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8 Articles in Volume 5, Issue #6
Botox Treatment of Chronic Refractory Low Back Pain
DEA Enforcement versus Pain Practice
Group Psychotherapy for Chronic Pain Patients
How Expert Testimony Distorts the Standard of Care
Neurostimulation in Chronic Pain Patients
Physiological Consequences of Guided Imagery
The Role of Tertiary Gain in Pain Disability
Treating Muscular Dysfunction of Upper Limbs

Treating Muscular Dysfunction of Upper Limbs

A surface electromyography (SEMG) approach to the investigation of muscular dysfunction and rehabilitation of upper limb muscles.

Muscular dysfunction of the upper limb muscles—from an array of etiologies—is associated with pain.1 Those etiologies can be classified in several categories: neural, vascular, osteo-capsular, myofascial, muscular, traumatic (including repetitive motion and chronic fatigue), endocrine, psychosomatic or somatoform, immuno-deficient (including autoimmune), or mixed. The categories listed above are not exhaustive, but they encompass the most frequent conditions that a clinical pain practitioner may need to rule out. In addition, one may have to consider whether the pain pattern is derived from the structures of the upper limb or may be secondary to a referred pattern from the viscera, including anginal type of pain.

The discussion below will refer mainly to musculo-skeletal dysfunction pain and other symptoms related mainly to myofascitis and other related traumatic etiologies.

Muscle Pain

Pain in muscles is usually associated with abnormal electric patterns. In terms of the upper limb muscular dysfunction, there is frequently a history of repetitive motion followed sequentially by lack of adequate rest, fatigue, and pain. SEMG testing has helped to clarify a number of functional clinical observations in regards to the fatigue-pain continuum often associated with repetitive motion injury.

Repetitive motion injury of muscles of the upper limb is a historical phenomenon. It is interesting to note the evolution of such injuries in the industrial era from primary shoulder injuries to elbow injuries and the recent epidemic of wrist injuries with the advent of work with the keyboard.

Acute upper limb pain usually lasts less than 6-12 weeks. Sub-acute pain and recurrent pain may last beyond 12 weeks. Chronic pain is usually the result of delayed or unresolved healing and may last for several months or years, until the underlying condition is resolved. Chronic upper limb muscular or myofascial pain may lead in time to hyperalgesia and allodynia.1,2,3 Phantom limb pain is a neural phenomenon more commonly associated with traumatic amputation of the limb or parts thereof.

Effects of Trauma

In the case of trauma to one limb, that limb tends to undergo a ‘guarded’ or ‘splinted’ posture for several days or weeks. Commonly, the contra-lateral limb will offer ‘protective guarding’ for as long as necessary. The upper limb has distinct joint functions but functions also as a ballistic or postural myotatic vector, with all the muscles subtending the same action at one given time. It is comprised of four myotatic units: shoulder, elbow, wrist and hand. A number of muscles participate in more than one primary joint unit because of their anatomy. Brachioradialis is a case in point.

Unless the healing of the injured upper limb occurs within a very short period of time, one result may be the loss of strength of the myofascial unit or vector involved.

The overall conditioning level of the entire injured myotatic unit or vector will decrease over time, even over the space of a few weeks. The suffering muscle may become shortened and the adjoining muscles from the unit may start functioning at a suboptimal length. The affected joint may have to function at a reduced range of motion (ROM).4 The protective guarding activity involves not only the contra-lateral limb but also the muscles of the proximal and distal joints of the affected limb.

