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Epidemiology of Stress Fracture Injuries Among US High School Athletes, 2005-2006 Through 2012-2013 Bradley G. Changstrom, Lina Brou, Morteza Khodaee, Cortney Braund and R. Dawn Comstock Am J Sports Med published online December 5, 2014 DOI: 10.1177/0363546514562739 The online version of this article can be found at: http://ajs.sagepub.com/content/early/2014/12/05/0363546514562739
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Epidemiology of Stress Fracture Injuries Among US High School Athletes, 2005-2006 Through 2012-2013 Bradley G. Changstrom,*y MD, Lina Brou,z§ MPH, Morteza Khodaee,|| MD, MPH, Cortney Braund,z MD, and R. Dawn Comstock,{ PhD Investigation performed at the University of Colorado School of Medicine, Aurora, Colorado, USA Background: High school athletes in the United States sustain millions of injuries annually, approximately 10% of which are fractures. However, there is no clear estimate of the number of stress fractures sustained by high school athletes annually despite reports that stress fractures account for 0.7% to 20% of injuries seen in sports medicine clinics. This suggests a high utilization of resources for a potentially preventable injury. In addition, stress fractures have been associated with low energy availability and disordered eating in young athletes, highlighting the importance of early recognition and intervention. Purpose: To investigate stress fracture rates and patterns in a large national sample of US high school athletes. Study Design: Descriptive epidemiologic study. Methods: Data from High School RIO (Reporting Information Online), a national sports injury surveillance study, were analyzed to describe rates and patterns of stress fracture injury sustained from 2005-2006 through 2012-2013, across sports and by sex. Results: From 2005-2006 through 2012-2013, a total of 51,773 injuries were sustained during 25,268,873 athlete-exposures, of which 389 (0.8%) were stress fractures, resulting in an overall stress fracture rate of 1.54 per 100,000 athlete-exposures. Rates per 100,000 athlete-exposures were highest in girls’ cross country (10.62), girls’ gymnastics (7.43), and boys’ cross country (5.42). In sex-comparable sports, girls sustained more stress fractures (63.3%) than did boys (36.7%) and had higher rates of stress fracture (2.22 vs 1.27; rate ratio, 1.75; 95% CI, 1.38-2.23). The most commonly injured sites were the lower leg (40.3% of all stress fractures), foot (34.9%), and lower back/lumbar spine/pelvis (15.2%). Management was nonsurgical in 98.7% of the cases, and 65.3% of injuries resulted in 3 weeks of time loss, medical disqualification, or an end to the season before athletes could return to play. Conclusion: Although a rare injury, stress fractures cause considerable morbidity for high school athletes of both sexes. Future research should evaluate risks of stress fractures to drive development of targeted prevention efforts. Keywords: stress fractures; High School RIO; injury surveillance; epidemiology; pediatric sports medicine; female athletes
Although there are multiple benefits to participation in sports, high school athletes are exposed to risk of injury, which can pose a significant personal and financial burden.10,13,15,26 A recent study reported that fractures represent 10% of all injuries sustained by high school athletes and are more common among males and in contact sports.30 In contrast, stress fractures have been reported to occur more commonly among females and athletes participating in sports associated with leanness.3,22,33 Stress fractures can require long periods of recovery, are often complicated by delays in diagnosis, and frequently require advanced imaging for diagnosis, suggesting high morbidity for athletes.2,5,6,11,19,23,31 Currently, there is no clear estimate of the number of stress fractures sustained by US
high school athletes annually despite reports that stress fractures account for 0.7% to 20% of injuries seen in sports medicine clinics.5 Adolescence is an important period of time for bone health given that peak bone mineral density, a major determinant of long-term risk of osteoporosis, is attained by early adulthood.5,8 While stress fractures are well studied in military recruits, college athletes, and runners of all ages, it is unclear whether these studies are generalizable to high school athletes, many of whom are skeletally immature.21,24,34 For example, military recruits have an annual incidence of stress fractures between 3% and 9%, and similar numbers are reported in general athlete populations,33 yet fewer National Collegiate Athletic Association Division I collegiate athletes (1.4%) sustain stress fractures annually.7 One study reported an incidence of 3.9% in female adolescent athletes, noting that participation in specific sports, including running, basketball, and cheerleading/ gymnastics, was a risk factor.5 However, rates and
The American Journal of Sports Medicine, Vol. XX, No. X DOI: 10.1177/0363546514562739 Ó 2014 The Author(s)
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patterns of stress fracture across high school sports and by sex, including boys’ sports, have not been well described. For example, in describing an expansion of the female athlete triad to include male sex, a recent consensus statement by the International Olympic Committee on Relative Energy Deficiency in Sport18 (RED-S) recognized the paucity of data regarding risks for stress fractures in males. We believe that understanding a pattern of injury is the first important step toward development of targeted stress fracture prevention efforts. Therefore, the objective of this study was to describe rates and patterns of stress fracture across multiple high school sports and by sex among a large national sample of US high school athletes.
MATERIALS AND METHODS Data We analyzed data from the National High School SportsRelated Injury Surveillance System, High School RIO (Reporting Information Online), an Internet-based sports injury surveillance system that has been described previously.27,29 In brief, high schools with 1 or more National Athletic Trainers’ Association–affiliated certified athletic trainers (ATs) with valid e-mail addresses were invited to participate. Responding high schools were categorized into 8 strata based on population (enrollment 1000 or .1000) and geographic region according to US census reports.32 For the 9 sports included in the study since 2005-2006 (football, boys’ and girls’ soccer, girls’ volleyball, boys’ and girls’ basketball, wrestling, baseball, and softball), 100 high schools were randomly chosen to participate (12 or 13 from each of the 8 strata). If a school dropped out of the study, a replacement from the same stratum was randomly selected to maintain the 100-school study population. Certified ATs from participating high schools reported injury and athlete-exposure information on the study website weekly throughout the academic year. For the additional 9 sports added to High School RIO since 2008-2009 (girls’ field hockey, girls’ gymnastics, boys’ ice hockey, boys’ and girls’ lacrosse, boys’ and girls’ track and field, boys’ and girls’ swimming and diving), as well as 2 sports added since 2009-2010 (cheerleading and boys’ volleyball) and 2 sports added since 2011-2012 (boys’ and girls’ cross country), not enough schools from each of the 8 strata volunteer annually to report for all
sports to provide a randomly selected sample. Thus, exposure and injury data for these sports were collected from a convenience sample of US high schools. In this study, all data reported by the randomly selected sample and convenience sample were combined to create the study dataset.
Definition of Injury and Exposure In High School RIO, an athlete-exposure (AE) is defined as 1 athlete participating in 1 school-sanctioned practice or competition. A reportable injury is one that (1) occurred as a result of participation in an organized practice, competition, or performance; (2) required medical attention by an AT or physician; and (3) resulted in restriction of the athlete’s participation for 1 or more days, although beginning in 2007-2008 the definition was expanded to include all concussions, fractures (including stress fractures), and dental injuries, even if there was no time lost from sports participation. For each injury, ATs completed detailed injury reports on the injured athlete (age, height, weight, etc), the injury (site, diagnosis, severity, etc), and the management of the injury (imaging, treatment, return to play, etc). Throughout the study, ATs were able to view previously submitted information and to update reports as needed. We included all stress fractures reported by certified ATs to High School RIO in this study.
Statistical Analysis We calculated rates and rate comparisons using unweighted case counts for the combined original and convenience samples for all 22 sports. We analyzed the data using SAS v9.3 (SAS Institute) and SPSS v19.0 (SPSS Inc). We calculated injury rates as the number of stress fractures per 100,000 AEs. Subgroup differences were evaluated with injury rate ratios (RRs) or injury odds ratios (ORs) and 95% confidence intervals (CIs). Any CIs not including 1.00 were considered statistically significant. The following is an example of the RR calculations:
RR5
#of stress fractures sustained by girls=#of total AEs for girls : #of stress fractures sustained by boys=# of total AEs for boys
This study was approved by the Institutional Review Board at Nationwide Children’s Hospital, Columbus,
*Address correspondence to Bradley G. Changstrom, MD, Department of Internal Medicine, University of Colorado School of Medicine, Academic Office One, 12631 E 17th Avenue, B177, Aurora, CO 80045, USA (e-mail: [email protected]). y Department of Internal Medicine, University of Colorado School of Medicine, Aurora, Colorado, USA. z Department of Emergency Medicine, The Children’s Hospital Colorado, Aurora, Colorado, USA. § Section of Emergency Medicine, Department of Pediatrics, University of Colorado School of Medicine, Aurora, Colorado, USA. || Department of Family Medicine, University of Colorado School of Medicine, Aurora, Colorado, USA. { Department of Epidemiology and Pediatric Injury Prevention, Education and Research (PIPER) Program, Colorado School of Public Health, Aurora, Colorado, USA. One or more of the authors has declared the following potential conflict of interest or source of funding: The content of this report was funded in part by the Centers for Disease Control and Prevention (grant No. R49/CE000674-01 and R49/CE001172-01). The content of this report is solely the responsibility of the authors and does not necessarily represent the official views of the Centers for Disease Control and Prevention. The authors also acknowledge the generous research funding contributions of the NFHS, NOCSAE, DonJoy Orthotics, and EyeBlack.
