History of Extracorporeal Shockwave Therapy
Extracorporeal Shockwave Therapy (ESWT) otherwise referred to as shockwave therapy, was first introduced into clinical practice in 1982 for the management of urologic conditions The success of this technology for the treatment of urinary stones quickly made it a first-line, non-invasive, and effective method. Subsequently, ESWT was studied in orthopaedics where it was identified that it could loosen the cement in total hip arthroplasty revisions. Further, animal studies conducted in the 1980s revealed that ESWT could augment the bone-cement interface, enhance osteogenic response and improve fracture healing. While shockwave therapy has been shown to be beneficial in fracture healing, most orthopaedic research has focused on upper and lower extremity tendinopathies, fasciopathies, and soft tissue conditions.
Physiology of ESWT
Shockwaves are sound waves that have specific physical characteristics, including nonlinearity, high peak pressure followed by low tensile amplitude, short rise time, and short duration (10 ms). They have a single pulse, a wide frequency range (0-20 MHz), and a high pressure amplitude (0-120 MPa)
These characteristics produce a positive and negative phase of shockwave. The positive phase produces direct mechanical forces, whereas the negative phase generates cavitation and gas bubbles that subsequently implode at high speeds, generating a second wave of shockwaves.]
In comparison to ultrasound waves, the shockwave peak pressure is approximately 1000 times greater than the peak pressure of an ultrasound wave.
Mechanism of Action
The effects of ESWT treatment are unknown. However, the proposed mechanisms of action for ESWT include the following: promote neovascularization at the tendon-bone junction, stimulate proliferation of tenocytes and osteoprogenitor differentiation, increase leukocyte infiltration, and amplify growth factor and protein synthesis to stimulate collagen synthesis and tissue remodelling.
Principles of Shockwave Therapy
Shockwaves are transient pressure disturbances that propagate rapidly in three-dimensional space. They are associated with a sudden rise from ambient pressure to their maximum pressure. Significant tissue effects include cavitation, which are consequent to the negative phase of the wave propagation.
Direct shockwave and indirect cavitation effects cause hematoma formation and focal cell death, which then stimulate new bone or tissue formation.
Indications for Shockwave Therapy
Shockwave therapy is primarily used in the treatment of common musculoskeletal conditions. These include:
- Upper and lower extremity tendinopathies
- Greater trochanteric pain syndrome
- Medial tibial stress syndrome
- Patellar tendinopathy
- Plantar fasciopathy.
- Adhesive capsulitis
- Non-union of long bone fracture
- Avascular necrosis of femoral head
- Osteoarthritis of the knee
There is no standardized ESWT protocol for the treatment of musculoskeletal conditions.
Contraindications to ESWT in Physiotherapy
- Over major blood vessels and nerves
- Pacemakers or other implanted devices
- Open wounds
- Joint replacements
- Blood clotting disorders including thrombosis
- Cancerous tissues
- A compromised mental status of the patient and/or the inability to cooperate.
Differences between ESWT and Therapeutic Ultrasound
Therapeutic ultrasound utilises high frequency sound waves, while ESWT utilises lower frequency waves. Ultrasound may produce either thermal or non-thermal effects in tissues, while ESWT does not result in heating effects.
Similarities between Therapeutic Ultrasound and ESWT
Both modalities employ acoustic waves to produce therapeutic benefits. They both make use of a coupling medium to transmit sound waves to the tissues being treated. They are both non-invasive forms of treatment.
According to a study performed by Rompe and co-workers, stretching exercises in combination with radial shock wave therapy is more efficient for the treatment of chronic symptoms of proximal plantar fasciopathy than repetitive radial pressure wave therapy alone. Patients were subjected to three sessions of 2000 radial pressure pulses (EFD = 0.16 mJ/mm 2) in weekly intervals, generated with a ballistic device (air compressor pressure 4 bar; rate 8 Hz) manufactured by Electro Medical Systems
A study to investigate the clinical outcomes of ESWT on calcaneal spurs of 108 patients and its correlation with radiologic changes were reported by Yalcin et al. All the patients underwent radial pressure wave therapy once a week for 5 weeks (2000 pressure waves starting at an EFD of 0.05 mJ/mm 2 and increasing up to 0.4 mJ/mm 2). After the therapy, approximately 67 % of the patients reported no pain; however, there was no correlation between clinical outcome and radiologic changes. The authors concluded that even without radiologic change.