CMS - bone & joints 1&2 Flashcards
How does bone growth change with age?
Different at stages of aging:
rapid in infants and slows as we age into childhood.
There is a growth spurt during adolescence.
By age 18, adult bone levels have been achieved.
What are the types of bone?
Cortical / compact / lamellar bone - outer layer
Cancellous / trabecular bone - inner layer. Contains bone marrow.
Woven bone - immature / pathologic bone. Higher vol of osteocytes.
What is Cortical / compact / lamellar bone ?
Bone that forms the shaft of long bones and outer layer of flat bones.
Highly organised.
Arranged in concentric rings of bones, adapted to withstand strain of pressure.
What is cancellous / trabecular bone ?
Found in flat bones and end of long bones.
Interconnected network of rods and plates of bones.
Allows for resistance of compression of loads.
Main site of turnover where mineral turnover occurs.
What is woven bone ?
A more disorganised type of bone.
Appears in early years or fracture sites. E.g. when sustaining an injury.
Also present in diseases with high bone turnover e.g. Paget’s disease.
What makes bone mineralisation important?
If the osteoid (collagen) is not mineralised, it would be soft and “bendy”, leading to bone disorders
What is hydroxyapatite?
Bone mineral
What are bones made of?
Calcified connective tissue
Matrix of collagen fibres containing osteocytes.
Type 1 collage (osteoid)- main protein forming parallel lamallae - offers different densities.
Non-collagen proteins e.g. osteopontin (bone remodelling) and osteocalcin, fibronectin (tissue repair)
Within the bone matrix, Ca and phosphate minerals are found abundantly - adds strength and density to the structure.
What are the receptors found on osteoblasts?
Express receptors for (Parathyroid hormone “PTH”, oestrogen, glucocorticoids, vitamin D, inflammatory cytokines and TGF beta) which influence bone modelling
An _______ is derived form local mesenchymal stem cells and synthesises bone. What happens during apoptosis?
Osteoblast
After they die, osteocytes will line the bone in its’ place.
What is an osteocyte?
cells derived from osteoblasts.
Activate bone formation by responding to mechanical strain. Key roles within bone resorption.
What is the bone cell involved in bone resorption?
Osteoclast
What are the functions of osteoclasts?
Rich in Alkaline phosphatase - regulates bone mineralisation.
Also express receptors for hormones etc that influence bone remodelling for instance - oestrogen, PTH, glucocorticoids, vit D, inflammatory cytokines and TGF-B (transforming growth factor beta – tumour suppressor).
Bone formation, metabolism and blood Ca levels are affected by _______________, ________________ and ___________.
parathyroid hormone, Vit D and calcitonin.
What are the effects of bone morphogenic proteins?
These proteins affect bone formation - available as recombinant proteins, they are sometimes used in grafting procedures or regeneration procedures in oral surgery.
The parathyroid hormone is regulated by blood ________, ____________, and ____________ levels.
blood calcium, vit D levels and phosphate levels.
When PTH is secreted, intestinal transport of calcium & phosphate are _________, and removal of Ca from bones is ____________.
Ca & phosphate promoted
Removal of CA from bone is accelerated
Dietary Vit D is fat soluble, and absorbed from the upper small intestine – which promotes _____________________________________________________________.
intestinal absorption of Ca and phosphate.
Vit D is also synthesised in the skin from UV sunlight. How is it converted from the skin?
Vit D in the skin is converted by the liver and then kidney into the most active metabolite.
Skin: 7-dehydrocholesterol
-> Cholecalciferol (Vit D3)
-> Liver: 25- hydroxycholecalciferol
-> Kidney: 1,25 - dihydroxycholecalciferol
How is Vit D from food converted in the body?
Ergosterol (Vit D2) is converted in the Liver to 25- hydroxycholecalciferol
-> then Kidney: 1,25 - dihydroxycholecalciferol
What is the active metabolite of Vit D, and its role in bone?
1,25 - dihydroxycholecalciferol
- controls bone metabolism & enhances Ca absorption.
The process is enhanced by the parathyroid hormone and low phosphate levels.
What is the role of calcitonin in bone?
apposes the action of PTH & lowers blood Ca levels mainly by promoting the deposition of Ca in the bones.
Which other hormones may affect bone formation & metabolism?
Growth hormone and oestrogen hormones
How does blood Ca level affect on the activity of Parathyroid hormone?
