Concept:Perpetuating Factors
Perpetuating factors are the systemic, structural, metabolic, and psychological conditions that keep myofascial trigger points (TrPs) active and prevent them from resolving spontaneously or with specific local treatment. Recognition and correction of perpetuating factors is, according to Travell and Simons, the most important single aspect of myofascial pain management, and the most neglected.
The clinical importance of this concept is illustrated by the apocryphal story of the man who stepped in a hole and broke his leg. The bones healed, but two months later he stepped in the same hole and broke the leg again. No one had patched the hole. If we treat myofascial pain syndromes without correcting the perpetuating factors that promptly reactivate TrPs, the patient is condemned to repeated cycles of treatment and relapse.
For patients with chronic myofascial pain who have suffered for many months or years, perpetuating factors often spell the difference between successful and failed therapy. When the patient fails to respond to specific myofascial therapy, or obtains only temporary relief, perpetuating factors must be ruled out as a major contributing cause.
Categories of Perpetuating Factors
Perpetuating factors fall into several distinct but frequently overlapping categories. Several are often present simultaneously in any one patient.
Mechanical Stress
Structural and postural factors that produce chronic muscle overloading are among the most common perpetuators.
Structural inadequacies include:
- Lower limb-length inequality (LLLI) — a difference as small as 0.5 cm (3/16 in) can be clinically critical; causes a compensatory scoliosis maintained by sustained muscular effort. See the correction procedure described in Chapter 48, Section 14
- Small hemipelvis — tilts the sacral base; produces compensatory scoliosis when seated or standing; more commonly overlooked than LLLI; corrected with an ischial lift ("sit-pad")
- Short upper arms — leaves the shoulders unsupported in most seated positions; perpetuates upper trapezius and levator scapulae TrPs
- Morton's foot (short first, long second metatarsal) — produces a characteristic gait imbalance that can perpetuate TrPs throughout the lower limb, trunk, and up to the jaw
Postural stresses include misfitting furniture, poor posture habits, sustained muscle contraction, repetitive movement overload, and immobility. See Neutral spine and Ergonomics for corrective principles. Postural correction is addressed in Chapter 41.
Constriction of muscles by tight clothing — brassiere straps, belts, tight collars, hosiery elastic — produces prolonged ischaemia and perpetuates TrPs in the compressed muscles.
Nutritional Inadequacies
Nutritional deficiencies are often crucial perpetuating factors and commonly occur alongside sources of mechanical stress. Low "normal" levels of vitamins B₁, B₆, B₁₂, and/or folic acid are suboptimal and frequently responsible for treatment failure. They are confirmed by serum measurement; symptoms usually respond to oral supplementation.
The five vitamins of special importance to myofascial pain syndromes are detailed in dedicated pages:
- Vitamin B₁ (Thiamine) and Trigger Points
- Vitamin B₆ (Pyridoxine) and Trigger Points
- Vitamin B₁₂ (Cobalamin) and Trigger Points
- Folic Acid and Trigger Points
- Vitamin C (Ascorbic Acid) and Trigger Points
Dietary minerals of clinical importance include iron, calcium, potassium, and magnesium — each addressed on its own page.
Metabolic and Endocrine Inadequacies
Any compromise of muscle energy metabolism aggravates and perpetuates myofascial TrPs. The three main metabolic perpetuators are:
- Hypometabolism (hypothyroidism) — even mild or subclinical hypothyroidism makes muscles more susceptible to TrP activation and produces only temporary relief from specific myofascial therapy. Correction of hypothyroidism can produce spontaneous resolution of TrPs and full recovery from MPS within 4–6 weeks. TSH should be screened in any patient with widespread or treatment-resistant TrPs.
- Hypoglycemia — both fasting and reactive (postprandial) hypoglycemia aggravate TrP activity through the mechanism of increased circulating epinephrine and impaired muscle energy supply
- Hyperuricemia and gout — TrPs respond poorly to spray and stretch when the patient is hyperuricemic; injection therapy is more effective than spray and stretch in these patients. Managed with standard uricosuric treatment.
