biomechanics lbp
TRANSCRIPT
8/2/2019 Biomechanics LBP
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Spine Biomechanics,
Intervertebral Disc &LBP
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Cervical Spine
Seven vertebrae – C 1-7
More flexible
Supports the head Wide range of motion
– Rotation to left and right
– Flexion Up and down
Peripheral nerves – Arms
– Shoulder, Chest and diaphragm
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Thoracic Spine
Mid-back or dorsal region
Twelve vertebrae
– T 1-12 Ribs attached to vertebrae
Relatively immobile
Peripheral nerves – Intercostal
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Lumbar Spine
Lower back
Five vertebrae
– L 1-5 Carries the the weight of the upper body
– Larger, broader
Peripheral nerves – Legs
– Pelvis
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Sacral and Coccygeal region
Sacrum
– Triangular structure
– Base of the spine – Connects spine to pelvis
– Nerves to pelvic organs
Coccyx – Few small bones
– Remnant of tail
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Lordosis
In the sagittal plane – ‘S’ shape
As a small child
– When starts to sit – Cervical lordosis
Toddler and adult
– When starts to stand
– Lumbar lordosis
– Allows spring-like action
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Compressive Strength of Spine
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Stress-Strain Curve
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Failure Strength of Spinal Ligaments
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Motion Segment
Two adjacent vertebrae
Intervertebral disc
Six degrees of freedom – Flexion-extension
– Lateral flexion
– Axial rotation
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Motion of Entire Spine
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Motion of Entire Spine
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Weight bearing properties of
motion segment unit
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Intervertebral Disc
Soft fibro-cartilaginous cushions – Between two vertebra
– Allows some motion
– Serve as shock absorbers
Total – 23 discs
¼ th of the spinal column's length
Avascular
Nutrients diffuse through end plates
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Intervertebral Disc Functions
Movement of fluid within the nucleus
– Allows vertebrae to rock back and forth
– Flexibility
Act to pad and maintain the space betweenthe twenty-four movable vertebrae
Act as shock absorbers Allow extension and flexion
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Intervertebral Disc Anatomy
Spongy center
– Nucleus pulposus
Surrounded by a
tougher outerfibrous ring
– Anulus fibrosus
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Annulus
In Bending
– Increased tensile force posteriorly
– Increased compressive force anteriorly
In Rotation
– Reorientation of collagenous fibers
– Tightening of fibers traveling in one direction
– Loosening of fibers traveling in oppositedirection
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Nucleus Pulposus
Has more water and PGs
PG are macro-molecules
– Attract and retain water – Hydrophilic gel –like matter
Resists compression
Amount of water
– Activity related
– Varies throughout the day
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Theory of weight bearing
Nucleus pulpous imbibes water
Develops internal pressure
Pressure exerted in all directions – Lateral forces
Against annulus
– Superiorly and inferiorly directed forces
Against end plates – Increases stiffness
Of end plate and annulus fibrosus
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Theory of weight bearing (cont’d)
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Mechanical Characteristics
Tensile stiffness of the disc annulus in different directionsHighest along – 150
Lowest along –
the disc axis
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Strength
Highest – Along normal direction of annulus fibers( 3 times stronger than that along horizontal direction)
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Stiffness Coefficients of IV disc
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Creep Characteristics
Grade 0 - Non-degenerative disc ( more viscoelastic)Grade 2 – Mild degenerative disc (less sustenance)
Grade 3 –
Severe degenerative disc ( more deformation)
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Shear & Tensile Characteristics
In direct shear tests
– Shear stiffness in horizontal direction
260 N/mm2
Spine rarely fails in pure shear Similarly under normal physiologic activities
– Pure tensile loading doesn’t occur
– But annulus undergoes tensile loading during
Bending
Axial rotation
Extension
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Compressive load characteristics
Cancellous bone
– Large deformation
Up to 9.5% before failure
Cortical bone
– Small deformation
Up to 2% before failure
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Measurements of In vivo Loads
Needle pressuretransducer
Calibrated
