Questions and Answers
Bone is a living tissue that responds to ______.
Load
______ ______ strain is where bone wants to live.
Optimal customary
If strain increases, bone deposition ______.
Increases
If strain decreases, bone deposition ______.
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______ protection by an implant shields the bone beneath it.
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Low strain leads to ______ of bone.
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Bone is a complex word and is used for both the ______ and the ______.
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Trabecular mesh contributes to ______ distribution.
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Collagen acts like cables that resist ______.
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Hydroxyapatite crystals resist ______.
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When compression is applied, failure tends to occur across ______ planes.
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What fracture pattern is caused by tension forces?
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What fracture pattern is caused by compression forces?
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What fracture pattern is caused by bending forces?
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What fracture pattern is caused by torsional forces?
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Rate of loading influences how bone fails. What results from a slow rate of loading?
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What changes do compressive forces cause acting on a shaft fracture?
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What changes do bending forces cause when acting on a shaft fracture?
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What changes do rotational forces cause when acting on a shaft fracture?
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What force is occurring in an avulsion fracture due to pull of tendon or ligament?
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Shear is an uncommon force and leads to damage to early callus.
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Implant properties include ______ and ______.
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How do implants resist loads? They share the load with the bone in ______ fractures.
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Plates are hardened to increase bending strength and reduce ability to ______.
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What materials are plates made of?
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Implant geometry must resist bending forces and is influenced by implant ______ properties.
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Area moment of inertia for circular structures is proportional to the ______ to the 4th power.
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Area moment of inertia for rectangular structures is calculated as width x ______^3.
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Study Notes
Bone Characteristics and Response
- Bone is dynamic and responds to loads and optimal customary strain.
- Increased strain leads to increased bone deposition, while decreased strain results in decreased deposition.
- An implant can provide stress protection by shielding the bone underneath, which can lead to bone resorption if the implant is too stiff.
Bone Composition
- Bone refers to both its material and structural aspects.
- Trabecular mesh plays a significant role in load distribution.
- Collagen fibers resist tension, while hydroxyapatite crystals resist compression.
- Under compression, failure occurs along shear planes between hydroxyapatite crystals.
Fracture Patterns
- Avulsion fractures are typically caused by tension forces and display a transverse pattern.
- Shear fractures arise from compression forces but are less common; these occur in pathologic conditions where the bone is weakened.
- Compression and bending fractures yield larger butterfly fragments; they are among the most frequent types, where tension creates transverse fractures on one side and compression on the other.
- Spiral fractures are associated with torsional forces.
Rate of Loading Effects
- A slow rate of loading generally results in a single fracture line due to the path of least resistance.
- A fast loading rate causes comminuted fractures, which dissipate energy rapidly, leading to multiple fracture lines.
Age-Related Bone Quality
- Bone properties differ by age; for example, younger dogs have different mechanics leading to fracture patterns compared to mature dogs.
- Simple transverse fractures typically occur from slower, less compressive load distributions, while comminuted fractures result from fast loading.
Forces and Shaft Fractures
- Axial collapse occurs due to compression from body weight and muscle contractions.
- Bending forces compress one side and create tension on the opposite side, common during foot-planting movement.
- Rotational forces cause a change in direction around the long axis of the bone.
- Tension from tendons or ligaments can lead to avulsion fractures; tension band wires are commonly used for fixation in these cases.
Shear Forces
- Shear is an uncommon but crucial force; minimizing relative motion between fracture fragments is vital to prevent early callus damage.
Implant Design and Material Characteristics
- Implants resist various forces based on their material properties and geometry; they can either share the load in reducible fractures or bear the entire load in non-reducible fractures with bridging designs.
- Plates are primarily made from hardened 316 L stainless steel for enhanced bending strength; other materials include malleable wires and intermediate hardness plates.
Geometry and Mechanical Properties
- Bending is the primary force that implants must counteract; it depends on implant material properties and the area moment of inertia, a geometric parameter influenced by the bending direction.
- Area moment of inertia for circular structures is calculated as the radius to the 4th power, where minor increases can significantly affect strength.
- For rectangular structures, the area moment of inertia is calculated as width x height^3, with height oriented in the direction of bending.
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Description
Test your knowledge on the principles of fracture classification with these flashcards from Week 1 of the AO course. Each card focuses on key concepts, terms, and definitions related to bone strain and its effects on bone tissue. Perfect for students and professionals in orthopaedics or related fields.
