The Pathogenesis and Pathophysiology of Myofascial Trigger Points (MTrPs) and Their Role in Myofascial Pain Syndrome (MPS). 

  • by 0016802157
  • 22 Oct, 2017

Notes Made from The Following Studies;

Regularly asked questions in practise are "what are (muscle) knots?" and " what causes them ?". 
Revising and digesting the two studies above on their pathology and physiology will hopefully answer those questions and give a good scientific knowledge as to why they occur.

Muscle "knots" are clinically known as myofascial trigger points (MTrP) and there is great confusion over what they are. Terminology, theories, concepts, and diagnostic criteria are inconsistent, incomplete, or controversial.

What is Myofascial Pain Syndrome (MPS)?
  • Shah et al., (2015) talks about myofascial pain syndrome (MPS) which is a fancy term used to describe painful muscle or surrounding connective tissue which can be acute (lasting less than 6 weeks) or chronic (lasting more than 3 to 6 months). 
  • MPS is an extremely common, but often overlooked source of muscle pain, discomfort, and dysfunction (Hoyle, 2006). 
  • Myofascial pain is characterized by contraction "knots" or "nodes" in the muscle that are hypersensitive on palpation, may stimulate local and/or referred pain, may elicit a local twitch response and may be eliminated by a local anesthetic or manual therapy.
  • It is a complex disorder related to the development of myofascial trigger points in muscle. These myofascial TrPs have been further defined by their clinical characteristics as being either "active" or "latent". 
  • An "active" trigger point is associated with a clinical pain complaint. 
  • A "latent" trigger point is tender on palpation and may be associated with restricted range of motion and stiffness but is not associated with spontaneous complaints of pain (Hoyle, 2006).
What is fascia?
"Fascia is classified by layer, as superficial fascia , deep fascia , and visceral  or parietal  fascia, or by its function and anatomical location."
What is Myofascia?
The term “myofascial” describes how both muscle and fascia contribute to the symptoms.

What Is A Myofascial Trigger Point (MTrP)?
  • MTrPs are fined as "hard, discrete, hyperirritable, palpable nodules in a taut band of skeletal muscle that may be spontaneously painful (i.e. active) or painful only on compression" (Shah et al., 2015).  
  • An active MTrP is clinically associated with spontaneous pain in the immediate surrounding tissue and/or to distant sites in specific referred pain patterns.
  • Strong digital pressure on the active MTrP exacerbates the patient's spontaneous pain complaint and mimics the patient's familiar pain experience.
  • MTrPs can also be classified as latent, i.e. lay "dormant" or "hidden" and asymptomatic as the MTrP is physically present but has not created a spontaneous pain complaint. 
  • However, pressure on the latent MTrP elicits local pain at the site of the nodule.
  • Latent and active MTrPs can be associated with muscle dysfunction, weakness, and limited joint range of movement.

History of MPS as a Diagnosis

  • Guillaume de Baillous (1538-1616) of France was one of the first to write in detail about muscle pain disorders. 
  • In 1816, the British physician Balfour associated “thickenings” and “nodular tumors” in muscle with local and regional muscle pain. 
  • Froriep in 1843 coined the term “muskelshwiele” (muscle callouses) to describe what he believed was a “callus” of deposited connective tissue in patients with rheumatic disorders. 
  • In 1904, Gowers suggested that inflammation of fibrous tissue (i.e., “fibrositis”), created the hard nodules. 
  • Schade (1919) later proposed that the nodules, which he called “myogeloses”, were high viscosity muscle colloids. 
  • In the mid 1900s, important work was conducted independently by Michael Gutstein in Germany, Michael Kelly in Australia, and J.H. Kellgren in Britain. By injecting hypertonic saline into various anatomical structures such as fascia, tendon, and muscle in healthy volunteers, Kellgren was able to chart zones of referred pain in neighbouring and distant tissue. 
  • U.S. physician Janet Travell, whose work on myofascial pain, dysfunction, and trigger points is arguably the most comprehensive to date. 
  • Travell and Rinzler coined the term “myofascial trigger point” in the 1950s, reflecting their finding that the nodules can be present and refer pain to both muscle and overlying fascia. 
  • The current use of the term “MPS” implies a specific condition which presents as regional pain, sometimes with referred pain, often accompanied by increased tension and decreased flexibility. 
  • MPS has also been associated with other pain conditions including radiculopathies, joint dysfunction, disk pathology, tendonitis, craniomandibular (jaw) dysfunction, migraines, tension type headaches, carpal tunnel syndrome, computer-related disorders, whiplash-associated disorders, spinal dysfunction, pelvic pain and other urologic syndromes, post-herpetic neuralgia, and complex regional pain syndrome.

