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Introduction to EMG & EMG guided manual therapy of lumbar spineSatyajit MohantyMSPT,MIAP, MHPC (UK)Senior Physiotherapist

Recovery Physiotherapy center

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Place of EMG as a investigating tool


Classifying MSK presentationsTo identify the source of MSK pain, patient's pain pattern is categorized either into Nonspecific pattern OR into one of 4 recognizable pathway patterns 1. Radicular 2. Dorsal ramus 3. Polyneuropathy 4. Sympathetic


How MSK conditions are investigated?

After having roughly identified the origin of Pain, investigations are carried out to confirm the source of pain. Investigative strategies in musculoskeletal sciences takes a comprehensive approach called THE PHYSIO-ANATOMIC APPROACH

Though function & structure are inseparable aspects of existence, physiological properties & structural integrity of the faulty tissues are separately studied in this approach.


THE PHYSIO-ANATOMIC APPROACH

The physiological approachBoth invasive & non-invasiveExample: EMG, NCV, biothesiometry etc The anatomical approachBoth invasive & non-invasiveExample: X-ray, CTscan, MRI,Diskography-enhancedcomputed tomography


Question 1: Why we are discussing investigative strategies?Investigative data can provide baseline data

This investigative data can be compared to normative data, which indicate the status of the condition

If these studies are permitted for intermittent assessment, then they provide crucial information on progression of the disease status

Real time information: Many times you can observe what is happening while you are actually performing a therapy. Thus recently real time ultrasound & EMG is used to guide treatment in rehabilitation.


Question 2: Whether it is permitted to employ EMG in the context of studying & guiding manual therapy?Physicians have been vehemently protesting EMG use by physiotherapists till 2005. One can check the stance of american acedamy of family physicians14. However, the next recommendation by Braddock et al (2007); Manual medicine guidelines for musculoskeletal injuries, National guideline clearinghouse (USA)7 electrodiagnostic studies for the application of manual therapy are indicated under following diagnostic circumstances: 1. Persistent neurological symptoms2. Conditions non-responsive to conservative care requiring determination of the severity of the deficit


* This recommendation (Braddock et al, 2007) remain silent about those studies involving real time EMG changes of electrodiagnostic parameters from manual therapy point of view.

* However EMG has been a common tool to numerous researchers for measuring muscle function before, during & after variety of procedures including manual therapy procedures.


Performing & interpreting Paraspinal EMG


Question 3 How the EMG is performed & interpreted?EMG: An electromyograph detects the electrical potential generated by muscle cell when these cells contract, and also when the cells are at rest. 2 types of EMG are there : Needle electrode guided & surface electrode guidedIn needle EMG only a small number of fibers are amenable but in sEMG much more area is exposed to the study


Surface & needle EMGs


EMG studies reveal normal muscle membrane potential is about -70mV with a frequency of discharge 720 Hz. EMG variables changes depending on the size of the muscle (eye muscles versus gluteal muscles), previous axonal damage, muscle damage and various other factors. The membrane potential in damaged motor units is expected in ranges between 450 and 780 mV13.


Focus of our discussion is surface EMG guided manual therapy of lumbar spine. In surface EMG guided lumbar area manual therapy the target muscles are the lumbar paraspinals. Hence the next question is.


Question 4 What is the difference between a paraspinal muscle EMG & EMG of other muscles like Tibialis anterior ?

EMG can be done in any skeletal muscle. In most situations (diagnostic situations) muscles innervated by ventral root is investigated (For example in L4-L5 disc prolapse cases the Tibialis anterior are studied who are innervated by ventral roots). But paraspinals are innervated by the dorsal roots of a corresponding spinal level. Hence the most fundamental difference lies in the anatomic root of stimulation. (see the following diagram)Second point is Tonic (paraspinal) versus Phasic muscle (tibialis anterior)


Typical spinal nerve


Question 5 Can we study lumbar spine dysfunction via paraspinal EMG?

Muscle is a informer of joints - EMG of the muscles where there is intrinsic pathology or defective nerve supply will reveal abnormal picture. More to that we can study different loading patterns, spasms in muscles via an EMG. Surface electromyography, (sEMG) has been used as a research tool to evaluate the performance of paraspinal muscles in patients with back pain and to further understand the etiology of low back pain11,12.


Example of Paraspinal EMG as an indicator of Lumbar dysfunction

a.Lumbar erector spinae flexion-relaxation phenomenon (FRP)

b.Thoracolumbar myoelectric asymmetry (TMA)


FRPFRP refers to electrical silence as recorded in EMG during trunk flexion. FRP leads to increased load sharing on passive structures and is a source of low back pain1. Loss of flexion/relaxation correlates with diminished pressure pain thresholds2.

A number of EMG studies have shown differences in the FRP between patients with chronic low back pain and healthy individuals.


