Processes

Question 1

Bone Turnover

Answer 1

1. Activation (3 days)
2. Resorption (30 days)
3. Formation (90 days)
4. Mineralisation (6 months)
5. Maturation

Question 2

Fracture Healing

Answer 2

ENDOCHONDRAL OSSIFICATION

1. Haematome and Granulation Tissue
2. Cartilaginous Callus
3. Boney callus and cartilaginous remnants.
4. Remodelling

Question 3

Role of PG in cartilage

Answer 3

1. Negative PGs stuck in matrix.
2. Positive ions attracted to PGs.
3. Increase concentration of ions in cartilage.
4. Water enters to equalise concentration.
5. Causes osmotic pressure.

Question 4

How are nutrients delivered to cartilage.

Answer 4

Diffusion of small molecules through the synovial fluid.

Convective transport for large molecules.

Question 5

Progression of OA - cartilage matrix alteration.

Answer 5

1. Fibrillation of cartilage surface.
2. Decrease in PG content.
3. Increase in water content.
4. Collagen II network damage.
5. Blood vessels crossing tidemarks.
6. Stiffening of subchondral bone.

Question 6

Progression of OA - Response of chondrocytes.

Answer 6

1. Chondrocytes detect damage.
2. Proliferate and synthesis matrix.
3. MMPs degrade matrix molecules.

The balance between 2 and 3 result in the stabilisation of matrix.

Question 7

Progression of OA - Decline in chondrocyte response.

Answer 7

1. Death of chondrocytes.
2. Down regulation of cells to anabolic signals.
3. Loss of cartilage.
4. Subchondral bone thickening.
5. Osteophyte bone formation at joint periphery.

Question 8

Joint replacement wear

Answer 8

1. debris leads to pseudosynovial membrane at interface between implant and bone.
2. Infiltration of fibrocytes and macrophages.
3. Activates osteocytes resorbing bone.
4. Aseptic loosening.

Question 9

Formation of menisci

Answer 9

1. Mesenchymal cells originating from chondrogenic blastema.
2. Cells arise from perichondrium and anlagen.
   Week 8: distinct structures in the knee.
   Week 8-16: Alignment of cells and beginning of EXM.
   As person mature number of cells decrease.

Question 10

Disc Degeneration

Answer 10

1. Increase fibre content of the nucleus.
2. Decreased hydration of nucleus and annulus.
   - decrease PG content and charge density.
3. Thickness of endplates become irregular.
4. Focal defects occur.
5. Alteration in distribution of collagen Type 1 and 2.

Question 11

Annular Injury

Answer 11

1. Rings softened, overstretched, torn.
2. Normal viscoelasticity exceeded.
3. Cannot stabilise/limit motion.
4. Nucleus pulposus exerts pressure on the weak part.
5. Buckling occurs.

Question 12

Healing process of tendon/ligaments

Answer 12

1. Inflammatory stage (3-7days)
   - infusion of blood to form a clot.
2. Proliferation stage (2-3 weeks)
   - fibroblasts synthesis in collagen.
3. Remodelling stage (< yr)
   - decrease in cell density.

Question 13

Muscle contraction

Answer 13

1. AP arrives at nerve ending resulting in an endplate potential
2. Endgate potential propagated to the motor unit
3. Rise in calcium ion levels
4. Ca2+ binds to troponin
5. Tropomyosin exposes a binding site on actin

Question 14

Joint Development

Answer 14

1. Mesenchymal condensation
2. Joint Initiation
3. Interzone Formation
4. Morphogenesis
5. Joint Maturation

Question 15

Mechanism of gout

Answer 15

1. High levels of urate in the blood.
2. Tophi - deposition of urate crystals.
3. Leukocytes seek out crystals and chondrocytes produce enzymes in response.
4. Osteoblast-mediated bone resorption amplified.

Question 16

Procedure of a spinal fusion

Answer 16

1. Remove the intervertebral disc
2. Insert an intervertebral cage if needed
3. Insert bone graft to promote bridging
4. Fix with screws, plates and/or rods

Question 17

Stages of Perthes Disease

Answer 17

1. Necrosis
2. Collapse
3. Repair
4. Remodelling