Over time, the functional changes, including the loss of strength (LOS) and the joint/ capsule range of motion (ROM) may contribute to the change in the spread of the neuromuscular cortical engram.5 Chronic muscular dysfunction and its pain harbinger may be associated with deleterious (negative, pathologic) neuroplastic changes until healing occurs.6

Evaluation and Diagnosis

The rehabilitation process of dysfunctional upper limb muscles needs to take into consideration a number of factors. These include, but are not exclusive to, the following: the diagnosis, current treatments, age, overall state of muscular conditioning, motivation to improve the overall muscular function to reduce pain, emotional make-up and emotional state, concurrent psycho-social, and familial change of roles related to the muscular dysfunction, and concurrent conditions.7

The evaluation of the muscular dysfunction and pain of the upper limb is done within the framework of a comprehensive physical examination.7 The next step involves the performance of objective assessments such as dynamometry for the measurement of the muscular strength and loss of strength (LOS). The ROM of the upper limb joints, i.e., the shoulder, elbow, wrist and hand is best measured with inclinometry according to established methods.4 Joint/ muscular proprioception needs to be assessed by semi-quantitative means, in comparison to the contra-lateral limb. The pain intensity may be assessed on a visual analogue scale, in a semi-quantitative fashion.8

The electrical potential changes associated with upper limb dysfunction, such as (electric potentials) spasm, hypertonus, hypotonus, co-contraction, co-activation, difficulty with control or achievement of the resting tonus, myokimia, fasciculations, loss of mirror image of segmental motions, utilization of increased numbers of contractile elements, fatigue (as evaluated by the use of the spectral analysis, median frequency), etc. can be achieved via the utilization of well documented dynamic protocols of surface electromyography (SEMG).9

“In general, the electric potentials pattern during movement through a classic joint ROM is such that more energy is expended by a dysfunctional muscle during any given motion, even if executed at the minimal level of effort.”

SEMG Modality

This electrophysiological modality has a dual application: (1) the investigation of the muscular dysfunction through motion and rest during the classic or functional upper limb ROM, and (2) the muscular re-education of the resting tonus and activity tonus of the dysfunctional muscles.

Both applications can be achieved by utilizing well established protocols, within the framework of the clinical presentation.7

This modality is rather unique in terms of the rehabilitation component: it is active. The healing process noticed peripherally on the upper limb muscles is related to the re-establishment of the neuro-motor engram and the positive neuroplastic process.

The availability of a database of the SEMG of the upper limb ROM of over 1,000 asymptomatic muscles, completed by the author, allows for a more focused and objective diagnostic and rehabilitative process.9,10 In addition to the SEMG amplitude potentials data of asymptomatic upper limb muscles, the author has compiled a similar data set for symptomatic upper limb muscles.10,11

In general, the electric potentials pattern during movement through a classic joint ROM is such that more energy is expended by a dysfunctional muscle during any given motion, even if executed at the minimal level of effort. The same pattern may be observed for the resting potential values. In other words, dysfunctional muscles need to use more contractile elements, therefore documenting an increased level of electric potentials on the SEMG amplitude domain.

This SEMG pattern has been observed in dysfunctional muscles of any part of the body to occur either during rest, during activity or during both states. The observation led to the empirical inquiry with the patients about their perception of the level of effort or difficulty of performance of different motions. Uniformly, the answers showed that there was a very high correspondence between the perception of effort or fatigue with repeated motion and the amplitude of the activity potentials on the screen for any muscle tested.

This response led to a reorganization of the sequence of joint ROM segments ‘from low to high’ in terms of overall muscular amplitude potentials values for both the investigative protocols and the rehabilitation protocols. Thus, for any given ROM protocol, the first segment became the one that required the least overall electrical effort of activity and the last segment of motion became the one that required the most effort.

Muscle Rehabilitation Considerations

It is well known that muscular fatigue usually precedes pain. The upper limb is usually subject to more repetitive motion than other parts of the body, therefore, by implication, more subject to fatigue and related pain. It can be shown that different muscles of the same myotatic unit contribute at different levels to the overall electrical level of energy consumption. This factor may be of great relevance in the program of rehabilitation or re-education of the upper limb muscles. The overall aim needs to be that of obtaining the most effective and efficient motion pattern, with the least muscular effort and fatigue.

