesis in Paget’s?
Increased osteoclastic bone resorption
Marrow fibrosis
Increased vascularity of bone
Increased osteoblast activity
The increased osteoclast and osteoblast activity leads to there being a mixed picture of lytic and sclerotic lesions
Histologically what would be seen in Paget’s?
Increased number of osteoclasts.
Osteoclast hypertrophy.
Inclusion bodies (nuclear aggregates) found in the osteoclasts.
What are the complications associated with Paget’s disease?
Bone deformity
Pathological fractures
Neurological*:
- deafness
- cranial nerve defects
- nerve root pain/spinal cord compression/spinal stenosis
Osteosarcoma rare but serious (poor prognosis)
Increased vascularity increases the risk of orthopaedic surgeries.
If bed bound patient is at risk of hypercalcaemia.
*Neurological problems are recognised complications due to enlargement of the affected bones and compression of nerve foramina.
How should suspected Paget’s be investigated?
LFT’s: often get an isolated picture of raised ALP.
(Not diagnostic as it may be normal if few bones are affected). Calcium
A radionuclide bone scan is a useful way of screening for the presence of PDB. - shows extent of bone involvement but can’t differentiate between pagets and sclerotic mets.
X-rays should be taken of any affected bones.
See lytic and sclerotic lesions (cotton wool) loss of distinction between cortex and trabecular
How is Paget’s treated?
Mainstay of treatment is pain management.
- Usually paracetamol +/- NSAIDs.
- Bisphosphonates
- Monitor ALP as disease marker
- Surgery to treat 2y complications e.g. fractures or nn entrapment
- Monitor for osteosarcoma
What is avascular necrosis?
Describe which cells are affected.
Avascular necrosis is death of a bone due to lack of blood supply or interupted venous drainage.
With iscaemia the marrow cells die after 12h and the blasts/clasts/cytes die within 24h.
Which bones are vulnerable to AVN and why?
Odontoid peg. Scaphoid. Femoral head. Lunate. Talus.
As they have a single blood supply, therefore if this gets damaged they will suffer AVN.
How is AVN usually managed?
Aim for prevention:
Recognition of scaphoid fractures
Hemiarthoplasty following intracapsular NOF#
What is a differential diagnosis on X-ray of AVN?
Charcot joint.
Lytic neoplastic lesion.
How would you determine someones risk of developing osteoporosis
FRAX score can be used in GP used for patients 40-90 years old.
Gives a risk of low, intermediate or high.
If low: reassurance
Intermediate: DEX scan offered
High: treatment advised
How should osteoporosis be managed?
Weekly bisphosphates in:
- over 75 post fracture
- anyone on steroids >7.5mg for over 3 months with T >-1.3
- anyone over 65 years with T >-3
- anyone over 65 and 1 RF >-2.5
- anyone post fracture 65-75 >-2.5
Consider AdCal (calcium and vitamin D supplement)
If premature menopause causing OP then HRT considered
Testosterone therapy in males with hypogonadism
Last line (calcitonin, recombinant PTH)
What factors put someone at risk of osteonecrosis
Fractures Perthes disease Malignancy and bone marrow infiltration Alcohol abuse Cushings, steroids, chemo Septic arthritis Diving Sickle cell anaemia
