Introduction to Biomechanics and Tissue Mechanics

Kinesiology

Study of human movement science

Anatomical Position

Body erect, facing forward, arms to the side, palms forward

Axial Skeleton

Includes the head, thorax (chest), and spinal column

Appendicular Skeleton

Includes the upper extremities, lower extremities, and girdles with attachments to the axial skeleton

Gliding

Flat bone slips over another

Flexion

Decreases the angle of a joint, usually along the sagittal plane

Extension

Increases the angle of a joint

Biomechanics (Hay)

The science that examines forces acting upon and within a biological structure and the effects produced by such forces

Biomechanics (Milburn)

Implies an understanding of three areas: (i) biological structures, (ii) mechanical analysis, and (iii) an understanding of movement

Gait analysis

Study of corrective surgical procedures, especially in children with cerebral palsy

Abduction

Movement of a limb away from the midline of the body

Adduction

Movement of a limb towards the midline of the body

Circumduction

Movement that describes a 'cone' in space

Rotation

Turning around a bone's own long axis

Supination

Movement of the forearm so that the palm faces anteriorly or superiorly

Pronation

Movement of the palm to a posterior or inferior-facing position

Inversion

Turning the sole of the foot medially

Eversion

Turning the sole of the foot laterally

Elevation

Lifting or moving superiorly along the frontal plane

Depression

Moving inferiorly along the frontal plane

Opposition

Occurs at the saddle joint in the thumb, touching the thumb to the tips of other fingers

Julius Wolff

German anatomist and surgeon who observed that bone changes its shape and architecture in response to stresses, known as Wolff's Law

Collagen

The strongest and most abundant protein in the body, composed of three interconnecting chains of proteins

Lamellar Bone

The most common type of bone, mechanically strong, constructed from sheets of lamella wrapped circumferentially around openings for blood vessels

Cortical Bone

Tightly packed lamellar and/or woven bone, forming the outer shell of most bones

Transversely isotropic

Material with one primary axis and is isotropic in the perpendicular plane to this axis

Anisotropic

Having strength properties that are both anisotropic and asymmetric

Viscoelastic Properties of Cortical Bone

When loaded to its yield point and then unloaded, permanent residual strains develop; modulus is reduced when reloaded

Viscoelastic Behavior

Acts like neither a viscous fluid nor an elastic solid, but something in between

Hysteresis

Phenomenon where the trajectory for unloading curve is lower than the loading curve

Creep

Phenomenon where constant stress applied leads to material deformation over time

Relaxation

Phenomenon where constant strain applied leads to stress decreasing over time

Fractures

Breaks in bones, with types including long bone fractures, lower extremity injuries, bending, and combined loading

Inflammation phase

First phase of fracture healing involving inflammation at the fracture site

Soft callus formation phase

Phase in fracture healing where a soft callus forms at the fracture site

Bony callus formation phase

Phase in fracture healing where a bony callus starts to form

Remodeling phase

Phase in fracture healing where bone remodeling occurs

Interfragmentary Strain Theory

Theory stating that only tissue capable of withstanding the present value of interfragmentary strain can form in the fracture gap

Delayed or Non Union of Fractures

Causes include inadequate blood supply, inadequate stabilization, separation of bone ends, infection, and soft-tissue imposition

Cartilaginous Tissue

Includes hyaline cartilage, elastic cartilage, and fibrocartilage distinguished by their composition and properties

Hyaline Cartilage

Glassy, smooth cartilage found in joints designed to withstand high loads

Articular Cartilage

Type of hyaline cartilage covering articulating surfaces of bones in joints

Poroelastic solid

Behavior of articular cartilage arising from intrinsic collagen-proteoglycan matrix and interstitial fluid flow

Osteoarthritis

Condition with decreased proteoglycan content and increased water content affecting cartilage load support

Tendon

Connects muscles to bones and contains type-I collagen, elastin, and proteoglycans

Ligament

Connects bones to bones and contains type-I collagen, elastin, and proteoglycans

Hierarchical Structures

Structures of tendon and ligament reflecting differences in functional forces

Progressive Failure

Failure in tendon and ligament structures as damage accumulates

ACL

Anterior cruciate ligament that can be separated into distinct structural bundles