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Emergency Radiology

, Volume 26, Issue 6, pp 639–645 | Cite as

Retrospective analysis of equestrian-related injuries presenting to a level 1 trauma center

  • Cameron R. Adler
  • Alix Hopp
  • Dawn Hrelic
  • Jim T. Patrie
  • Michael G. FoxEmail author
Original Article

Abstract

Objective

Report the incidence, pattern, and severity of equestrian-related injuries presenting to a rural level 1 trauma center and detail the total radiation dose, imaging, and hospital charges related to those injuries.

Methods

An IRB-approved retrospective review of patients presenting to our facility following equine-related trauma was conducted. Demographics, mechanism of injury, types and number of imaging exams, approximate radiation dose administered, imaging findings, Injury Severity Score (ISS), rate/length of hospitalization, and approximate cost of care were recorded.

Results

A total of 222 patients (161 F:61 M; mean age 38.5 years (range 4–79)) presented to our emergency department following horse-related injury. Mechanisms of injury included the following: fall (n = 186), kick (n = 18), stepped on (n = 9), and other (n = 9). Body part injured included extremity (26.1%), torso (26.6%), spine (25.7%), and head/neck (18.5%). Longer hospital admission, higher expenditure, increased CT/MR imaging, higher ISS, and radiation dose were noted in older patients and those injured by a fall or kick. Head injuries were more frequent following a horse kick (p = 0.006). Spinal and torso injuries were more common in patients older than 54 years (p = < 0.001) and those with falls (p < 0.04). Extremity injuries were more common in older patients (p < 0.001).

Conclusion

Patient age greater than 54 years and mechanism of injury are strong predictors of the ISS, injury localization, healthcare expenditure, and mean hospital stay. With the exception of obvious minor wounds, full trauma work-ups (CT chest/abdomen/pelvis and cervical spine) are encouraged for equestrian-related injuries in older patients and those injured by a fall.

Keywords

Equestrian Horse riding Trauma Falls Hospital charges Injury Severity Score 

Introduction

Horses are immensely popular in the United States, with nearly 2 million US households reporting ownership and over 3% of the population being exposed to horses every year [1]. It is estimated that more than 30 million Americans ride horses annually and 1 in 63 Americans are exposed to horses on a monthly basis [2]. The CDC estimates that more than 100,000 horse-related injuries occur every year and 28 injuries requiring hospitalization occur for every 100,000 hours of horseback riding [3, 4]. Prior surveys have found that up to 86% of equestrians suffer from horse-related injuries [5]. The combination of relatively high exposure and injury rates that exceed motorcycle riding and skiing result in a significant number of horse-related traumatic injuries, including 25% of all lethal sports injuries in children [6, 7, 8].

The mechanisms of horse-related injuries vary and include bites, falls, kicks, and trampling. Many horses weigh over 1000 lb, can attain top speeds of greater than 35 miles per hour, and can deliver up to 1 ton of force with a kick. These factors explain why horseback riding can result in severe injuries, including quadriplegia, and the highest sport-related mortality, greater than even motorcycle and automobile racing [9, 10, 11, 12].

Despite the high volume of horse-related traumatic injuries, there is a paucity of research in this area. To our knowledge, no reports in the radiology literature describe the frequency, type, estimated radiation dose, and cost related to imaging. The goal of this study is to quantify the incidence, type, severity, radiation dose, and total hospital charge per patient presenting with equestrian-related injury to a rural level 1 trauma center and then determine if differences related to age and gender exist.

Materials and methods

A retrospective electronic medical record review was performed for patients presenting to our level 1 trauma center for horse-related injuries between January 1, 2010, and December 31, 2013. Approval for this study was granted by the Institutional Review Board and was exempt from requiring informed consent.

Data recorded included patient age and gender, mechanism of injury, entry point into facility, types and number of imaging studies (X-ray, CT, MRI), types and number of injuries, estimated radiation dose administered during work-up, severity of injury, rate and duration of hospitalization admission/stay, and estimated cost of care for this single episode. The patients were divided into the following age groups (4–19, 20–39, 40–54, and 55–79 years) and subdivided into the following mechanisms of injury (fall, kicked, stepped on/trampled, and other) for further analysis. The “other” injury category included bites, allergies, and being pinned between the horse and another structure. The imaging reports were retrospectively reviewed by a 4th-year radiology resident for the types of injuries which were then cataloged into head/soft tissue neck, chest/abdomen/pelvis, spinal, or extremity. Estimated radiation dose was calculated using department standards for various types of radiographic and computed tomography exams, with the actual calculated dose utilized for any fluoroscopic exams. The rate of hospital admission was determined from EMR review as was the total length of the hospital stay, rounded up to the next full day. The severity of injury was calculated using the Injury Severity Score (ISS), which is commonly used to determine the degree of trauma with some using a score greater than 10 or 11 as a gauge of severe trauma. The estimated cost of care was determined from data provided by the institution’s finance division using the Medicare rates present at the time the study was conducted and included the cost from the time of emergency department presentation to discharge. The estimate did not include the cost of follow-up care, future surgeries, or any treatment obtained at other institutions.