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TABLE 1 Total Number of Stress Fractures, Rates of Stress Fractures per 100,000 AEs by Sport, and Rate Ratio for Stress Fractures in Sex-Comparable Sportsa
Total Sex-comparable boys Sex-comparable girls Girls:boys total Football Soccer Boys Girls Volleyball Boysc Girls Basketball Boys Girls Wrestling Baseball Softball Girls’ field hockeye Girls’ gymnasticse Boys’ ice hockeye Lacrossee Boys Girls Swimming and divinge Boys Girls Track and fielde Boys Girls Cheerleadingc Cross countryf Boys Girls
Stress Fractures, n
Total AEs, n
Proportion, %
Rate per 100,000, %
Rate Ratiob
95% CI
389 106 183 210:179 64
25,268,873 8,365,282 8,233,425
100.0 36.7 63.3
1.54 1.27 2.22
1.75
1.38-2.23
1.84
1.51-2.24
5,034,718
16.5
1.27
32 37
1,895,874 1,607,052
8.2 9.5
1.69 2.30
1.36
0.84-2.19
0 20
56,208 1,683,815
0.0 5.1
0.00 1.19
—d
24 50 8 13 3 15 6 1
2,286,793 1,846,699 1,713,203 1,735,120 1,294,271 478,503 80,739 311,817
6.2 12.9 2.1 3.3 0.8 3.9 1.5 0.3
1.05 2.71 0.47 0.75 0.23 3.13 7.43 0.32
2.58
1.59-4.20
0.31
0.09-1.10
6 11
529,268 382,340
1.5 2.8
1.13 2.88
2.54
0.94-6.86
1 0
444,915 503,077
0.3 0.0
0.22 0.00
—d
23 50 6
1,287,860 1,051,186 803,171
5.9 12.9 1.5
1.79 4.76 0.75
2.66
1.63-4.36
7 12
129,244 113,000
1.8 3.1
5.42 10.62
1.96
0.77-4.98
a National High School Sports-Related Injury Surveillance Study, 2005-2006 through 2012-2013. Rates and rate ratios were calculated using only sex-comparable sports including soccer, volleyball, basketball, baseball/softball, swimming and diving, track and field, and cross country. AE, athlete-exposure. b Compares the stress fracture rates between sex-comparable girls’ and boys’ sports (girls:boys). c Data collected from 2009-2010 to 2012-2013. d Rate ratios could not be calculated because there were no stress fractures. e Data collected from 2008-2009 to 2012-2013. f Data collected from 2011-2012 to 2012-2013.
Ohio, and at the Colorado Multiple Institutional Review Board, Aurora, Colorado.
RESULTS Overall From 2005-2006 through 2012-2013, High School RIO captured 51,773 injuries sustained during 25,268,873 AEs, of which 389 (0.8%) were stress fractures, resulting in an overall stress fracture rate of 1.54 per 100,000 AEs. Stress fracture rates were highest in girls’ cross country (10.62), girls’ gymnastics (7.43), and boys’ cross country (5.42) and lowest in boys’ swimming and diving (0.22), boys’ ice
hockey (0.32), and cheerleading (0.75) (Table 1). The ATs did not report any stress fractures in boys’ volleyball and girls’ swimming and diving. Although football had a relatively low rate of stress fracture (1.27/100,000 AEs), this sport had the highest total number of injuries (n = 64), accounting for 16.5% of all stress fractures reported. Of note, several of the higher risk sports by rate had fewer years of data collection compared with the sports included since the inception of the study.
Demographics of Injured Athletes The age range for injured athletes was 13 to 19 years (mean age, 15.8 years; median age, 16 years). The body mass index (BMI) ranged from 15.6 to 41.5, with a mean
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TABLE 2 Location of Stress Fracture Injuries by Sport (n = 387 Injuries)a Sport Football (n = 64) Soccer Boys (n = 32) Girls (n = 37) Volleyball Boys (n = 0)c Girls (n = 20) Basketball Boys (n = 24) Girls (n = 50) Wrestling (n = 8) Baseball (n = 13) Softball (n = 3) Girls’ field hockey (n = 13)d Girls’ gymnastics (n = 6)d Boys’ ice hockey (n = 1)d Lacrossed Boys (n = 6) Girls (n = 11) Swimming and divingd Boys (n = 1) Girls (n = 0) Track and fieldd Boys (n = 23) Girls (n = 50) Cheerleading (n = 6)c Cross countrye Boys (n = 7) Girls (n = 12)
Upper Extremityb (n = 11)
Lower Back/Lumbar Spine/Pelvis (n = 59)
Hip (n = 4)
Thigh/Upper Leg (n = 4)
Knee (n = 6)
Lower Leg (n = 156)
Ankle (n = 12)
Foot (n = 135)
4
21
0
0
0
13
4
22
0 0
7 4
0 0
0 0
2 1
10 15
3 1
10 16
0 0
0 6
0 0
0 0
0 0
0 5
0 0
0 9
0 1 0 3 2 0 0 0
2 2 4 4 0 1 2 0
0 0 0 1 0 1 0 0
0 2 0 0 0 0 0 0
0 0 0 0 0 0 1 0
4 23 2 2 0 7 3 0
1 1 0 1 0 0 0 0
17 21 2 2 1 4 0 1
1 0
1 0
0 0
0 0
0 0
1 3
1 0
2 8
0 0
1 0
0 0
0 0
0 0
0 0
0 0
0 0
0 0 0
2 1 1
1 0 0
0 1 0
1 1 0
14 39 2
0 0 0
5 8 3
0 0
0 0
0 1
1 0
0 0
5 8
0 0
1 3
a National High School Sports-Related Injury Surveillance Study, 2005-2006 through 2012-2013. Values in the table are numbers of injuries. Two injuries were excluded, as data on the location of injury was missing. b Upper extremity injuries included shoulder, forearm, wrist, hand, chest/thoracic spine/ribs. c Data collected from 2009-2010 to 2012-2013. d Data collected from 2008-2009 to 2012-2013. e Data collected from 2011-2012 to 2012-2013.
of 22.7. Mean BMI was 21.3 and 24.0 for injured females and males, respectively.
Patient Sex Across all sports, more stress fractures occurred in girls’ sports (54.0%) than in boys’ sports (46.0%). In sex-comparable sports, a higher proportion of stress fractures was also reported in girls (63.3%) compared with boys (36.7%). Additionally, in sex-comparable sports, there was a statistically significant difference between rates of stress fracture in girls (2.22/100,000 AEs) compared with boys (1.27/100,000 AEs) (RR, 1.75; 95% CI, 1.38-2.23). More specifically, stress fracture rates were significantly higher for girls than for boys in track and field (RR, 2.66; 95% CI, 1.63-4.36) and basketball (RR, 2.58; 95% CI, 1.59-4.20). There was no statistically significant difference between girls’ and boys’ lacrosse (RR, 2.54; 95% CI, 0.94-6.86]), girls’ and boys’ cross country (RR, 1.96; 95% CI, 0.77-4.98), girls’ and boys’ soccer (RR, 1.36;
95% CI, 0.84-2.19), and baseball and softball (RR, 0.31; 95% CI, 0.09-1.10). Rate ratios for volleyball and swimming and diving could not be calculated because no stress fractures were reported for boys’ volleyball and girls’ swimming and diving.
