Tissue Properties & Bone Loading Flashcards
(17 cards)
What is Young’s modulus?
A material’s stiffness—the slope of its stress-strain curve.
What is Wolff’s Law?
Bone remodels based on the mechanical loads it experiences.
What is the difference in bone strength under tension and compression?
Long bones are stronger in compression (~190 MPa) than tension (~130 MPa).
What is meant by bone being anisotropic?
Its strength and stiffness depend on the direction of the load applied .
What is hysteresis in viscoelastic materials?
The energy lost during a loading-unloading cycle, visible as a loop in the stress-strain curve; reflects internal damping.
Define viscoelasticity.
The property of biological tissues that exhibit both time-dependent viscous and elastic behaviours during loading.
What is meant by anisotropic behaviour in bone?
Bone responds differently depending on the direction of the applied load—stronger in axial than transverse loading.
What is the difference between strain and stress?
Strain is deformation relative to original length (unitless), while stress is the internal force per area (measured in Pascals).
Define the concept of polar moment of inertia in bone.
A measure of a bone’s resistance to torsional (twisting) forces, influenced by outer and inner radius of the cortical structure.
How does plate fixation affect bone remodelling?
It can cause stress shielding, leading to local osteopenia; gradual reloading is necessary after plate removal.
What is force relaxation in viscoelastic tissue?
When a tissue is held at a constant length, the resisting force decreases over time as internal tension reduces.
What are three characteristics of viscoelastic materials?
Creep (continued deformation under constant load), hysteresis (energy loss during load/unload), and strain-rate dependence (behaviour changes with loading speed).
How can a chronic injury develop from loading?
Repetitive submaximal loading over many cycles can exceed tissue repair capacity, leading to degeneration.
What is bionegative loading?
Loading outside of optimal thresholds like immobilisation, space flight, or overload.
Which load type is applied during torsion?
A combination of tension, compression, and shear.
What is Hooke’s Law?
Force is proportional to extension within the elastic limit.
Q: What are two positive and two negative factors for bone formation?
A: Positive: Weight-bearing exercise, calcium intake. Negative: Immobilisation, ageing
