KINESIOLOGY FOR ORTHOPEDICS

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INTERVERTEBRAL DISK BASIC SCIENCE
Richard E. Hughes, Ph.D. Orthopaedic Research
Laboratories University of Michigan
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OUTLINE

• Disk structure
• Anatomy
• Biochemistry
• Disk biomechanics
• Disk degeneration
• Disc herniation

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OUTLINE

• Disk structure
• Anatomy
• Biochemistry
• Disk biomechanics
• Disk degeneration
• Disc herniation

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ANATOMY
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ANATOMY
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ANATOMY
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ANATOMY
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ANATOMY
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ANATOMY
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OUTLINE

• Disk structure
• Anatomy
• Biochemistry
• Disk biomechanics
• Disk degeneration
• Disc herniation

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BIOCHEMICAL COMPOSITION

• Collagen
• tensile strength
• 70 dry weight of outer annulus
• lt20 dry weight of nucleus in young
• Proteoglycans
• stiffness, resistance to compression, and
  viscoelasticity
• 3 dry weight of outer annulus
• 50 dry weight of nucleus of young

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COLLAGEN
Eyre, D.R. and Muir, H. (1977) Biochimica et
Biophysica Acta 49229-42
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OUTLINE

• Disk structure
• Anatomy
• Biochemistry
• Disk biomechanics
• Disk degeneration
• Disc herniation

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Ax CCW moment By CW moment
x, y are moment arms
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SPINAL LOADING

• Lifting carbon pieces out of smelter
  electrochemical cell
• Pieces weigh 890 N (200 lbs)
• 3327 N (748 lbs) lumbar compression

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SPINE MECHANICS
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DISC CONTRIBUTION TOSEGMENTAL STIFFNESS
LOAD (Kgs)
x 0.01 mm displacement
Nachemson, A. (1962) J. Hosp. Jt. Diseases
23130-143
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INTER-DISCAL PRESSURE
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OUTLINE

• Disk structure
• Anatomy
• Biochemistry
• Disk biomechanics
• Disk degeneration
• Disc herniation

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DISK DEGENERATION
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DEGENERATION AND AGE
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AGING EFFECTS

• Anatomic
• Loss of disk height
• Protrusion of central disk into body
• Bulging or buckling of annulus
• Biochemical
• Fewer viable cells in nucleus
• Decreased proteoglycans and water in nucleus
• Collagen increases in nucleus

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NUCLEUS PROPERTIES
SHEAR MODULUS
Iatridis, J.C. et al. (1997) JOR 15318-322
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KINEMATICS

• L4-5
• 34 spines
• Disc degeneration graded on radiographic
  appearance
• F/E testing
• Instant center computed

Gertzbein, S.D. et al. (1985) Spine 10257-261
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B
C
A
D
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B
C
A
D
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KINEMATICS

• L4-5
• 34 spines
• Disc degeneration graded on radiographic
  appearance
• F/E testing
• Instant center computed

Gertzbein, S.D. et al. (1985) Spine 10257-261
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KINEMATICS
NORMAL
MILD
SEVERE
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OUTLINE

• Disk structure
• Anatomy
• Biochemistry
• Disk biomechanics
• Disk degeneration
• Disc herniation

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DISK HERNIATION
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BIOMECHANICS
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THANK YOU
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COLLAGEN

• Annulus
• 60 Type II and 40 Type I
• 10 Type VI
• 3 Type V and XI
• Nucleus
• 80 Type II and no Type I
• gt15 Type VI
• 3 Type V and XI
• Heavily cross-linked

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EM OF PROTEOGLYCANS
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DISK DEGENERATION
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OUTLINE

• Disk structure
• Anatomy
• Biochemistry
• Disk biomechanics
• Disk degeneration

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ANATOMY
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DEGENERATION THEORIES

• Reduced nutrient transport
• Decreased viable cells
• Cell senescence
• Apoptotic debris
• Loss of proteoglycans
• Fatigue failure of matrix
• MMP degradation of matrix