MPS Is Different To Fibromyalgia

  • It is known to coincide with other diseases and syndromes associated with pain, e.g. rheumatic diseases and fibromyalgia.
  • Unlike MPS, fibromyalgia is a widespread and symmetrically-distributed pain condition associated with sleep and mood disturbances. 
  • The pain of MPS is usually local or regional and may be found in a limited number of select quadrants of the body.
  • MPS has traditionally been thought to present independently of mood or sleep abnormalities, recent studies indicate that MPS is associated with both mood and sleep disruptions. 
  • The definition and pathogenesis of MPS is still not fully understood, and disagreement persists about whether MPS is a disease or process, rather than a syndrome.

Diagnosis For MTrPs; Not Straight Forward

  • The current gold standard for the diagnosis of MPS is the physical examination as described in The Trigger Point Manual :

  1. Palpation of a taut band; Diagnosis of MPS has been tissue specific and anatomically based on palpation of the skeletal muscle for MTrPs.
  2. Identification of an exquisitely tender nodule (MTrP) in the taut band. 
  3. Reproduction of the patient's symptomatic pain with sustained pressure.
MPS  & MTrP is Not Fully Understood

  • An MTrP is a common physical finding and often overlooked of non-articular musculoskeletal pain as its pathophysiology (explanation) is not fully understood. 
  • Digital palpation has several limitations. For instance, it lacks adequate sensitivity and specificity.
  • Besides the use of palpation, there are currently no accepted criteria for identifying or describing MTrPs. 
  • Further research is needed to determine not only the role of the MTrP, but also its surrounding area.
  • Diagnostic criteria are imprecise, and the full impact of MPS on life activity and function is not fully understood. 
  • To complicate this issue further, MTrPs are associated clinically with a variety of medical conditions including those of metabolic, visceral, endocrine, infectious, and psychological origin and are present across a wide range of musculoskeletal disorders. 
  • If the MTrP is frequently associated with other musculoskeletal pain syndromes, it would make this finding non-specific — if it is not, it would make the MTrP specific for MPS.
  • Muscle pain displays unique clinical characteristics compared to cutaneous (skin) and neuropathic pain, the nature of the symptoms are highly dependent upon the individual's perception of its characteristic qualities (e.g., boring, aching, sharp, etc.), intensity, distribution, and duration. 
  • Characteristics like the quality of the pain, its distribution, and whether it radiates, have never been required for the diagnosis of MPS.
  • Accurate diagnosis depends upon the examiner's clinical acumen, experience, index of suspicion, training, and palpation skills. 

