Bone disease Flashcards
What does Arthritis mean?
- Inflammation of joints
What does Arthrosis mean?
- Non inflammatory joint disease
What does Arthralgia mean?
- Joint pain
What is bone?
- Mineralised connective tissue
- It is load bearing
- It is dynamic (continuously changing)
- It is self repairing
What is the bone turnover cycle?
- Bone removed by osteoclasts
- Bone Deposited by osteoblasts
- Osteoclasts eat away at bone matrix
- Replaced by osteoblasts that deposit osteoid matrix
- Matrix undergoes collagen formation/mineralisation
- Bone formation takes 3-6months
What is required in bone turnover cycle?
- Correct amounts of
- Calcium
- Phosphate
- Vitamin D
Why is bone turnover necessary?
- In order to maintain calcium homeostasis to replace hypermineralised foci with younger tougher tissue
- Restore bone that has become defective through development and propagation of microfractures
How are Bone and Calcium linked?
- Bone forms a store for calcium
- Some is exchangeable and some isn’t
- Exchangeable calcium moves from bone to extracellular fluid and calcium absorbed from gut through ECF
- Calcium lost through gut and urine
- Bone and ECF work together and parathyroid hormone used to ensure correct level of calcium maintained
Why is it important calcium is maintained at precise level in blood?
- Normal body function
- Involved in nerve and muscle function
How does low dietary calcium affect the body?
- Reduction in plasma calcium
- Increased Parathyroid hormone secretion
1. Increases active vitamin D which increases intestinal calcium absorption
2. Decreases urinary calcium which increases conservation of dietary calcium
3. Increases bone loss which increase bone calcium release - All lead to restoration of normal plasma calcium levels
What does the parathyroid hormone do?
- Found in parathyroid glands
- Maintains serum calcium level
- Raises if calcium levels fall
- Increases calcium release from bone
- Decreases renal calcium excretion
What is hypoparathyroidism?
- Low conc of parathyroid hormone
- Results in low serum calcium
What is hyperparathyroidism?
Primary
- Due to gland dysfunction like a tumour
- Results in high serum calcium
- Inappropriate activation of osteoclasts
Secondary
- Occur when low serum calcium
- Increase activation of osteoclasts to maintain appropriate calcium level
- Both result in increased bone reabsorption (resorption)
- See radiolucency in radiographs on bone where reabsorption occurs
How is Vitamin D absorbed by body?
- Can be absorbed from UV ray from sun or from 7-dehydrocholestrol in diet
- Get absorbed as Cholecalciferol in skin
- Becomes bound Cholecalciferol in blood
- Becomes 25-hydroxycholecalciferol in liver
- Becomes 1,25-dihydroxyxolecalciferol in kidneys which is the active component necessary for calcium absorption in the GIT
- Calcium needed for muscle and bone health
What foods can you get Vitamin D from?
- Orange juice
- Fish
- Milk
- Supplements
What are some vitamin D problems?
Low sunlight exposure can be problem
- Housebound
- Dark skinned in Northern country as they absorb sunlight less efficiently
- Diet is more relied upon
Poor GI absorption
- Due to poor nutrition
- Small intestinal disease can lead to malabsorption
Drug interactions
- Some antiepileptic drugs like carbamazepine, Phenytoin can interfere with vit D synthesis
Vit D deficiency is usually a combo of factors
What is Osteomalacia?
- Softening of bones typically through vit D or calcium deficiency
- Normal bone matrix formed but not calcified properly
- Poorly mineralised osteoid matrix
- Poorly mineralised cartilage growth plate
- Normal amount of osteoid but not enough mineralisation so softening occurs
What is Osteoporosis?
- Reduced quantity of normally mineralised bone
- Age related change and is inevitable
- Weakens bones so very easily breakable
What disease occurs when Osteomalacia occurs during bone formation?
- Rickets develops then turns into osteomalacia when bone formation completed
- Calcium deficiency
- Serum calcium is preserved in expense of bone mineralisation
- When calcium in short supply during bone formation can lead to soft bone developing that can bend under pressure
What are the effects on bone of Osteomalacia?
- Bones bend under pressure and can be seen as ‘bow legs’ in children
- Vertebral compression is seen in adults and cause bone aching to touch
What are the Hypocalcaemia effects of Osteomalacia?
- Muscle weakness
- Show signs of Trousseau and Chvostek leading to carpal muscle spasm and facial twitching from CN VII tapping
What is Alkaline Phosphatase a measure of?
- Measure of bone turnover
- Very high when issues with calcium levels
What levels in blood are we expecting with Osteomalacia investigations?
- Serum Calcium decreased
- Serum Phosphate Decreased
- Alkaline Phosphatase Very high
- Plasma creatine increased due to renal cause
- Plasma Parathyroid hormone increased due to secondary hyperparathyroidism
How is Osteomalacia managed?
Firstly correct the cause
If malnutrition - Control GI disease and get more vit D in diet via supplement
If sunlight exposure - 30mins X 5weekly