Statistical analysis

Descriptive summaries

For descriptive purposes, categorical data are summarized by frequencies and percentages and continuous scaled variable are summarized by the mean and the range of the empirical distribution.

Statistical methods

Patient demographics, hospital admission rates, hospital length of stay, injury severity, radiation dose, and hospital-related costs were examined by mechanism and type of injury. Patient age and gender demographics were compared between the different “mechanism of injury” categories and between the different “type of injury” categories by way of Pearson’s chi-squared exact tests and Wilcoxon rank-sum tests, respectively. Hospital admission rates were compared between the different “mechanism of injury” categories and between the different “type of injury” categories by way of a binomial generalized linear model. Injury severity scores and hospital length of stay were compared between the different “mechanism of injury” categories and between the different “type of injury” categories by way of a negative binomial generalized linear model. Radiation dose was compared on the loge- mSv scale between the different “mechanism of injury” categories and between the different “type of injury” categories by way of a linear mixed model. Hospital-related cost was compared between the different “mechanism of injury” categories and between the different “type of injury” categories by way of a set of cumulative frequency distribution log-rank tests. With regard to hypothesis testing, a two-sided p ≤ 0.05 null hypothesis rejection rule was established a priori as the null hypothesis rejection criterion for all between “mechanism of injury” comparisons and for all between “type of injury” comparisons.

Statistical software

SAS version 9.4 (SAS Institute Inc., Cary, NC) was the statistical software package that was used to conduct the statistical analyses.

Results

Demographics

The retrospective search identified 281 patients with equestrian-related injuries that presented to our trauma center over the 4 year period. Of these patients, 222 presented to the emergency department (ED) and 59 were evaluated in other clinics. The 59 patients (mean age 38.7 years) not presenting to the ED were excluded from the remainder of the study as they all had relatively minor injuries; 37 with an ISS of “0,” 21 with an ISS of “1,” and one patient with an ISS of “4.” None were admitted. Of the 222 patients that presented to the ED, the mean patient age was 38.5 years (range 4–79) with a mean age of 36.7 years (range 5–79) for the 161 female equestrians and 43.3 years (range 4–76) for the 61 male riders (p = 0.042). The patients were categorized by age into the following 4 groups: 4–19 years (n = 50), 20–39 years (n = 60), 40–54 years (n = 50), and 55–79 years (n = 62).

Mechanism of injury

Injuries related to a fall from a horse accounted for 83.2% (186/222) of the patients, including 85.7% of females (138/161) and 78.7% of males (48/61) with a mean patient age of 39.0 years (Fig. 1a,b). Overall, patients who fell from a horse were more likely to have spinal injuries (odds ratio 4.36 [95% CI 1.28, 14.86], p = 0.018) and torso injuries (odds ratio 3.25 [95% CI 1.10, 9.66], p = 0.034) compared to those injured in another manner (Fig. 2a,b). Patients who suffered falls had the highest mean ISS, were most likely to be admitted to the hospital, had the most imaging exams performed, and tied with kick-related injuries for the longest mean hospital stay (Tables 1 and 2).
Fig. 1

A 16-year-old female patient injured following a fall while horseback riding. Axial unenhanced computed tomography images of the head demonstrates (a) intraventricular and (b) intraparenchymal hemorrhage (white arrows)

Fig. 2

A 36-year-old female injured from a fall while horseback riding. (a) Axial CT image demonstrates renal laceration with extravasation (white arrows). (b) Angiographic images of the left kidney demonstrating a renal laceration with extravasation (dotted white arrow) in the middle third of the kidney persisting despite embolization coil placement (white arrow)

Table 1

Anatomic region of injury categorized by mechanism of injury

Mechanism

Head injury (%)

Torso injury (%)

Spine injury (%)

Extremity injury (%)

Fall

16.1

29.6

29.0

26.9

Kicked

44.4

16.7

5.6

16.7

Stepped on

11.1

11.1

22.2

33.3

Other

25.0

0

0

25.0

Table 2

Mean ISS, mean dose, admission rate, mean hospital stay, and mean and median expenditure categorized by mechanism of injury

Mechanism

Mean ISS

Mean dose (mSv)

% Admitted

Mean hospital stay (days)

