Article Review

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Article Review Critique presented by Danielle
Holmes Mai Huong Ho-TranGraduate Studies in
Physical Therapy UCSF/SFSUPT 212 Muscle
Nerve Biology I II

• Effects of Low-Voltage Amperage Stimulation
• on Tendon Healing
• in Rats
• Chan HKF, Fung DTC, Ng GYF. JOSPT. 200737(7)
  399-403.

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Background

• LVMAS low current, prolonged duration
• Body has energy/currents, disruption of flow
  tissue damage/injury
• Use LVMAS to cause currents to flow normally ?
  tissue healing
• Lacks exp. studies from biomechanical outcome
  measures view

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Therapeutic Effects

• RATS
• Facilitates osteogenesis
• Regenerates nerves
• Epithelialization

• HUMANS (fibroblasts)
• ? ATP
• Promotes AA uptake
• Enhances protein synthesis
• --------------------------
• Intensities of 50-1000?A ? ? skin ulcers

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Purpose

• Examine effects of transcutaneous low-voltage
  microamperage stimulation on the mechanical
  strength of Achilles tendon repair in rats at 4
  weeks after injury

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Biomechanical Measures

• Strength of tendon healing
• Tensile Longitudinal Strength
• Load Relaxation
• Stiffness

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Methods

• Subjects
• Design
• Instrumentation
• Procedures
• Data Analysis

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Subjects

• N 14
• 3-month old Sprague-Dawley rats
• Male
• Average weight 381.4 grams

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Design

• Randomized controlled perspective experimental
  study
• Medial transection of Achilles tendon (mimic
  partial rupture)

1 experimental group LVMAS (IV) Rx
1 control group LVMAS Placebo

• Rx 2.5 V µA/cm², 10 pps, () current 30
  min/day, 6 days/week, 22 days

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Procedures

• Anode over site of injury
• Cathode 1cm above site of injury _at_ 25 w/ ()
  (-) pulsed current
• --------------------------------------------------
  
• Lateral band of Achilles tendon removed glued
  to 2 pieces of plastic

Mixed Signal Oscilloscope
Tendon
Extensometer MTS Synergy 200
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Biomechanical Testing

• Load Relaxation
• L1 (baseline) 10 oscillations of 2.5 strain
  for 10 mm/min
• Tissue elongated
• L2 2.5 strain for 5 min
• ?(L1 L2) x 100 LR
• L1

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Biomechanical Testing

• Tensile Strength / Failure Test
• Load tissue 500 mm/min
• Maximal load taken Ultimate Tensile Strength
  (UTS)

UTS
Time
Loading Capacity
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Biomechanical Testing

• Stiffness Slope (y mx b) prior to failure
  point (submaximal loading)

Stiffness
Time
Load Capacity
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Instrumentation

• LVMAS MICRO Plus Electrical Stimulator
• Biomechanical Life Systems, Vista, CA
• Oscillation Measures MS06014A Mixed Signal
  Oscilloscope
• Agilent Technologies, Santa Clara, CA
• Extensometer MTS Synergie 200
• MTS Systems Corporation, Cary, NC

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Data Analysis

• Values normalized by comparing to medial portion
  of normal (L) LE Achilles tendons
• Independent t tests with ? set at .05

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Results

• Tensile tendon strength (UTS) higher in
  experimental group (110.5 25) vs. control
  group (75.3 20.8) (P.014)
• No significant difference was found between
  groups for Stiffness (P.239) Load Relaxation
  (P.350)
• Results of transcutaneous study similar to
  implanted electrodes

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Results Explained!

• Greater tensile strength increased ability to
  perform movement
• Higher stiffness can hold load for a longer
  period of time before snapping
• Less Load Relaxation strong elastic property
  (not as saggy)

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Discussion ConclusionsLimitations

• Physiology
• Pathology
• Wound intensity
• Co-morbidities
• Pain perception
• Broken ruptured ends vs. clean surgical ends

• Skin impedence
• Electrode site
• Tissue sensitivity
• Dosage
• High microamperage
• Current, density, duration, continuous vs. pulsed

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Whos the real RAT?
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THANKS!Danielle Mai Huong