Exam 2 (week 6-week 10)

Muscle functions and biomechanics

-Acceleration- ability of a muscle to exert force on the bony lever to produce movement around the fulcrum to the extent intended. -Deceleration- muscle being able to relax at a controlled rate. -Shock absorption- if the muscles don't absorb the shock the ligaments take up the stress, this can lead to sprains or ligament tears. If the ligaments fail bones can fracture. -Inability to dissipate shock causes: shin splints, plantar fasciitis, Achilles tendinitis, lateral epicondylitis, some forms of back pain, among other conditions.

Stretch deformation

-All CT has a combo of two qualities: elastic and plastic stretch -"Stretch"- elongation in a linear direction and an increase in length -Elastic stretch: spring-like behavior, elongation produced by tensile loading being recovered after the load is removed. This is temporary or recoverable. -Plastic (viscous) stretch: putty-like behavior, linear deformation produced by tensile stress remains even after the stress is removed. Nonrecoverable of permanent elongation.

spinal ligaments

-Allow smooth movement within the normal ROM -Protect the spinal cord by limiting excessive motion and absorbing loads

stress to the disc

-Axial rotation of the spine produces tensile stresses in the disc. -Greatest tensile capabilities of the disc are in the anterior and posterior regions. -Weakest tensile capabilities of the disc is in the center. -Torsional forces cause shear stress in the horizontal and axial planes. -Shear stress acts in the horizontal plane, perpendicular to the long axis of the spine. -These can be injury-causing load factors. -During normal movements the disc is protected from excessive torsion and shear forces by the lumbar facet joints

sress to the disc

-Axial tensile stresses are produced in the annulus during flexion, extension and lateral flexion. -The motions create compression stresses ipsilaterally and tensile stress contralaterally. -Bulging (buckling) on the concave side -Contraction on the convex side of the disc

compressive loads in the body

-Circumferential tears in the annulus of a disc can occur when a compressive load is applied with torque around the long axis. -Bones become shorter and wider due to compression loading (axial loading) on bone which creates equal and opposite loads towards the surface a compressive stress and strain inward. -Failure to withstand compressive forces can result in compression fractures of the vertebral body.

compression forces

-Compression- when a load produces forces that push the material together, creating a deforming stress. -The length and how far or long the load is applied with effect the behavior of a structure in compression. -Compressive forces are transmitted to the vertebral body and IVD, the nucleus pulposis is incompressible and distorts under compressive loads it dissipates the compressive force be redirecting it radially. -Bending loads are a combination of tensile and compressive loads- fractures to long bones frequently occur through this mechanism.

Forces on the disc

-Distraction force- tension on the annular fibers increases and the internal pressure of the nucleus decreases. -Axial compression force applied symmetricallyinternal pressure of the nucleus increases and transmits this force to the annular fibers. The vertical force is transformed into a lateral force, applying pressure outward. -Asymmetric movements of flexion, extension, and lateral flexion- compressive force is applied to the side of movement and a tensile force occurs on the opposite side. The tension is transmitted from the nucleus to the annular fibers which helps restore the functional unit to its original position by producing a "bow-string-like" tension on the annular fibers.

Facet joints

-Each spinal segment has two posterior spinal articulations, paired they are called the zygapophyseal ("oval offshoot") joints with a synovial membrane and are enveloped in a somewhat baggy capsule with some degree of elasticity. Each facet is lined with articular cartilage. -Must control patterns of motion, protect discs from shear forces, and provide support to the spinal column -The orientation of the surface largely dictates the degree of freedom each region can accomplish.