TMASignificant myoelectric differences are reported in thoracolumbar myoelectric activity of involved & uninvolved sides of the back pain.

sEMG also shows contralateral responsivity i.e. increased myoelectric activity in opposite the side of leg pain. Hence EMG technique could be used to detect muscle dysfunction related to LBP. However research of sEMG correlations with measures of the manipulability of a lesion is sought.


Comparison of right & left paraspinal activity with a right sided LBAFollowing diagram shows prolonged muscle activity pattern of the upper lumbar paraspinals (the first is right side & the lower one is the left side) in a degenerative PID of L2-L3 discs. The sharp burst of muscle activity corresponded directly to heel strike of stance phase during ambulation.


Scheme of conducting an EMG for back muscles to assess back muscle impairment

1. The electrodes are strategically placed at specific anatomical locations corresponding to contralateral and ipsilateral paraspinal muscles. 2. Differences in the variable mapped at the beginning and end of a fatigue-inducing contraction are analyzed to assess impairment.

3. Muscle contractions are submaximal constant-force isometric contractions in which the duration of the contraction is predetermined.


Which EMG parameter (variable) is more indicative?Recent researchers are more concerned about frequency rather than amplitude of the signal.

Explanation

During sustained contractions, the EMG signal propagates at a slower velocity and undergoes an alteration in shape (De Luca CJ, 1985). This is called "myoelectric manifestations of fatigue" and are typically measured during a contraction as a decrease in the median or mean frequency (MF) of the EMG signal.


Question 6 How much reliable is the EMG measurements in lumbar paraspinals?

Within-day reliability for control subjects tested in the BAS (back analysis system) result in low (2% -6%) errors.

Between-day variability is low performed 5 days apart. (Thompson and Biedermann)

Which is the more reliable lumbar paraspinal for EMG study?: Thompson and Biedermann reported large & positive correlation coefficients (within a range of .75 to .96) for frequency values recorded from the multifidus and iliocostalis muscles. However, reliability of frequency measurements is consistently higher for the iliocostalis muscle than for the multifidus muscle.


The multifidus & Iliocostalis muscles: Lumbar area muscles for EMG studies


Source of variability of paraspinal surface EMGAccording to Roy et al & Thompson DA et al the source of measurement variability are: Electrode placement accuracy: Errors in relocating the electrodes at the same site when repeating a test. Crosstalk: Inability to completely isolate EMG signals from a single muscle. The amount of crosstalk between adjacent erector spinae muscles has been estimated using crosstalk index. Crosstalk index is the ratio between the amplitudes of the EMG signals recorded from the non-stimulated and stimulated muscles. Crosstalk index is in the range of 6% to 7%.


Studies of EMG guiding Lumbar spine manual therapy


The final & the most important questionQuestion 7 Can EMG be employed to evaluate effectiveness of lumbar spine manual therapy?


Being one the most popular treatment modality for lower back conditions, manual therapy has not been sufficiently researched on objective physiological yardsticks like EMG & NCV studies. However, recently many researches have poured in that validates EMG studies especially the real-time EMG, as a manual therapy guide. In the following section we are presenting studies in lumbar spine manual therapy with EMG as a variable. We will be discussing 3 studies which has real time EMG monitoring with lumbar spine manual therapy application.


Study 1 (A real time EMG study)Colloca et al (2001) investigated dynamic stiffness measurements (force/velocity) & concomitant neuromuscular response to extract more information concerning mechanical properties of the low back. This is the first study that demonstrate neuromuscular reflex responses associated with manually assisted spinal manipulative therapy in patients with low back pain.


Colloca et al employed surface EMG recordings obtained from electrodes (8 leads) located over the L3 and L5 paraspinal musculature to monitor the bilateral neuromuscular activity of the erector spinae group during the PA thrusts.

Results:

1. Increased spinal stiffness index and positive neuromuscular reflex responses in subjects with frequent or constant LBP as compared with intermittent or no LBP.


2. Thrusts applied over the transverse process produce more positive EMG responses in comparison with thrusts applied over the spinous processes.

3. Left side thrusts and right side thrusts over the transverse processes elicit positive contralateral EMG responses. 4. Patients with frequent to constant low back pain symptoms tend to have a more marked EMG response in comparison with patients with occasional to intermittent low back pain.


Conclusion:This study concluded identification of neuromuscular characteristics, together with a comprehensive assessment of patients clinical status, may provide for clarification of the significance of spinal manipulative therapy in eliciting accepted conservative therapeutic benefits.


Study 2 (A Real time study)In clinical situations, many times, posterior spinal exercises are co-prescribed with manual therapy or as maintenance therapy of achieved therapeutic goal.

Investigators studying the effects of back exercise on EMG spectral parameters found these parameters to be sensitive to back muscle adaptations.

However there are no studies that substantiate that spinal manipulative therapy (SMT) may help augmenting the effects of these exercises. It is also less researched what is the appropriate time to implement spinal exercises after SMT.


By an EMG guided study Keller et al (2000) investigated whether lumbar spinal manipulative therapy (SMT) affects its paraspinal muscle strength on 40 subjects.