Body Site Across all sports, the most commonly injured body sites were the lower leg (40.3%), foot (34.9%), and lower back/ lumbar spine/pelvis (15.2%). Based on how the data were reported, additional details on the exact location of the injuries could not be provided (Table 2). For example, stress fractures to the foot could be located in any one of the metatarsal or sesamoid bones, whereas stress fractures in the lower leg could be located in the tibia or fibula; therefore, the high-risk or low-risk nature of the injuries by location could not be determined. The foot was the most common site of stress fracture in the majority of sports, including
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girls’ lacrosse (72.7%), boys’ basketball (70.8%), cheerleading (50.0%), girls’ volleyball (45.0%), girls’ soccer (43.2%), football (34.4%), boys’ lacrosse (33.3%), and boys’ soccer (31.3%). The lower leg was the most common site of stress fracture in boys’ and girls’ track and field (60.9% and 78.0%), boys’ and girls’ cross country (71.4% and 66.7%), girls’ field hockey (53.8%), and girls’ basketball (46.0%). There was no significant difference between boys and girls regarding risk of upper extremity stress fractures (RR, 2.35; 95% CI, 0.59-9.22). Of the stress fracture injuries that occurred in the upper body (ie, elbow, shoulder, forearm, wrist, hand, chest/thoracic spine/ribs), which represented 2.8% of all stress fractures, nearly all were sustained by athletes playing sports that involve overhead activities as key components of the sport, such as baseball, softball, lacrosse, and football. Caution should be used when interpreting this, however, as stress fractures to the trunk and upper body were uncommon.
Diagnosis and Imaging Most stress fractures (90.8%) were assessed by a physician, and more than half (55.0%) were evaluated by an orthopaedic specialist. The majority of stress fractures were evaluated with a plain radiograph (82.7%); magnetic resonance imaging (MRI; 32.3%) and computed tomography (CT) scan (6.6%) were used less frequently. Other modalities were used 11% of the time, but this surveillance system did not capture how many of these were diagnosed clinically—without imaging—or were evaluated with a bone scan or other diagnostic and/or imaging technique. Of the few trunk and upper extremity stress fractures, 80% were evaluated by a physician or an orthopaedic specialist, 80% had a plain radiograph, and 30% had an MRI.
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TABLE 3 Recurrent Stress Fractures by Body Parta Stress Fractures, % Total Body Part Injured
New
Recurrent
Shoulder (n = 1) Elbow (n = 1) Forearm (n = 1) Wrist (n = 1) Hand (n = 2) Chest/thoracic spine/ribs (n = 4) Lower back/lumbar spine/pelvis (n = 57) Hip (n = 4) Thigh/upper leg (n = 4) Knee (n = 6) Lower leg (n = 153) Ankle (n = 12) Foot (n = 135) Total (n = 381)b
100.0 100.0 100.0 100.0 100.0 100.0 61.0 75.0 100.0 100.0 81.7 83.3 88.9 313
0 0 0 0 0 0 39.0 25.0 0 0 18.3 16.7 11.1 69
a National High School Sports-Related Injury Surveillance Study, 2005-2006 through 2012-2013. b Seven injuries did not have data available on whether they were new or recurrent injuries, and 1 injury did not have data available on location of injury; these were therefore excluded from this analysis.
significantly affect return to play (OR, 1.2; 95% CI, 0.682.10). Interestingly, 39.0% of all lower back/lumbar spine/ pelvis injuries were recurrent injuries (Table 3). Recurrent injuries were also more frequent in stress fractures of the hip (25.0%), lower leg (18.3%), ankle (16.7%), and foot (11.1%). None of the upper extremity injuries (shoulder, elbow, forearm, wrist, hand, and chest/thoracic spine/ ribs) were recurrent injuries.
Outcomes Return to play was reported to High School RIO as a categorical variable, and 3 weeks was the largest time variable available to ATs to select for outcomes of stress fracture injuries. Overall, a large proportion (65.3%) of stress fractures required a prolonged recovery; 32.8% required more than 3 weeks before return to play, 18.1% were medically disqualified, and 14.1% had an end to the season before return to play. Only 34.7% of athletes who sustained stress fractures returned to play within 3 weeks of injury; interestingly, most of the athletes with upper extremity injuries (68%) returned to play within this time period. There was no significant difference for prolonged return to play between stress fractures to the lower body and upper body (OR, 3.93; 95% CI, 0.97-16.00). The majority of stress fractures across nearly all sports involved prolonged time away from participation. Nearly all (98.7%) stress fractures were managed nonoperatively; only 5 total injuries were treated surgically.
History of Injury Of all stress fractures, 18.1% were reported to be recurrent rather than new injuries. History of stress fracture did not
DISCUSSION To our knowledge, few studies have examined stress fractures in the adolescent population across a variety of both boys’ and girls’ sports.1,9 This study evaluates data from the National High School Sports-Related Injury Surveillance System to study stress fractures among a large national sample of high school athletes participating in 22 sports from 2005-2006 through 2012-2013, resulting in the largest study of stress fractures among high school athletes to date. Our findings demonstrate that although a rare injury, stress fractures cause considerable morbidity to high school athletes of both sexes, with rates and patterns of stress fracture injuries varying by sport and sex. Risk stratification by sport is an essential piece of information for targeted prevention-management strategies. Consistent with previous investigators, we found that stress fracture rates in both boys’ and girls’ track and field and cross country and gymnastics were among the highest for all sports evaluated.5,16 Additional high-risk sports in our study included field hockey and basketball for girls and soccer for boys. Although a previous study identified girls’ basketball as a high-risk sport, our study also
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uniquely identified girls’ field hockey and boys’ soccer in this category.5 We could not find any previously published studies reporting these as high-risk sports. Other studies have suggested that cheerleading is a high-risk sport, but our data could not corroborate this finding.5,16 Interestingly, a large number of the total stress fractures documented in this study occurred in football players. Given the large number of high school athletes playing football, clinicians should expect to treat football players who have various stress fractures despite the relatively low rates of stress fracture in this sport. In general, female sex is a well-known risk factor for stress fracture.1,20 Overall, girls were at increased risk of stress fracture compared with boys across sex-comparable sports in our study (RR, 1.75; 95% CI, 1.38-2.23) as well as in most sex-comparable sports such as track and field and basketball. Interestingly, in sex-comparable sports, boys’ baseball was the only sport in which boys may be at greater risk for stress fracture than girls when compared with girls’ softball, although this difference was not statistically significant (RR, 0.31; 95% CI, 0.09-1.10) and there are limitations in comparing these sports. The relative risk calculated in this study is consistent with previous studies that demonstrated a risk of stress fracture of approximately 1.5 to 3.5 in women compared with men.2,6,11,23 Although girls remain at a higher risk of stress fracture compared with boys in general and in most sports, several boys’ sports demonstrated high rates of stress fractures (including cross country, track and field, and soccer), and stress fractures occurred in nearly all high school sports. Stress fractures in adolescent boys have not been well described1,18,31; this study represents one of the largest studies of stress fractures in boys’ high school sports, with 179 total stress fractures reported in boys’ sports alone. These data support the recent consensus statement by the International Olympic Committee (RED-S)18 that both men and women may be susceptible to relative energy deficiency in sport as evidenced by stress fractures, and this study provides additional data regarding risks for stress fracture in this population. Although further research to understand any underlying sex differences that place girls at higher risk is certainly indicated, including male sex in future research is paramount given the lack of previous research in these athletes. This study was too limited to describe risks on an individual basis by sport, and future research should include research on sports that have previously been poorly characterized. Such sports include boys’ soccer and girls’ field hockey because of the high rates of stress fracture as well as football because of the high rate of participation. Certified ATs reported stress fractures to High School RIO by general body site, but our dataset did not have any available information on exact location or severity of injury. The majority of stress fractures were lower extremity fractures, and lower extremity stress fractures were common across all sports. Of the small number of upper extremity fractures observed in this study, these occurred nearly exclusively in sports that involved overhead activities, including baseball, softball, lacrosse, and football; 1 injury to the wrist was reported in girls’ basketball.
