Characterization of the use of shock wave therapy among equine veterinarians

Abstract

Extracorporeal shock wave therapy (ESWT) research has prioritized mechanism of action and efficacy. Data regarding frequency of use and clinical opinion are not available. A web-based survey was offered to members of the American Association of Equine Practitioners; 144 responses were obtained. Frequency of ESWT use by respondents was as follows: daily by 8.3% (12/144), at least once weekly by 36.8% (53/144), at least once per month by 22.9% (33/144), less than once per month by 19.4% (28/144), and never by 12.5% (18/144) of respondents. The most common reason for use was to treat ligamentous injuries. Opinion of efficacy was variable.

Shock wave therapy (extracorporeal shock wave therapy, ESWT) was originally developed for dissolution of urinary calculi in humans, but has evolved into a treatment modality for musculoskeletal injuries in animals and humans. Research has concentrated on the mechanism of action of ESWT and efficacy of treatment for both experimentally induced and naturally occurring musculoskeletal diseases in rats, dogs, horses, and humans (1–3). Types of ESWT generators, treatment protocols, indications for use, and evidence and definition of efficacy vary in the scientific literature (1). Data regarding the use of ESWT in equine veterinary clinical practice are not available.

The objective of this survey was to characterize the use of ESWT among equine veterinary practitioners regarding: frequency of use, conditions treated, and clinical opinion of treatment efficacy. A 21-question web-based survey (surveymonkey.com, Portland, Oregon, USA) was initially pre-tested by 10 equine veterinarians. The survey was then offered to the 7787 members of the American Association of Equine Practitioners (AAEP). An advertisement and a link for the survey were e-mailed by the AAEP to members on behalf of the authors. The University of Saskatchewan Research Ethics Board reviewed the survey and determined that ethics approval was not required. The survey was available between April 25 and June 6, 2016. E-mail reminders were circulated 1 and 3 wk after release of the survey by the AAEP. Respondents could choose to remain anonymous and could exit the survey at any time. A reward was not offered for participation. Frequency of ESWT use, machine type, conditions treated, opinion of efficacy and tolerance, use of sedation, and practice demographics were evaluated. Demographic information included: type of practice, percentage of work that was equine, complementary therapies offered, and types of horses worked on (grouped by discipline).

Frequency of ESWT use was classified as daily, at least once per week, at least once per month, less than once per month, and never. The brands of ESWT machines used were elicited to determine which types of shock wave generators were being used. Responses were classified as focused, radial, or dual (focused and radial) machines based on information freely available from the manufacturers. Respondents were asked which 5 common conditions they treated with ESWT (desmitis, tendinitis, muscle pain, osteoarthritis, navicular syndrome) and were provided with space for comments. Opinion of how well equine patients tolerate application of ESWT to various body regions was rated on a scale of 1 to 4, with 1 being intolerable and 4 being completely tolerable. Clinical opinion of the efficacy of ESWT as a single treatment option for various musculoskeletal conditions was rated on a scale of 1 to 5, with 1 being completely ineffective and 5 being highly effective. Based on a clustered response distribution, this scale was condensed into a 3 point descriptive scale: ineffective (ratings 1 and 2), somewhat effective (rating 3), and highly effective (ratings 4 and 5).

Respondents were asked to identify the type of practice in which they worked. Based on distribution, responses were categorized into 4 distinct types of practice: general/ambulatory equine practice, specialist/referral equine practice, racetrack/sport horse practice, and mixed practice. Types of horses seen were divided by generic discipline, and respondents could select all that applied. Reporting the percentage of work in the veterinary practice that was on horses was recategorized into 2 groups: 100% equine work (equine-only), or all other responses (not equine-only).

All surveys that were received were reviewed for completion and errors. All available responses were included in the analysis. Numerical data were tested for normality using Shapiro-Wilks test for normality. Responses were summarized and percentages were calculated for all questions. Associations were assessed using Fisher’s exact test for binary outcome variables, and 95% confidence intervals (CI) were calculated for proportions. Predictors included amount of equine work and if complementary therapies, such as acupuncture, were offered by the practice. The outcome variable examined was frequency of ESWT use recategorized into a binary variable based on the previously described options: do not use ESWT (never, less than once per month) and use ESWT (daily, at least once per week, at least once per month). Statistical analysis was performed using Stata version 14.2 (StataCorp LP, College Station, Texas, USA). Significance was set at P < 0.05.

