Association Between Severity of Musculoskeletal Injury and Risk of Subsequent Injury in Children and Adolescents on the Basis of Parental Recall

Objectives  To describe the frequency of subsequent injuries in children who were seen at an emergency department (ED) for a musculoskeletal injury and to explore factors associated with sustaining a subsequent injury within a year.

Design  This was a prospective cohort study of children aged 1 through 17 years who sought care at an ED for an injury. Subsequent injuries were assessed through telephone interviews.

Setting  Subjects were recruited from a national database of childhood injury after they presented to a hospital ED at 1 of the 2 pediatric trauma centers in Montreal, Quebec.

Patients/Participants  A consecutive sample of 7640 children aged 1 through 17 years who sought care for a fracture or a soft-tissue injury to an arm or a leg; 6182 completed both telephone interviews (80.9% response rate).

Main Exposure  Having a more severe injury was defined in 2 ways: (1) fracture of a limb or (2) injury that required follow-up or admission.

Main Outcome Measure  Having a subsequent injury during 12-month follow-up.

Results  Subjects with an index fracture were at lower risk of subsequent injury than were those with a soft-tissue injury (13.5% compared with 17.7%; adjusted odds ratio, 0.74; 95% confidence interval, 0.63-0.87). Subjects whose injury needed a follow-up were also at lower risk of subsequent injury than those whose injury was treated only in the ED (17.7% compared with 14.3%; adjusted odds ratio, 0.79; 95% confidence interval, 0.67-0.93) as were those who were admitted (17.7% compared with 8.7%; adjusted odds ratio, 0.51; 95% confidence interval, 0.26-0.99).

Conclusions  Having had a severe musculoskeletal injury may be associated with a decreased risk of subsequent injury in children and adolescents. A possible explanation could be reduced exposure to risk.

Among children who seek medical care for an injury, an estimated 73% have done so for more than 1 injury by age 9 years.¹ Between 15% and 32% of children younger than 18 years visited an emergency department (ED) within a year for at least 2 separate injury events.^2,3 Among children who had a fracture, 40% had another fracture before adulthood.⁴

In children, determinants of injury risk such as sex and age,^2,5 socioeconomic status,^6,7 and type of activity at the time of injury⁸ are well known. Factors associated with risk of reinjury are somewhat similar to those associated with risk of injury and include sex,^1,2,9,10 age,^11,12 and socioeconomic status.^9,12,13

Although information about the influence of severity of an initial injury on subsequent injury in children is scant, results of studies among adults suggest that severity of the first injury may be associated with risk of subsequent injuries. Results of one study¹⁴ indicated that patients (mean age, 28.5 years) with severe injuries such as intracranial injury, fractures, and wounds to the head and neck, tend to have fewer subsequent injuries than do patients with more minor injuries such as muscle sprains. Authors of a study on injured soldiers observed that subjects who saw only a medic, as opposed to a physician, for their injury were at a 72% increased risk of sustaining a subsequent injury.¹⁵

It is important to identify additional characteristics of the children who are most at risk of subsequent injuries so appropriate prevention strategies can be developed. It is plausible that compared with children who have a mild injury, children who have a severe injury may learn ways to avoid future injury or may receive better medical and rehabilitation services that reduce potential residual motor problems and thus their risk of subsequent injury. The objectives of this study were, therefore, to describe the frequency of subsequent injuries in children who were seen at an ED according to severity (defined by injury type and level of treatment) and to explore factors associated with sustaining a subsequent injury within a year.

Subjects were recruited through an injury surveillance system, the Canadian Hospitals Injury Reporting and Prevention Program,¹⁶ in place at 2 tertiary care pediatric hospitals (Montreal Children's Hospital and Sainte-Justine Hospital) in Montreal, Quebec. These hospitals are designated trauma centers and have both participated in the program for more than a decade. Parents of children presenting for an injury to one of the participating hospital's EDs are asked to fill out a questionnaire detailing the circumstances of the injury event. For each patient, the diagnosis and site of the injury, as noted by the attending physician, are coded on the back of the form. Disposition is also coded according to level of treatment provided by the ED physician: treated only in ED, return appointment scheduled, or admitted to hospital.