Mean/median expenditure

Fall

5.5

22.0

55.9

3.0

$30,818/$19,505

Kicked

4.6

24.6

50.0

3.0

$39,275/$25,758

Stepped-on

2.3

5.1

22.2

1.1

$9 593/$2 773

Other

1.9

15.9

33.3

1.9

$6 479/$3 201

Injuries related to a horse kick accounted for 8.1% (18/222) of the patients (mean age 34), including 6.8% (11/161) of females and 11.5% (7/61) of males. Patients injured by a kick suffered a head injury more often than those injured by other mechanisms (odds ratio 4.12 [95% CI 1.51, 11.24], p = 0.006) (Fig. 3a,b). Patients who were kicked had the highest mean expenditure and radiation dose. These patients had the second highest mean ISS and hospital admission rate (Tables 1 and 2).
Fig. 3

A 21-year-old female injured following a horse kick. (a) Axial unenhanced computed tomography image of the head demonstrates numerous facial fractures (white arrows). (b) 3-Dimensional reconstruction of the same patient (black arrows)

Injuries related to being stepped on by a horse accounted for 4.1% (11/222) of the patients (mean age 38), including 4.3% of females (7/161) and 3.3% of males (2/61). Patients who were stepped on had the highest rate of extremity injury, but this was not statistically significant (Tables 1 and 2). Of the 12 patients who did not suffer from falls, kicks, or being stepped on, two suffered extremity injuries and two suffered head injuries (Fig. 4) (Tables 1 and 2).
Fig. 4

Patient injured following bite from horse. AP hand radiograph demonstrates an oblique, angulated fracture of the little finger proximal phalanx (white arrow)

Overall, multivariate analysis demonstrated that the mechanism of injury was highly associated with number of radiographs ordered (p = 0.001), MRI/CT exams ordered (< 0.001), head injury (0.006), spine injury (0.019), torso injury (p = 0.036), radiation dose (< 0.001), and cost of care (p < 0.001).

Age of injured patient

Head injuries were most common in the 4–19-year-old age group (Tables 3 and 4). With the exception of head injuries, overall injury rates were slightly higher in the 20–39 and even more so in the 40–54-year-old age groups compared to the 4–19-year-olds, especially spine and extremity injuries. The 40–54-year-old group also had a higher hospital admission rate and median expenditure (Tables 3 and 4). Patients greater than 54 years of age were twice as likely to suffer spinal injuries and nearly 3.5 times as likely to suffer torso injuries compared to younger patients(p = < 0.001) (Fig. 5). They also had the highest rate of extremity injuries (Tables 3 and 4).
Table 3

Anatomic region of injury categorized by patient age

Age (yrs)

Head injury (%)

Torso injury (%)

Spine injury (%)

Extremity injury (%)

4–19

26.0

10.0

14.0

10.0

20–39

13.6

16.9

15.3

22.0

40–54

20.0

20.0

32.0

30.0

55–87

16.1

54.8

40.3

40.3

Table 4

Mean ISS, mean dose, admission rate, mean hospital stay, and mean and median expenditure categorized by patient age

Age (yrs)

Mean ISS

Mean dose (mSv)

% Admitted

Mean hospital stay (days)

Mean/median expenditure

4–19

4.1

13.9

40.0

2.2

$21,005/$7414

20–39

3.6

20.3

38.3

2.0

$24,612/$9 667

40–54

4.2

20.6

50.0

2.0

$25,558/$13,150

55–87

8.3

27.8

80.6

4.9

$44,511/$30,496

Fig. 5

A 63-year-old male patient injured from fall while horseback riding. Sagittal reformatted computed tomography image of the thoracic spine demonstrates spinous process (white arrows) and endplate fractures (dotted white arrow)

Overall, multivariate analysis revealed that increased age was highly associated with the mean number of imaging exams ordered (p < 0.001), length of hospital admission (p = 0.001), number of radiographs ordered (p = 0.015), number of CT/MRI ordered (p = < 0.001), ISS (p = 0.017), medical costs (p < 0.001), extremity injury (p < 0.001), spine injury (p < 0.001), torso injury (p < 0.001), and radiation dose (p = 0.003).

Gender

We found no differences in the rate of injury, type of injury, length of hospital stay, number of imaging exams ordered, ISS, radiation exposure, or medical costs based on patient gender using multivariate analysis. The only difference we found associated with gender was that injured females were younger than injured males (p = 0.042).

Discussion

Horses are magnificent and beautiful animals that are enjoyed by many. They are also extremely powerful and potentially dangerous animals with everyone in their immediate vicinity at risk for injury, including riders, caretakers, and bystanders. While prior studies have reviewed injury patterns and demographics of patients suffering horse-related injuries, few if any have reported the radiologic aspects of their care, including mean radiation exposure, mean number of imaging exams, injuries revealed via imaging, and the cost of providing care to these patients [13]. Our goal was to evaluate these areas and determine if any difference existed based on age, gender, or mechanism of injury.

