EQUINE VETERINARY EDUCATION Equine vet. Educ. (2019) 31 (5) 271-277 doi: 10.1111/eve.12780


Review Article


Review of the application and efficacy of extracorporeal shockwave therapy in equine tendon and ligament injuries


A. F. Yocom* and L. D. Bass Department of Clinical Sciences, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins, Colorado, USA. *Corresponding author email: afyocom@gmail.com


Keywords: horse; shockwave; tendon; ligament; therapy


Summary Extracorporeal shockwave therapy (ESWT) has been implemented as a treatment for musculoskeletal injuries in horses. ESWT uses acoustic waves applied to a region of injury, and has been shown to improve lameness, decrease time of healing and improve ultrasonographic appearance of tendon and ligament injuries. However, much of the current literature surrounding the use of ESWT in veterinary medicine is positively biased and most studies have lower levels of evidence-based experimental design. Randomised clinical trials are needed to determine specific energy settings, dose, frequency and case selection for different anatomical regions, and to investigate long-term effects of ESWT as well as interactions between ESWT and regenerative biological therapies.


Introduction


Extracorporeal shockwave therapy (ESWT) was developed as a method of lithotripsy in man to break up calculi in the renal or biliary tracts (Coombs et al. 2000). While used for lithotripsy, shock waves were found to interact with the pelvis, causing increased bone density (Bischofberger et al. 2006). It has since become an adjuvant therapy for the management of various musculoskeletal injuries including tendinopathy (Waugh et al. 2015), osteoarthritis (Dahlberg et al. 2005; Zhao et al. 2013), nonunion and delayed union fractures (Kuo et al. 2015), and treatment for other musculoskeletal conditions and pathologies with variable results. Tendon and ligament injuries, osteoarthritis, and fractures


are recognised causes of lameness in horses and can be career limiting or ending. Treatment may include confinement and box stall rest, nonsteroidal anti-inflammatory medications, physiotherapy and, more recently, regenerative therapies. Shockwave therapy has demonstrated a quicker return to performance in horses with proximal suspensory ligament desmitis (PSD) (Crowe et al. 2004), a shorter interval


for formation of longitudinal fibre patterns in superficial digital flexor tendon (SDFT) injuries (Bathe 2006), analgesia and reduction in lameness (McClure and Weinberger 2003; Frisbie et al. 2009), and improved performance in horses with back pain (Bathe 2006; Allen et al. 2010). Although not the focus of this review, ESWT has also been used to treat several other conditions in horses, including but not limited to: osteoarthritis (Revenaugh 2005; Kawcak et al. 2011), bone spavin, caudal heel pain, fractures, dorsal metacarpal disease (McClure and Weinberger 2003), wounds (Link et al. 2013), and carpus valgus in foals (Bussy et al. 2013).


In man, ESWT has been implemented in the treatment of


plantar fasciitis, shoulder adhesive capsulitis, calcific tendinopathy of the rotator cuff, epicondylitis and enthesiopathies (Perez et al. 2003; Chen et al. 2014a,b). In patients with shoulder adhesive capsulitis, those treated with ESWT had improved range of motion and ability to perform daily activities faster than those patients treated with oral steroids (Chen et al. 2014a). Successful outcomes were seen in patients treated with ESWT for chronic proximal plantar fasciitis in 70% of cases 3 months after a single ESWT session, and in 77% of cases 12 months after treatment (Chuckpaiwong et al. 2009). In patients with tennis elbow of at least 12 months’ duration, there was a 50% or greater reduction in pain in 65% of patients treated with ESWT compared to a sham treated group (Rompe et al. 2004). These cases show promising results in tendon and ligament injuries treated with ESWT in man. This article provides a literature-based review of the use of


shockwave therapy in treating equine tendon and ligament injuries, and will help provide general guidelines for the use of shockwave therapy in horses based on anatomical location of injury.


Physics


Extracorporeal shockwave therapy functions by creating acoustic pressure waves that can be applied to a focal region of pain or pathology. Shock waves are characterised by a rapid rise in pressure, followed by a rapid decline to a negative pressure. During the shock wave, there are direct and indirect generations of mechanical forces. The primary effect is the direct generation of mechanical forces, which occurs during the positive rise in pressure (Wang 2012). The indirect generation of mechanical forces occurs by cavitation; a process in which the tensile forces of the shock wave exceed the dynamic tensile strength of water, and as a result, cavitation bubbles are formed (Waugh et al. 2015). The cavitation bubbles implode, resulting in a secondary energy wave, which may cause a negative effect or damage to the tissues (Ogden et al. 2001; Wang 2012; Waugh et al. 2015). Focused extracorporeal shock waves can be generated


by electrohydraulic, electromagnetic or piezoelectric mechanisms, all of which concentrate shock waves into small focal areas (Ogden et al. 2001; Speed 2013). Conversely, radial pulse waves (radial pressure waves, RPWs) are not focused, act superficially on the target tissues, and their penetration depth is not adjustable, as it is with focused


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