One-hundred-and-forty-four (144/7787) responses were collected (1.8% response rate). Thirteen surveys were incomplete; available responses from incomplete surveys were included in the analysis. The data were not normally distributed. Most respondents indicated that their practice was equine-only (108/131; 82.4%). Practice demographics are detailed in Table 1. English performance horses were the most common type of horses seen by respondents (Table 1). Most respondents (92/131, 70.2%) offered complementary therapies for their clients; only 39/131 (29.8%) respondents did not. Many respondents offered more than one type of complementary therapy.

Table 1.

Number and percent of responses to the possible choices from key survey questions regarding ESWT use and demographic information.^a,^b

Variable explored	Possible response	Number of responses # (%)
Frequency of ESWT use (N = 144)	Daily	12 (8.3)
	At least once weekly	53 (36.8)
	At least once per month	33 (22.9)
	Less than once per month	28 (19.4)
	Never	18 (12.5)
Type of ESWT used (N = 121)	Focused	92 (73.6)
	Radial	17 (13.6)
	Both or dual	6 (4.8)
	Unsure	10 (8.0)
Common conditions treated with ESWT (N = 125)	Desmitis	118 (94.4)
	Tendon injuries	96 (76.8)
	Muscle pain	79 (63.2)
Respondents could select all that applied	Osteoarthritis	64 (51.2)
	Navicular syndrome	34 (27.2)
Opinion of ESWT efficacy (N = 133)
Ligament injuries	Highly effective	77 (57.9)
	Somewhat effective	36 (27.1)
	Ineffective	20 (15.0)
Muscle pain	Highly effective	62 (46.6)
	Somewhat effective	39 (29.3)
	Ineffective	32 (24.1)
Tendon injuries	Highly effective	51 (38.3)
	Somewhat effective	44 (33.1)
	Ineffective	38 (28.6)
Osteoarthritis	Highly effective	27 (20.3)
	Somewhat effective	43 (32.3)
	Ineffective	63 (47.4)
Navicular syndrome	Highly effective	19 (14.3)
	Somewhat effective	36 (27.0)
	Ineffective	78 (58.7)
Practice type (N = 131)	General/ambulatory equine practice	60 (45.8)
	Specialist/referral equine practice	22 (16.8)
	Racetrack/sport horse practice	40 (30.5)
	Mixed practice	9 (6.9)
Types of horses seen (N = 131)	English performance	103 (78.6)
	Companion/pleasure	86 (65.7)
Respondents could select all that applied	Western performance	77 (58.8)
	Thoroughbred/Quarter Horse racing	59 (45.0)
	Rodeo	43 (32.8)
	Breeding	39 (29.8)
	Halter	33 (25.2)
	Standardbred racing	26 (19.9)

^aESWT — extracorporeal shock wave therapy.

^bIf not stated, respondents could only choose 1 option.

Frequency of ESWT use and type of machine used by respondents are listed in Table 1. Respondents who never used ESWT indicated that a lack of scientific evidence supporting its use and a lack of access to the technology were their primary reasons. Multiple respondents commented that ESWT is now available to lay people, which may result in use without veterinary supervision and allow for the misuse and abuse of ESWT in equine patients. Extracorporeal shock wave therapy was used more frequently if the practice was 100% equine [0.75 (95% CI: 0.66, 0.83) versus 0.52 (95% CI: 0.31, 0.73); P = 0.04] and if complementary therapies were also offered by the veterinarian [0.8 (95% CI: 0.71, 0.88) versus 0.49 (95% CI: 0.32, 0.65); P = 0.001].

Respondents reported their use of ESWT for 5 common conditions (Table 1). Other indications for ESWT use reported by respondents included wounds, proximal sesamoiditis, non-healing fractures, periostitis of the third metacarpal bone, sacroiliac pain, generalized back pain, sclerosis of the third carpal bone, cervical vertebral pain, injury to the second and fourth metacarpal or tarsal bones, and digital cushion pain. Most respondents (110/118, 93.2%) indicated that they prefer to use ESWT in conjunction with other medically appropriate therapies, depending on the injury. Sedation was always used to administer ESWT to horses by 50% (59/118) of respondents. Of the 50% that did not always use sedation, 16/59 (27%) rarely or never used sedation to administer ESWT. Most respondents indicated that equine patients were moderately to completely tolerable of ESWT, regardless of the body region (data not shown).

Extracorporeal shock wave therapy was viewed as a highly effective treatment option for ligament injuries and ineffective for the treatment of navicular syndrome by most respondents. Opinion on effectiveness for muscle pain, osteoarthritis, and treatment of tendon injuries was mixed (Table 1). More than one respondent commented that they were unsure of the true efficacy of ESWT for healing of musculoskeletal injuries, but the clinically observed reduction in pain was a useful benefit.