The tables in the following sections represent the amplitude potential values of muscles from the myotatic units of the shoulder, elbow and wrist through the performance of the classic segments of ROM at the minimal level of conscious effort. The full extent of the data can be consulted in specialized texts and articles. The tables for the shoulder and wrist present only a limited number of muscles for illustrative purposes within the context of this article; the content and discussion of the hand muscles will be the subject of another article altogether. The main purpose of the author is to illustrate, in the present context, the organization and clinical manipulation of upper limb muscles in both the diagnostic and rehabilitative domains.

SEMG of Shoulder ROM

Table 1 represents the SEMG amplitude potentials of six shoulder muscles within the framework of performance of six shoulder segmental motions. You will note that the table has been organized in an overall amplitude potential (descending) ranking order from the muscle consuming most energy to the one consuming the least energy during the ROM performance. Thus, in this group the muscle that utilizes most energy during the shoulder ROM performance is the middle deltoid and the muscle utilizing the least is the pectoralis major. Overall, the ratio of energy consumption between the two muscles is almost 4:1.

SHOULDER ROM SEGMENTS
Muscle External Rotation Abduction Lateral Flexion Anterior Flexion Posterior Flexion Internal Rotation Average
Middle Deltoid 36.8 44.5 33.4 37.3 29.1 25.5 34.4
Anterior Deltoid 31.3 48.6 33.8 39.8 12.8 20.5 31.1
Posterior Deltoid 20.4 22.2 30.1 12.2 31 18.7 22.4
Rhomboid Major 29.3 14.3 22.1 26 17.3 18.7 21.3
Supraspinatus 22.9 22.1 26.5 15.7 15.1 18.7 20.2
Pectoralis Major 6.5 9.5 7.2 12.5 11.5 7.5 9.1

Table 1. Average SEMG Amplitude Potentials (µV RMS) of 6 Muscles Tested with SEMG through the Shoulder ROM Segments

When deciding the muscular retraining sequencing during rehabilitation for muscular dysfunction and pain of the shoulder muscles, the rehabilitative or even the re-education process should be structured to produce the least level of fatigue and pain in the patient.

Clinicians involved with SEMG/ biofeedback or neuromuscular retraining know that individuals more easily learn to control muscles that require less energy of motion and are less-easily fatigued.

Thus, the experienced SEMG clinician will logically make the choice of retraining the six shoulder muscles presented ‘from low to high,’ i.e., pectoralis major first, followed by supraspinatus, rhomboid major, posterior deltoid, anterior deltoid and training the middle deltoid last.

The table allows the clinician to choose the segments of motion of each muscle to be retrained also ‘from low to high,’ i.e., from the motion requiring the lowest potential amplitude of activity to the highest. Thus, in the case of the middle deltoid, one would choose the first segment of motion to be that of internal rotation, followed by posterior flexion, lateral flexion, external rotation, anterior flexion and saving the motion of abduction for last. The sequence of retraining the segments of motion may be different from muscle to muscle.

Table 2 presents the data from Table 1 from a different perspective, in order to illustrate the decision making of the clinician in terms of choice ‘by motion,’ as may commonly be the case in the fields of physical or occupational therapy.

SHOULDER MYOTATIC UNIT
Shoulder ROM Middle Deltoid Anterior Deltoid Posterior Deltoid Rhomboid Major Supraspinatus Pectoralis Major Average
Abduction 44.5 48.6 22.2 14.3 22.1 9.5 26.9
External Rotation 36.8 41.3 20.4 29.3 22.9 6.5 26.2
Lateral Flexion 33.4 33.8 30.1 22.1 26.5 7.2 25.5
Anterior Flexion 37.3 39.8 12.2 26 15.7 12.5 23.9
Posterior Flexion 29 12.8 31 17.3 15.1 11.5 19.5
Internal Rotation 25.5 20.5 18.7 18.7 18.7 7.5 18.3

Table 2. SEMG of the Shoulder Joint ROM for the Shoulder Primary Myotatic Unit.

