Electrical Stimulation to Augment Muscle Strengthening: Guidelines for Surgical Procedures, Diagnosis and Co-Morbidities

1
Electrical Stimulation to Augment Muscle
Strengthening Guidelines for Surgical
Procedures, Diagnosis and Co-Morbidities

• Tara Jo Manal PT, OCS, SCS
• Director of Clinical Services
• Orthopedic Residency Director
• University of Delaware Physical Therapy
  Department
• Tarajo_at_udel.edu 302-831-8893

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Properties of Electrical Stimulation

• Tara Jo Manal PT, OCS, SCS
• University of Delaware

3
Properties of Electric Stimulation

• Voltage
• Voltage represents the driving force that repels
  like charges and attracts opposite charges
• Current
• Current is the movement of charged particles in
  response to voltage
• Ampere represents an amount of charge moving per
  unit time
• The higher the voltage, the higher the current

4
Magnitude of Charge Flow

• Conductance
• Relative ease of movement of charged particles in
  a charged medium
• If the ease of movement is high, the resistance
  to movement is low
• Resistance
• Opposition to movement of charged particles
• Lower resistance provides greater
  comfort/tolerance by patient for higher intensity
  stimulation since less charge is needed to
  penetrate the skin

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Ohms Law

• I V/R
• Current increases as the driving force (V) is
  increased or as the Resistance (R) to movement is
  decreased
• As the skin resistance decreases, more of the
  current can flow, increasing the response

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Properties

• Impedance
• Opposition to alternating currents
• Higher frequency stimulation can pass with
  greater ease
• Impedance is the best word to describe resistance
  to flow in human tissue since it is comprised of
  the tissue resistance and the insulator
  (subcutaneous fat) effects of tissue
• Greater the impedance, greater the intensity
  required to achieve therapeutic goal
• High frequency stimulation is more comfortable
  because impedance is lower

7
Current Density

• Represents the intensity/area under a stimulation
  pad
• At fixed voltage
• smaller the electrode the greater the intensity
  of the stimulation compared to larger electrode
• Caution in setting intensity level with smaller
  electrodes or damaged electrodes
• Very high current density can be related to
  biological damage or burns
• Large electrodes
• Can the unit produce sufficient current intensity?

8
Current Modulation

• Timing
• Altering the time characteristics of stimulation
• Train
• a continuous, repetitive series of pulses at a
  fixed frequency

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Current Modulation

• Burst
• a package of train pulses
• delivered at a specified frequency
• e.g. 2 bursts per second

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Carrier Characteristics

• Carrier frequency
• Pulse duration is 1/f
• To increase pulse duration to improve muscle
  force output you would decrease the train
  frequency
• 2000Hz 1/2000 or 500?second pulse duration
• 1000Hz 1/1000 or 1000?second (1 millisecond)
  pulse duration

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Frequency and Pulse Duration
If the f is 5 Hz or 5 cycles/second The duration
is 1/5 or 20milliseconds
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Pulse Duration

• Increases recruitment of motor units
• Improves the muscle contraction
• Often labeled width or pulse width

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How to Achieve High Force

• Activate more motor units (recruitment)
• Drive the motor units more quickly (Rate coding)

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NMES Increasing Recruitment

• How to recruit more motor units electrically?
• Increase recruitment via
• ? phase charge
• How to increase phase charge
• Increase amplitude
• Increase pulse duration
• Or BOTH

Phase Charge
Mixed Nerve
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Frequency

• Increasing frequency
• Tetanic contraction
• Force production reaches a plateau maximum
  between 50-80 pulses per second
• For muscle strengthening you want 50-80
  pulses/second or 50-80 bursts/second

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Frequency Controls

• Usually labeled Rate or Pulse Rate
• Set the number of pulses (or AC cycles) delivered
  through each channel per second
• As frequency is increased, impedance is decreased

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NMES Increasing frequency

• How to achieve high force
• Rate Coding
• Increase the frequency of stimulation
• But increased frequency ? increased fatigue

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Quality of Contraction

• Goal strong tetanic contraction
• Stimulation frequency 50-80 pps

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Understanding the Manuals

• Presets
• Advantages Disadvantages
• Adjustable Controls
• Waveform Selection
• Amplitude Controls
• AC generally have a maximum of 100 200mA
• Independent vs. Shared amplitude control for
  multiple channels

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Cycle time controls

• On Off Time
• Duration of stimulation and rest
• Rest time dependent on goal of treatment
• Strengthening- Adequate rest to avoid fatigue

