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2014). A separate study using bone marrow-derived mesenchymal stem cells (BMDMNCs) in vivo showed that, when used in conjunction, cardiac tissue treated with ESWT- treated BMDMNCs had the lowest expression of indices of inflammation compared to cardiac tissue treated with ESWT or BMDMNCs alone (Sheu et al. 2015). These human studies used lower energy settings and fewer pulses compared to the Raabe et al. (2013) study, which used similar settings to studies evaluating ESWT treatment of tendon and ligament injuries in horses. Further studies need to be performed to investigate whether unfocused, low energy ESWT could be beneficial if used in conjunction with stem cell therapy in tendon and ligament injuries in horses. There is not currently a published standard recommendation


for a duration of time between administration of local stem cell injection and ESWT; however, based on these findings the concurrent use of ESWTwith local stem cell injectionmay not be advisable. There are no studies to determine the efficacy of performing ESWT prior to stem cell administration, but this may also be a consideration for some practitioners.


Safety


There have been reports of detrimental effects of ESWT. In a study using ESWT on ultrasonographically normal flexor and extensor tendons, as well as suspensory ligaments, histological changes were seen after treatment (Bosch et al. 2009). These tendons and ligaments were treated with 600 shocks at 0.14 mJ/mm2 and were evaluated both 6 weeks and 3 h after ESWT. There were increased numbers of irregularly distributed tenocytes, loss of regular collagen wave pattern, and disruption of collagen fibres in the ESWT treated tendons. In addition, it was noted that none of the ponies in the study showed any lameness following ESWT, but all ponies had mild swelling and pain on palpation in the superficial digital flexor tendon for 2–3 days following treatment to this region. Based on this study, it may be contraindicated to perform ESWT on normal tendons or ligaments, and so clinicians should be encouraged to focus their ESWT on the region of injury and not move into normal tissues if possible. Conversely, there are reports indicating that ESWT is a


safe, effective therapy. ESWT stimulated osteogenesis in the long bones of rabbits (Qin et al. 2010), and one study in the horse revealed that although high levels of energy resulted in bone formation, no damage to surrounding soft tissues and no signs of bone microfractures were seen (McClure et al. 2000). A separate study treated the origin of the suspensory ligament and the fourth metatarsal bone with two separate ESWT treatments, and showed no evidence of cortical microfracture (Bischofberger et al. 2006). It is not recommended to use ESWT on active physes, as


studies have demonstrated premature closing of physes in laboratory animals after ESWT (McClure and Weinberger 2003).


Analgesia


In human patients, ESWT can provide pain relief for 3–4 days after treatment, although this mechanism of action remains unknown (McClure and Weinberger 2003). In one human study using ESWT for the treatment of chronic plantar fasciitis, patients reported a statistically significant decrease in pain score in 25 out of 30 patients after a single treatment. Results


were recorded between 33 and 255 days after treatment (Hyer et al. 2005). Horses with experimentally induced osteoarthritis showed


decreased lameness scores 7 days following ESWT, suggesting this finding was due to decreased inflammation rather than an immediate analgesic effect (Frisbie et al. 2009). Additionally, a series of case studies reported that horses that were refractory to intra-articular injections for the treatment of osteoarthritis had improved lameness scores after shockwave therapy (Revenaugh 2005). In horses treated with ESWT for chronic unilateral forelimb


lameness, no significant decrease in observable lameness was seen; however, a significant increase in peak vertical force of the lame limb was noted both 8 h and 2 days following ESWT. This increase in peak vertical force would indicate the horses were more willing to bear weight on the lame limb, and could be correlated to an improvement in lameness. These findings suggest that analgesia caused by ESWT may last at least up to 2 days and thus horses should not be exercised heavily immediately following ESWT (Dahlberg et al. 2006). Contrary to these studies, one report of 16 horses with


confirmed proximal palmar metacarpal or plantar metatarsal pain and either confirmed or presumptive PSD could not demonstrate an analgesic effect resulting in any immediate reduction in lameness after one ESWT treatment (Imboden et al. 2009). In the same study, no changes in skin sensitivity or in thermographic imaging were noted after ESWT. It may be possible that if this study had included peak vertical force in their measurements, the results may have been similar to those of Dahlberg et al. (2006). Additionally, in a separate study, no attenuation in skin sensation was seen in horses up to 48 h after being treated with either focused or RPW therapies directly over the palmar digital nerve (Waldern et al. 2005). Because of the potential analgesic and gait altering


effects listed above, the use of ESWT is regulated in equine competitions. Currently, F


ed eration Equestre Internationale


regulations state that shockwave therapy is not permitted during the period of the event, nor in the 5 days prior to the start of the period of the event (F


ed eration Equestre


Internationale Veterinary Regulations 2016). The National Thoroughbred Racing Association’s 2016 Safety and Integrity Alliance Code of Standards states that any horse that receives shockwave therapy may not breeze or race for 10 days following treatment and that any ESWT or RPWT machine must be registered and approved, and only used by a licensed veterinarian. It also states that the use of ESWT or RPWT must be reported within 24 h prior to treatment and that any horse treated shall be added to a list of ineligible horses. The US Equestrian Federation’s 2016 Guidelines for Drugs and Medications recommends a 3-day withdrawal from competition following extracorporeal shockwave therapy, and prohibits the use of any shockwave therapy within the 12 h prior to competition. US Equestrian Federation guidelines do allow extracorporeal shockwave therapy to be administered by a licensed veterinarian within 3 days prior to competition, but only to the back and dorsal pelvis area. Rules and regulations should be investigated prior to administering ESWT to competition horses.


Equipment


There are various shockwave machines available for use in equine practice. Each machine may be equipped with © 2017 EVJ Ltd


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