Psychological Factors
Psychological factors can contribute to perpetuation of TrPs. The physician must be careful not to assume that psychological factors are primary — it is all too easy to blame the patient's psyche for the inability of the physician to recognise the musculoskeletal sources of the pain.
Factors include hopelessness (often from prior misdiagnosis as untreatable), depression (closely associated with chronic pain, bidirectionally), anxiety and tension (expressed as sustained muscle contraction), the "good sport" syndrome (stoic over-activity that overloads muscles), and secondary gain behaviors.
Chronic Infection and Infestations
Chronic bacterial disease and some parasitic infestations can prevent recovery from myofascial pain syndromes. Of specific clinical relevance:
- Viral disease — including acute and chronic viral infections
- Bacterial infection — chronic bacterial disease as a background perpetuator
- Giardia lamblia — one of the most common intestinal parasites causing chronic malabsorption; confirmed by stool examination; causes malabsorption of carbohydrate, fat, and vitamin B₁₂
- Entamoeba histolytica — causes tissue invasion with ulceration; malabsorption perpetuates TrPs; diagnosis by stool examination or biopsy; treatment requires a combination of drugs
Other Factors
- Allergic rhinitis — hypersensitivity to allergens with histamine release acts as a perpetuating factor; allergy control significantly improves TrP treatment response
- Impaired sleep — disruption of restorative non-REM sleep perpetuates TrPs; addressed by correcting sleep posture and treating underlying sleep disorders
- Nerve impingement — radiculopathy and peripheral nerve entrapment maintain TrP irritability; TrPs and radiculopathy are diagnosed and treated independently
Screening Laboratory Tests
The most useful routine tests to identify perpetuating factors are:
| Test | What it screens for |
|---|---|
| Serum vitamin levels — B₁, B₆, B₁₂, folic acid, vitamin C | Vitamin inadequacies; values in the lower quartile of normal are highly suspect as TrP perpetuators |
| Blood chemistry profile | Elevated cholesterol (hypothyroidism, folate deficiency); elevated uric acid (gout); low calcium (suspect ionised calcium); low potassium (aggravates TrPs); elevated fasting blood sugar (diabetes); elevated liver enzymes |
| Complete blood count (CBC) with indices | Low haemoglobin and haematocrit (anaemia); low MCV (iron deficiency); high MCV >92 fl (suspect folate or B₁₂ deficiency); elevated eosinophils (allergy or parasitic infestation); >50% mononuclear cells (viral infection or low thyroid function) |
| Erythrocyte sedimentation rate (ESR) | Elevated ESR: chronic bacterial infection, polymyositis, polymyalgia rheumatica, cancer; normal ESR helps exclude chronic bacterial infection |
| Thyroid tests — sTSH, FT₄ | Hypothyroidism; sTSH is the preferred initial test; if low, FT₄ and microsomal antibodies obtained; if borderline, CK and cholesterol help determine thyroid status |
Key principle: Values in the lower quartile of normal for water-soluble vitamins are less than optimal and are highly suspect as perpetuators of myofascial TrPs. Since a battery of B₁₂ and folic acid levels is readily available and not unreasonably expensive, it should be obtained routinely in patients with chronic myofascial pain. These patients are a select group who are more likely than most patients to have vitamin inadequacy.
Related Pages
- Vitamin B₁ (Thiamine) and Trigger Points
- Vitamin B₆ (Pyridoxine) and Trigger Points
- Vitamin B₁₂ (Cobalamin) and Trigger Points
- Folic Acid and Trigger Points
- Vitamin C (Ascorbic Acid) and Trigger Points
- Iron and Trigger Points
- Calcium and Trigger Points
References
- Travell JG, Simons DG. Myofascial Pain and Dysfunction: The Trigger Point Manual, Volume 1: The Upper Half of Body. 2nd ed. Baltimore: Williams & Wilkins; 1999. Chapter 4. With contributions by Robert D. Gerwin, MD.