Descriptive information regarding ESWT use among equine practitioners was previously not available. This survey outlines the clinical use of ESWT in the equine veterinary field. There is conflicting evidence supporting the use of ESWT in equine veterinary practice. Multiple studies have shown that treatment with ESWT alleviated pain and lameness in horses while being used to treat different diseases (4–6). Experimental studies have demonstrated a potential benefit of ESWT for improving the healing process of suspensory desmitis (7,8) and wounds (9). However, other studies have failed to show a positive effect on disease modulation (5,10) or analgesia (11), and some groups have even demonstrated that ESWT can damage normal tissues in experimental situations (12). It has been shown that the effects on cells are dose-dependent, with lower energy doses stimulating growth factor production and high energy doses causing cell damage (13). Despite this information, optimal dosage ranges for specific injuries in horses have not been established, and it is not known if treatment with ESWT improves final outcomes for musculoskeletal injuries compared to negative controls or other available treatments (3). Difficulties exist in interpretation of the current literature and are beyond the scope of this paper, in part because the studies are widely varied in design, use of appropriate blinding and negative controls, and sample size.

The current survey established that equine veterinary practitioners have a positive view regarding the efficacy of ESWT for treating ligament injuries in horses. However, respondents were simply asked to provide a rating; a definition of efficacy was not provided or allowed to be stated by the respondent. Efficacy could have been interpreted in multiple ways. For example, one practitioner could have deemed ESWT to be efficacious in treating osteoarthritis if the patient’s lameness was alleviated with no change in radiographic evidence of disease. Another practitioner could conclude that ESWT was efficacious in treating a tendinopathy based on improvement in ultrasonographic appearance, regardless of the degree of lameness improvement. This survey was a tool to examine practitioner use and opinion of ESWT and provides a starting point for more precise investigations. However, this lack of a definition of efficacy as used in this survey may not have allowed for an accurate evaluation of respondents’ opinions; it simply provided an estimate. This highlights the need to provide defined, concrete, endpoints in both surveys and equine scientific literature.

The low survey response rate (1.8%) and undetermined possible biases were important limitations of this study. A previous survey of a similar population elicited 831 responses, or a 7.6% response rate (14). The pool of respondents was limited to those with access to e-mail and Internet. In addition, voluntary surveys can produce non-response bias, which poses a significant risk to the accuracy of the results, given the possibility that the responses of the respondents could differ from those that would be provided by non-respondents (15). In this survey, ESWT users may have been more likely to voluntarily participate. However, based on demographic responses, our population was similar to that of a previous survey investigating intra-articular injection practices of equine veterinarians. Ferris et al (14) reported that 80.3% of their respondents worked in a practice that saw 100% equine cases. This is similar to our result of 82.4%, indicating that our population of respondents may represent the entire population sampled. However, the AAEP published demographic information for 2016 stated that 45.4% of their 7787 members worked in a practice that saw 100% equine cases (16), suggesting that non-response bias could be present. It is possible that non-response bias existed both due to the conflicting scientific evidence supporting ESWT, and due to the interests of equine-only practitioners. Both the subject of the current survey and the previous survey of the same population were more likely to be of interest to veterinarians who were equine-only practitioners.

The current survey attempted to gather a large volume of information regarding ESWT use and had a small number of respondents. Further work on this topic should attempt to improve response rate and decrease potential non-response bias. Methods to achieve this include mailing out surveys, conducting phone surveys, offering a small reward for survey completion, decreasing the length of the survey, increasing the duration that the survey is available, or establishing the statistical difference between responses of early and late respondents to estimate the amount of sampling bias (17). Information that would improve the available body of literature regarding ESWT include therapy protocols used for defined injuries (including frequency, dose, and duration of therapy), type of ESWT generator used, and specific outcome measures used to indicate treatment success. Expanding the survey population to a wider range of veterinarians may improve response rate, and expanding the survey topic to include other species may result in a more accurate assessment of ESWT use by the entire veterinary population.

In conclusion, ESWT was commonly used by the equine practitioners who participated in this survey. The therapy was used to treat a diverse range of injuries in the horse. Respondents had variable opinions of the efficacy of ESWT, depending on the condition being treated. Practitioners in equine-only practice were more likely to use ESWT than those who worked in mixed practice. Non-response bias likely affected the results of this survey. Further work should include efforts to reduce non-response bias. Future surveys of practitioners regarding ESWT should focus on the clinical use of the technology.