Monday, November 2, 2009

Viewing lumbar spine manual therapy from Lumbar paraspinal muscle EMG perspective

Introduction to approaches to investigating strategies in musculoskeletal conditions

The approach is a comprehensive approach called physioanatomic approach that combines both anatomic approaches & physiological approach of investigation. Either the patient's pain pattern is categorized into a nonspecific pattern or into one of 4 recognizable pathway patterns i.e. radicular, dorsal ramus, polyneuropathy, and sympathetic.
The goal of anatomic component of physioanatomic (both noninvasive and invasive) evaluation is to increase specificity by differentiating pain generators from asymptomatic underlying pathologic conditions. The physiologic component deals with function, reactivity & responsiveness of the designated or speculated pathologic tissues.
There are 2 types of anatomic imaging approach i.e. invasive & noninvasive. Example of noninvasive anatomic imaging is computed tomography, single-photon emission-computed tomographic bone scan, and magnetic resonance imaging. The above said 3 tests have significant diagnostic accuracy in detecting pathologic conditions. Example of invasive anatomic approach diskography-enhanced computed tomography.
Physiologic approach also can be invasive & noninvasive, however common physiologic approach are EMG (surface & percuteneous), NCV, biothesiometry etc. In our context, we will discuss about “what EMG & NCV studies tell us on lumbar spine manual therapy”. Before-after EMG & NCV studies in connection with manual therapy of lumbar spine are rare. However we are trying to present following mini-review on this issue. Further we will try to present a case study of physioanatomic approach to see the changes in physiological & anatomical parameters by manual therapy administration.

Electro physiological studies for manual therapy applications: 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 circumstances:
1. Persistent neurological symptoms necessitating differentiation of radicular vs. peripheral neuropathy
2. Conditions non-responsive to conservative care requiring determination of the severity of the deficit
Pre and post changes of electrodiagnostic studies from prognostic & therapeutic effective-ness point of view are not considered by this recommendation.

I. EMG as an indicator of Lumbar dysfunction

a. Lumbar erector spinae flexion-relaxation phenomenon (FRP):
A number of EMG studies have shown differences in the FRP between patients with chronic low back pain and healthy individuals. Presence of the FRP during trunk flexion represents myoelectric silence. This 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.

b. Thoracolumbar myoelectric asymmetry:
Paraspinal surface electromyographic (SEMG) study reveals significant myoelectric differences between thoracolubmar myoelectric activity between involved & uninvolved sides of the back pain. It also shows contralateral responsivity i.e. increased myoelectric activity opposite the side of leg pain.
Hence this 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 warranted.

II. Basis of classification of LBA on EMG8,10

Historically, paraspinal muscle impairment has been quantitatively assessed by the use of dynamometers to supplement standard clinical assessment procedures (Roy SH, 1992). But once it is known that EMG can provide data about lumbar spine dysfunction the next question arises whether on the basis of EMG can LBA be classified? Persons with LBP often have reduced muscle strength and endurance, which may compromise the functional capacity of the spine and increase the likelihood of re-injury (Andersson, 1989). Hence an existing lumbar pathology reflects in muscle physiology of lumbar paraspinals.

Specific clinical correlation between the pathology & EMG of lumbar paraspinals has been studied by many researchers. Normative data in this context is also available8. Normative data of lumbar paraspinals for comparative purposes are of great help in classifying LBA cases. Many authorities are trying to classify LBA on assessments based on surface electromyographic (EMG) techniques to overcome some of the problems inherent in the use of dynamometers for back muscle evaluation and classification (Merletti R, 1994).

Recent approach of EMG variable is derived from the frequency rather than from amplitude of the signal. This is partly due to the fact that during a sustained contraction, the EMG signal propagates at a slower velocity and undergoes an alteration in shape associated with changes to the depolarization zone of the muscle membrane (De Luca CJ, 1985). These phenomena are referred to as "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.

Scheme of conducting an EMG for back muscles:

The performance state of the paraspinals muscles can be described by variables obtained from an array of EMG electrodes (De Luca CJ, 1993). Here is a description of how to conduct it

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

2. The issue of muscle performance objectivity the test is limited to the performance of submaximal constant-force isometric contractions in which the duration of the contraction is predetermined.