– Introduced into nucleuspulpous of cadavericfunctional unit
Inserted in vivo in L3-
4 disc
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Pathology of Intervertebral Disc Injury
Annular Injury – Annular rings
Softened
Overstretched Torn
– Normal viscoelasticity is exceeded
– Cannot stabilize or limit motion
– Nucleus pulposus exerts pressure on weak part
– Buckling occurs - Disc Bulge
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Pathology of Intervertebral Disc Injury
Extrusion
– Fragmentation of
nucleus pulposus – Nuclear material
dissects its waythrough breaches inannulus fibrosus
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Pathology of Intervertebral Disc Injury
Prolapses
– Fissures providepathway for irritating
nuclear fluid toescape ontoperineural tissue *
Persistent and chronicback pain
* - Hampton et al
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Back Pain
Pain is a protective mechanism
Nerve endings near the spine receive abnormalstimulation
Signals are transmitted from affected area to thebrain – They are interpreted as pain
A reflex action follows in the back
– Muscles go into spasm To protect the back
To keep the damaged area immobile
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Types of pain
Based on source – Mechanical
– Chemical
Based on affected region – Local
– Referred
Based on nature
– Transient – Acute
– Chronic
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Causes of LBP
Dysfunction
Predisposing factors
– Postural stress
– Work related stress
– Disuse and loss of mobility
– Obesity
– Debilitating conditions
Precipitating factors
– Misuse
– Overuse
– Abuse or trauma
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Examinations to locate back pain
Standing
– Observation and Palpation
Iliac crest
Posterior superior iliac spine (PSIS)
Anterior superior iliac spine (ASIS)
Spinous processes
Muscle tightness Gait
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Examinations of back pain
Movement Testing
– Forward bending
– Backward bending
– Lateral bending
– Rotation
– Leg extension and backward bending
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Forward bending
Hands are pushing inopposite direction
Tissues from skin tocentral core
– Elongate posterior – Compress anterior
Assessing lumbo-pelviccongruency – Palpation from cervical spine
to pelvis
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Back Examination
Nerve tension signs
Nerve compression signs
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Examination of back pain
Supine Testing – Passive hip flexion
– Faber position
– Straight leg raise (SLR)
– Force is directed to right femur
Posterior to anterior force directed to femur
– In flexed and vertical position
– Passive knee flexion in a prone position – Passive internal and external hip rotation
knee at 900 of flexion
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Passive hip flexion
Hip hyperflexed
– Lumbar spine flattened
Over 900 of flexion
Force transmission – To extensor of hip
Posterior rotarymovement on ilium
– Spinal flexion
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Straight leg raise (SLR)
Straight leg raised
Femoral flexion
Adduction
Internal rotation Increase in tensile
force – On sciatic nerve
Related to ischialtuberosity
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Phases of Treatment for
lumbopelvic disorders
Treatment of pain Modalities
Medication
– Support the region
– Biomechanical counseling / rest
Continue support
– Begin non-destructive movement
– Decrease destructive behavior
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Phases of Treatment for
lumbopelvic disorders (cont’d)
Discontinue support
– Begin proprioceptive and kinesthetic strength training
Neuromuscular efficiency
Dynamic stabilization
Establishment of limits Movement
Loads
Positions
Frequencies
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Treatment Options
Cryotherapy
Thermotherapy
– Superficial heating
– Deep Heat
Injection Therapy & Soft tissue injections
Electrotherapy – Transcutaneous electrical nerve stimulation
(TENS)
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Treatment Options (cont’d)
Manipulation
Traction
Massage Physical therapy and exercises
Acupuncture
Corsets and braces Surgerical treatment
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Scoliosis
A medio-lateralcurve of thevertebral column
Exceeding 10 0
– Types
Structural
Neuromuscular
Idiopathic
Non-structural
– Treatment
Exercises
Bracing
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Detection of Scoliosis
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Kyphosis
An exaggerated curvature in thesagittal plane
Long rounded curve(round back)
Sharp posterior angulation(hump back)
Possible causes
– Wedge compression fracture – Ankylosing spondylitis
– Senile osteoporosis
– Destructive tumors of spine
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Video on description of Spinal Column
http://www.spineuniverse.com/displayarticle.php/article1331.html