The Role of Muscle and The Cinderella Hyposthesis

  • The Cinderella Fiber Hypothesis was first proposed by Hagg (1990) which explains how low level muscle damage could be brought on via low-threshold motor units (MUs) within muscles which are continuously activated during low level static exertions (LLSEs).
  • Types of LLSEs or exertions are typically utilized by occupational groups such as  office workers, musicians, hair dressers and dentists.  
  • "Cinderella" fibers are small low threshold muscle fibres which can become continuously overloaded and more prone to develop into myofascial trigger points since they are activated longer and are more likely to be metabolically exhausted before other fibres.  
  • A study by Treaster et al. supports the Cinderella Hypothesis by demonstrating that low-level, continuous muscle contractions in office workers during 30 minutes of typing induced formation of MTrPs.
  • In contrast, larger motor muscle fibers do not work as hard and spend less time being activated.
Critique of This Theory:
  • The "Cinderella" fiber theory, alone, fails to explain all aspects of injury related to LLSEs. 
  • It fails to explain the exact origin and mechanism of muscle pain as evidence suggests that muscle fiber activity and motor unit recruitment may be a consequence of pain rather than a cause. 
  • Low-threshold muscle fibers may fatigue and become metabolically exhausted but this does not explain how pain occurs. 
The Energy (ATP) Deficit Hypothesis  
  • A more widely accepted hypothesis is that trigger points develop because some initiating event causes an excessive release of acetylocholine (ACh) from the motor endplates resulting in increased fiber tension and localized ischemia. 
  • The localized ischemia restricts the blood flow and insufficient ATP synthesis which is needed to restore energy. The increased demand and reduced supply of ATP forms the energy crisis and encourages the release of neuroreactive substances and metabolic byproducts (i.e., bradykinin (BK), substance P (SP), serotonin (5-HT)) which causes the peripheral nociceptors to become sensitive.
  • Without ATP, the sarcoplasmic reticulum does not function correctly and the muscle sarcomeres remain contracted as the lack of energy (ATP) means that the the actin and myosin cross-bridges cannot disengage or release. 
  • ATP is also needed by the calcium (Ca2+) pump to remove calcium (Ca2+) from the muscle binding sites and restore them to the sarcoplasmic reticulum. Calcium (Ca2+) is needed and binds to troponin on the muscle fibers, which makes the muscle fibers contract.
  • Localized areas containing "contraction knots" are believed to release sensitizing agents and additional acetylcholine (ACh) that cycles back to cause increased fiber tension. 
  • A feedback loop to maintain contraction is created and a self perpetuating cycle is established. 
  • Until this positive-feedback loop is interrupted, the muscle sarcomeres at the TrP remain in a shortened state, resulting in a local energy crisis.

Critique to the Energy Deficit Theory

  • There is no explanation or description for the initiating event that causes the excessive release of ACh to occur in the first place.
  • This theory also assumes that the motor endplates are the focus of attention for trigger point development.
  • There is no evidence suggesting that the endplates are responsible for trigger point development.
  • This theory fails to explain why MTrPs are more prevalent at certain 15 muscle locations than others. 

Muscle Overuse and What Happens When Hyaluronic Acid (HA) Levels Rise 

  • HA functions as a lubricant that helps muscle fibers glide between each other without friction.
  • With muscle overuse or traumatic injury, the sliding layers start to produce immense amounts of HA which then aggregate into supermolecular structures changing both its configuration, viscoelasticity and viscosity.
  • Due to its increased viscosity, HA can no longer function as an effective lubricant which increases resistance in the sliding layers and leads to densification of fascia or abnormal sliding in muscle fibers.
  • Interference with sliding can impact range of motion and cause difficulty with movement, including quality of movement and stiffness. In addition, under abnormal conditions, the friction results in increased neural hyperstimulation (irritation), which then hypersensitizes mechanoreceptors and nociceptors embedded within the fascia.
  • This hypersensitization correlates with a patient's experience of pain, allodynia, paresthesia, abnormal proprioception, and altered movement.

References
Marieb, Elaine Nicpon; Hoehn, Katja (2007). Human anatomy & physiology . Pearson Education. p. 133. ISBN   978-0-321-37294-9 .

Shah, J.P., Thaker, N., Heimur, J., et al. (2015) Myofascial Trigger Points Then & Now: A Historical and Scientific Perpective. Physical Medicine and Rehabilitation, 7:746-61.

 J, Hoyle. (2006)EFFECTS OF POSTURAL AND VISUAL STRESSORS ON TRIGGER POINT DEVELOPMENT, MUSCLE ACTIVITY, BLINK RATE, AND DISCOMFORT DURING COMPUTER WORK, Ohio University, MSC.

by 0016802157 13 Oct, 2017

ByunghHo J. K., JungHoon, A., HeeCheol, C., DongYun, K., TaeYeong, Kim., BumChul, Y. (2015) Rehabilitation with Osteopathic Manipulative Treatment (OMT) After Lumbar Disc Surgery: A Randomised, Controlled Pilot Study , IJOM: 18; 181-188.

