Risk factors for recurrent injuries in victims of suspected non-accidental trauma: a retrospective cohort study

Non-accidental trauma (NAT) is a leading cause of injury and death throughout early childhood [1, 2]. Repeated evaluations in the medical setting for traumatic injuries should raise concerns that these injuries may be caused by either negligent behavior on the part of the caretaker or by recurrent intentional mechanisms.

Rates of recurrent non-accidental traumatic injuries have been reported to be as high as 30-50%, and are associated with increased morbidity and mortality [3–8]. Previously reported predictors of recurrent NAT include prior child protective services involvement, history of domestic violence, chronicity of maltreatment, child’s age, parental history of maltreatment as a child, and parental substance abuse, criminal record, and mental health issues, or after specific injuries [5, 6, 9–13]. These previous studies are limited in that they either do not assess risk factors related specifically to trauma, such as sentinel traumatic events, or they do not address recurrence of maltreatment. The purpose of this study was to identify patterns of injuries and factors associated with suspected episodes of recurrent NAT in a cohort of young children enrolled in a Medicaid managed care program who had at least one highly suspicious encounter for NAT.

Many children who are victims of NAT may not experience it as a single isolated event, but rather as part of a pattern of recurrent violence that represents the normative structure of their social environment. This study used administrative claims data from a pediatric Medicaid accountable care organization to identify children with repeated medical encounters for injuries that are suspicious for NAT. We have identified several demographic and injury characteristics that are associated with an increased risk for suspected recurrent NAT events. These include living in a rural area, younger age at an event, fewer injuries at an initial event, and specific injury categories including dislocations, superficial injuries, and open wounds. In addition, suspected recurrent NAT events were often observed months after the initial event and the time to a next event decreased with each subsequent event.

Missing child abuse at initial presentation can lead to significant subsequent morbidity [6, 19]. With regards to NAT related to TBI, 30% of children hospitalized with abusive head injuries had a sentinel injury [12]. Data from our group using the Ohio State Trauma Registry suggests that victims of recurrent NAT who are hospitalized for their injuries have higher mortality rates compared to victims of single episodes of NAT (25% vs. 10%) [8]. By gaining a better understanding of the types and timing of injuries that portend risk to a child for recurrent NAT, we may be able to develop targeted screening tools and appropriate interventions that can be used to prevent recurrent NAT and its associated morbidity and mortality.

Previously identified risk factors for recurrent NAT include prior child protective services involvement, chronicity of maltreatment, child’s age, and parental history including domestic violence, substance abuse, criminal record, mental health issues, and being maltreated as a child [9–11]. In addition, several case series have described recurrence of maltreatment following specific injuries [5, 6, 12, 13]. On a population level, Friedlaender et al., used Medicaid claims data to demonstrate that victims of maltreatment changed ambulatory care providers with greater frequency in the year before their first episode than those children who were not abused [20]. The current study is the first to utilize system-level administrative data to identify patterns of injuries and factors associated with suspected episodes of recurrent NAT. This population-based approach allows us to examine all medical encounters for a patient, including episodes of care that occur outside the patient’s usual hospital or health care system. Using this approach, we identified several trauma-related risk factors for suspected recurrent NAT.

In this study, more than a quarter of children had a recurrent event within just one year of their first event. Risk factors a recurrent event included having fewer injuries (≤2 injuries) or having a dislocation, open wound, or and superficial injury at the previous event. These data potentially identify a bias in either the diagnosis of abuse and/or the variable response of child protective services to children based on the number and severity of physically evident injuries. Children with fewer or less severe injuries may not be reported to child protective services or are not removed from the unsafe environment leading to subsequent events. Identification of these more minor injuries as potential targets for additional screening or referral to child abuse specialists warrants further prospective study.

This study also found that the median length of time between the first and second suspected NAT events was 191 days (IQR 69, 389). This is important to note because the average length of child protective services involvement with a family may be significantly shorter. In addition, the risk of having a subsequent event increased with each event; 26% of children who experienced a first event proceeded to experience a second event within a year, whereas 60% children who experienced a 4th event proceeded to experience a fifth event within a year. Understanding both the prolonged length of time between a first and second event, as well as the increasing risks with recurrent events may inform secondary prevention strategies for both medical and child welfare staff.

Several limitations inherent in using system-level administrative claims data are relevant to this study. First, approximately 35% of patients had at least one break in Medicaid enrollment. In our analysis, we included these children as if they had remained continuously in the cohort throughout the study period. With this approach, there is the potential that children suffered a recurrent event during the time of non-enrollment, and therefore our data would be an underestimate of the number of recurrent events. However, the appropriateness of this assumption is increased by the finding of similar results in the subgroup of children with continuous enrollment in PFK from birth until the end of the study period. Second, some children who were removed from their home by child welfare after their initial event were lost to follow-up in this study. Whether or not a child remains in PFK after out-of-home placement varies by county in Ohio. Thus, we are unsure of the exact number of children lost to follow-up for this reason. However, when analyses were repeated in children who remained in PFK for at least 2 months after their first event, the results were very similar. Third, we are limited in the sensitivity and specificity of the ICD-9 coding practices used to identify key variables. In particular, ICD-9 coding performed after discharge is likely to underestimate the actual prevalence of abusive injuries in part because physicians may be reticent to assign intentional causality without confirmation from a multi-disciplinary team of social workers and law enforcement agents whose consensus is not often available until after discharge. In addition, ICD-9 codes provide limited ability to distinguish between different types of abuse. In this study, we aimed to focus on suspected physical abuse, but some of the codes chosen to define abuse could have certainly represented instances of emotional or sexual abuse, or child neglect. Furthermore, we were fairly liberal in our definition of potentially abusive injuries. Although some of the injury-only events could have involved accidental injuries, it is important to note that the rate of injury-only episodes was remarkably high in this population (177 events per 1000 person-years), a rate more than 40 times the rate of 3.17 events per 1000 person-years that was reported in a general population of 0–3 year olds [21]. This extraordinarily high injury rate is concerning, regardless of whether the injuries were purposefully inflicted or represent neglect. An additional limitation of this study is that, administrative datasets provide limited data on covariates of interest. For example, this study would have benefited from additional data on race, parental characteristics, and family-level SES characteristics. By integrating US Census data, however, it was possible to evaluate zip-code level SES characteristics. Although the above limitations were unavoidable in the use of this administrative database, it is likely that they mainly resulted in under-identification of suspected NAT events and therefore minimized, rather than exaggerated our findings.

Factors associated with an increased risk for suspected recurrent NAT events in this study include rural residence, younger age, fewer initially detected injuries, and specific injury types at a previous event. Recurrent events often occur months after the initial event. These findings potentially identify a bias in either the diagnosis of NAT or the response of child protective services to children who present with less severe or less numerous injuries.