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Ramp Controls

• Controls the rate the amplitude increases
• Provide for more comfortable onset and cessation
  of stimulus when very high levels of stimulation
  are required
• Can adjust if contraction is coming on too
  quickly or stopping too quickly

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Waveform type

• Waveform
• Patient dependent
• Delitto Rose PT 1986
• UD PT Clinic
• Versastim
• Empi

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Stimulation Parameters

• What can we modify?
• Pulse Duration
• Pulse Frequency
• Waveform type
• Off time (time between contractions)
• Ramp time

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Stimulator Controls

• Programmed Stimulation Pattern Controls
• Found on various stimulation devices, mostly
• Can be limiting, if user is unable to program
  stimulation patterns for a specific application
• Output Channel Selection
• Simultaneous
• Alternate or reciprocal mode

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Line vs. Battery Powered
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Test The Unit
Empi 300 PV
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EMPI 300PV

• Empi 300PV
• 1-800-328-2536

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Dose of NMES

• Maximal tolerable current and device dependent-
  MVIC above blue line

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Dose of NMES

• Be sure your machine is capable of current
  necessary

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Test The Electrodes
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Electrodes

• How to improve the lifespan
• Proper storage
• Keep them moist
• Placed properly on plastic
• Improves conductivity

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Another Brand of Electrodes
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Same Intensity- Different Electrodes
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Electrodes

• Model F216
• Size 3 x 5
• 8 x 13 cm
• Rectangle
• Qty 2
• 1-800-538-4675

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Electrodes

• Reflex Tantone 624
• Ref EC89270
• Size 2in x 2in
• 5.08cm x 5.08cm
• Qty 4
• Tyco/Heathcare
• Unipatch
• 1-800-328-9454

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Tens Clean Cote

• Uni-Patch
• 1-800-328-9454
• Function
• Improves conductivity

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Pad Placement

• Typically include motor points of muscle of
  interest

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Pad Placement

• Relationship between Pad placement and current-
  Non-tetanic contraction

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Pad Placement

• Increase current, contraction becomes tetanic

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Treatment Administration

• Patient motivation factors
• Assist your patient in tolerating treatment
• Monitor
• set targets, watch output, give article
• Blunter
• wear headphones, towel over head, body relaxation
• (Delitto et al PT 1992)

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Give the Patient Control

• Self trigger if possible
• Therapist manually resuming stim
• Count down to the stim
• Explain to the patient the value of the modality

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What we do when things are not going well

• General
• Tens Clean Cote
• Change the waveform
• Decrease pulse duration
• may need to also increase the frequency for
  comfort

• Specific
• Increase ramp time
• Self trigger
• Increase rest time
• Only if you see them fatiguing drastically

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Evidence to support the clinical use of
electrical stimulation for muscle strengthening
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Increased Functional Load

• For muscle to hypertrophy and/or gain strength
  the overload principle of high weight at low
  repetitions is necessary
• Currier and Mann
• Looked at healthy male college students
• Utilized an intensity of at least 60 MVIC
  paralleling voluntary exercise protocols for
  functional overload
• Conclusion NMES and volitional exercise were
  equivalent training stimuli
• (Delitto,Snyder-Mackler, 1990)

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Increased Functional Load

• Kots
• Therapeutic efficacy reported for electrical
  stimulation greater than volitional exercise,
  when strengthening healthy muscle
• Intensity was 10-30 greater than MVC
• Strength gains of 30-40
• (Delitto,Snyder-Mackler, 1990)

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Increased Functional Load

• Conclusions on Overload
• Significant strength gains can be achieved in
  healthy muscle with an electrically augmented
  training program
• The intensity however needs to be extremely high
  (gt100MVIC)
• Electrical stimulation offers equivalent muscle
  strengthening effects to voluntary exercise in
  healthy subjects
• If intensity level parallels volitional exercise
  intensities
• (Delitto,Snyder-Mackler, 1990)

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Increased Functional Load

• Conclusion on Overload
• Lower loads may still help in muscle recovering
  from injury/surgery
• Most studies using subjects other than healthy
  male college students demonstrated greater
  strength gains in subjects training with NMES
  compared to volitional exercise alone
• (Delitto,Snyder-Mackler, 1990)

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Electrical Stimulation for Strength