Prospective trials showed that tibial stress fractures were the most common stress fractures in high school female runners and metatarsal stress fractures were the most common stress fractures in high school male runners.31 Although our data on location of injuries in stress fractures are limited, our findings can help clinicians stratify risk of overuse injuries by general location of injury through additional knowledge on the high-risk locations of stress fractures by sport. The expense of imaging during evaluation can be prohibitive to high school athletes and their families.4,12 We found that 82.7% of stress fractures in this patient population were evaluated by plain radiograph. As a plain radiograph is the initial recommended step in management of stress fractures, we expected many patients to have had a plain radiograph.25,28 However, plain radiographs may miss early stress injuries, as these radiographs have a sensitivity between 10% and 70% depending on the timing of imaging and onset of symptoms.5,14 It was not uncommon for providers to choose other modalities of imaging, such as MRI (32.3%) and CT scans (6.6%). These data did not capture how many stress fractures were diagnosed clinically or by a bone scan, although 10.4% of ATs selected ‘‘other’’ as an imaging modality. It is interesting but not surprising to see that such a high number of these injuries received an imaging technique other than plain radiograph for diagnosis, given the limitations of plain radiography specifically for stress fracture. An MRI is generally the preferred follow-up imaging technique for suspected stress fractures, and nearly one-third of stress fractures diagnosed in our study included MRI.6 A recent study by Nattiv et al19 demonstrated correlation between degree of severity of MRI findings and return to play for collegiate track and field athletes, which could be another future direction of study not captured by these data. Other than clinical diagnosis, plain radiography is the least expensive of these imaging modalities.25 The balance between the cost of imaging, severity of injury, and implications for return to play must be investigated further to identify which athletes will benefit most from advanced imaging such as MRI. Early detection of stress fractures is important, as delays in diagnosis and treatment can result in delayed return to activity or progression of injury.24,25 Our findings demonstrated that stress fractures have high morbidity, evidenced by delayed return to activity or removal of the student-athlete from participation. This is consistent with previous studies that reported return to play following stress fractures was between 4 and 12 weeks or longer.17,24 However, a striking number of athletes with stress fractures returned to play within 3 weeks (34.7%). This may reflect the possibility that clinicians are incorrectly diagnosing injuries as stress fractures or that they are not following current return-to-play protocols.6 Finally, it may demonstrate that some injuries, such as injuries to the upper extremity, may not require long delays in recovery. Given the rarity of upper extremity injuries, it may be difficult to ever develop guidelines on evidence-based management of these injuries other than through symptombased return to play. Because of the complexity of recovery
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based on severity and location of injuries, we recommend location and symptom-based return-to-play protocols with consideration of the female athlete triad.3,4 Fortunately, management was nonsurgical for 98.7% of stress fractures. The infrequent need for surgery that was reported may be because clinicians are more aware of stress fractures and are appropriately withholding return to play for athletes, or it may be because some stress fractures that require surgical management are not recognized as stress-related injuries and may not be reported as a stress fracture by physicians or ATs. Finally, this number may reflect the true incidence of an injury that generally requires nonsurgical management. A history of stress fractures was common, as 18.1% of injuries were described as recurrent injuries. This finding was not surprising; a recent study also demonstrated that prior stress fracture was the most common risk factor for stress fractures in adolescent male runners.31 Identification of the age at which these athletes experience their first stress fracture was not included in the dataset, but doing so would be essential to determine the timing of preventative strategies. None of the upper extremity injuries were classified as recurrent injuries. This finding may reflect the fact that many of these injuries represented initial stress fractures for these athletes, and it may therefore underrepresent the overall risk of a history of stress fracture for future stress fractures. Given the complexities of adolescent growth, bone development, and injuries, more information is needed about the individual athletes experiencing these fractures to further identify specific risks. There were several limitations to our study. First, our data were limited to high schools with certified ATs, which restricted our population. However, 90.8% of the stress fractures were evaluated by a physician, and all injuries were reported to High School RIO by certified ATs, which we believe increased our data quality. The High School RIO database relies on the professional opinion of the ATs in the participating high schools to determine which injuries met the diagnostic criteria for stress fracture. Although uniform criteria for a diagnosis of stress fracture were not established for this injury surveillance system, the data reflect high school athletes who have been managed as if they have a stress fracture. To reduce reporter burden, the High School RIO surveillance system captures athleteexposures as unit based rather than time based, and therefore we were unable to report injury rates by minute or hour of practice and competition. Of note, both samples concurrently enrolled in High School RIO, the original randomly selected nationally representative sample and the convenience sample, were combined in this report. Even though our inclusion of the convenience sample of high schools did not allow us to provide national estimates for stress fractures, including these data increased our sample size, which allowed comparison of rates and patterns of injury across a large number of sports. Therefore, although the data may not be nationally representative, this study remains the largest nationwide epidemiologic study describing stress fractures in US high school athletes in boys’ and girls’ sports. The reporting system was limited by several variables, including the inability to input continuous data to
7
determine average time before return to play or to input the precise location of injury. These are important limitations because the anatomic location of a stress fracture can have implications regarding whether it is considered a high- or low-risk injury.4 In addition, many stress fractures require substantially longer than 3 weeks for return to play, and the duration of recovery could not be calculated with the categorical data reported in this study. Finally, we were not able to analyze for predisposing factors such as disordered eating.
CONCLUSION Both male and female high school athletes and athletes across a wide range of high school sports are at risk for stress fractures. It is important to keep this in mind because stress injuries may serve as warning signs for care providers that major disruptions in energy balance may be present. Consequences of stress fractures include expensive diagnostic techniques and prolonged recovery, in addition to other comorbidities that may be present. Our findings highlight the need for further research in both boys’ and girls’ sports to provide evidence needed to drive the development of targeted stress fracture prevention programs. High school athletes will continue to struggle with pressures of competition, exposing themselves to the risks of stress fractures until effective intervention measures aimed at prevention and early detection are implemented.
ACKNOWLEDGMENT The authors thank the certified athletic trainers for their hard work and dedication in providing us with complete and accurate data. In addition, the authors thank the staff at High School RIO for their efforts in website management. Without their efforts, this study would not have been possible. Finally, they thank Nicole T. Townsend for critical feedback regarding the manuscript.
REFERENCES 1. Barrack MT, Ackerman KE, Gibbs JC. Update on the female athlete triad. Curr Rev Musculoskelet Med. 2013;6(2):195-204. 2. Brunet ME, Cook SD, Brinker MR, Dickinson JA. A survey of running injuries in 1505 competitive and recreational runners. J Sports Med Phys Fitness. 1990;30:307-315. 3. De Souza MJ, Nattiv A, Joy E, et al. 2014 Female Athlete Triad Coalition Consensus Statement on Treatment and Return to Play of the Female Athlete Triad: 1st International Conference held in San Francisco, California, May 2012 and 2nd International Conference held in Indianapolis, Indiana, May 2013. Br J Sports Med. 2014;48(4):289. 4. Diehl JJ, Best TM, Kaeding CC. Classification and return-to-play considerations for stress fractures. Clin Sports Med. 2006;25:17-28. 5. Field AE, Gordon CM, Pierce LM, Ramappa A, Kocher MS. Prospective study of physical activity and risk of developing a stress fracture among preadolescent and adolescent girls. Arch Pediatr Adolesc Med. 2011;165(8):723-728. 6. Fredericson M, Jennings F, Beaulieu C, Matheson GO. Stress fractures in athletes. Top Magn Reson Imaging. 2006;17(5):309-325.
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7. Hame SL. Fractures in the collegiate athlete. Am J Sports Med. 2004;32(2):446-451. 8. Hergenroeder AC. Bone mineralization, hypothalamic amenorrhea, and sex steroid therapy in female adolescents and young adults. J Pediatr. 1995;126(5 pt 1):683-689. 9. Heyworth BE, Green DW. Lower extremity stress fractures in pediatric and adolescent athletes. Curr Opin Pediatr. 2008;20(1):58-61. 10. Hyman JE, Gaffney JT, Epps HR, Matsumoto H. Impact of fractures on school attendance. J Pediatr Orthop. 2011;31(2):113-116. 11. Johnson AW, Weiss CB, Wheeler DL. Stress fractures of the femoral shaft in athletes—more common than expected: a new clinical test. Am J Sports Med. 1994;22(2):248-256. 12. Kaeding CC, Yu JR, Wright R, Amendola A, Spindler KP. Management and return to play of stress fractures. Clin J Sport Med. 2005;15(6):442-447. 13. Khan KM, Thompson AM, Blair SN, et al. Sport and exercise as contributors to the health of nations. Lancet. 2012;380(9836):59-64. 14. Kiuru MJ, Pihlajama¨ki HK, Ahovuo JA. Bone stress injuries. Acta Radiol. 2004;45(3):317-326. 15. Knowles SB, Marshall SW, Miller T, et al. Cost of injuries from a prospective cohort study of North Carolina high school athletes. Inj Prev. 2007;13(6):416-421. 16. Loud KJ, Gordon CM, Micheli LJ, Field AE. Correlates of stress fractures among preadolescent and adolescent girls. Pediatrics. 2005;115(4):e399-e406. 17. Matheson GO, Clement DB, McKenzie DC, Taunton JE, Lloyd-Smith DR, MacIntyre JG. Stress fractures in athletes: a study of 320 cases. Am J Sports Med. 1987;15(1):46-58. 18. Mountjoy M, Sundgot-Borgen J, Burke L, et al. The IOC consensus statement: beyond the female athlete triad—Relative Energy Deficiency in Sport (RED-S). Br J Sports Med. 2014;48(7):491-497. 19. Nattiv A, Kennedy G, Barrack MT, et al. Correlation of MRI grading of bone stress injuries with clinical risk factors and return to play: a 5year prospective study in collegiate track and field athletes. Am J Sports Med. 2013;41(8):1930-1941. 20. Nattiv A, Loucks AB, Manore MM, Sanborn CF, Sundgot-Borgen J, Warren MP. American College of Sports Medicine position stand: the female athlete triad. Med Sci Sports Exerc. 2007;39(10):1867-1882.