Subjects were patients and their parents who filled out a Canadian Hospitals Injury Reporting and Prevention Program form between December 14, 2000, and March 31, 2003, at the participating hospitals and gave their consent to be telephoned with regard to the child's injury. They represent a subsample of children recruited as part of a larger study examining the risk of second head injury in children. In the context of this larger study, controls were recruited among those presenting to the ED with a musculoskeletal injury (fracture, laceration, sprain, and soft-tissue injury) to the extremities. Children who presented with any other injury were excluded. The present study examines risk of subsequent injuries among the total sample of controls (ie, children aged 1-17 years who did not have a head injury but who presented to the ED with a musculoskeletal injury to an arm or a leg). Of the consecutive sample of 7640 children (mean age, 10 years), 6182 completed both telephone interviews (80.9% response rate at 12 months) and thus were retained for analysis. Responders and nonresponders were highly comparable with respect to sex, age, type of index injury, treatment received for index injury, and body part involved.

Severity scores, such as the Abbreviated Injury Score and the Injury Severity Score, offer little help when trying to differentiate severity from a fracture from that of a sprain or a bruise of the forearm because both would be coded as minor (ie, less than 2 on a scale from 1 to 6).¹⁷ We therefore chose to define severity according to type of injury (ie, we contend that upper or lower limb fractures usually require more medical services than do lacerations, bruises, and sprains) or level of treatment.

In addition to the injury data, telephone interviews with the parents were conducted by trained individuals at 6 and 12 months after the index ED visit to provide information about subsequent injuries. Parents were asked questions about whether their child sought medical care for any injury during the last 6 months. They also provided details about discharge recommendations for the index injury regarding activity restrictions, as well as the usual level of activity of their child compared with that of children of the same age, sex, and sociodemographic data (mother's educational level and parental structure). There were no specific questions pertaining to subsequent exposure (ie, whether the child stopped participating in some activities) among children with musculoskeletal index injuries.

The institutional review boards at both hospitals approved this study, and parents gave verbal consent to be interviewed.

The rate of subsequent injuries is reported according to the severity of the index injury by using 2 proxy measures: type of musculoskeletal injury (fracture vs soft tissue) and level of treatment provided in the ED. Univariate analyses were performed to determine the factors associated with subsequent injuries. These factors were patient related (age, sex, family structure, maternal educational level, and child's level of activity compared with children of the same age and sex) and index injury related (injury type, extremity injured, whether the child was involved in a recreational activity at time of injury, and if the child received discharge information about activity restrictions).

Multivariate analysis included the calculation of 2 logistic regression models to evaluate factors associated with risk of subsequent injuries: one with index injury type (fracture vs soft tissue) as the independent variable and the other with level of treatment received (treated only in ED, return appointment scheduled, or admitted to hospital) for the index injury. Covariates included patient-related and index injury–related variables. Statistical analyses were conducted with commercially available software (SPSS version 11.0; SPSS Inc, Chicago, Ill).

There were 6182 children in our cohort: 58.5% were boys and 41.5% were girls; their mean ± SD age was 10 ± 4.5 years. The type of injuries were distributed as follows: 3262 had an index fracture (52.8%), and 2920 (47.2%) had an index soft-tissue injury (eg, laceration, sprain, or bruise). The overall rate of having a subsequent injury within a year of the index injury was 15.5% (n = 958); 513 patients (8.3%) reported a subsequent injury during the first 6 months and 445 patients (7.2%) reported another injury between 6 and 12 months following the index injury. Of those whose index injury was a fracture (n = 3262), 440 children (13.5%) reported seeking medical care for another injury within the following year compared with 518 children (17.7%) who had an initial soft-tissue injury. Across 12 months, children who sustained an index fracture were less likely to seek care for another injury compared with children who had an initial soft-tissue injury (odds ratio [OR], 0.72; 95% confidence interval [CI], 0.63-0.83).