• Snyder-Mackler et al., 1991
• Purpose To ascertain the effects of electrically
  elicited co-contraction of the thigh muscles on
  several parameters of gait and on isokinetic
  performance of muscles in patients who had
  reconstruction of the ACL
• 2 groups NMES volitional exercise
• Volitional exercise only
• Treatment intervention from 3rd to 6th week
  post-op

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Electrical Stimulation for Strength

• Snyder-Mackler et al., 1991
• Results
• Significantly greater average and peak torque of
  the quadriceps femoris at both 90/sec and
  120/sec in the NMES group
• No significant difference in performance of the
  hamstring muscles between groups
• Torque produced in the involved hamstrings
  averaged 80 of the strength in the uninvolved leg

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Electrical Stimulation for Strength

• Snyder-Mackler et al., 1991
• Conclusions
• The quadriceps muscles of these patients were
  stronger in the eighth post-operative week than
  reported averages for similar patients even years
  after surgery

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Electrical Stimulation for Strength

• Snyder-Mackler et al., 1995
• Purpose To assess the effectiveness of common
  regimens of electrical stimulation as an adjunct
  to ongoing intensive rehabilitation in the early
  postoperative phase after reconstructions of the
  anterior cruciate ligament

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Electrical Stimulation for Strength

• Snyder-Mackler et al., 1995
• Training Intervention 4 Groups
• High intensity NMES volitional exercise
• High level volitional exercise
• Low intensity NMES volitional exercise
• Combined high low intensity NMES volitional
  exercise

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Electrical Stimulation for Strength

• Snyder-Mackler et al., 1995
• High Intensity NMES
• 15 electrically elicited isometric contractions
• 2500Hz triangular AC current
• Burst rate of 75bps
• Amplitude to maximal tolerance
• Low Intensity NMES
• Portable electrical stimulation
• Pulse duration of 300 microseconds
• Frequency of 55pps
• Amplitude gt50mA to maximal tolerance
• 15 minutes 4 times/day

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Electrical Stimulation for Strength

• Snyder-Mackler et al., 1995
• High Level Volitional Exercise
• 3 sets of 15 repetitions of the quadriceps
  femoris
• Intensity was maximum effort for 8 seconds
• Visual Feedback provided
• High Intensity and Low Intensity Electrical
  Stimulation Combined
• All groups followed a standard volitional
  exercise protocol beyond the experimental
  treatment interventions

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Electrical Stimulation for Strength

• Snyder-Mackler et al., 1995
• At least 70 recovery of the quadriceps by 6
  weeks after the operation, vs. 51 in the groups
  that did not include high intensity stimulation
• High intensity electrical stimulation leads to
  more normal excursions of the knee joint during
  stance

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Electrical Stimulation for Strength
Snyder-Mackler et al, 1995 Conclusion For
quadriceps weakness, high-level NMES with
volitional exercise is more successful than
volitional exercise alone
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Modified NMES Protocol for Quadriceps Strength

• Fitzgerald et. al., 2003
• Subjects receiving the modified NMES treatment
  combined with exercise demonstrated greater
  quadriceps strength and higher ADLS scores than
  the comparison group

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Fitzgerald et. al., 2003

• Their data support the modified NMES protocol in
  clinics without access to a dynamometer
• Option of using a dynamometer
• Authors choose the high intensity NMES protocol

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NMES for Strength in the Early Post-op Phase

• Haug et al., 1988
• Purpose Efficacy of NMES of the quadriceps
  femoris during CPM following total knee
  arthroplasty
• CPM/NMES group
• Intensity at maximum tolerance
• 3 times per day for 1 hour
• Pulse width 300 microseconds
• Frequency 35pps
• On 15sec off 20 seconds at 40 setting and 65sec
  at 90 setting
• Ramp time 2 seconds up and 1 second down
• CPM group

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NMES for Strength in the Early Post-op Phase

• Haug et al., 1988
• Results Stimulation group had significant
  reduction of extension lag, and spent fewer days
  in the hospital
• Intensity level was low compared to the other
  studies mentioned
• Conclusion Electrical stimulation combined with
  CPM in the treatment of patients with total knee
  arthroplasty is a worthwhile adjunctive therapy

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Role of Strength in Physical Therapy Management

• Strength losses can result in loss of the ability
  to perform activities of daily living
• Strength recovery following surgery is often
  incomplete
• Strength deficits can place patients at risk of
  further injury
• (Snyder-Mackler, 1991)

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Neuromuscular Electrical Stimulators

• Indication
• Muscular strength deficits
• lt80MVIC

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Neuromuscular Electrical Stimulation