3. Furthermore, the useful information from the EMG signals is not derived from a single muscle group or a single parameter, but rather is the result of the concurrent behavior or mapping of many co-active muscle groups. It is hypothesized that the subject is likely to be unaware of, and cannot volitionally control, parameters derived from such a measurement scheme.

Roy et al used this method of EMG-based approach to assess and classify paraspinal muscle impairment in persons with LBP. An EMG device used to implement this technique, referred to as a Back Analysis System (BAS).

According to Oddsson et al (1998) basing on EMG initial results are promising for identification of 2 kinds of LBP impairments observed during constant-force isometric tasks:

(1) Excessive fatigue due to muscle de-conditioning and
(2) Inhibition of muscle activation secondary to pain or pain-related behaviors.

Classification procedures used to identify such impairments on the basis of EMG spectral measures have relied primarily on discriminant analysis methods. Hence newer and possibly more effective techniques are described as an area for future development10.

How much reliable is the EMG measurements in lumbar paraspinals?8

Reliability of measurements obtained for EMG variables such as the frequency of EMG signals from paraspinal muscles during isometric trunk extension has been investigated by many researchers.

1. Within-day reliability for control subjects tested in the BAS (back analysis system) resulted in 2% -6% errors.
2. Between-day variability performed 5 days apart (Thompson and Biedermann) reported correlation coefficients within a range of .75 to .96 (large & positive) for frequency values recorded from the multifidus and iliocostalis muscles.
3. Thompson and Biedermann reported reliability of frequency measurements consistently higher for the iliocostalis muscle than for the multifidus muscle.

Some other researchers (Roy et al & Thompson DA et al) have identified source of measurement variability. Following two points are pointed out by them as sources of variability.
1. Electrode placement accuracy: Errors in relocating the electrodes at the same site when repeating a test.
2. Crosstalk: Crosstalk is a source of measurement variability because surface EMG techniques do not completely isolate EMG signals from a single muscle. The amount of crosstalk between adjacent erector spinae muscles has been estimated using a technique in which EMG electrodes are placed on the contralateral muscle and only one muscle is electrically stimulated.

* 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%.

III. EMG studies indicating effectiveness of manual therapy:
Manual therapy is one of the most popular treatments for lower back conditions. Famous task forces on low back pain such as Quebec task force have emphasized more on strengthening of back muscles than manual therapy. Being one the most popular treatment modality for such conditions, one is forced to consider that manual therapy has not been researched on objective physiological yardsticks like EMG & NCV studies. However, recently many more researches are pored into this area so that the picture is getting clearer day by day. In the following section we are trying to present a picture of studies in manual therapy with EMG variable. We have provided examples of 4 studies first two studies are exploratory studies where as later two studies are clinical studies.
Colloca CJ et al reported consistent, but relatively localized, reflex responses occurred in response to the localized, brief duration MFMA (mechanical force-manually assisted) thrusts delivered to the thoracolumbar spine and SI joints. These authors also reported, overall, 20 treatments produce systematic and significantly different sEMG responses, particularly for thrusts delivered to the lumbosacral spine4,5.
Most of the therapeutic assessment and treatment movements in spinal manual therapy are identical. SPAM, is not only used for assessment but SPAM is commonly utilized to teat lumbar pain & restriction with or without referred pain. Detection of neuromuscular reflex responses during the maneuver may serve to guide an efficient & very objective treatment delivery. Neuromuscular reflex responses also imply progression & changes in the condition by the imparted module.

