In vitro shock wave is a mechanical wave with acoustic, optical and mechanical properties, which can propagate in three dimensions. The best transmission medium is water and gelatin, and the acoustic impedance of skin, fat, muscle and other tissues is close to that of water, so the shock wave has less damage to skin, fat, muscle and connective tissue. After the shock wave is generated, it carries great energy and is delivered by the water capsule. Through secondary focusing, the energy flow is concentrated in the target lesion to produce the effect and play a therapeutic role on the lesion. For many orthopedic diseases extracorporeal shock wave therapy is a safe, effective, non-invasive and ideal treatment method.
I. The way of extracorporeal shock wave generation
Extracorporeal shock waves can be generated by the following three physical effects.
(1) electro-hydraulic effect: the use of two electrodes placed in the water, through the rapid release of high-voltage electricity so that the water near the electrodes quickly vaporized, the pressure and temperature rose sharply, causing the water around the electrodes with this sudden shock wave to push outward to generate energy.
(2) electromagnetic effect: let the high energy pulsed current pass through the disk coil to produce electromagnetic field, through the inverse induction effect at the insulating membrane to produce repulsive magnetic field, electromagnetic energy encountered insulating membrane refracted to the water capsule to produce plane shock wave, and then by the concave acoustic lens to focus the shock wave and into the local area to be treated.
(3) piezoelectric effect: the use of piezoelectric ceramic body piezoelectric effect into mechanical effects produced by the inverse piezoelectric effect.
Second, the mechanism of action of extracorporeal shock wave
Shock wave in the conduction process in the different acoustic impedance of the material interface, the formation of reflection and refraction, will produce stress effects at the interface, and the formation of energy attenuation inside the material, impedance of large absorption of energy, impedance of small absorption of energy less, the formation of different effects. Extracorporeal shock wave therapy is the use of shock waves on human internal tissues, cells to produce a series of biological effects to achieve therapeutic purposes. The mechanism of action is as follows.
1, mechanical pressure effect
When the shock wave enters the body, due to the different media contacted, such as fat, tendons, ligaments and other soft tissues, as well as skeletal tissues, etc., therefore, at the interface of different tissues can produce different mechanical stress effects, expressed as different tensile and compressive stresses on the cells. Tensile stress can cause the relaxation between tissues and promote microcirculation; compressive stress can make the cell elastic deformation and increase cellular oxygen uptake, so as to achieve therapeutic purposes.
2.Piezoelectric effect
Shock wave as a mechanical force applied to the bone, the first increased the stress of the bone tissue, resulting in polarization potential, causing piezoelectric effect. This piezoelectric effect on the bone tissue and the impact of the shock wave energy size. Many animal experiments have found that high-energy shock waves can cause bone fractures in animals, and low-energy shock waves can stimulate bone production.
3.Cavitation effect
Human tissue contains a large number of tiny bubbles in the shock wave under the action of rapid expansion, rupture, the emergence of high-speed liquid micro-jet, resulting in the impact effect. The cavitation effect is conducive to unblocking the occluded microscopic blood vessels and loosening the adhesions of joint soft tissues.
4.Anti-pain effect
(1) Due to the strong action of extracorporeal shock wave on human tissues, it can directly inhibit the nerve endings cells, thus relieving pain;
(2) Extracorporeal shock wave can change the frequency of pain acceptance by injury receptors, thus relieving pain;
(3) In vitro shock waves inhibit the transmission of pain information by changing the composition of chemical mediators around the injury receptors;
(4) Extracorporeal shock waves can cause local congestion, thus promoting the remission of inflammation.
Third, the clinical application of extracorporeal shock wave
As an emerging non-invasive and non-invasive treatment method, extracorporeal shock wave has been widely used in the treatment of bone defects, bone discontinuity, delayed fracture healing, frozen shoulder, external humeral epicondylitis (tennis elbow), heel pain, plantar fasciitis and many other bone and joint disorders.
And the efficacy is remarkable. The US FDA has made extracorporeal shock wave a routine treatment for heel pain.
1.The application of extracorporeal shock wave in osteoarthritic disorders
Tendon disorders: including frozen shoulder, medial/external humeral epicondylitis (tennis elbow/golf elbow), tendonitis, bursitis, patellar tendonitis, Achilles tendon tenosynovitis, plantar fasciitis and calcific tendonitis, etc.
Bone and osteochondral disorders: including fracture non-union/delayed healing, post-fracture pseudoarthrosis, heel spur, femoral epiphyseal osteochondrosis, Osgood Schlatter disease (tibial tubercle osteochondrosis) and Kohler disease (aseptic necrosis of the navicular bone), etc.
2. Contraindications to extracorporeal shock wave
The following patients are not suitable for extracorporeal shock wave treatment: pregnant women, patients with abnormal coagulation function, patients with peripheral neuropathy, patients with epiphyseal cartilage in adolescence, and patients with pacemakers or unstable angina or congestive heart failure.
3.The side effects of extracorporeal shock wave
Due to the strong energy of extracorporeal shock wave, the patient may feel the pain like pins and needles during the treatment. Therefore, we should explain to the patient before treatment. In addition, patients should be reminded not to do strenuous activities on the day of treatment, if there is increased pain, should be immediately rechecked.
The energy of extracorporeal shock wave is generally divided into low, medium and high levels: below 0.08 mJ/cm2 is low energy; around 0.28 mJ/cm2 is medium energy; above 0.6 mJ/cm2 is high energy. Usually there are no significant side effects for low/medium energy, but only for high energy shock waves there are some minor side effects such as bleeding or nerve damage during the treatment.