21. Nattiv A. Stress fractures and bone health in track and field athletes. J Sci Med Sport. 2000;3(3):268-279. 22. Nichols JF, Rauh MJ, Lawson MJ, Ji M, Barkai H-S. Prevalence of the female athlete triad syndrome among high school athletes. Arch Pediatr Adolesc Med. 2006;160(2):137-142. 23. O’Toole ML. Prevention and treatment of injuries to runners. Med Sci Sports Exerc. 1992;24(9 suppl):S360-S363. 24. Ohta-Fukushima M, Mutoh Y, Takasugi S, Iwata H, Ishii S. Characteristics of stress fractures in young athletes under 20 years. J Sports Med Phys Fitness. 2002;42(2):198-206. 25. Patel DS, Roth M, Kapil N. Stress fractures: diagnosis, treatment, and prevention. Am Fam Physician. 2011;83(1):39-46. 26. Powell JW, Barber-Foss KD. Injury patterns in selected high school sports: a review of the 1995-1997 seasons. J Athl Train. 1999;34(3):277-284. 27. Rechel JA, Yard EE, Comstock RD. An epidemiologic comparison of high school sports injuries sustained in practice and competition. J Athl Train. 2008;43(2):197-204. 28. Sanderlin BW, Raspa RF. Common stress fractures. Am Fam Physician. 2003;68(8):1527-1532. 29. Sports-related injuries among high school athletes—United States, 2005-06 school year. MMWR Morb Mortal Wkly Rep. 2006; 55(38):1037-1040. 30. Swenson DDM, Henke NMN, Collins CL, Fields SK, Comstock RD. Epidemiology of United States high school sports-related fractures, 2008-09 to 2010-11. Am J Sports Med. 2012;40(9):2078-2084. 31. Tenforde AS, Sayres LC, McCurdy ML, Sainani KL, Fredericson M. Identifying sex-specific risk factors for stress fractures in adolescent runners. Med Sci Sports Exerc. 2013;45(10):1843-1851. 32. US Census Bureau. Census regions and divisions of the United States, 2010. http://www.census.gov/geo/maps-data/maps/pdfs/ reference/us_regdiv.pdf. Accessed November 30, 2014. 33. Wentz L, Liu P-Y, Haymes E, Ilich JZ. Females have a greater incidence of stress fractures than males in both military and athletic populations: a systemic review. Mil Med. 2011;176(4):420-430. 34. Yagi S, Muneta T, Sekiya I. Incidence and risk factors for medial tibial stress syndrome and tibial stress fracture in high school runners. Knee Surg Sports Traumatol Arthrosc. 2013;21(3):556-563.
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Epidemiology of Stress Fracture Injuries Among US High School Athletes, 2005-2006 Through 2012-2013 Bradley G. Changstrom, Lina Brou, Morteza Khodaee, Cortney Braund and R. Dawn Comstock Am J Sports Med published online December 5, 2014 DOI: 10.1177/0363546514562739 The online version of this article can be found at: http://ajs.sagepub.com/content/early/2014/12/05/0363546514562739
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On behalf of: American Orthopaedic Society for Sports Medicine
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Epidemiology of Stress Fracture Injuries Among US High School Athletes, 2005-2006 Through 2012-2013 Bradley G. Changstrom,*y MD, Lina Brou,z§ MPH, Morteza Khodaee,|| MD, MPH, Cortney Braund,z MD, and R. Dawn Comstock,{ PhD Investigation performed at the University of Colorado School of Medicine, Aurora, Colorado, USA Background: High school athletes in the United States sustain millions of injuries annually, approximately 10% of which are fractures. However, there is no clear estimate of the number of stress fractures sustained by high school athletes annually despite reports that stress fractures account for 0.7% to 20% of injuries seen in sports medicine clinics. This suggests a high utilization of resources for a potentially preventable injury. In addition, stress fractures have been associated with low energy availability and disordered eating in young athletes, highlighting the importance of early recognition and intervention. Purpose: To investigate stress fracture rates and patterns in a large national sample of US high school athletes. Study Design: Descriptive epidemiologic study. Methods: Data from High School RIO (Reporting Information Online), a national sports injury surveillance study, were analyzed to describe rates and patterns of stress fracture injury sustained from 2005-2006 through 2012-2013, across sports and by sex. Results: From 2005-2006 through 2012-2013, a total of 51,773 injuries were sustained during 25,268,873 athlete-exposures, of which 389 (0.8%) were stress fractures, resulting in an overall stress fracture rate of 1.54 per 100,000 athlete-exposures. Rates per 100,000 athlete-exposures were highest in girls’ cross country (10.62), girls’ gymnastics (7.43), and boys’ cross country (5.42). In sex-comparable sports, girls sustained more stress fractures (63.3%) than did boys (36.7%) and had higher rates of stress fracture (2.22 vs 1.27; rate ratio, 1.75; 95% CI, 1.38-2.23). The most commonly injured sites were the lower leg (40.3% of all stress fractures), foot (34.9%), and lower back/lumbar spine/pelvis (15.2%). Management was nonsurgical in 98.7% of the cases, and 65.3% of injuries resulted in 3 weeks of time loss, medical disqualification, or an end to the season before athletes could return to play. Conclusion: Although a rare injury, stress fractures cause considerable morbidity for high school athletes of both sexes. Future research should evaluate risks of stress fractures to drive development of targeted prevention efforts. Keywords: stress fractures; High School RIO; injury surveillance; epidemiology; pediatric sports medicine; female athletes
Although there are multiple benefits to participation in sports, high school athletes are exposed to risk of injury, which can pose a significant personal and financial burden.10,13,15,26 A recent study reported that fractures represent 10% of all injuries sustained by high school athletes and are more common among males and in contact sports.30 In contrast, stress fractures have been reported to occur more commonly among females and athletes participating in sports associated with leanness.3,22,33 Stress fractures can require long periods of recovery, are often complicated by delays in diagnosis, and frequently require advanced imaging for diagnosis, suggesting high morbidity for athletes.2,5,6,11,19,23,31 Currently, there is no clear estimate of the number of stress fractures sustained by US
high school athletes annually despite reports that stress fractures account for 0.7% to 20% of injuries seen in sports medicine clinics.5 Adolescence is an important period of time for bone health given that peak bone mineral density, a major determinant of long-term risk of osteoporosis, is attained by early adulthood.5,8 While stress fractures are well studied in military recruits, college athletes, and runners of all ages, it is unclear whether these studies are generalizable to high school athletes, many of whom are skeletally immature.21,24,34 For example, military recruits have an annual incidence of stress fractures between 3% and 9%, and similar numbers are reported in general athlete populations,33 yet fewer National Collegiate Athletic Association Division I collegiate athletes (1.4%) sustain stress fractures annually.7 One study reported an incidence of 3.9% in female adolescent athletes, noting that participation in specific sports, including running, basketball, and cheerleading/ gymnastics, was a risk factor.5 However, rates and
The American Journal of Sports Medicine, Vol. XX, No. X DOI: 10.1177/0363546514562739 Ó 2014 The Author(s)
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patterns of stress fracture across high school sports and by sex, including boys’ sports, have not been well described. For example, in describing an expansion of the female athlete triad to include male sex, a recent consensus statement by the International Olympic Committee on Relative Energy Deficiency in Sport18 (RED-S) recognized the paucity of data regarding risks for stress fractures in males. We believe that understanding a pattern of injury is the first important step toward development of targeted stress fracture prevention efforts. Therefore, the objective of this study was to describe rates and patterns of stress fracture across multiple high school sports and by sex among a large national sample of US high school athletes.
