Study Guide on Magnetotherapy, Ultrasound, and Shock Wave Therapy

Magnetotherapy (Magnetoterapia)

• Definition: Magnetotherapy is the clinical use of artificial magnetic fields applied to various pathologies.

• Mechanisms of Production:

  • Magnetotherapy: Generally refers to production via pulsatile electric current.

  • Imanterapia (Magnet therapy): Specifically refers to production via static magnets.

• Magnetotherapy Apparatus and Applicators:

  • Applicator or Solenoid:

    • This component produces the magnetic field.

    • Proximity is critical: The zone to be treated must be near the solenoid as there is a higher concentration of waves in that area.

    • These exist as movable units on the treatment table and come in various sizes.

  • Local Applicators:

    • Consist of round or square plates, usually placed facing each other.

    • The interior often contains gypsum (yeso).

    • The treatment zone should be centered between plates for the highest wave concentration.

• Physiological Effects:

  • Physical-chemical Effects:

    • Deviation of moving particles that possess an electrical charge.

    • Increased solubility of certain substances in water.

    • Piezoelectric effect on bone and collagen tissues.

  • Biological Effects:

    • Stimulation of cellular metabolism.

    • Increased synthesis of Adenosine Triphosphate ($ATP$ ).

    • Stimulation of protein synthesis.

  • Scientific Status: It is important to note that there is currently no consensus among researchers regarding these specific physiological effects.

• Clinical Applications and Evidence:

  • Fractures: Cited for its capacity for bone repair, though this remains in controversy.

    • References: Pickering, S. and B. Scammell (2002), "Electromagnetic fields for bone healing"; Hannemann et al (2011), "Pulsed Electromagnetic Fields in the treatment of fresh scaphoid fractures. A multicenter, prospective, double blind, placebo controlled, randomized trial."

  • Osteoarthritis and Degenerative Conditions: Effectiveness is yet to be demonstrated.

    • Reference: Sutbeyaz et al (2006), "The effect of pulsed electromagnetic fields in the treatment of cervical osteoarthritis: a randomized, double-blind, sham-controlled trial."

  • Wound Healing: Shows no benefit or contradictory results.

    • Reference: Aziz, Z. et al (2011), "Electromagnetic therapy for treating venous leg ulcers. Cochrane Database Syst Rev."

  • Musculoskeletal and Soft Tissue Lesions: Lacks high-quality evidence.

    • Reference: Owegi, R. and M. T. Johnson (2006), "Localized pulsed magnetic fields for tendonitis therapy."

  • Pain Relief: Evidence exists for several conditions including:

    • Osteoarthritis (primarily the knee).

    • Menstrual pain.

    • Diabetic neuropathy (diabetic foot).

    • Articular pain in Rheumatoid Arthritis ($RA$).

    • Fibromyalgia.

    • Chronic low back pain.

    • Reference: Eccles NK (2005) "A critical review of randomized controlled trials of static magnets for pain relief."

  • Carpal Tunnel Syndrome: Only demonstrates an analgesic (pain relief) effect.

    • Reference: Weintraub MI, Cole SP. (2008).

  • Local Circulatory Effect: Yet to be proven.

    • Reference: Steyn et al (2000), "Effect of a static magnetic field on blood flow to the metacarpus in horses."

  • Primary Real-World Uses: Despite the lack of sufficient evidence, the most common applications are bone repair after damage/fracture, pain management, and wound repair (to a lesser extent).

• Patient Instructions and Contraindications:

  • Patient Instructions: The patient may remain dressed but must remove their watch. Patients should avoid X-rays or radiotherapy during the treatment period.

  • Contraindications: There are no absolute contraindications, but it is advised against in the following cases:

    • Pacemaker carriers.

    • Pregnant women.

    • Children.

    • Viral diseases.

    • Hemorrhages.

    • Hypotension.

    • Metal plates and implants (though the possibility of heating is remote).

  • Inconveniences: Treatments are often of long duration and may cause claustrophobia in some patients.

Ultrasound (Ultrasonidos)

• Definition: The use of high-frequency acoustic waves (normally between $1$ and $3\,\text{MHz}$) transmitted to body tissue to produce therapeutic effects.

• Sub-categories:

  • Ultrasonotherapy: Therapeutic application of US with frequencies between $1\,\text{MHz}$ and $3\,\text{MHz}$.

  • Ultrasonoforesis (Sonophoresis): The introduction of medicinal substances into the body using ultrasound waves.

• Production Mechanism:

  • Produced by the vibration of materials (crystals), creating a high-frequency longitudinal mechanical wave.

  • Inverted Piezoelectric Effect: The application of electricity produces material deformation (of the crystal), which in turn produces compression and decompression, resulting in the wave.

• Physical Parameters and Units:

  • Acoustic Impedance: The greater the difference in impedance between tissues, the greater the reflection and the lower the transmission of energy.

  • Power: The amount of energy produced by the transducer per unit of time, measured in Watts ($W$).

  • Intensity: Power per unit of area of the head, measured in $W/cm^2$.

  • ERA (Effective Radiation Area): The actual area of radiation, which is smaller than the geometric area of the applicator head.

• Emission Modes:

  • Continuous: Produces a thermal effect (heating).

  • Pulsed: Can produce thermal or non-thermal effects. To ensure no temperature increase, a pulsed mode at $20\%$ is used.

• Duty Cycle (Ciclo de Trabajo):

  • The proportion of total treatment time in which the US is active, expressed as a ratio or percentage.