The mechanisms of injury in our patient population are similar to those in prior studies, with 83.2% resulting from falls and 8.1% from kicks compared to 43–82 and 8–29%, respectively [5, 6, 14, 15]. The demographics of our patients are also similar with prior studies reporting 59–88% of injuries occurring to females compared to 72.5% in our study [10, 16, 17, 18, 19]. Mean age in our study was 38.5 years, at the higher end of the age range of 30–38 years reported in prior studies [18, 19, 20]. In our study, both torso and spine injuries occurred in ~ 25% of patients, whereas prior studies have reported torso injury rates between 9 and 16% and spine injuries between 12 and 29% [10, 16, 17, 20]. This incidence at the upper range of the prior studies is likely due to the older age of our patients.

The distribution of ISS scores of patients in our study is similar to that in prior studies evaluating equestrian injuries with 15.3% of patients rated as severely injured (ISS greater than 11) and 70.3% of patients rated as mildly injured (ISS less than 6) compared to 10.5 and 80% of patients reported by Bilaniuk et al. [19], respectively. The injury severity score (ISS) has been shown to correlate with mortality, morbidity, and hospital stay and is calculated by scoring injuries in 6 body regions using the Abbreviated Injury Scale (AIS), with 0 indicating no injury and 6 indicating the injury is not survivable. If any region receives an AIS of 6, the ISS is automatically given 75 which is the highest possible score. Otherwise, each region’s AIS is squared and then summed [21]. More importantly, patients over the age of 54 had a mean ISS more than double any other age group with patients injured by falls or kicks also having a higher ISS. However, the mechanism of injury was less of a factor compared to patient age.

We calculated an overall mean expenditure per injured patient of $29,737 with the total costs sustained by all of the patients in the study exceeding $6.5 million, numbers similar to a prior study reported in the surgical literature [18]. The mean and median expenditure were significantly higher for patients older than 54 years which is likely due to the longer mean hospital stay per admission and the fact that older patients had a much higher rate of spinal and torso injuries resulting in increased imaging. The mean expenditure was also noted to be higher than the median expenditure in each category. This gap in expenditure is due to a smaller number of “outlier” patients with very severe injuries accounting for a large portion of the healthcare expenditure. This gap was most pronounced in patients injured by horse kicks with more than $13,000 difference in mean and median expenditure. Unlike kicks to an extremity, horse kicks to the head result in severe head and facial injuries more than 70% of the time, resulting in greater expenditure [22].

Limitations included the lack of availability of the frequency of use of protective equipment by the injured individuals, including helmets and body protection vests. This precluded our ability to consider that variable in the multivariate analyses and determine if variations in safety practices played a role in the severity of injuries or anatomic region of bodily injury. However, prior studies have suggested a statistically significant increase in ISS among individuals who were not wearing helmets [19, 23]. The lack of the actual radiation dose and the exact cost of each study are also limitations; however, by using the average radiation dose and the Medicare reimbursement rates allowed for a uniform comparison. A more significant limitation is the lack of the inclusion of costs related to the injury but outside the time period of the hospital presentation and admission to include costs associated with rehabilitation, future hospitalizations required for additional reconstructive surgeries, costs associated with work absence, disability, and decreased quality of life.

Conclusion

We found that patient age and to a lesser extent mechanism of injury were the strongest predictors of injury severity, use of radiology resources, length of hospital stay, and overall healthcare expenditure. Since patients over 54 years of age sustained over half of the most severe injuries, we recommend full trauma protocol workups to include CT of the chest/abdomen and pelvis as well as cervical spine for patients in this age group with the exception of those patients with obvious limited injuries. We also suggest injury prevention strategies targeted towards older people exposed to horses, including the possible use of protective body equipment, since patients in this group sustained more spine and torso injuries [24]. Additional studies examining the use of this equipment as well as the small percentage of patients that suffered the most severe injuries may provide more targeted means of preventing disabling and costly injuries.

Notes

Acknowledgments

The data for this study originated from and was provided by the University of Virginia.

Compliance with ethical standards

Conflict of interest

All the authors verify that they have no relevant financial disclosures or conflicts of interest.

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Copyright information

© American Society of Emergency Radiology 2019

Authors and Affiliations

  1. 1.Mayo Clinic ArizonaPhoenixUSA
  2. 2.Medical Center RadiologistsVirginia BeachUSA
  3. 3.Department of Radiology and Medical ImagingUniversity of VirginiaCharlottesvilleUSA
  4. 4.Department of Public Health SciencesUniversity of VirginiaCharlottesvilleUSA

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