Table 2 indicates that for the 6 muscles tested, the ranking order of muscular effort (at the minimal level of effort) per shoulder segmental motion is (1) abduction, (2) lateral flexion, (3) anterior flexion, (4) external rotation, (5) posterior flexion and (6) internal rotation.

It should be clear that the ranking order by motion could vary according to the number of shoulder muscles tested. However, even if the study were done on the 19 shoulder muscles tested for the shoulder ROM, internal rotation is the motion that requires the least amount of electrical potentials of activity. Hence, it should be the first motion to be used in a neuromuscular shoulder rehabilitation program unless clinically indicated otherwise. Within the group of muscles shown in Table 2, abduction should be the segmental motion to be exercised last in a rehabilitation program.

SEMG of Elbow ROM

Table 3 represents the SEMG amplitude potentials of five elbow muscles within the framework of performance of four elbow segmental motions.

ELBOW ROM SEGMENTS
Muscle Extension Flexion Pronation Supination Average
Anconeus 31.7 26.3 43.6 29.4 32.8
Biceps Brachii 27.1 36.9 7 27.4 24.6
Brachioradialis 16.7 17.8 9.7 14.7 14.7
Brachialis 15.9 14.8 10.8 16.4 14.5
Triceps 14.4 9.6 17.9 6.3 12.1

Table 3. Average SEMG Amplitude Potentials (µV RMS) of 5 Muscles Tested with SEMG through the Elbow ROM Segments.

This table has been organized in an overall amplitude potential (descending) ranking order, from the muscle requiring most energy to the one requiring the least energy during the elbow joint ROM performance. Thus, in this group the muscle that utilizes most energy during the elbow ROM performance is the anconeus and the muscle utilizing the least is the triceps. Overall, the ratio of energy consumption between the two muscles is almost 2.7:1.

Rehabilitation of the elbow should be structured to elicit the least level of fatigue and pain in the patient. The anconeus is a prime target for tennis elbow pain. An inspection of this table throws light on the subject: anconeus is the most active muscle in this group, thus more easily fatigued and prone to pain. Thus, the experienced SEMG clinician will retrain the six elbow joint muscles presented ‘from low to high,’ i.e., triceps first, followed by brachialis, brachioradialis, biceps, and the anconeus last.

Table 3 also allows the clinician to choose the elbow segments of motion of each muscle to be retrained ‘from low to high,’ i.e., from the motion requiring the lowest potential amplitude of activity to the highest. Thus, in the case of the anconeus, one would choose the first segment of motion to be that of elbow flexion, followed by supination, extension, and saving the motion of pronation for last. The sequence of retraining the elbow joints segments of motion may be different from muscle to muscle.

Table 4 presents the data from Table 3 in a different pattern, in order to illustrate the decision-making of the clinician in terms of choice of elbow joint retraining ‘by motion’ (in the context of physical or occupational therapy).

ELBOW MYOTATIC UNIT
Elbow ROM Anconeus Biceps Brachii Brachioradialis Brachialis Triceps Average
Extension 31.7 27.1 16.7 15.9 14.4 21.2
Flexion 26.3 36.9 17.8 14.8 9.6 21.1
Supination 29.4 27.4 14.7 16.4 6.4 18.8
Pronation 43.6 7 9.7 10.8 17.9 17.8

Table 4. SEMG of the Elbow Joint ROM for the Elbow Primary Myotatic Unit.

Table 4 indicates that for the 5 muscles tested, the descending ranking order of muscular effort (at the minimal level of effort) per elbow segmental motion is (1) extension, (2) flexion, (3) supination and (4) pronation. It should be clear that the ranking order by motion could vary according to the number of elbow joint muscles tested.

This table suggests that the first motion to be used in a neuromuscular elbow joint rehabilitation program should be that of pronation unless otherwise clinically indicated. Within the group of muscles shown on Table 4, elbow extension should be the segmental motion to be exercised last in a rehabilitation program.

