Week 1.pptx

Biomechanics of the Spine A chiropractic perspective on functional anatomy, statics and dynamics of the human spine and pelvis Student Learning Outcomes 1 The student will better understand normal movements of the vertebral segments. The student will be able to describe normal and abnormal movemen...

Biomechanics of the Spine A chiropractic perspective on functional anatomy, statics and dynamics of the human spine and pelvis Student Learning Outcomes 1 The student will better understand normal movements of the vertebral segments. The student will be able to describe normal and abnormal movements and joint positions 2 including the use of the orthogonal system. 3 The student will be better equipped to interpret Chiropractic listing systems. The student will build on past anatomy knowledge and get a firmer grasp of the functional 4 anatomy of the spine. The student will understand and be able to articulate ideas such as springiness, stiffness, 5 joint play and slack. The student will understand that normal biomechanical loading is necessary for spinal 6 health. The student will appreciate that excessive loads or repetitive loads may cause damage to 7 the spine.] 8 The student will grasp basic arthrokinematics such as the convex/concave rule and 9 start applying these principles in clinical courses. The student will have a better knowledge of common spinal conditions and how they are 10 managed by Chiropractors. Course Grading Breakdown Midterm: Unit 1 Final: Comprehensive Week 6 – Friday 9:30 100 pts Week 11 – TBD 100 pts What is Biomechanics? • Bio: life • Mechanics: branch of physics concerned with the effects of internal and external forces acting on an object • Biomechanics: The application of mechanical principles to living organisms • Statics – the study of objects at rest/equilibrium • Dynamics – the study of bodies in motion • Perspective: the spine as a mechanical structure Biomechanical Functions of the Spine Transfer Transfer weights and resulting moments from head, trunk, weights lifted to the pelvis Allow Allow physiologic motions between head, trunk, pelvis Protect Protect the spinal cord from potentially damaging forces and motions; those caused by both physiologic movements and trauma This Photo by Unknown Author is licensed under CC BY- Spinal Anatomy Review Structure of Typical Vertebra Anteriorly • Vertebral body • Cylinder shape • Wider than it is tall Posteriorly • Vertebral arch • Pedicles • Laminae • Spinous process • Transverse processes • Articular processes Functional Spinal Unit (FSU) • Smallest functional unit of the spine • Two adjacent vertebrae, the disc and all the ligaments that connect them Intervertebral Disc • Nucleus Pulposus • Annular Fibrosus • Cartilagenous endplate This Photo by Unknown Author is licensed under CC BY-NC-ND Spinal Ligaments • Intervertebral disc • Anterior longitudinal ligament • Posterior longitudinal ligament • Ligamentum flavum • Capsular ligaments • Intertspinous ligaments • Supraspinous ligaments • Intertransvere ligaments Spinal column: 3 columns • Major column • Stacked vertebral bodies • Attached by intervertebral discs • Two minor columns • Stacked articular processes • Attached by planar synovial joints Spinal Curvatures • Coronal view • Straight, slight lateral curve • Sagittal view • Primary curves (Kyphosis) • Sacrum • Thoracic spine • Secondary curves (Lordosis) • Lumbar spine • Cervical spine This Photo by Unknown Author is licensed under CC BY Fundamentals of Force What is Force? • Any action that changes the motion of bodies • Electromagnetic, nuclear, spiritual • Mechanical force – push or pull • Changes motion of interacting objects • Changes shape of objects This Photo by Unknown Author is licensed under CC BY-SA Types of Mechanical Forces Normal Forces Forces that are perpendicular to the surface of the body they are acting on Shearing Forces Forces that are parallel to the surface of the body they are acting on Quantity: Anything that can be measured • Scalar • Fully described by magnitude, size, or amount • Speed, length, mass, distance, time, temperature • Vector • Fully described with both magnitude and direction • Velocity, acceleration, displacement, force Drawing Vectors • Reference Frame • XY coordinate system • Two dimensional • XYZ coordinate system • Three dimensional • Right-hand rule Force Vectors • Magnitude (length of arrow) • Amount of force • Measured in Newtons (N) • Direction (arrowhead) • Defined using frame of reference • Cartesian Coordinate system • Point of Application (the tip of the arrow) • Contact point on the object • Angle of Application (in relation to axes) • Where the force is coming from in relation to point of application Force Magnitude and Change in Motion • Force Magnitude measured in Newtons (N) • 1 N = the amount of force required to accelerate a 1 kg of mass by 1 m/s every second • Key Concept: • Force causes acceleration, or a change in velocity Motion • Motion is a change in position with time • A series of discrete steps, like individual frames of a movie • Each motion step consists of a pair of positions separated by a time interval • AKA displacement Types of Motion • Linear Motion – Translation • The motion of an object in which a straight line through like points of the object always remains parallel to itself Types of Motion • Angular motion – Rotation • The motion of an object in which a certain straight line (axis of rotation) of the object remains motionless • The primary movements of every vertebra are considered to be rotations. Speed, Velocity, Acceleration Speed • the rate at which an object covers distance • How fast an object is moving Velocity Acceleration • Change in displacemen t divided by time • How fast an object