MATERIALS AND METHODS Data We analyzed data from the National High School SportsRelated Injury Surveillance System, High School RIO (Reporting Information Online), an Internet-based sports injury surveillance system that has been described previously.27,29 In brief, high schools with 1 or more National Athletic Trainers’ Association–affiliated certified athletic trainers (ATs) with valid e-mail addresses were invited to participate. Responding high schools were categorized into 8 strata based on population (enrollment 1000 or .1000) and geographic region according to US census reports.32 For the 9 sports included in the study since 2005-2006 (football, boys’ and girls’ soccer, girls’ volleyball, boys’ and girls’ basketball, wrestling, baseball, and softball), 100 high schools were randomly chosen to participate (12 or 13 from each of the 8 strata). If a school dropped out of the study, a replacement from the same stratum was randomly selected to maintain the 100-school study population. Certified ATs from participating high schools reported injury and athlete-exposure information on the study website weekly throughout the academic year. For the additional 9 sports added to High School RIO since 2008-2009 (girls’ field hockey, girls’ gymnastics, boys’ ice hockey, boys’ and girls’ lacrosse, boys’ and girls’ track and field, boys’ and girls’ swimming and diving), as well as 2 sports added since 2009-2010 (cheerleading and boys’ volleyball) and 2 sports added since 2011-2012 (boys’ and girls’ cross country), not enough schools from each of the 8 strata volunteer annually to report for all
sports to provide a randomly selected sample. Thus, exposure and injury data for these sports were collected from a convenience sample of US high schools. In this study, all data reported by the randomly selected sample and convenience sample were combined to create the study dataset.
Definition of Injury and Exposure In High School RIO, an athlete-exposure (AE) is defined as 1 athlete participating in 1 school-sanctioned practice or competition. A reportable injury is one that (1) occurred as a result of participation in an organized practice, competition, or performance; (2) required medical attention by an AT or physician; and (3) resulted in restriction of the athlete’s participation for 1 or more days, although beginning in 2007-2008 the definition was expanded to include all concussions, fractures (including stress fractures), and dental injuries, even if there was no time lost from sports participation. For each injury, ATs completed detailed injury reports on the injured athlete (age, height, weight, etc), the injury (site, diagnosis, severity, etc), and the management of the injury (imaging, treatment, return to play, etc). Throughout the study, ATs were able to view previously submitted information and to update reports as needed. We included all stress fractures reported by certified ATs to High School RIO in this study.
Statistical Analysis We calculated rates and rate comparisons using unweighted case counts for the combined original and convenience samples for all 22 sports. We analyzed the data using SAS v9.3 (SAS Institute) and SPSS v19.0 (SPSS Inc). We calculated injury rates as the number of stress fractures per 100,000 AEs. Subgroup differences were evaluated with injury rate ratios (RRs) or injury odds ratios (ORs) and 95% confidence intervals (CIs). Any CIs not including 1.00 were considered statistically significant. The following is an example of the RR calculations:
RR5
#of stress fractures sustained by girls=#of total AEs for girls : #of stress fractures sustained by boys=# of total AEs for boys
This study was approved by the Institutional Review Board at Nationwide Children’s Hospital, Columbus,
*Address correspondence to Bradley G. Changstrom, MD, Department of Internal Medicine, University of Colorado School of Medicine, Academic Office One, 12631 E 17th Avenue, B177, Aurora, CO 80045, USA (e-mail: [email protected]). y Department of Internal Medicine, University of Colorado School of Medicine, Aurora, Colorado, USA. z Department of Emergency Medicine, The Children’s Hospital Colorado, Aurora, Colorado, USA. § Section of Emergency Medicine, Department of Pediatrics, University of Colorado School of Medicine, Aurora, Colorado, USA. || Department of Family Medicine, University of Colorado School of Medicine, Aurora, Colorado, USA. { Department of Epidemiology and Pediatric Injury Prevention, Education and Research (PIPER) Program, Colorado School of Public Health, Aurora, Colorado, USA. One or more of the authors has declared the following potential conflict of interest or source of funding: The content of this report was funded in part by the Centers for Disease Control and Prevention (grant No. R49/CE000674-01 and R49/CE001172-01). The content of this report is solely the responsibility of the authors and does not necessarily represent the official views of the Centers for Disease Control and Prevention. The authors also acknowledge the generous research funding contributions of the NFHS, NOCSAE, DonJoy Orthotics, and EyeBlack.
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TABLE 1 Total Number of Stress Fractures, Rates of Stress Fractures per 100,000 AEs by Sport, and Rate Ratio for Stress Fractures in Sex-Comparable Sportsa
Total Sex-comparable boys Sex-comparable girls Girls:boys total Football Soccer Boys Girls Volleyball Boysc Girls Basketball Boys Girls Wrestling Baseball Softball Girls’ field hockeye Girls’ gymnasticse Boys’ ice hockeye Lacrossee Boys Girls Swimming and divinge Boys Girls Track and fielde Boys Girls Cheerleadingc Cross countryf Boys Girls
Stress Fractures, n
Total AEs, n
Proportion, %
Rate per 100,000, %
Rate Ratiob
95% CI
389 106 183 210:179 64
25,268,873 8,365,282 8,233,425
100.0 36.7 63.3
1.54 1.27 2.22
1.75
1.38-2.23
1.84
1.51-2.24
5,034,718
16.5
1.27
32 37
1,895,874 1,607,052
8.2 9.5
1.69 2.30
1.36
0.84-2.19
0 20
56,208 1,683,815
0.0 5.1
0.00 1.19
—d
24 50 8 13 3 15 6 1
2,286,793 1,846,699 1,713,203 1,735,120 1,294,271 478,503 80,739 311,817
6.2 12.9 2.1 3.3 0.8 3.9 1.5 0.3
1.05 2.71 0.47 0.75 0.23 3.13 7.43 0.32
2.58
1.59-4.20
0.31
0.09-1.10
6 11
529,268 382,340
1.5 2.8
1.13 2.88
2.54
0.94-6.86
1 0
444,915 503,077
0.3 0.0
0.22 0.00
—d
23 50 6
1,287,860 1,051,186 803,171
5.9 12.9 1.5
1.79 4.76 0.75
2.66
1.63-4.36
7 12
129,244 113,000
1.8 3.1
5.42 10.62
1.96
0.77-4.98
a National High School Sports-Related Injury Surveillance Study, 2005-2006 through 2012-2013. Rates and rate ratios were calculated using only sex-comparable sports including soccer, volleyball, basketball, baseball/softball, swimming and diving, track and field, and cross country. AE, athlete-exposure. b Compares the stress fracture rates between sex-comparable girls’ and boys’ sports (girls:boys). c Data collected from 2009-2010 to 2012-2013. d Rate ratios could not be calculated because there were no stress fractures. e Data collected from 2008-2009 to 2012-2013. f Data collected from 2011-2012 to 2012-2013.
Ohio, and at the Colorado Multiple Institutional Review Board, Aurora, Colorado.
RESULTS Overall From 2005-2006 through 2012-2013, High School RIO captured 51,773 injuries sustained during 25,268,873 AEs, of which 389 (0.8%) were stress fractures, resulting in an overall stress fracture rate of 1.54 per 100,000 AEs. Stress fracture rates were highest in girls’ cross country (10.62), girls’ gymnastics (7.43), and boys’ cross country (5.42) and lowest in boys’ swimming and diving (0.22), boys’ ice
hockey (0.32), and cheerleading (0.75) (Table 1). The ATs did not report any stress fractures in boys’ volleyball and girls’ swimming and diving. Although football had a relatively low rate of stress fracture (1.27/100,000 AEs), this sport had the highest total number of injuries (n = 64), accounting for 16.5% of all stress fractures reported. Of note, several of the higher risk sports by rate had fewer years of data collection compared with the sports included since the inception of the study.