  • Continuous: $100\%$

  • Pulsed 1:1: $50\%$

  • Pulsed 1:2: $33\%$

  • Pulsed 1:3: $25\%$

  • Pulsed 1:4: $20\%$

• Thermal Effects:

  • Associated with continuous emission, $100\%$ duty cycle, and a $3\,\text{MHz}$ head.

  • High intensities combined with a static head can cause periosteum pain due to temperature spikes.

  • The patient’s thermal sensation determines the intensity applied.

• Tissue Interaction and Absorption:

  • Absorption by Content: Tissues with higher protein/collagen content absorb US better than those with high water content.

  • High Absorption Tissues: Ligaments, tendons, fascia, joint capsules, and scars.

  • Penetration Depth:

    • $3\,\text{MHz}$: Superficial absorption; less penetration. Medium penetration is $1.5 - 3\,\text{cm}$ (half-power distance). Total depth ($10\%$ power) is $3 - 4\,\text{cm}$.

    • $1\,\text{MHz}$: Less superficial absorption; deeper penetration. Medium penetration is $4 - 5\,\text{cm}$. Total depth ($10\%$ power) is $10 - 12\,\text{cm}$.

• Physiological Effects:

  • Vasodilation and increased local metabolism.

  • Increased flexibility and mobility.

  • Facilitation of fluid accumulation dispersion.

  • These effects result from vibrations caused by US within cells.

• Clinical Applications in Tissue Repair (Watson, 2008):

  • Inflammatory Phase: Stimulates mast cells to promote the inflammatory response.

  • Proliferative Phase: Stimulates fibroblasts, endothelial cells, and myofibroblasts to maximize efficiency.

  • Remodeling Phase: Improves fiber orientation and the transition from Type III collagen to Type I collagen.

  • The US only stimulates or augments these natural phases; it does not replace them.

• Recommendations and Contraindications:

  • Acute Inflammation/Rheumatism: Use pulsed US.

  • Post-Trauma: Do NOT use in the first $24 - 36$ hours due to risks of hemorrhage and myositis ossificans.

  • Eyes/Eyelids: Risk of retinal detachment.

  • Testicles: Risk of chromosomal alterations.

  • Uterus: Contraindicated during pregnancy and for patients with an IUD.

  • Others: Contraindicated for tumors and cemented prostheses.

• Precautions:

  • Cardiac Area: Risks with pacemakers.

  • Circulation: Thrombophlebitis and varicose veins.

  • Lungs: High surface tension in alveoli; use pulsed $3\,\text{MHz}$ on the thoracic wall.

  • Ovaries: Only low doses.

  • Epiphyseal Plates: Low dose, pulsed mode only. Not recommended for those under $18$ years old.

  • Metallic Objects: Continuous mode is contraindicated for endoprostheses and osteosynthesis.

  • Sympathetic Ganglia: Risk of neurovegetative alterations, especially the Stellated ganglion ($C7 - D1$).

• Administration:

  • Sessions: Typically $10 - 20$ sessions with a $1$-month rest between periods.

  • Acute Pathology: $1$ session every $24$ hours.

  • Chronic Pathology: $2 - 3$ times per week.

  • Techniques: Direct treatment, through water, or sonophoresis.

Shock Waves (Ondas de Choque)

• Introduction:

  • Extracorporeal shock wave therapy has been used since the 1980s for gallstones.

  • It involves very high-energy acoustic waves applied via a head to the affected area.

  • In the last $10 - 15$ years, it has become a primary option for chronic plantar fasciitis, lateral epicondylalgia (tennis elbow), calcifying tendonitis of the shoulder, patellar tendinopathy, and Achilles tendinopathy.

• Types of Shock Waves:

  • Focal: Waves directed at a single point with little dispersion. It offers greater tissue penetration but can be painful during application.

  • Radial: Developed in 1999. Used for superficial soft tissues. It is more commonly indicated for musculoskeletal disorders and is the more widely used type.

• Parameters and Mechanism:

  • The physics is complex and not fully understood. Key parameters include pressure distribution, energy flux density, and total acoustic energy.

  • Method of Production: A tube contains compressed air ($1 - 4\,\text{bar}$) and a "bullet" that is fired to hit the applicator. The applicator transforms this into kinetic energy, expanding pressure waves with low penetration power.

  • Cavitación (Cavitation): The waves produce bubbles in the tissue. When these bubbles burst, they release energy that can break calcium deposits and cause micro-hematomas that stimulate bone callus creation.

• Physiological Effects:

  • Mechanical and Physiological: Cavitation, neoformation, and modification of collagen fiber tension.

  • Metabolism: Changes in permeability favor tissue metabolism.

  • Regeneration: Causes microscopic interstitial and extracellular responses leading to tissue regeneration.

• Clinical Hypotheses for Effectiveness:

  • Analgesia: Pain reduction through hyperstimulation or influencing pain transmission.

  • Tissue Regeneration: Mechanotransduction leads to the destruction of calcifications and repair.

• Contraindications:

  • Acute inflammation or infection.

  • Thoracic and pulmonary regions.

  • Pregnancy.

  • Polyneuropathies and neoplasias.

  • Hemorrhages and coagulopathies.

  • Rheumatic diseases.

  • Fractures where plates have been applied (in children and adults).

• Secondary Effects:

  • Pain during/after application.

  • Hematomas (bruising) and Erythema (redness) in the application zone.

  • Lesions to soft tissues or bone.

  • Infrequent possibility of elevated blood pressure.