 Study Summary:

  • 33 patients who had underwent lumbar microdiscectomy were randomly assigned to one of two intervention groups; either exercise programme or an OMT group post surgery.
  • Both intervention programmes (Exercise and OMT) consisted of 8 individual sessions which were performed twice a week for 4 weeks.
  • Each session was 30 minutes and all patients in both groups were prescribed supplementary anti inflammatory medication, analgesics and a muscle relaxant by surgeon.
  • Results showed reduced residual leg pain after the lumbar discectomy in the OMT group with a 53% reduction compared to the exercise group which had a 17% reduction.
  • Residual lower back pain also decreased in both interventions with a 37% reduction in the OMT group and a 10% reduction in the exercise group.
  • No side effects or complications from any intervention were reported.
  • Patients in the groups required less frequent use of medication with an 87% reduction in the OMT and 73% in the exercise.
  • An overall improvement was found in the lumbar spine active ROM with patients being able to move without pain in both the OMT group and exercise groups.

Introduction

  • Low back pain is a worldwide health problem with a lifetime prevalence rate of 80% and can affect daily physical activity (1.).
  • Lumbar disc pain accounts for less than 5-10% of lower back pain (LBP) and is one of the most common reasons for lumbar spine surgery (2).
  •   Lumbar discectomy is one of the most commonly performed operations for lower back pain to relieve nerve root pain and reduce physical disability.
  • The most common unsatisfactory complaints complications observed in patients following lumbar discectomy are;

  1. Continued post operative physical disability affecting daily activities.
  2. Residual lower back pain and leg pain (3.).

Post surgical intervention has been considered important to reduce post surgical physical complications and increase the success rate for patients post surgery.

This study performed a pilot study comparing Osteopathic Manipulative Treatment (OMT)  with exercise following lumbar disc surgery to assess the feasibility for a future randomised control trial.

Study Method

  • 48 patients who met the eligibility criteria and wanted to participate in the study were interviewed and screened by two research surgeons.
  • The study was a randomised controlled pilot study and conducted at a major metropolitan spine surgery hospital where all participants underwent lumbar microdiscectomy.
  • Two research spinal surgeons registered in Korea and a research osteopath registered in the UK conducted patient recruitment and screening.
  • The study protocol was approved by the institutional review board of the University of Korea, and all participants provided written informed consent.
  • Patients between 20 and 65 years of age who had lower back pain and referred leg pain resulting from a herniated lumbar disc and underwent lumbar microdiscectomy were identified by hospital nurses.

Patient Exclusion Criteria:

  • A requirement of revision surgery or other forms of combined surgery.
  • A refusal to participate
  • Contraindication for participation including pregnancy, metastatic disease, or a mental disorder.
  • Of the 48 patients, 15 were excluded and the remaining 33 were randomly allocated to either the OMT group or the exercise programme group.

Study Procedure

  • 33 patients who had underwent lumbar microdiscectomy by 2 neurosurgeons at the spine surgery hospital returned to the hospital 2 to 3 weeks after surgery for baseline measurements and the first rehabilitation intervention.
  • Each participant was randomly assigned to one of two intervention groups; either exercise programme or an OMT group.
  • The allocations were conducted using simple randomisation.
  • Both intervention programmes (Exercise and OMT) consisted of eight individual sessions which were performed twice a week for 4 weeks. Each session was 30 minutes and all patients in both groups were prescribed supplementary anti inflammatory medication, analgesics and a muscle relaxant by surgeons.

Intervention OMT Rehabilitation & Techniques Used:

  • All patients underwent physical assessment before each intervention.
  • The same practitioner applied a combination of techniques in the standardised protocol for the OMT but the intensity and sequence of the techniques were modified for each patient depending on their tolerance to treatment and other post-operative physical conditions.
  • The protocol did not include spinal high-velocity, low-amplitude thrust (HVLAT) manipulation of the lumbar segments where the surgery was performed.
  • The focus of the OMT protocol was to reduce biomechanical overload on the lumbar spine by functionally improving the motion of adjacent spinal segments or joints including the thoracic and cervical segments and the sacroiliac joint.
  • The protocol included techniques applied to myofascial structures to reduce post-operative physical tension and stiffness generated in the body.
  • Each OMT intervention was performed by two osteopathic students under the supervision of a qualified osteopath.
  • Each treatment process was documented and reviewed by a research osteopath and surgeon.