SEMG of Wrist ROM

Table 5 below represents the SEMG amplitude potentials of seven wrist joint muscles within the framework of the performance of five wrist segmental motions.

WRIST ROM SEGMENTS
Muscle Ulnar Deviation Extension Radial Deviation Flexion Average
Extensor Carpi Ulnaris (ECU) 57.9 36.6 26.3 25.1 36.5
Extensor Carpi Radialis (ECR) 22.4 31.8 23.7 21.2 24.8
Flexor Carpi Radialis (FCR) 15.9 21.8 26.6 17.9 20.6
Flexor Carpi Ulnaris (FCU) 19.3 17.2 17 24.1 19.4
Supinator 12 16 12.4 11.6 13
Pronator Quadratus 13.3 8.8 12.6 16.8 12.9
Pronator Teres 10 12.8 10.7 10.1 10.9

Table 5. Average SEMG Amplitude Potentials (µV RMS) of 7 Muscles Tested with SEMG through the Wrist ROM Segments

Table 5 has been organized in an overall amplitude potential (descending) ranking order from the muscle requiring the most energy to the one requiring the least energy during the wrist joint ROM performance. Thus, in this group the muscle that utilizes most energy during the wrist ROM performance is the ECU and the muscle utilizing the least is the pronator teres. Overall, the ratio of energy consumption between the two muscles is almost 3.3:1.

The same cautions apply to the wrist muscles regarding early fatigue and pain as in any rehabiliation or occupational therapy. These muscles are susceptible to repetitive motion injury as exemplified by carpal tunnel syndrome (CTS). In particular, ECU is a prime target for CTS pain. Most CTS sufferers complain of ECU area pain. Since the clinicians think mainly of injuries of the median nerve at the wrist, they find the ECU pain radiation as something unusual and difficult to explain. However, an inspection of this table shows that the ECU is the most active muscle in this group, thus more easily fatigued and prone to pain.

In this case, the experienced SEMG clinician will retrain the seven wrist joint muscles presented ‘from low to high,’ i.e., pronator teres first, followed by pronator quadratus, supinator, FCU, FCR, ECR, and the ECU last.

Table 5 also allows the clinician to choose the wrist segments of motion of each muscle to be retrained ‘from low to high,’ i.e., from the motion requiring the lowest potential amplitude of activity to the highest. Thus, in the case of the ECU, one will choose the first segment of motion to be that of wrist flexion, followed by radial deviation, extension, and saving the motion of ulnar deviation for last. The sequence of retraining the wrist joints segments of motion may be different from muscle to muscle.

Table 6 presents the data from Table 5 in a different pattern, in order to illustrate the decision making of the clinician in terms of choice of elbow joint retraining ‘by motion,’ (in the context of physical or occupational therapy).

WRIST MYOTATIC UNIT
Wrist ROM ECU ECR FCR FCU Supinator P. Quadratus P. Teres Average
Ulnar Deviation 57.9 22.4 15.9 19.3 12 13.3 10 21.5
Extension 36.6 31.8 21.8 17.2 16 8.8 12.8 20.7
Radial Deviation 26.3 23.7 26.6 17 12.4 12.6 10.7 18.5
Flexion 25.1 21.2 17.9 24.1 11.6 16.8 10.1 18.1

Table 6. SEMG of the Wrist Joint ROM for the Wrist Primary Myotatic Unit

Table 6 indicates that for the 7 muscles tested, the descending ranking order of muscular effort (at the minimal level of effort) per wrist segmental motion is (1) ulnar deviation, (2) wrist extension, (3) radial deviation and (4) wrist flexion. It should be clear that the ranking order by motion could vary according to the number of wrist joint muscles tested.

This table shows that the first motion to be used in a neuromuscular wrist joint rehabilitation program should be that of wrist flexion unless clinically indicated otherwise. Within the group of muscles shown on Table 6, ulnar deviation should be the segmental motion to be exercised last in a rehabilitation program.