Demographics of Injured Athletes The age range for injured athletes was 13 to 19 years (mean age, 15.8 years; median age, 16 years). The body mass index (BMI) ranged from 15.6 to 41.5, with a mean
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TABLE 2 Location of Stress Fracture Injuries by Sport (n = 387 Injuries)a Sport Football (n = 64) Soccer Boys (n = 32) Girls (n = 37) Volleyball Boys (n = 0)c Girls (n = 20) Basketball Boys (n = 24) Girls (n = 50) Wrestling (n = 8) Baseball (n = 13) Softball (n = 3) Girls’ field hockey (n = 13)d Girls’ gymnastics (n = 6)d Boys’ ice hockey (n = 1)d Lacrossed Boys (n = 6) Girls (n = 11) Swimming and divingd Boys (n = 1) Girls (n = 0) Track and fieldd Boys (n = 23) Girls (n = 50) Cheerleading (n = 6)c Cross countrye Boys (n = 7) Girls (n = 12)
Upper Extremityb (n = 11)
Lower Back/Lumbar Spine/Pelvis (n = 59)
Hip (n = 4)
Thigh/Upper Leg (n = 4)
Knee (n = 6)
Lower Leg (n = 156)
Ankle (n = 12)
Foot (n = 135)
4
21
0
0
0
13
4
22
0 0
7 4
0 0
0 0
2 1
10 15
3 1
10 16
0 0
0 6
0 0
0 0
0 0
0 5
0 0
0 9
0 1 0 3 2 0 0 0
2 2 4 4 0 1 2 0
0 0 0 1 0 1 0 0
0 2 0 0 0 0 0 0
0 0 0 0 0 0 1 0
4 23 2 2 0 7 3 0
1 1 0 1 0 0 0 0
17 21 2 2 1 4 0 1
1 0
1 0
0 0
0 0
0 0
1 3
1 0
2 8
0 0
1 0
0 0
0 0
0 0
0 0
0 0
0 0
0 0 0
2 1 1
1 0 0
0 1 0
1 1 0
14 39 2
0 0 0
5 8 3
0 0
0 0
0 1
1 0
0 0
5 8
0 0
1 3
a National High School Sports-Related Injury Surveillance Study, 2005-2006 through 2012-2013. Values in the table are numbers of injuries. Two injuries were excluded, as data on the location of injury was missing. b Upper extremity injuries included shoulder, forearm, wrist, hand, chest/thoracic spine/ribs. c Data collected from 2009-2010 to 2012-2013. d Data collected from 2008-2009 to 2012-2013. e Data collected from 2011-2012 to 2012-2013.
of 22.7. Mean BMI was 21.3 and 24.0 for injured females and males, respectively.
Patient Sex Across all sports, more stress fractures occurred in girls’ sports (54.0%) than in boys’ sports (46.0%). In sex-comparable sports, a higher proportion of stress fractures was also reported in girls (63.3%) compared with boys (36.7%). Additionally, in sex-comparable sports, there was a statistically significant difference between rates of stress fracture in girls (2.22/100,000 AEs) compared with boys (1.27/100,000 AEs) (RR, 1.75; 95% CI, 1.38-2.23). More specifically, stress fracture rates were significantly higher for girls than for boys in track and field (RR, 2.66; 95% CI, 1.63-4.36) and basketball (RR, 2.58; 95% CI, 1.59-4.20). There was no statistically significant difference between girls’ and boys’ lacrosse (RR, 2.54; 95% CI, 0.94-6.86]), girls’ and boys’ cross country (RR, 1.96; 95% CI, 0.77-4.98), girls’ and boys’ soccer (RR, 1.36;
95% CI, 0.84-2.19), and baseball and softball (RR, 0.31; 95% CI, 0.09-1.10). Rate ratios for volleyball and swimming and diving could not be calculated because no stress fractures were reported for boys’ volleyball and girls’ swimming and diving.
Body Site Across all sports, the most commonly injured body sites were the lower leg (40.3%), foot (34.9%), and lower back/ lumbar spine/pelvis (15.2%). Based on how the data were reported, additional details on the exact location of the injuries could not be provided (Table 2). For example, stress fractures to the foot could be located in any one of the metatarsal or sesamoid bones, whereas stress fractures in the lower leg could be located in the tibia or fibula; therefore, the high-risk or low-risk nature of the injuries by location could not be determined. The foot was the most common site of stress fracture in the majority of sports, including
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girls’ lacrosse (72.7%), boys’ basketball (70.8%), cheerleading (50.0%), girls’ volleyball (45.0%), girls’ soccer (43.2%), football (34.4%), boys’ lacrosse (33.3%), and boys’ soccer (31.3%). The lower leg was the most common site of stress fracture in boys’ and girls’ track and field (60.9% and 78.0%), boys’ and girls’ cross country (71.4% and 66.7%), girls’ field hockey (53.8%), and girls’ basketball (46.0%). There was no significant difference between boys and girls regarding risk of upper extremity stress fractures (RR, 2.35; 95% CI, 0.59-9.22). Of the stress fracture injuries that occurred in the upper body (ie, elbow, shoulder, forearm, wrist, hand, chest/thoracic spine/ribs), which represented 2.8% of all stress fractures, nearly all were sustained by athletes playing sports that involve overhead activities as key components of the sport, such as baseball, softball, lacrosse, and football. Caution should be used when interpreting this, however, as stress fractures to the trunk and upper body were uncommon.
Diagnosis and Imaging Most stress fractures (90.8%) were assessed by a physician, and more than half (55.0%) were evaluated by an orthopaedic specialist. The majority of stress fractures were evaluated with a plain radiograph (82.7%); magnetic resonance imaging (MRI; 32.3%) and computed tomography (CT) scan (6.6%) were used less frequently. Other modalities were used 11% of the time, but this surveillance system did not capture how many of these were diagnosed clinically—without imaging—or were evaluated with a bone scan or other diagnostic and/or imaging technique. Of the few trunk and upper extremity stress fractures, 80% were evaluated by a physician or an orthopaedic specialist, 80% had a plain radiograph, and 30% had an MRI.
5
TABLE 3 Recurrent Stress Fractures by Body Parta Stress Fractures, % Total Body Part Injured
New
Recurrent
Shoulder (n = 1) Elbow (n = 1) Forearm (n = 1) Wrist (n = 1) Hand (n = 2) Chest/thoracic spine/ribs (n = 4) Lower back/lumbar spine/pelvis (n = 57) Hip (n = 4) Thigh/upper leg (n = 4) Knee (n = 6) Lower leg (n = 153) Ankle (n = 12) Foot (n = 135) Total (n = 381)b
100.0 100.0 100.0 100.0 100.0 100.0 61.0 75.0 100.0 100.0 81.7 83.3 88.9 313
0 0 0 0 0 0 39.0 25.0 0 0 18.3 16.7 11.1 69
a National High School Sports-Related Injury Surveillance Study, 2005-2006 through 2012-2013. b Seven injuries did not have data available on whether they were new or recurrent injuries, and 1 injury did not have data available on location of injury; these were therefore excluded from this analysis.
significantly affect return to play (OR, 1.2; 95% CI, 0.682.10). Interestingly, 39.0% of all lower back/lumbar spine/ pelvis injuries were recurrent injuries (Table 3). Recurrent injuries were also more frequent in stress fractures of the hip (25.0%), lower leg (18.3%), ankle (16.7%), and foot (11.1%). None of the upper extremity injuries (shoulder, elbow, forearm, wrist, hand, and chest/thoracic spine/ ribs) were recurrent injuries.
Outcomes Return to play was reported to High School RIO as a categorical variable, and 3 weeks was the largest time variable available to ATs to select for outcomes of stress fracture injuries. Overall, a large proportion (65.3%) of stress fractures required a prolonged recovery; 32.8% required more than 3 weeks before return to play, 18.1% were medically disqualified, and 14.1% had an end to the season before return to play. Only 34.7% of athletes who sustained stress fractures returned to play within 3 weeks of injury; interestingly, most of the athletes with upper extremity injuries (68%) returned to play within this time period. There was no significant difference for prolonged return to play between stress fractures to the lower body and upper body (OR, 3.93; 95% CI, 0.97-16.00). The majority of stress fractures across nearly all sports involved prolonged time away from participation. Nearly all (98.7%) stress fractures were managed nonoperatively; only 5 total injuries were treated surgically.
