Pathology: Bone/Joint Flashcards
1
Q
Composition of Bone
A
60% Mineral (inorganic) - Ca, PO4 crystals arrayed in a protein matrix - Resist compressive forces 30% Organic: - CT - Resistance to bending and/or torsion
2
Q
Osteoclasts
A
- Hematopoietic stem cell (bone marrow) -> monocyte -> tissue macrophage -> osteoclast
- Breakdown bone
- Highly active - high energy requirements
- Short lifespan
- Many nuclei
- Polarised
- Creates ‘sealing zone’ with bone where it releases enzymes and acid -> causes bone breakdown
3
Q
Osteoblasts
A
- Lay down osteoid which then becomes mineralised
4
Q
Bone Strength
A
= bone quality and bone density
- Determines fracture risk
5
Q
Regulators of Bone Metabolism
A
Endocrine - Parathyroid hormone - Estrogen - Vit D Autocrine - OPG - RANKL - Sclerostin - Inflam cytokines Drugs - Bisphosphates - Calcitonin
6
Q
Bone Resorption Control
A
- Controlled by RANKL:OPG ratio
- More OPG = no resorption
- More RANKL = bone resorption
7
Q
Osteoporosis
A
- Systemic skeletal disorder characterised by a decrease in total bone mass and density
- Diagnosis: BMD 2.5 SD below mean peak in young adults of same race and T score -2.5 (measured by DXA)
8
Q
Osteoporosis: Morphology
A
- Global disease ie all bones affected
- Trabecular bone is initially effected, then cortical bone
- Preferential loss of trabecular bone in various regions
- Decreased bone density
- Normal mineral content in remaining bone
9
Q
Osteoporosis: Prevention
A
- Nutrition: Vit D
- Exercise
- Smoking cessation
10
Q
Osteoporosis: Treatment
A
- Anti resorptive agents e.g. bisphosphonate, oestrogen analog, selective oestrogen receptors modulators (SERMs)
- Anabolic agents
- RANKL antibody (denosumab)
- Calcium and Vit D supplement
11
Q
Metabolic Diseases: Rickets and Osteomalacia
A
Rickets: - rare in developed countries - developing bones in children, 6-24 months Osteomalacia: - the disease in adults - under mineralised in remodelling
- Balanced bone formation and resorption
- Defective mineralisation of the organic matrix of the skeleton
- Less mineralised trabecular bone/unit
12
Q
Aetiology: Rickets
A
Nutritional - Lack of Vit D in diet - Lack of calcium and phophorus - In association with malabsorption - Inadequate sunlight Vitamin D dependent: gene abnormalities Vitamin D resistant: hypophosphatemia, decrease phosphate
13
Q
Aetiology: Osteomalacia
A
Insufficient calcium absorption
- Deficiency of/or resistance to Vit D
Phosphate deficiency
- Increased renal loss or decreased intestinal absorption
14
Q
Rickets and Osteomalacia
A
- Softer and weaker bones
- Tendency to become bowed (especially in children)
- Maybe loss of trabecular bone and cortical thinning
- Fractures occur with normal load levels
Treatment - Identify underlying cause and treat
- Calcium and Vit D
15
Q
Paget’s Disease
A
- 3rd decade of life
- Male > female
- 3-5% of Australians
- Genetic predisposition and environmental trigger