Although there were more boys among the children who had index fractures than who had soft-tissue injuries (62.0% compared with 54.6%), for boys and girls, fractures were associated with a lower risk of subsequent injury. Table 1 summarizes the results of the univariate analyses for 12 months.

Multiple logistic regression analysis confirmed that having had a fracture was associated with a lower risk of subsequent injury after adjusting for sex, age, lower extremity vs upper extremity, receipt of discharge information about return to activities, involvement in recreational activity at the time of index injury, activity level in comparison with that of other children of the same age and sex, maternal educational level, and parental structure (adjusted OR, 0.74; P < .001). Other factors associated with lower risk of subsequent injury were being less active than or equally as active as other children of the same age and sex, lower maternal education, and being aged 1 through 4 years (Table 2).

Compared with the OR for children who were treated only in the ED for their index injury, the OR for those who had a return appointment scheduled was 0.77 (95% CI, 0.67-0.89), and the OR for those admitted to the hospital was 0.45 (95% CI, 0.24-0.83) (Table 1). Controlling for confounding factors in the multiple logistic regression model, this classification of severity yielded adjusted ORs that still were associated with lower risk of subsequent injury as the severity of index injury increased (Table 3). Other similarly associated factors were being aged 1 through 4 years, lower maternal education, and being less active than or equally as active as children of the same sex and age.

Finally, because a fractured limb, compared with a soft-tissue injury, is often immobilized for a longer time, thus limiting a child's exposure to participating fully in regular activities, we also examined the association between risk of subsequent injury and severity of index injury during the 6 to 12 months after the index injury. Of all the children who had a fracture, only 6.3% (205/3262) sought medical care for a subsequent injury during this period compared with 8.3% (242/2920) for those with a soft-tissue injury (OR, 0.75; 95% CI, 0.62-0.91). Although not a statistically significant finding, of the children whose index injury required follow-up or hospital admission, 6.6% sought medical care for a subsequent injury compared with 8.2% for those whose index injury was treated only in the ED (OR, 0.70; 95% CI, 0.42-1.17).

The present study's results suggest that having had a severe index injury, defined by either injury type or level of treatment, compared with having had a minor injury to an extremity reduces the risk of subsequent injury. The observed overall rate of 15.5% for subsequent injury lies within the range found in other studies in which children with all types of injuries to all body regions (eg, 15%² and 32%³) were examined. Our results also concur with those of Williams et al¹⁴ who found that patients (mean age, 28.5 years) with more severe injuries (defined as intracranial injury, fractures, and wounds to the head and neck) tended to have less subsequent injury than those with more minor injuries such as muscle sprains; their explanation involves a reduction of exposure because of limited activity levels in the more severely injured group. The level of treatment also was reported as a factor by Schneider et al¹⁵ who observed a lower risk of subsequent injury for soldiers who sought more care for their injuries. As an explanation for these results, the authors remarked that these patients might not have sought sufficient care because medics are limited in the level of care they can provide, especially regarding activity restrictions.

Our results showed that the reduced risk of a severe injury was present as long as 12 months after the index injury. Although a severe injury could limit a child physically and diminish the child's exposure to further injuries, the follow-up of a year allowed for a potentially complete recovery from the index injury. In other words, the child's injury probably did not prevent the child from participating in sports for a whole year. Investigators in one study¹⁸ found that children with fractures of long bones in their arms and legs reported being restricted in their activities for a maximum of 71 days.

The reduced exposure to risk can be explained from many angles. Physically, children with fractures in this study may have had a persistent reduced exposure. Psychologically, children with more severe injuries may have adopted safer behaviors when they returned to their activities to avoid a similar traumatic event. Also possible is a shift in parental attitude toward more risky activities; children with more severe injury may find themselves forbidden to continue practicing activities parents deem too dangerous.

Changes in behavior have been observed after milder as well as more serious injuries.¹⁹ Gagnon et al²⁰ found that children who had a mild head injury appear to lack confidence in their ability to perform physical activities compared with their attitude before their injury. Subtle problems of balance and response time can persist for 12 weeks in children having sustained only a mild head injury.²⁰ It is unclear whether this difficulty is a result of a physiological effect (immature bone structure) or the result of behavioral or environmental differences in this age group.

