Extracorporeal Shock Wave Therapy (ESWT)

By Amy Straut, DVM, CCRT
angell.org/rehab
physicalrehab@angell.org
781-902-8400

January 2022

What Is Extracorporeal Shock Wave Therapy (ESWT)

Shockwaves are sound waves that carry energy and travel through tissues, gas, liquids, and solids. These sound waves are non-linear pressure waves that have both a positive and negative phase that affects interfaces between tissues with different densities¹. The positive phase has a direct mechanical tensile force, and the negative phase creates a secondary effect via cavitation, as bubbles are formed and collide and explode, generating a second indirect shockwave effect².

Acting as a mechanical stimulus, ESWT promotes healing through mechanotransduction³, in which cells sense and respond to mechanical stimuli by converting them to biochemical signals that elicit specific cellular responses.

Studies conclude that shockwaves generate interstitial and extracellular responses, producing beneficial effects such as;

• Tissue Regeneration, via neovascularization, protein biosynthesis, and cell proliferation⁴
• Pain Relief, via decreasing concentration of pro-inflammatory mediators and instigating release of endorphins by activating descending inhibitory systems⁵
• Destruction of calcification in musculoskeletal structures, via mechanical fragmentation, phagocytosis⁶

Combining these effects can lead to improved functional outcomes of injured tissues.

Shock wave treatment is administered via a hand-held device called a trode. The trode is placed directly on the treated area of the body and is typically optimized for transmission using a conductive gel.

Types of ESWT

Focused Shock Wave (FSWT) – Delivered from a device that generates a pressure field that converges at a selected depth in body tissues where maximum pressure is reached.

The fundamental differences between focused and radial ESWT.⁴

Radial Shock Wave (RSWT) – Delivered by a device that reaches maximal pressure at the device source itself and is relayed into tissues.

The fundamental differences between focused and radial ESWT.⁴

Comparing Focused ESWT with Radial ESWT

FSWT is termed “Focused” because the generated pressure field converges at an adjustable focus at a selected depth in the body tissues. This focus point is where the maximum pressure is reached. These waves are generated in water within the trode, which allows for a more natural transference of waves into the body (limited reflection).

RSWT produces radial waves that produce their maximal pressure at the source of generation (trode). These waves are generated in air, where a projectile hits the end of the trode, which then transmits the generated pressures waves into the body.

As a result, RSWT has a more superficial effect than FSWT, penetrating and focusing their energy much deeper into the body.

Uses of ESWT

A shockwave is a non-invasive modality, making it an alternative for non-surgical patients. It may also be an excellent supplemental modality for pain management as part of a physical rehabilitation plan.

ESWT Is Commonly Used For

• Tendon & Ligament Healing (Supraspinatus, Biceps, Achilles, & Patellar tendinopathies)
• Osteoarthritis (elbow, stifle, hip)
• Bone Healing (delayed union, slow fracture healing)

Contraindications of ESWT

• Bone tumors
• Metabolic bone conditions where bone may be too fragile
• Location at open growth plate
• Area where active infection is present
• Over body cavities where air/gas is present (abdomen, thorax)

Clinical Use

The typical shock wave treatment session is relatively quick (5-10 mins), and for some patients that require lower energy settings, sedation is often not needed. However, treatment at higher energy settings can be loud and may be acutely painful, and sedation may be required. Light sedation with oral administration of Gabapentin and Trazodone before the appointment may be adequate. If a higher level of sedation is needed, it is reasonable to administer dexmedetomidine +/- analgesic in a healthy dog.

Treatment of musculoskeletal conditions is recommended every three weeks for one to three treatments or until clinical improvement is achieved. Disease resolution is not normally expected when ESWT is used to manage osteoarthritis, so the treatment protocol is often repeated every 6-12 months (1-3 treatments).

Patients typically begin experiencing the pain relief benefits of ESWT within 24 to 48 hours but can be mildly uncomfortable during the initial post-administration waiting period. NSAIDs are usually adequate coverage for pain management during this waiting time.

ESWT is typically used in conjunction with a physical rehabilitation program, including activity control and therapeutic exercises for return to best function. Please get in touch with our Physical Rehabilitation Services Team with questions regarding the integration of ESTW into a patient’s treatment protocol.

The MSPCA Angell hospitals in Waltham and Boston are equipped with cutting-edge ProPulseVersaTron FSWT equipment. Our orthopedic surgeons in both locations can evaluate and recommend a shock wave treatment protocol for a post-surgery plan or as a possible alternative treatment plan to surgery.

Referral for shockwave treatment directly with our Physical Rehabilitation Team requires a veterinary orthopedic surgeon to evaluate the pet, and shockwave has been approved as an appropriate treatment plan.

Referral forms for both Surgery and Physical Rehabilitation services can be easily submitted online at https://www.mspca.org/angell_services/referral-services/

References

1. Leeman J, Shaw K et al. Extracorporeal shockwave therapy and therapeutic exercise for supraspinatus and biceps tendinopathies in 29 dogs. Vet Rec. 2016; Oct 15; 179(15):385.
2. Cleveland R. The acoustics of shock wave lithotripsy. AIP Conf Proc. 2007 (1): 900.
3. Khan K, Scott A, Mechanotherapy: how physical therapists’ prescription of exercise promotes tissue repair. Br J Sports Med. 2009; 43(4): 247-252.
4. Simplicio C, Purita J et al. Extracorporeal shock wave therapy mechanisms in musculoskeletal regenerative medicine. J Clin Ortho and Trauma. 2020; (11): S309-S318.
5. Saggini R, Di Stefano A et al. Clinical application of shock wave therapy in musculoskeletal disorders. J Biol Regul Homeost Agents. 2015 (3) 533-545.
6. Lowe M et al. Shockwave therapy if effective for chronic calcifying tendonitis of the shoulder. J Bone Joint Surg Br. 1999, 81: 863-867.