IDEAS OF WHERE TORSION IS RESISTED IN THE SPINE

-Farfan et al (1) estimated the approximately 90% of the resistance to torque of a motion segment is provided by its disc. More specifically the annulus provides torsional resistance. With torsional injury, the annulus layers will tear, leading to disc degeneration. -Adams and Hutton (2) disagreed with Farfan and demonstrated the facets primarily resist the torsion of the lumbar spine and the compressed facet was the first structure to yield and the limit of torsion. -Others (3,4) suggest the posterior elements of the spine, facet joints and ligaments, play a role in resisting torsion forces

Intervertebral discs (IVD)

-Fibrocartilaginous mucopolysaccharide structures that lie between adjoining vertebral bodies. -In adults there are 23 discs, named numerically based on the segment above. L5 disc lies between L5 and the sacrum. -Discs make up about ¼ of the height of the vertebral column. -The greater the height of the disc in relation to the vertebral body, the greater the spinal segment mobility. -Cervical spine- 2:5 (greatest), thoracic spine- 1:5 (least), lumbar spine- 1:3 -The anterior portion of the disc, along with the vertebral bodies, is responsible for bearing weight and dissipating shock. It distributes loads, acts as a flexible buffer between the rigid vertebrae, permits adequate motion at low loads, and provides stability at higher loads.

5 qualities of joint motion

-For normal joint motion five qualities must be present: joint play, active range of motion, passive range of motion, end feel or play, and paraphysiologic movement. -These movements begin from a neutral close packed position -Both joint play and end-feel are though to be necessary for the normal functioning of the joint. The loss of either can result in a restriction of motion, pain, and most likely, both. -Cavitation occurs when the joint is taken through the elastic barrier

force ad duration of application

-Force and time = major factors affecting CT deformation -These have an inverse relationship -Elastic deformation- force great enough to overcome joint resistance applied over a short period -Plastic deformation- same force applied over a long period -is likely to occur during awkward sleep postures and stationary standing

tissues and types of forces matter

-Internal, external forces constantly stress and deform tissue. -External loads/forces- compression, torsion, translation (shearing) and tensile loading. -Tissues: Bone, muscle, ligaments, and other soft tissues resist forces.

LIGAMENTS, PROPRIOCEPTION, AND SPINAL ADJUSTING

-Jiang identified that stretching of spinal ligaments results in "a barrage of sensory feedback from several spinal cord levels on both sides of the spinal cord." -This sensory information ascends to many higher (cortical) centers. -This suggests spinal ligaments, along with Z joint capsules and small muscles of the spine play in important role in mechanisms related to spinal proprioception and may play a role in the neural activity related to spinal adjusting.

Ligament injury

-Large loads are capable of overcoming the tensile resistance of ligaments, resulting in complete- or partial- tear injuries. -Inflammation, repair and remodeling is how ligaments heal. -Strong muscular activity is seen when loads that can cause permanent damage to the ligament are applied, indicating that spastic muscle activity and possibly pain can be caused by ligament overloading.

Muscle contraction

-Muscle contraction- development of tension within the muscle -Isotonic contraction- muscle shortens its fibers under a constant load. Allows work to occur. -Isometric contraction- length of the muscle does not change. Tension is produced but no work. -Concentric contraction- muscle develops enough tension to overcome a resistance so the muscle visibly shortens and moves the body part. -Eccentric contraction- a given resistance overcomes the muscle tension so that the muscle lengthens

connective tissue after injury

-Reparative CT often impedes the body's function it may abnormally limit a joint's ROM because fibrotic tissue replaces elastic tissue. -Chiropractor's often deal with scar tissue, adhesions, and fibrotic contractures in their patient visits.

Muscles

-Role- to move bone and allow the human body to perform work -Male- muscle makes up 40-50% of body weight -Female- muscle makes up about 30% of body weight -White muscle- fast-twitch or phasic, rapid contractions, contains large amount of glycolytic enzyme. Allows for rapid function for quick contractions for short periods. -Red muscle- slow-twitch or tonic, slower contractions, contains more myoglobin and oxidative enzymes. Important for static activities that require sustained effort over longer periods (standing).

shear forces

-Shear force creates sliding or resistance to sliding. Causes a structure to deform internally in an angular manner as a result of a load applied parallel to the surface of the structure. -Facet joints and fibers of the annulus fibrosis resist shear forces in the spinal motion segment. -If disc space narrows abnormally high forces can be placed on the facets, the limit of resistance to such forces is not well documented. -In the lower lumbar segments, the facet joints provide resistance to shear stress. -Cancellous bone is most prone to fracture from shear loading. -Femoral condyles and tibial plateaus often fracture from shear forces as well.