• 2.5 KHz (400 microsecond pulse duration)
• 50-75 bursts per second
• 2-5 second ramp
• 12-15 seconds on, 50 - 80 seconds off
• Amplitude to maximal tolerance of patient
• With dynamometer feedback
• Minimum of 50 MVIC for ACL reconstruction
• Minimum of 30 MVIC for TKA

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NMES for Quad Strengthening
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Procedure Modified Rehabilitation
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NMES Post ACL Reconstruction

• Knee stabilized isometrically at 60 degrees of
  knee flexion
• Single Channel two electrode placement
• Below the AIIS
• Vastus medialis
• Target 50 MVIC
• Minimum Intensity

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Various Surgical Grafts

• Hamstring Autograft/Allograft
• Positioned at 60 of knee flexion
• Bone-Tendon-Bone Autograft
• Positioned in most comfortable angle
• flexion position gt 40

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NMES Post ACL Reconstruction

• Amplitude to minimum of 50 MVIC
• Patient encouraged to increase the intensity to
  maximum tolerated
• Dose-response curve demonstrates greater
  intensities lead to greater strength gains
• (Snyder-Mackler et al., 1994)

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NMES for Muscle Strengthening

• On time- sufficient for strong tetanic
  contraction 10-15 seconds
• Off time- sufficient for rest/recovery before
  next contraction 30-90 seconds
• Ramp time- as needed for comfort
• Dose- maximal tolerable (no less than that needed
  for strength gains to be seen)
• Frequency 2-3 times/week until strength recovers
• Average 18 visits

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NMES for Quadriceps Strengthening

• Following injury or surgery to the knee,
  quadriceps weakness can be major impairment
• We utilize electrical stimulation on all patients
  who demonstrate quadriceps weakness of 80
  involved/uninvolved ratio or less

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Post Operative Modification to ACL Protocol for
Other Knee Problems

• PCL 30 Knee Flexion
• MCL 30-60 Knee Flexion
• Meniscal Excision/ Repair None
• Chondroplasty None
• Post surgical intervention- follow soft tissue
  healing 8wks to protect surgical site or 12 weeks
  for bony healing

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Knee Flexion Angle

• If Pain if limiting toleration use most
  comfortable angle
• If Range of motion is limiting toleration use
  most comfortable angle
• As long as modification does not risk surgical
  procedure
• Perform with support from the referring physician

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Patellofemoral Joint Syndrome

• We perform burst superimposition testing on all
  PFJ evaluations
• Identify true maximal force generating
  capability
• Identify presence or absence of inhibition
• Central activation deficit
• NMES is performed at the most comfortable knee
  joint angle
• Tape is often applied for pain control
• When necessary, treatments to calm irritated
  structures are added

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Patellofemoral Joint Syndrome

• Joint angle adjusted to patient comfort
• Determined by volitional contraction
• Subluxing Patella
• Joint angle adjusted to increase congruency to
  prevent subluxation
• Greater than 70
• Patella taped medially

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Proximal-Distal Patellar Realignment

• Knee stabilized isometrically at 30 degrees of
  knee flexion
• Patella taped medially
• Electrodes over the proximal quadriceps/ distal
  pad is moved central and superior (avoiding the
  VMO)

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Proximal/Distal Realignment Precautions

• Initiate 1st Week of Treatment
• Precautions
• Proximal Realignment
• No MVIC for 8 weeks
• Proximal/Distal Realignment
• No MVIC for 12 weeks
• Dosage is maximal tolerable rather than MVIC

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Why NMES following TKA?

• Strength deficits can be profound
• Quad weakness decreased by 60 following surgery
• Impaired ability to perform ADLs
• Increased fall risk

Stevens et al JOR 2003
Wolfson et al 1995 J Gerontol A Biol Sci Med
Chandler et al 1998 Arch Phys Med Rehab
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Goal of NMES

• Quality muscle contraction
• Quantity sufficient enough to produce strength
  gains
• Strength gains reflect intensity tolerated
• Therefore
• Ultimate goal is to generate the greatest
  tolerable force output

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Total Joint Arthroplasty

• Amplitude targeted at a minimum of 30 MVIC
  (Snyder-Mackler et al., 1994)
• Ramp time, frequency adjusted to increase comfort
  and tolerance for higher intensity stimulation
• Modification of pulse duration by decreasing
  frequency to 2000Hz or 1500Hz (inc. pulse
  duration from 400 to 500 or 666 microseconds)

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NMES for Quadriceps Strengthening Cannot Do It
Alone

• Weakness can lead to compensation strategies for
  daily activities

COMPENSATIONS MUST BE PREVENTED!!!
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Compensation Strategies

• Unweighting involved leg for sit to stand

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Compensation Strategies

• Shifting weight in standing to uninvolved leg

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Compensation Strategies

• Not utilizing full extension during stance phase
  of gait

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Lack of use can lead to...