Study 1: Colloca et al (2001) investigated dynamic stiffness measurements (force/velocity) and concomitant neuromuscular response to extract more information concerning mechanical properties of the low back. This is the first study that demonstrated neuromuscular reflex responses associated with manually assisted spinal manipulative therapy in patients with low back pain4,5.
Little objective evidence is available concerning variations in PA stiffness and their clinical significance. Manually assisted spinal manipulative therapy is based on commonly assessed objective data like SPAM (spine PA movement) TPAM (transverse process posterior anterior movement) to assess spinal stiffness. However SPAM has been reported to vary with spinal level, body type, and lumbar extensor muscle activity during spinal stiffness assessment. But it is easy to discriminate asymptomatic and those who have low back pain on this4,5.
Hence Colloca et al employed surface electromyographic (sEMG) 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. This study is the first to assess erector spinae neuromuscular reflex responses simultaneously during spinal stiffness examination4,5.
This study by Colloca et al demonstrated increased spinal stiffness index and positive neuromuscular reflex responses in subjects with frequent or constant LBP as compared with those reporting intermittent or no LBP. Some other findings include4,5
1. Thrusts applied over the transverse processes produced more positive sEMG responses in comparison with thrusts applied over the spinous processes.
2. Left side thrusts and right side thrusts over the transverse processes elicited positive contralateral sEMG responses.
3. Patients with frequent to constant low back pain symptoms tended to have a more marked sEMG response in comparison with patients with occasional to intermittent low back pain.
Hence Colloca et al concluded identification of neuromuscular characteristics, together with a comprehensive assessment of patient clinical status, may provide for clarification of the significance of spinal manipulative therapy in eliciting putative conservative therapeutic benefits in patients with pain of musculoskeletal origin4,5.
Study 2: On clinical situation most of the times the 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 parameters to be sensitive to back muscle adaptations. However there are no studies that substantiate that manually-assisted (MFMA) 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 MFMA SMT.

Keller et al investigated whether mechanical force, manually-assisted (MFMA) spinal manipulative therapy (SMT) affects paraspinal muscle strength assessed through use of surface electromyography (sEMG) on 40 subjects grouped into 3 (1 active treatment group and 2 control groups). The results of this clinical trial demonstrated that MFMA SMT results in a significant increase in sEMG erector spinae isometric MVC (maximal voluntary contraction) muscle output6. Hence these findings indicate that altered muscle function may be a potential short-term therapeutic effect of MFMA SMT.

This study goad researchers for a randomized, controlled clinical trial to further investigate acute and long-term changes in low back function6. It also creates interest in keen researchers to explore the short & long term effects of addition of isometric back muscle contractions immediately after MFMA SMT.

Study 3. A chiropractic case study by Morningstar MW et al (2006): Lumbar disc herniation is a problem frequently encountered in manual medicine. While manual therapy has shown reasonable success in symptomatic management of these cases, little information is known how manual therapy may affect the structure and function of the lumbar disc itself. In cases where lumbar disc herniation is accompanied by radicular symptoms, electrodiagnostic testing has been used to provide objective clinical information on nerve function3.

Case Presentation by Morningstar et al
An elderly male patient presenting with right-sided foot drop had all sensory, motor, and reflex findings in the right leg and foot were absent due to lumbar disc herniation. This was validated on prior electromyography and nerve conduction velocity testing. Patient was treated using spinal manipulation twice-weekly and wobble chair exercises three times daily for 90 days total. Following this treatment, the patient was referred for follow-up electrodiagnostic studies. Significant improvements were made in these studies as well as self-rated daily function3.

Hence the authors have concluded that motion-based therapies, as part of a comprehensive rehabilitation program, may contribute to the restoration of daily function and the reversal of neurological insult as detected by electrodiagnostic testing. Electrodiagnostic testing may be a useful clinical tool to evaluate the progress of patients with lumbar disc herniation and radicular pain syndromes3.

Study 4: Bertolucci LF et al 1st facsia research congress Howard medical school, Boston, 20079.

Bertolucci et al displayed their work at 1st facsia research congress Howard medical school, Boston, 2007. His work was further published in journal of body & movement therapy, 2008. His work revolves around recording of EMG signals coming from paraspinals muscles during his self styled myofascial treatments.

Working on a specific mode of myofascial release called muscle repositioning Bertolucci considers detecting EMG activity during the maneuvers, brings a high degree of objectivity to the procedure under execution. EMG recording could be used to guide & monitor appropriateness of manual touch & manual therapy procedures could be more precise, objective & reproducible.

References:

1. 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 therapy

4. 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.

*All Rights Reserved. No Parts Of This Publication Shall Be Reproduced, Stored In A Retrieval System, Or Transmitted, In Any Form Or By Any Means, Without The Prior Permission Of The Author.


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