History of Injury Of all stress fractures, 18.1% were reported to be recurrent rather than new injuries. History of stress fracture did not
DISCUSSION To our knowledge, few studies have examined stress fractures in the adolescent population across a variety of both boys’ and girls’ sports.1,9 This study evaluates data from the National High School Sports-Related Injury Surveillance System to study stress fractures among a large national sample of high school athletes participating in 22 sports from 2005-2006 through 2012-2013, resulting in the largest study of stress fractures among high school athletes to date. Our findings demonstrate that although a rare injury, stress fractures cause considerable morbidity to high school athletes of both sexes, with rates and patterns of stress fracture injuries varying by sport and sex. Risk stratification by sport is an essential piece of information for targeted prevention-management strategies. Consistent with previous investigators, we found that stress fracture rates in both boys’ and girls’ track and field and cross country and gymnastics were among the highest for all sports evaluated.5,16 Additional high-risk sports in our study included field hockey and basketball for girls and soccer for boys. Although a previous study identified girls’ basketball as a high-risk sport, our study also
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uniquely identified girls’ field hockey and boys’ soccer in this category.5 We could not find any previously published studies reporting these as high-risk sports. Other studies have suggested that cheerleading is a high-risk sport, but our data could not corroborate this finding.5,16 Interestingly, a large number of the total stress fractures documented in this study occurred in football players. Given the large number of high school athletes playing football, clinicians should expect to treat football players who have various stress fractures despite the relatively low rates of stress fracture in this sport. In general, female sex is a well-known risk factor for stress fracture.1,20 Overall, girls were at increased risk of stress fracture compared with boys across sex-comparable sports in our study (RR, 1.75; 95% CI, 1.38-2.23) as well as in most sex-comparable sports such as track and field and basketball. Interestingly, in sex-comparable sports, boys’ baseball was the only sport in which boys may be at greater risk for stress fracture than girls when compared with girls’ softball, although this difference was not statistically significant (RR, 0.31; 95% CI, 0.09-1.10) and there are limitations in comparing these sports. The relative risk calculated in this study is consistent with previous studies that demonstrated a risk of stress fracture of approximately 1.5 to 3.5 in women compared with men.2,6,11,23 Although girls remain at a higher risk of stress fracture compared with boys in general and in most sports, several boys’ sports demonstrated high rates of stress fractures (including cross country, track and field, and soccer), and stress fractures occurred in nearly all high school sports. Stress fractures in adolescent boys have not been well described1,18,31; this study represents one of the largest studies of stress fractures in boys’ high school sports, with 179 total stress fractures reported in boys’ sports alone. These data support the recent consensus statement by the International Olympic Committee (RED-S)18 that both men and women may be susceptible to relative energy deficiency in sport as evidenced by stress fractures, and this study provides additional data regarding risks for stress fracture in this population. Although further research to understand any underlying sex differences that place girls at higher risk is certainly indicated, including male sex in future research is paramount given the lack of previous research in these athletes. This study was too limited to describe risks on an individual basis by sport, and future research should include research on sports that have previously been poorly characterized. Such sports include boys’ soccer and girls’ field hockey because of the high rates of stress fracture as well as football because of the high rate of participation. Certified ATs reported stress fractures to High School RIO by general body site, but our dataset did not have any available information on exact location or severity of injury. The majority of stress fractures were lower extremity fractures, and lower extremity stress fractures were common across all sports. Of the small number of upper extremity fractures observed in this study, these occurred nearly exclusively in sports that involved overhead activities, including baseball, softball, lacrosse, and football; 1 injury to the wrist was reported in girls’ basketball.
Prospective trials showed that tibial stress fractures were the most common stress fractures in high school female runners and metatarsal stress fractures were the most common stress fractures in high school male runners.31 Although our data on location of injuries in stress fractures are limited, our findings can help clinicians stratify risk of overuse injuries by general location of injury through additional knowledge on the high-risk locations of stress fractures by sport. The expense of imaging during evaluation can be prohibitive to high school athletes and their families.4,12 We found that 82.7% of stress fractures in this patient population were evaluated by plain radiograph. As a plain radiograph is the initial recommended step in management of stress fractures, we expected many patients to have had a plain radiograph.25,28 However, plain radiographs may miss early stress injuries, as these radiographs have a sensitivity between 10% and 70% depending on the timing of imaging and onset of symptoms.5,14 It was not uncommon for providers to choose other modalities of imaging, such as MRI (32.3%) and CT scans (6.6%). These data did not capture how many stress fractures were diagnosed clinically or by a bone scan, although 10.4% of ATs selected ‘‘other’’ as an imaging modality. It is interesting but not surprising to see that such a high number of these injuries received an imaging technique other than plain radiograph for diagnosis, given the limitations of plain radiography specifically for stress fracture. An MRI is generally the preferred follow-up imaging technique for suspected stress fractures, and nearly one-third of stress fractures diagnosed in our study included MRI.6 A recent study by Nattiv et al19 demonstrated correlation between degree of severity of MRI findings and return to play for collegiate track and field athletes, which could be another future direction of study not captured by these data. Other than clinical diagnosis, plain radiography is the least expensive of these imaging modalities.25 The balance between the cost of imaging, severity of injury, and implications for return to play must be investigated further to identify which athletes will benefit most from advanced imaging such as MRI. Early detection of stress fractures is important, as delays in diagnosis and treatment can result in delayed return to activity or progression of injury.24,25 Our findings demonstrated that stress fractures have high morbidity, evidenced by delayed return to activity or removal of the student-athlete from participation. This is consistent with previous studies that reported return to play following stress fractures was between 4 and 12 weeks or longer.17,24 However, a striking number of athletes with stress fractures returned to play within 3 weeks (34.7%). This may reflect the possibility that clinicians are incorrectly diagnosing injuries as stress fractures or that they are not following current return-to-play protocols.6 Finally, it may demonstrate that some injuries, such as injuries to the upper extremity, may not require long delays in recovery. Given the rarity of upper extremity injuries, it may be difficult to ever develop guidelines on evidence-based management of these injuries other than through symptombased return to play. Because of the complexity of recovery
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based on severity and location of injuries, we recommend location and symptom-based return-to-play protocols with consideration of the female athlete triad.3,4 Fortunately, management was nonsurgical for 98.7% of stress fractures. The infrequent need for surgery that was reported may be because clinicians are more aware of stress fractures and are appropriately withholding return to play for athletes, or it may be because some stress fractures that require surgical management are not recognized as stress-related injuries and may not be reported as a stress fracture by physicians or ATs. Finally, this number may reflect the true incidence of an injury that generally requires nonsurgical management. A history of stress fractures was common, as 18.1% of injuries were described as recurrent injuries. This finding was not surprising; a recent study also demonstrated that prior stress fracture was the most common risk factor for stress fractures in adolescent male runners.31 Identification of the age at which these athletes experience their first stress fracture was not included in the dataset, but doing so would be essential to determine the timing of preventative strategies. None of the upper extremity injuries were classified as recurrent injuries. This finding may reflect the fact that many of these injuries represented initial stress fractures for these athletes, and it may therefore underrepresent the overall risk of a history of stress fracture for future stress fractures. Given the complexities of adolescent growth, bone development, and injuries, more information is needed about the individual athletes experiencing these fractures to further identify specific risks. There were several limitations to our study. First, our data were limited to high schools with certified ATs, which restricted our population. However, 90.8% of the stress fractures were evaluated by a physician, and all injuries were reported to High School RIO by certified ATs, which we believe increased our data quality. The High School RIO database relies on the professional opinion of the ATs in the participating high schools to determine which injuries met the diagnostic criteria for stress fracture. Although uniform criteria for a diagnosis of stress fracture were not established for this injury surveillance system, the data reflect high school athletes who have been managed as if they have a stress fracture. To reduce reporter burden, the High School RIO surveillance system captures athleteexposures as unit based rather than time based, and therefore we were unable to report injury rates by minute or hour of practice and competition. Of note, both samples concurrently enrolled in High School RIO, the original randomly selected nationally representative sample and the convenience sample, were combined in this report. Even though our inclusion of the convenience sample of high schools did not allow us to provide national estimates for stress fractures, including these data increased our sample size, which allowed comparison of rates and patterns of injury across a large number of sports. Therefore, although the data may not be nationally representative, this study remains the largest nationwide epidemiologic study describing stress fractures in US high school athletes in boys’ and girls’ sports. The reporting system was limited by several variables, including the inability to input continuous data to
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determine average time before return to play or to input the precise location of injury. These are important limitations because the anatomic location of a stress fracture can have implications regarding whether it is considered a high- or low-risk injury.4 In addition, many stress fractures require substantially longer than 3 weeks for return to play, and the duration of recovery could not be calculated with the categorical data reported in this study. Finally, we were not able to analyze for predisposing factors such as disordered eating.
CONCLUSION Both male and female high school athletes and athletes across a wide range of high school sports are at risk for stress fractures. It is important to keep this in mind because stress injuries may serve as warning signs for care providers that major disruptions in energy balance may be present. Consequences of stress fractures include expensive diagnostic techniques and prolonged recovery, in addition to other comorbidities that may be present. Our findings highlight the need for further research in both boys’ and girls’ sports to provide evidence needed to drive the development of targeted stress fracture prevention programs. High school athletes will continue to struggle with pressures of competition, exposing themselves to the risks of stress fractures until effective intervention measures aimed at prevention and early detection are implemented.
ACKNOWLEDGMENT The authors thank the certified athletic trainers for their hard work and dedication in providing us with complete and accurate data. In addition, the authors thank the staff at High School RIO for their efforts in website management. Without their efforts, this study would not have been possible. Finally, they thank Nicole T. Townsend for critical feedback regarding the manuscript.
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