Age and Lumbar Z-joints

-Taylor and Twomey studied the effects of age on the z-joints. -Cadaver transections of lumbar spine from fetus to 84 years old. -Fetal and infant lumbar z-joints are coronally oriented, only later in early childhood do they become curved or biplanar joints. -In adults the z-joints have a coronal component in the anterior third and a sagittal component in the posterior two thirds of the joint. -The anterior 1/3 of the joint tend to show changes related to loading the joint in flexion. -The posterior part shows a variety of different changes related to age. Shearing forces might be a cause. The subchondral bone thickens as it ages and is wedge-shaped. These changes occur because of. loading stresses from flexion

Compression of the discs

-The disc is a major load carrying element of the spine. -Axial compression forces continually affect the disc during upright posture. Nucleus bears 75% of this force initially, but redistributes some to the annulus. -Disc has the ability to imbibe water which causes it to "swell" within its inextensible casing. In a healthy disc, the pressure in the disc is never zero. This is called a preloaded state. This gives the disc a greater resistance to forces of compression and explains the elastic properties of the disc. -Age and exposure to biomechanical stresses- chemical nature of the disc changes and becomes more fibrous. Results in reduced imbibition and preloaded state. This leads to decreased flexibility and more pressure on the annulus and peripheral areas of the endplate. -An injured disc deforms more than a healthy one. -Under compression the disc bulges in the horizontal plane.

Facet joints and loading

-The posterior facet joints can share about 1/3 of the weight with the IVD. -If the disc degenerates and loses height, more weight-bearing function will fall on the facets. -Axial loading periods cause discs to lose height, so the facets have to bear more weight on a daily basis. -Lumbar z-joints can resist most of the intervertebral shear force only when the spine is in a lordotic posture.

Passive resistance

-The principle sources of passive resistance at the normal extremes of joint motion include ligaments, tendons, and muscles. -In normal ROM of most joints it is one or more CT structures which limit the ROM.

Connective tissue (CT)

-The response of connective tissue to various stress loads contributes significantly to the soft tissue component of joint dysfunction. -The fibers, ground substance, and cells (biologic materials of CT) blend in various proportions based on the mechanical demands of the joint. -CT contributes to kinetic joint stability and integrity by resisting rotatory moments of force. -Large forces require considerable CT power to produce the joint stability and integrity.

Torque forces

-Torsion occurs when an object twists, the force that causes twisting is called torque. -Torque is a load produced by parallel forces in opposite directions about the long axis of a structure. -In a curved structure, think spine, bending also occurs when a torque force is applied. -Spiral fractures are a result of torsional loads applied to long bones.

joint immobilization and CT

-When at joint is immobilized the CT elements lose their extensibility. -Water is released from proteoglycan molecules allowing the cross- linking of CT fibers. -It is hypothesized the manual therapy can break the cross-linking and any interarticular capsular fiber fatty adhesions thereby providing free motion and allowing water inhibition to occur.

axes of movement / 6 degrees of freedom

-an axis is a line around which motion occurs. cardinal axes are oriented at right angles to one another -the three dimensional coordinate system uses X, Y, and Z to mark the axes -rotational movements: occur about an axis -translational movements: linear movements along an axis -curvilinear movements: translational and rotational movements combined

3 components to an IVD: nucleus pulposus (NP)

-central portion of the disc and embryologic derivative of the notochord. -Approx 40% of the disc is a semifluid gel that deforms easily, but is considered incompressible. -Loose network of fine fibrous strands that lie in mucoprotein matrix of mucopolysaccharides, chondroitin sulfate, hyaluronic acid, and keratin sulfate. These molecules are highly hydrophilic capable of binding nearly nine times their volume of water. The water content steadily decreases with age. -Maintains an internal pressure of nearly 30 pounds per square inch. -The NP is a resilient spacer that allows motion between segments, and while not truly a shock absorber, serves as a means to distribute compressive forces.