Exercise Programme

  • Overall, 8 exercise sessions were conducted over a course of 4 weeks.
  • The aim of the exercise programme was to improve spinal mobility and stabilise the lumbar segments.
  • For the first week, practitioners focused on stretching exercises for the back and abdominal muscles with the patient in the supine position.
  • For the 2nd and 3rd week, practitioners focused on isometric strengthening exercises for the back and hip extensors with the patient in the prone position or sitting on a gym ball.
  • In the final 4th week, the intensity of the previous exercises was increased and back stability exercises were performed using a pilates exercise apparatus.

Outcome measures

  • Outcome measures were assessed after 2 and 3 weeks post surgery and post-intervention.
  • A post-intervention evaluation was conducted 7 to 8 weeks post surgery which was otherwise a week after the final rehabilitation session.
  • Primary outcome measures were evaluated for post-operative disability and residual pain in the legs and lower back.
  • Outcome measure questionnaires used were the Rolande Morris Disability Questionnaire (RMQ) with a 24-point scale and the Visual Analogue Scale (VAS) with 0 indicating ‘no pain’ and 100 indicating ‘the worst pain’.
  • Secondary outcomes included lumbar range of motion (ROM), use of medication, and patient satisfaction.
  • The lumbar spine ROM at which the patients could move without pain was measured with a double inclinometer by a physiotherapist who was not involved in any intervention.
  • The number of supplemental medications taken per week was used to assess medication consumption.
  • Patients were also asked to fill in a self-grading questionnaire to evaluate their satisfaction for their rehabilitation intervention which indicated ‘dissatisfaction’, ‘moderate satisfaction’ and ‘total satisfaction’.
  • Patients were asked whether they would recommend the rehabilitation intervention they received to a family member or friend with a similar condition.

Statistical Analysis

  • The Shapiroe Wilk test was used to assess normality of distribution of the data. Medians are shown for the range of movement found in lumbar spine extension and left side-bending, and for the number of times medication was used.
  • The categorical data was analysed using the chi-square test or Fisher’s exact test to account for baseline variations.
  • The Student‘s t-test or the Manne Whitney U test was applied to compare the differences between the groups. SPSS statistical software (Version 12.0, SPSS Inc., Chicago, IL) was used for the analyses. Two-sided tests and a significance level of 0.05 were used for all statistical analyses.
  • Subjects Of the 48 patients deemed eligible for inclusion, 33 (69%) were enrolled and randomly allocated to either the OMT or exercise group.
  • There were no significant differences in baseline characteristics and baseline measures between the two groups.
  • The primary reason for non-enrolment was lack of interest in participation. Of the enrolled patients, 6% were lost to follow-up at the primary study endpoint (2 of 33, 1 in each group). All 33 patients who were randomly assigned to a group were analysed on an intention-to-treat basis.

Primary Outcome Results

  • Primary outcomes OMT and the exercise programme improved all primary outcomes.
  • Post-surgical physical disability questionnaire results showed that patients improved more after OMT rehabilitation than the exercise group.
  • Residual leg pain after the lumbar discectomy decreased in the OMT group with a 53% reduction compared to the exercise group which had a 17% reduction.
  • Residual lower back pain also decreased in both interventions with a 37% reduction in the OMT group and a 10% reduction in the exercise group.

Secondary Outcome Results

  • An overall improvement was found in the lumbar spine active ROM with patients being able to move without pain in both the OMT group and exercise groups.
  • Patients in the groups required less frequent use of medication with an 87% reduction in the OMT and 73% in the exercise.
  • Patients in both groups responded that they were highly satisfied with the post-operative rehabilitation and answered that they would recommend the post-operative rehabilitation to a family member or a friend undergoing spinal surgery.
  • No side effects or complications from any intervention were reported.

Table Of Results
by 0016802157 16 Aug, 2017
Article written by Sally Raine and Lance Twomey (1994).
by 0016802157 27 Jul, 2017
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