When controlling for either injury type or level of treatment for the index injury, we found that being less active than or equally as active as other children of the same age and sex was associated with a lower risk of subsequent injury. Such children may participate less in high-risk activities such as sports or recreational activities (eg, skateboarding or cycling), thus reducing their risk of subsequent injury. Our findings of an association between mother's educational level and risk of subsequent injury do not concur with those of Brook and Heim.¹² Mothers with postsecondary education may be more likely to work outside the home, so their children receive less supervision. However, we believe that the relationship is better explained by mothers with postsecondary education being more easily able to afford the fees associated with organized sports activities, so these children have a greater exposure to injury-related events.

Our study has several limitations. We may not have collected all pertinent data to assess the influence of injury severity on possible subsequent injury. For example, data about preexisting medical conditions could not be collected (eg, osteogenesis imperfecta renders bones more susceptible to fractures²¹). The children classified with minor injuries may have had fractures that were undiagnosed at the time of presentation to the ED (ie, the calcium deposition was not yet visible on a radiograph). However, it is unlikely they were classified with minor injuries rather than more severe injuries because of lack of appropriate medical care. There also may be a bias toward parents of children classified with severe index injury being more inclined to seek medical care for a subsequent injury, even a minor one, than children whose index injury was not severe. In other words, the results may be explained partly by the possibility of confounding by health care use (ie, higher use by those with minor injury). Both of these scenarios, however, would lead to underestimation of the true association between a severe injury and the risk of subsequent injury. Finally, because this study was conducted in children who visited an urban trauma pediatric hospital within a universal health care system, generalizing these findings may be limited to these specific types of settings.

We were not able to identify specific reasons why a severe injury is associated with a lower risk of subsequent injuries. Psychological factors related to a child's return to activities might have played a role. Possibly, having had a severe injury may generate fear in children or parents so that they subsequently adopt safer behaviors.

Finally, these data are based on parental recall, so there is a potential for recall bias. Parents' recall of their child's injury diminishes with time and differs with the severity of the injury.²² We cannot exclude the possibility that parents of children with soft-tissue injury were less able to recall consulting for a subsequent injury. If this is the case, it would not diminish the relationship but rather lead to underestimation of its true value.

This study's results suggest that children who had minor injuries are more likely to injure themselves again compared with children who had severe injuries. Possible explanations could include the minimization of some injuries, such as lacerations, bruises, and sprains, by society and clinicians. These results highlight the need for appropriate interventions in targeting children with injuries to prevent them from repeatedly injuring themselves. The time spent in the ED, although often short, could be an ideal setting for injury prevention. In conclusion, the results provide evidence that the severity of an injury to an arm or a leg is associated with the risk of sustaining another injury within the next 12 months.

Correspondence: Bonnie Swaine, PhD, School of Rehabilitation, Physiotherapy Program, University of Montreal, C.P. 6128, Succursale Centre-Ville, Montreal, Quebec, Canada H3C 3J7 (bonnie.swaine@umontreal.ca).

Accepted for Publication: February 1, 2006.

Author Contributions:Study concept and design: Keays, Swaine, and Ehrmann-Feldman. Acquisition of data: Keays and Swaine. Analysis and interpretation of data: Keays, Swaine, and Ehrmann-Feldman. Drafting of the manuscript: Keays, Swaine, and Ehrmann-Feldman. Critical revision of the manuscript for important intellectual content: Keays, Swaine, and Ehrmann-Feldman. Statistical analysis: Keays, Swaine, and Ehrmann-Feldman. Obtained funding: Swaine. Administrative, technical, and material support: Swaine. Study supervision: Keays, Swaine, and Ehrmann-Feldman.

Funding/Support: We acknowledge the financial support of the Canadian Institutes of Health Research. This research was conducted at the Research Center of the Centre de recherche interdisciplinaire en réadaption.