Discussion

Muscular dysfunction of the upper limb can be assessed within the electrical domains of frequency and amplitude with SEMG. The tables presented above reflect the amplitude potentials data of the electric potentials during the primary range of motion of three of the four myotatic units of the upper limb. The tables present data gathered from asymptomatic muscles. Data from symptomatic muscles are found within the realm of abnormal electric patterns of activity potentials.11 Those data generally show higher amplitude potentials, usually 150-200% higher than those presented above. The most common SEMG abnormal patterns reflect electric spasm and hypertonus. Sometimes, one finds patterns of co-contraction or co-activation and, even less frequently, one finds patterns of hypotonus.

The muscles of the upper limb are distributed rather unevenly among the three joints discussed in this article. Thus, one finds that the shoulder joint is surrounded by at least 16 muscles, the elbow joint by 5 muscles, the wrist by at least 9 muscles. A number of muscles do ‘double duty,’ in terms of spanning across more than one joint. A case in point is that of the brachioradialis.

A joint subtended by a larger number of muscles is more protected from muscular fatigue and pain. SEMG investigation shows clearly that all the muscles participate in all the segments of motion, thus the overall effort is well ‘spread’ and no muscle is required to work too hard by itself. Furthermore, the larger the muscle size, the larger the number of potential contractile elements that a given muscle may recruit when the need arises for increased ‘duty.’ This may be the case of the shoulder joint, where, for instance, the deltoid muscle (including the three partitions) is one of the largest muscles of the body.

The elbow is a joint subtended by only five muscles. Anconeus is the smallest muscle and, as shown on Table 3, the one that utilizes most energy in the group. Tennis elbow is associated with rather severe pain in the area of the anconeus and brachioradialis, the muscle that spans between the humerus and the distal radius at the wrist.

The wrist joint is rather unique in that it is subtended partly by muscles pertaining only to the forearm but functioning in terms of wrist activities, e.g. the supinator and the two pronators, by the flexors and extensors of the wrist proper and also by muscles originating in the forearm and primary to the hand myotatic unit.

SEMG Data Utilization

The documentation shown in this article is meant for the astute clinician who needs quantitative data for diagnostic decision making as well as for relevant questions of upper limb muscle rehabilitation.

First of all, one can document that all the muscles tested are active (at least) through the segments of motion of the primary joint ROM. No muscle is inactive through any motion. The topic of muscular agonism & antagonism is discussed elsewhere.11,12,13 Suffice it to say that neither SEMG nor any other electrophysiological modality shows any evidence to support the concept ‘while the agonist moves, the antagonist is inhibited.’

Secondly, the fact that SEMG testing allows for a ranking of the amplitude potentials of activity of asymptomatic muscles of the upper limb may be very relevant for pain practitioners. Diagnostic testing of symptomatic muscles may show different ranking results from those shown in the tables above. Therefore, the clinician may compare the results of the symptomatic muscles with those of the database and identify at a glance which muscles’ electrical potentials of activity differ from those expected.10

Last, but not least, the ranking of the muscles shown on the tables above can be used with scientific precision in terms of the rehabilitation program. By retraining the segments of motion of any given muscle ‘from low to high,’ one would expect the least early fatigue and pain during a rehabilitation program. Likewise, by retraining the muscles of any upper limb myotatic unit in the order from ‘the least total electrical output for the given joint ROM/muscle toward the highest output/muscle,’ one helps to retrain muscles with the least risk of fatigue and pain.

Summary

The upper limb is a complex formation of several joints. Each joint primary myotatic unit is unique in its structure and function. Each unit may work by itself, but, at the same time subtends part of the total myotatic vector of the upper limb. The muscles shown in Tables 1 through 6 have been extensively tested with SEMG.10,12 Appropriate ranking in terms of the pattern of activity through the primary joint ROM may have both diagnostic and rehabilitation utilization for the pain practitioner.

Last updated on: January 5, 2012
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