is moving and in which direction • Rate of change of velocity • How quickly or slowly the velocity is changing Gravity, mass and stability Gravity: The Ultimate Force • Constant, helps shape human bodies during development • Pulling force toward the center of large mass • Earth’s gravitational force • 9.81 m/s/s • If gravity is constant, why are we all not being sucked into the center of the earth? This Photo by Unknown Author is licensed under CC BY-SA- Mass vs. Weight Mass Total amount of substance in an object Weigh t Amount of mass x acceleration of gravity Densi ty Describes concentration of mass within an object Center of Mass (CoM) • The distribution of mass is equal in all directions • Average position of all the particles of an object’s mass • Point at which uniform force on the object acts • Does not depend on gravity Center of Gravity (CoG) • The point through which gravity acts on an object • For small objects in a uniform gravitational field – CoG is the same as CoM Center of Mass and Balance Point • Important in understanding movement and injury • CoM correlates with the balance point of an object • CoM will be directly above balance point • Humans standing posture CoM • approx. 5 cm anterior to second sacral tuberosity This Photo by Unknown Author is licensed under CC BY-NC- Moments created by Mass • Moment • Turning or bending force • Acts at a distance from turning point • Moment = force x distance from pivot • Segmental CoM • Each body segment has its own mass • Each segment is linked by a rotation point – joints • When gravity acts on a segmental CoM, a moment is created at the joint This Photo by Unknown Author is licensed under CC BY- Thought Exercise • Considering gravitational moments and stability of segments, what would ideal posture look like? • Least amount of muscle work • Least amount of stress on tissues Ideal Posture Places the CoM of each segment close to the joint center Stability • Definition: an object’s ability to return to its original position after experiencing a force • Center of Gravity lies within Base of Support • Base of Support (BoS) • Area defined by the perimeter around all the object’s points in contact with supporting surface • Wider base of support – typically more stability • Narrow base of support – typically less stability This Photo by Unknown Author is licensed under CC BY Forces and Motion Newton’s three Laws of Motion explain the interaction between forces and motions of object. Inertia • Definition • The property of an object to resist changes in motion • Comes from Latin word for laziness • Directly correlated to mass • Law of Inertia • “Every body perseveres in its state of being at rest or of moving uniformly straight forward, except insofar as it is compelled to change its state by force impressed.” Newton’s First Law of Motion • An object maintains its state of rest or uniform motion unless acted upon by another force This Photo by Unknown Author is licensed under CC BY Moment of Inertia • Object’s resistance to rotation • Must factor in the distribution of mass in relation to the point upon which it is rotating • I = mr2 • I – moment of inertia • m – object mass • r – distance from the point of rotation Linear Momentum • Force of movement • The mass of an object multiplied by its velocity • Momentum = mass x velocity • p = mv • If an object is moving, it has momentum • Changing the momentum of an object requires force • Linear momentum acts to move body in straight lines in relation to CoM (sitting to standing) • Achieved through rotation of peripheral joints and trunks • Rotational momentum Rotational Momentum • Recall: change in direction can only be achieved by force • Two forces that work at right angles to each other • 1- forward motion • 2- changes the direction of the object so that it moves in a circle • Centripetal force – pulls toward center • Centrifugal force – pushes away from center This Photo by Unknown Author is licensed under CC BY-SA Conservation of Angular Momentum • Law: Total momentum of all objects will always be the same • If moment of inertia increases, angular velocity will decrease • If moment of inertia decreases, angular velocity will increase • Example: figure skating This Photo by Unknown Author is licensed under CC BY Newton’s Second Law of Motion • Law of Acceleration • Acceleration of an object depends on force applied on the object and mass of the object • Force = mass x acceleration • How does this apply in chiropractic? • Law of Action and Reaction • For every action there will be an equal and opposite reaction • Example: wall pushup Newton’s Third Law of Motion • Example: two pool balls colliding • Chiropractic example? This Photo by Unknown Author is licensed under CC BY-SA Pressure • Applied force divided by surface area • Example: Pressure sores in bed-bound patients • Example: doctor’s contact during adjustments This Photo by Unknown Author is licensed under CC BY-NC-ND Center of Pressure (CoP) • Location of the average point of all the pressure applied to an object • Symmetrical and balanced standing posture • Coincides with CoM • Shift CoM to right • CoP moves to the right This Photo by Unknown Author is licensed under CC BY-SA Friction • Resisting force • Opposes the movement of one object over another • Sliding friction opposes the sliding motion of an object over another object • Two factors • Weight • Coefficient of friction • Measure of the roughness of the surface • Force of friction = weight x coefficient of friction This Photo by Unknown Author is licensed under CC BY-NC-ND Friction - examples • Curling • Tendon sheaths • Synovial joints This Photo by Unknown Author is licensed under CC BY-SA This Photo by Unknown Author is licensed under CC BY-SA-NC