• Patellar baja
• Lack of superior patellar migration with
  quadriceps contraction
• Quad dysplasia

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Functional Use of Quadriceps

• Use of quadriceps during daily activities must be
  relearned in order to eliminate compensation
  strategies.
• If it gets to this pointyou are in a hole!

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Use of Strength in Daily Activities

• Composite overview of muscle performance
• Functional Testing
• Observation of compensatory patterns
• Avoidance patterns
• Lack of progress with a strengthening program
• Re-education in order to retain strength gains

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Case Report

• 17 y/o female soccer player 4 months s/p ACL
  reconstruction
• Quad Index (involved/uninvolved)
• Pre-operative 77 (533 N)
• 2 month post-operative 87 (601 N)
• 4 month post-operative 29 (200 N)

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Patient Examination

• KOS-ADLS 66 pre-operative
• 53 4 months post- operative
• Severe pain at infrapatellar tendon and medial
  border of patella
• Compensations to avoid use of involved leg with
  functional activities secondary to anterior knee
  pain

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Patient Examination

• No quadriceps inhibition with burst
  superimposition test
• Decreased superior migration of patella with quad
  set and superior patellar hypomobility

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Treatment Intervention

• Superior patellar mobilizations
• Pain control modalities
• Quadriceps strengthening
• Quadriceps re-education
• Biofeedback
• Education to avoid compensation strategies

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Quadriceps Re-education

• Two 4 x 6 inch pads over distal VMO and proximal
  bulk of quad
• Intensity maximum contraction patient can
  tolerate

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Exercises with Electrical Stimulation

• Sit to Stand

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Exercises with Electrical Stimulation

• Standing Terminal Knee Extensions

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Exercises with Electrical Stimulation

• Seated Knee Extensions

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Quad Index

• Pre-operative QI 77
• 2 month post-operative QI 87
• 4 month post-operative QI 29
• 6 months post-op (16 visits) QI 51
• 7 months post-op (28 visits) QI 72
• 8 months post-op (37 visits) QI 98

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Patients Strength Over Time
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Return to Soccer

• Progression
• Self-management
• Coaching support

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Rotator Cuff Strengthening

• Patient Position
• Involved arm belted to the body with the elbow at
  90 for isometric contraction
• Forearm is blocked to avoid rotation during the
  contraction

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Rotator Cuff Repair

• Parameters
• NMES Protocol
• Current Intensity Maximal tolerable with visible
  contraction causing movement of the arm against
  the restraint

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Achilles Tendon Repair

• Early Phase - Tendon Gliding
• 10days 4wks
• Modified surgical procedure (loop tightens under
  tension)
• Patient prone, knee resting in gt50 of flexion
  and ankle in full plantar flexion
• Single Channel on the
  medial/lateral gastroc
• Current Intensity
• Visible tendon gliding

102
Achilles Tendon Repair

• Late Phase Muscle Contraction
• gt10weeks post op
• Patient prone with knee extended and ankle in
  resting position
• Can increase to isometric against the wall

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Achilles Tendon Repair

• Current Intensity
• Look for visible contraction
• Maximal tolerable contraction by the patient
• Continue treatment until patient has full active
  plantar flexion

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Lumbar Rehabilitation

• Patient Positioning - Isometric Prone over
  pillows
• Pelvis strapped to the table in posterior pelvic
  tilt
• Assess movement to active lumbar extension and
  tighten as necessary

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Lumbar Rehabilitation

• High Intensity Electrical stimulation
• A single channel is placed on the right and left
  side of the spine

106
Lumbar Rehabilitation

• Look for visible contraction

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Current Intensity

• Maximal tolerable contraction by the patient

108
Thank You

• Noel Goodstadt PT, OCS, CSCS
• Laura Schmitt PT, DPT, OCS, SCS, ATC
• Airelle Hunter PT
• Faculty, Residents, and Staff at UD
• Patients who endure e-stim at UD
• Tarajo_at_udel.edu
• 302-831-8893
• www.udel.edu/PT/manal/estim