The results of this study demonstrated that SMT results in a significant immediate increase in sEMG erector spinae isometric MVC (maximal voluntary contraction) muscle output.

Hence this altered muscle function may only be a potential short-term therapeutic benefit of SMT. This effect should be exploited in clinical set ups.


Study 3 (A real time study)Bertolucci LF displayed his work at 1st facsia research congress Howard medical school, Boston, 2007. His work was later on published in journal of body & movement therapy, 2008. Bertoluccis original work was on cervical area but currently he has extended his research to lumbar area (ref:http://www.youtube.com/watch?v=HLk_wMK0Ecg ).His work revolves around recording of EMG signals coming from paraspinals muscles during his self styled myofascial treatments.


Working on a specific mode of manual therapy called muscle repositioning he found post manual therapy paraspinal EMG pattern mimics pandiculation.

What is pandiculation?We like to stretch our whole body after getting off the bed which usually comes with a yawning. This according to modern neuroscientists leads to muscle realignment which further leads to axial & apendicular joint alignment & stability. According to Fraser & Walusinski pandiculation has a role in the development and maintenance of the musculoskeletal system.


Pandiculation


What Bertolucci reports while performing muscle repositioning?

Real time Paraspinal EMG activity revealsa. Progressive isometric activity of the lumbar erectors. Spreading of EMG activity away from the immediate recipient area which feels like a bipolar expansion in the bodys longitudinal axis. There seems a segmental integration of different body segments mimicking pandiculation. b. Firmer the feel to the clinicians hand, the higher the EMG signals i.e.: the degree of firmness is possibly related to the intensity of the tonic reaction.c. It is also noted that firmer the feeling to the touch, the more effective the maneuver.


Hence it is supposed that clinical efficacy of the maneuvers is related to the tonic reactions (a neural reflex) during the clinical practice is a desired clinical effect. Hence Bertolucci considers detecting EMG activity during the maneuvers, brings a high degree of objectivity to the procedure under execution.


Conclusion:EMG recording could be used to guide & monitor appropriateness of manual touch & manual therapy procedures so that they could be more precise, objective & reproducible. Hence in articular or motion directed therapies, muscle function via EMG monitoring becomes essential.


References1. Colloca CJ et al; The biomechanical and clinical significance of the lumbar erector spinae flexion-relaxation phenomenon: a review of literature; J Manipulative Physiol Ther. 2005 Oct;28(8):623-31. 2. Leach RA et al; Correlates of myoelectric asymmetry detected in low back pain patients using hand-held post-style surface electromyography; J Manipulative Physiol Ther. 1993 Mar-Apr;16(3):140-9. 3. Morningstar MW et al (2006); Improvement of lower extremity electrodiagnostic findings following a trial of spinal manipulation and motion-based therapy4. Colloca CJ et al; J Manipulative Physiol Ther.; Stiffness and neuromuscular reflex response of the human spine to posteroanterior manipulative thrusts in patients with low back pain. 2001 Oct;24(8):489-500. 5. Colloca CJ et al; Electromyographic reflex responses to mechanical force, manually assisted spinal manipulative therapy, Spine (Phila Pa 1976). 2001 May 15;26(10):1117-24.


6. Keller TS et al; J Manipulative Physiol Ther. 2000 Nov-Dec;23(9):585-95. Mechanical force spinal manipulation increases trunk muscle strength assessed by electromyography: a comparative clinical trial.7. Manual medicine guidelines for musculoskeletal injuries (Reference: http://www.guideline.gov/summary/summary.aspx?ss=15&doc_id=10798&nbr=5626)Braddock E, Greenlee J, Hammer RE, Johnson SF, Martello MJ, O'Connell MR, Rinzler R, Snider M, Swanson MR, Tain L, Walsh G. Manual medicine guidelines for musculoskeletal injuries. California: Academy for Chiropractic Education; 2007 Apr 1. 33 p.8. Roy SH et al, Journal of Rehabilitation Research and Development Vol . 34 No . 4, October 1997 Pages 405-414. Classification of back muscle impairment based on the surface electromyographic signal. 9. Bertolucci LF et al, J Body Mov Ther. 2008 Jul;12(3):213-24. Epub 2008 Jul 7.10. Oddsson et al; Physical Therapy; An investigation of the reliability and validity of posteroanterior spinal stiffness judgments made using a reference-based protocol, aug 1998. 11. Greenough et al;Assessment of spinal musculature using surface electromyographic spectral color mapping. Spine 1998;23:768-74 12. DeLuca CJ; Use of the surface EMG signal for performance evaluation of back muscles. Muscle Nerve 1993;16(2):210-16 13. http://encyclopedia.thefreedictionary.com/electrodiagnostic14.http://www.aafp.org/online/etc/medialib/aafp_org/documents/policy/state/emg.Par.0001.File.tmp/stateadvocacy_EMG.pdf


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