L1 Biomechanics

zijimubo1's version from 2017-01-03 05:32

Introduction to Biomechanics

Question Answer
What is biomechanics?Study of how biological tissues respond when subjected to mechanical force.
What causes torque in musculoskeletal?Muscle contraction(force) causing a rotation.
List examples of intrinsic properties of musculoskeletal tissue?Material properties: tissue arrangement, fiber size, cells, organization, matrix
Define stress.Force per unit Area; stress = F/A
What is deformation?Change in shape and/or size and is quantified as strain.
Define strain.Change in length per initial length.
List the four types of complexes stresses and strains muscoloskeletal tissue undergo.Compression, Tension, Torsion, Bending
What kind of stress/strain does bone typically undergo?Compression
What kind of stress/strain do ligaments and tendons typically undergo?Tensile

Stress Strain Curve

Question Answer
What is the purpose of the stress-strain curve?To assess the structural and material properties of musculoskeletal tissues.
How is the stress-strain curve derived?By placing tissue under a specific load and measuring the amount of tissue displacement and failure point.
What kind of information can be determined from the stress-strain curve?Biochemical characteristics of tissues that determine normal parameters for that tissue.
Why is it important to understand the normal parameters of musculoskeletal tissues?To understand how disease or injury and their treatment may affect the tissue's mechanical properties.

Material Properties Definitions

Question Answer
Define creep.How a material reacts to a constant load by undergoing increased deformation over time.
Define stress(force) relaxation.When a material decreases in stress while under constant strain.
Define crimping.Waves/undulations seen in tendons and ligament fibrils microscopically when unloaded.
Define the toe region.Region in the stress-strain curve where loading results in the recruitment of slack collagen fibrils.
Define isotropy.A material property that does not depend on what direction the load is applied.
Define anisotropy.A material property that is dependent on the loading direction.
Define viscoelastic.A material that has a time dependent behavior to strain rat
Define hysteresis.Dissipitation of mechanical energy.
Define fatigue.When a subject is subjected to repeat loading cycles at or below physiological loads, resulting in FAILURE at a lower stress.
Define a microcrack.Fatigue damage in bones, typically repaired in bone remodeling, but could lead to stress fractures that occur in tibia or runners or metatarsals of marchers(march fracture).

Effects of Age or Diseases

Question Answer
At what age does peak bone accrual occur?25
Define osteoporosis.Bone loss that increases risk of fractures.
What changes(3) occur in advancing age that lead to osteoporosis?Hormonal changes(reduced estrogen/testosterone), reduced physical activity(load), and nutritional deficiencies.
What kind of bone is initially loss?Canecellous (trabecular, spongy) bone. **Followed by cortical bone.
What regions of the skeleton experience are commonly affected with increase risk of fractures?Weight bearing (or falling); Ex: Proximal femur and vertebrae
How can bone loss be assessed?By measuring the bone mineral density (BMD), which can predict fracture risk.
How does the stress-strain curve change(2) with aging?Stiffness declines (decreased slope) and both toughness (energy) and ultimate strength is reduced (smaller domain).
What is significant about the increase risk of bone fractures in diabetes patients?Most diabetic patients have normal to increased BMD. The risk is due to abnormal collagen fibril formation that is brittle and accumulate microdamage.
How does the stress-strain curve change with diabetes patients?The post-yield point properties are reduced; plastic and toughness.
What is the composition(3) of articular cartilage?Proteoglycans(PG), collagen network, and water.
What provides articular cartilage the ability to perform biomechanical functions within the joint including wear resistance, load-bearing, and shock absorption?Its viscoelastic properties (PGs)
What is the consequence(2) of the progressive loss of proteoglycans as a result of ageing?Reduced stiffness and ability of cartilage to withstand shear force.
What are two diseases associated with loss of PG?osteoarthritis(OA) and inflammatory joint disorder(RA, joint infection)