3 components of IVD: 3. cartilaginous endplates

-hyaline cartilage helps attach disc to vertebral body -Compressive forces are transmitted from end plate to endplate from the annulus and the nucleus. -Under large loads, the endplate will fracture (Schmorl note) or the anterior vertebral body will collapse.

why does coupled motion matter?

-pure roll movement tends to result in joint dislocation -pure slide movement causes joint surface impingement -coupling is anatomically important because LESS ARTICULAR CARTILAGE IS NECESSARY in a joint to allow movement and may DECREASE WEAR on joints

the concave-convex rule

-when a concave surface moves on a convex surface, roll and slide movements should occur in the same direction -when a convex surface moves on a concave surface, roll and slide should occur in opposite directions -this rule applies to the expected coupling of rotational (roll) and translational (slide) movements

two perspective on movement:

1. the proximal segment can roatate around a fixed distal segment 2. the distal segment can rotate around a fixed proimal segment

Newton's 1st law of motion Law of inertia

1st law of motion states that a body remains at rest or in constant velocity except when compelled by an external force to change its state. -Some type of force is required to start, stop, or alter linear motion. -Inertia is related to the amount of energy required to alter the velocity of the body or overcome its resistance. -Center of mass- the point of a body where all of it's mass is evenly distributed, where the acceleration of gravity acts on the body. -For the entire upright human body, the center or mass lies just anterior to the second sacral vertebra.

Newton's 2nd law of motion: law of acceleration

2nd law states that the acceleration of the body is directly proportional to the force causing it, takes place in the same direction in which the force acts, and is inversely proportional to the mass of the body. F=ma Work is equal to the product of the force applied to an object and the distance the object moves.

Newton's 3rd law of motion:

3rd law states that for every action there is an equal and opposite reaction. -In every interaction there is a pair of forces acting on the two interacting objects. -The size of the force on the first object equals the size of the force on the second object. -The direction of force on the first object is opposite to the direction of force on the second object. -This is a law of the fundamental symmetry principles of the universe

forces on the disc

Axial rotation- some layers of the annulus are stretched and some are compressed (slackened). -Tension forces reach a maximum within the internal layers of the annulus. -This has a strong compressive force on the nucleus and causes an increased internal pressure proportional to the degree of rotation.

Ligaments

Cordlike or bandlike structures made of dense collagenous CT similar to tendons. Composed of Type I and III collagen with intervening rows of fibrocytes. Interwoven are elastin fibers.

arthrokinematic movements

Definition: specific movements that occur at the articulating joint surfaces -considers the forces applied to the joint and include the accessory motion present in a particular articulation -it is important to relate orthokinematics movement to arthrokinematics movement when evaluating joint motion. this involves determining the movement of the mechanical axis of the moving bone relative to the stationary joint surface

midsagittal plane

Joint movement: -flexion and extension -lateral to medial and medial to lateral glide -Axial rotation is used to describe movements of medial (internal) and latera (external) rotation in the extremities and spine. The midsagittal plane is the reference point for this. -exceptions: rotation of the scapula is movement about a sagittal axis, the terms clockwise or counterclockwise are used. Movements around this plane are listed in the orthogonal system as + or - X

Transverse plane

Joint movement: -medial and lateral rotation (axial rotation) -inferior to superior and superior to inferior glide (compression, distraction) movements around this plane are listed in the orthogonal system as + and - Y

Transverse plane

Joint movement: -medial and lateral rotation (axial rotation) -inferior to superior and superior to interior glide (compression, distraction) movements around this plane are listed in the orthogonal system as + or - Y

Muscle stretching

Muscle stretching is recommended, but only if the underlying joint is freely mobile... so it might be better to adjust before you stretch a patient.

