Extracorporeal shockwave treatment (ESWT), also known as orthotripsy, has been available since the early 1980s for the treatment of renal stones and has been widely investigated for the treatment of biliary stones. Shock waves create a transient pressure disturbance, which disrupts solid structures, breaking them into smaller fragments, thus allowing spontaneous passage and/or removal of stones. The mechanism by which ESWT might have an effect on musculoskeletal conditions is not well defined. Chronic musculoskeletal conditions, such as tendinitis, can be associated with a substantial degree of scarring and calcium deposition. Calcium deposits may restrict motion and encroach on other structures such as nerves and blood vessels, causing pain and decreased function. One hypothesis is that disruption of these calcific deposits by shock waves may loosen adjacent structures and promote resorption of calcium, thereby decreasing pain and improving function.
Other functions are also thought to be involved. Physical stimuli are known to activate endogenous pain control systems and activation by shock waves may “reset” the endogenous pain receptors. Damage to endothelial tissue from ESWT may result in increased vessel wall permeability, causing increased diffusion of cytokines, which may in turn promote healing. Microtrauma induced by ESWT may promote angiogenesis and thus aid in healing. Finally, shock waves have been shown to stimulate osteogenesis and promote callous formation in animals, which is the rationale for trials of ESWT in delayed union or non-union of bone fractures.
Currently, five ESWT devices are approved for marketing by the U.S. Food and Drug Administration (FDA). The OssaTron® device (HealthTronics, Marietta, GA), an electrohydraulic delivery system was approved by the FDA on July 20, 2000, for patients with chronic proximal plantar fasciitis (i.e., pain persisting more than six months and not responding to conservative management). It is also FDA approved for treatment of lateral epicondylitis (tennis elbow). The Epos™ Ultra (Dornier, Germering, Germany), an electromagnetic delivery system, was approved by the FDA on January 15, 2002, for plantar fasciitis. The SONOCUR® Basic (Seimans, Erlangen, Germany) also uses an electromagnetic delivery system and was approved by the FDA for use in chronic lateral epicondylitis (symptoms unresponsive to conservative therapy for more than six months) on July 19, 2002. In 2005, the Orthospec™ Orthopedic ESWT (Medispec Ltd, Germantown, MD), an electrohydraulic spark-gap device, and the Orbasone™ Pain Relief System (Orthometrix, White Plains, NY), a high-energy sonic wave system, received approval for treatment of chronic proximal plantar fasciitis in patients 18 years of age or older.
Both high-dose and low-dose protocols have been investigated. A high-dose protocol consists of a single treatment of high energy shock waves (1300mJ/mm2). This painful procedure requires anesthesia. A low-dose protocol consists of multiple treatments, spaced one week to one month apart, in which a lower dose of shock waves is applied. This protocol does not require anesthesia. The FDA-labeled indication for the OssaTron® and Epos™ Ultra device specifically describes a high-dose protocol, while the labeled indication for the SONOCUR® device describes a low-dose protocol.
Another type of ESWT, radial ESWT (rESWT) received FDA pre-market approval (PMA) in May 2007. The FDA-approved device is the Doloclast (spelled Dolorclast in the PMA summary) from EMS Electro Medical Systems, Nyon, Switzerland. Radial ESWT is generated ballistically by accelerating a bullet to hit an applicator, which transforms the kinetic energy into radially expanding shock waves. Other types of ESWT produce focused shock waves that show deeper tissue penetration with significantly higher energies concentrated to a small focus. Radial ESWT is described as an alternative to focused ESWT and is said to address larger treatment areas, thus providing potential advantages in superficial applications like tendinopathies.
Pulsed Acoustic Cellular Expression (PACE) is a new ESWT modality utilizing the dermaPACE® device. This device delivers high-energy acoustic pressure waves in the shock wave spectrum to produce compressive and tensile stresses on cells and tissue structures to promote angiogenic and positive inflammatory responses, and quickly initiate the healing cascade. The PACE treatment modality is said to result in revascularization and microcirculatory improvement, including the production of angiogenic growth factors, enhanced new blood vessel formation (angiogenesis), and the subsequent regeneration of tissue such as skin, musculoskeletal and vascular structures.