Decreased Ca in blood will stimulate parathyroid gland to secrete PTH (increased), leading to:
1) ↑ Osteoclast bone resorption (taking Ca from bone)
2) ↑ Synthesis of 1,25- dihydroxyvitamin D3 (active D3 to absorb Ca and PO4 from intestines)
3) ↑ Intestinal Ca absorption (taking Ca from intestines)
4) ↑ Renal tubular resorption Ca (taking Ca from kidneys)
So increasing Ca in the blood
How does a damage to liver and kidneys lead to Vitamin D deficiency?
Vitamin D is converted into the most active form by the liver and kidneys as a result of parathyroid hormone and low Ca and PO4 levels.
So damage leads to deficiency.
What common features of illness are seen in elderly pts?
- Nonspecific presentation
- Multiple pathology and consequent polypharmacy
- Interaction between conditions and between medications
- Loss of functional independence
- Impaired homeostasis, resistance to disease and recovery.
What common issues affect elderly pts?
- systemic and mental
- Incontinence
- Instability (falls)
- Immobility
- Intellectual impairment(dementia and delirium).
What considerations should be made prior to prescribing for elderly pts?
- Some antibiotics interact with Warfarin
- Azole antifungals affect blood clotting – increase INR.
- Make sure their medications do not react with LA. E.g. anti-parkinsonism drugs – may need to lower dose / avoid adrenaline. Check BNF.
What are the stages of healing of bone fractures?
Initial stages: Haemotoma formed with granulation tissue
Vascular stage: re-vascularisation & resorption
Primary callus formation: osteoid replaced with mature bone. Fracture is very stable.
Mature callus – months to years where new bone is laid down along lines of stress. Unnecessary bone replaced.
When bone fractures, healing occurs. Describe the initial inflammatory Cellular stage.
- When the bone is fractured, the blood will rush into the area, forming Haematoma (source of hemopoietic cells & Growth Factors which are useful for repairing).
Then, inflammatory cells (Macrophages, neutrophils and platelets) will migrate to the fractured area secreting Cytokines which attract more cells (Fibroblasts & mesenchymal cells) into the fractured site, producing Granulation tissue (vascular tissue) around the fracture ends to stabilise it.
What happens in bone healing after the inflammatory cellular stage?
Then the inflammatory Vascular stage occurs:
- Neovascularisation occurs (new blood vessels formation), leading to Hyperaemia (increased blood flow). Then, Osteoclasts will absorb the fractured margins.
What happens in the Inflammatory Primary callus “Lump” stage of healing after a bone fracture?
- Osteoblasts (bone-production), chondrocytes (cartilage-production), fibroblasts (CT-production) will proliferate and start to produce their products (bone, cartilage and connective tissue), forming a Callus (primary soft fibrous scar “cartilage” which is not visible radiographically)
What happens in the Reparative Bony callus stage of healing after a bone fracture?
4) Reparative Bony callus stage:
- The primary soft Callus (cartilage) is being produced quickly, stabilising the fracture temporarily.
Then, Endochondral ossification converts soft Callus (cartilage “Osteoid”) to hard Callus (woven bone), stabilising the fracture
Remodelling stage during bone fracture healing can take months & years. What happens during this time?
Remodelling stage (months & years):
- The hard Bony callus (woven bone) will be resorbed (by Osteoclast) & remodelled (by Osteoblast) into hard lamellar bone (bone’s original cortex structure) and the bone marrow cavity will be restored
What are the different types of bone disease?
- Genetic
- Acquired
- Joint disorders
- Arthritides
- Muscular dystrophies
What are the genetic bone diseases?
Osteogenesis imperfecta
Cleidocranial dysplasia
Osteopetrosis (Albers-Schonberg Disease)
What is Osteogenesis imperfecta?
A rare, autosomal dominant genetic disorder. Has 4 types.
Causes a defect in collagen. Can cause multiple bone fractures easily.
What are the effects of osteogenesis imperfecta on the body?
- Blue sclera of eyes (connective tissue in eyes thinner)
- Deafness
- Easy bruising
- Loose / hypermobile joints / tendons
- May have cardiac complications
How can osteogenesis imperfecta affect dental management?
Care with extractions – fracture risk
GA risk – chest deformity / cardiac issues
Teeth – brown/purple/wear/soft dentine
What is Cleidocranial dysplasia?
Rare genetic defect – mainly involving skull and clavicle.
Autosomal dominant
What are the clinical features of Cleidocranial dysplasia?
-Clavicles absent or defective – characteristic look
- Brachycephalic (broad short skull)
-Hypoplastic midface = mandibular protrusion +/- clefts
Other skeletal defects
What are the dental implications of Cleidocranial dysplasia?
- Hyperdontia
- Supernumeraries
- Retained deciduous dentition
- Abnormalities with dentition e.g root formation, cysts et