Tension elements of body

Soft tissues (fascia, muscle, ligaments, and connective tissue) -These are an integral part of the body's construction -Ligaments are loaded in tension in the spine. -IVD- tensile forces occur during rotational movements of flexion, extension, axial rotation, and lateral flexion. -Nucleus bears compressive load -Annular fibers bear tensile load

force

an action exerted on a body that causes it to deform or to move

biomechanics

application of mechanical principles to living structures

kinematics

branch of mechanics that deals with the geometry of the motion of object, including displacement, velocity, and acceleration, without taking into account the forces that produce the motion

Muscle contracture

decrease in muscle elasticity. This can occur when a joint is immobilized, however the mechanism is unclear.

osteokinematic movement

definition: physiological movement possible at each joint when MUSCLES CONTRACT OR GRAVITY ACTS on bones to move it. This describes how each bone joint partner moves relative to the other

3 components to an IVD: 1. Annulus fibrosis

fibrocartilage ring that encloses and retains the nucleus pulposus. The fibrous tissue is arranged in concentric, laminated bands, which appear to cross one another obliquely, each forming an angle of about 30o to the vertebral body. -The weakest point of the annulus is the is the posterolateral aspect, this is the most likely location for a disc herniation in the lumbar spine. -Sharpey fibers attach the outer layer directly to the osseous tissue of the vertebral body -Very little elastic tissue, can only stretch 1.04 times it's original length -Functions: enclosing and retaining the nucleus pulposus, absorbing compressive shocks, forming a structural unit between vertebral bodies, and allowing and restricting motion.

coronal plane

joint movement: -abduction and adduction (lateral flexion) -lateral flexion is usually coupled with rotation in the human body -anterior to posterior and posterior to anterior glide movements around this plane are listed in the orthogonal system as + or - Z

Loose-packed position

joint surfaces are less congruent and the ligaments and capsule are relatively slackened -Loose-packed for most synovial joints is towards flexion -A joint moving towards its loose-packed position is undergoing distraction

movements in relation to a joint axis

mechanical axis of a joint- line that passes through the moving bone to which it is perpendicular while contacting the center of the stationary joint surface when one joint surface moves relative to the other, spin, roll, slide, or combinations occur

Viscoelastic

most biologic tissue -tissue the represents both viscous and elastic properties -possess time-dependent or rate-sensitive stress-strain relationships viscous-permit time-dependent plastic or permanent deformation Elastic- elastic or recoverable deformation, allows for rebound to the previous size, shape and length

slide (joint movements)

one point on the moving joint surface contacts various points on the opposing joint surface `

roll and spin is restored by

passive range-of-motion procedures that iduce the arthrokinematic movements of the dysfunctional joint

roll (joint movements)

point on the surface of one bone contact points at the same interval of the other bone

Maximal loose-packed position

resting or neutral position when the joint capsule is most relaxed and the greatest amount of joint play is possible -When injured, a joint often seeks this maximum loose-packed position to allow for swelling

manipulative (thrust) techniques are needed to...

restore SLIDE movements and can ALSO be used FOR ROLL AND SPIN problems

spine (joint movements)

rotational movement around the mechanical axis -possible as pure movement only in the hip, shoulder, and proximal radius

mechanics

study of forces and their effects

biomechanics

the application of mechanical laws of living structures, specifically to the locomotor system of the human body

Close-packed position

the position of maximal joint congruency (close to the end range of motion) -Most ligaments are taut and there is maximal contact between the articular surfaces making the joint very stable and difficult to move or separate -A joint moving towards its close-packed position is undergoing compression

ergonomic science

the study of people in relation to their job includes: environment aspects of the workplace temperature, light, noise, adequate airflow, and they physical arrangement of the workplace

kinetics

the study of the relationship between the force system acting on a body and the changes it produces in body motion

ligament crimping

this s a shock-absorbing mechanism ligaments have which contributes to the flexibility of the ligaments

tension:

when a structure is stretched longitudinally. -Tensile loading is a stretching action the created equal and opposite loads outward from the surface and tensile stress and strain inward. -Tensile forces tend to pull structures apart decreasing the cross-sectional area -When a material is stretched in the direction of a pull, it contracts in the other two directions 1* force is tensile = 2* stress is compressive (and vice versa)