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Lumbar Spine Biomechanics: Difference between revisions
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| Rotation || All the points on a bone move in parallel around a curved path that is centred on a fixed point, but to different extents depending on their distance from the centre of rotation. May be due to two opposed muscular actions, or muscular action and ligamentous resistance, or gravity opposed by either muscular action or ligamentous resistance. || Two unaligned forces acting in opposing directions on different parts of the bone forming a force couple || Torque | | Rotation || All the points on a bone move in parallel around a curved path that is centred on a fixed point, but to different extents depending on their distance from the centre of rotation. May be due to two opposed muscular actions, or muscular action and ligamentous resistance, or gravity opposed by either muscular action or ligamentous resistance. || Two unaligned forces acting in opposing directions on different parts of the bone forming a force couple || Torque | ||
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*Axis of rotation | |||
**Formal definition = that region that does not move when two or more opposing, unaligned forces act on a bone. | |||
**With rotation of a bone, all the points on the bone can be grouped into individual planes that lie parallel to the direction of movement. | |||
**In each plane, the points move about a centre located in that plane | |||
**When all the centres of all the planes line up they depict a straight line forming the axis of rotation of the bone. | |||
**It is a region where all opposing forces cancel out, and there is no net force acting, and so it stays stationary. | |||
**Different forces create different axes of rotation. | |||
==Planes of Movement== | |||
==Stress-Strain== | |||
*With stretching of a collagen fibre, the fibre resists elongation due to a resistance force from the chemical bonds between the collagen fibrils, between tropocollagen molecules, between collagen fibres, and between collagen fibres and proteoglycans. | |||
*'''Stress''' = the applied elongating force, measured in units of force (newtons) | |||
*'''Strain''' = the extent to which a fibre is elongated, measured as the fractional or percentage increase in length relative to the initial length. | |||
A fibre of length L<sub>0</sub> when stretched to a new length L<sub>1</sub> undergoes a strain of | |||
L<sub>1</sub>/L<sub>0</sub> or L<sub>1</sub>/L<sub>0</sub> x 100% | |||
==Stiffness== | |||
==Initial Range of Movement== | |||
==Creep== | |||
==Hysteresis== | |||
==Fatigue Failure== | |||
==Forces and Moments== | |||
[[Category:Lumbar Spine]] | [[Category:Lumbar Spine]] | ||
Revision as of 06:38, 11 May 2021
This article is a stub.
Movements
| Movement | Description | Movement occurs when | Force |
|---|---|---|---|
| Translation | Every point on a bone moving in the same direction and to the same extent | Single force or net single force acts on a bone | Shear force |
| Rotation | All the points on a bone move in parallel around a curved path that is centred on a fixed point, but to different extents depending on their distance from the centre of rotation. May be due to two opposed muscular actions, or muscular action and ligamentous resistance, or gravity opposed by either muscular action or ligamentous resistance. | Two unaligned forces acting in opposing directions on different parts of the bone forming a force couple | Torque |
- Axis of rotation
- Formal definition = that region that does not move when two or more opposing, unaligned forces act on a bone.
- With rotation of a bone, all the points on the bone can be grouped into individual planes that lie parallel to the direction of movement.
- In each plane, the points move about a centre located in that plane
- When all the centres of all the planes line up they depict a straight line forming the axis of rotation of the bone.
- It is a region where all opposing forces cancel out, and there is no net force acting, and so it stays stationary.
- Different forces create different axes of rotation.
Planes of Movement
Stress-Strain
- With stretching of a collagen fibre, the fibre resists elongation due to a resistance force from the chemical bonds between the collagen fibrils, between tropocollagen molecules, between collagen fibres, and between collagen fibres and proteoglycans.
- Stress = the applied elongating force, measured in units of force (newtons)
- Strain = the extent to which a fibre is elongated, measured as the fractional or percentage increase in length relative to the initial length.
A fibre of length L0 when stretched to a new length L1 undergoes a strain of L1/L0 or L1/L0 x 100%
