History of concussion and risk of subsequent injury in athletes and service members: A systematic review and meta-analysis

Highlights

• A concussion confers increased risk of injury in athletes and service members.

• After a concussion, the odds of a second concussion is nearly 3.73 times higher.

• The odds of sustaining a lower extremity injury is 1.60 higher after a concussion.

• The rate lower extremity injury per athlete exposure is higher after a concussion.

Abstract

Risk of secondary injury after a primary concussion in sports and military contexts is an emerging area of interest in research. The purpose of this review was to provide an evidence synthesis describing risk of injury in athletic and military populations with and without a history of concussion.

Electronic database searches were completed through September 7, 2018 in PubMed, EMBASE, CINAHL and SCOPUS. Peer-reviewed observational studies of any design with participants who were athletes or service members; measured the outcome of any type of injury; and compared injury between those with and without a history of concussion were included. Risk of bias was assessed using the Q-Coh II. Twenty-seven articles were included. Seventeen meta-analyses were completed for risk of any injury, risk of concussion, and risk of extremity injury using odds, hazard, and rate ratios. The results indicate significantly increased odds of all injuries (OR = 2.55; 95%CI 1.85,3.52); concussion (OR = 3.73; 95%CI 2.41,5.78); and lower extremity injuries (OR = 1.60; 95%CI 1.32,1.94) in those with a history of concussion compared to those without. Additional analyses reveal this increased risk is apparent when looking at time to event data and rate of injury based on number of exposures. While the reasons for the increased incidence of secondary injury associated with a concussion are not yet understood, there are potentially behavioral attributes and motor control deficits that contribute. It is suggested that research is needed to determine if active therapeutic treatment for disturbances in sensorimotor and neuromotor control after concussion could attenuate the increased risk for injury.

Introduction

In sports and military contexts, physical injuries are often sustained which limit participation and decrease performance. Concussion has emerged as one of the most concerning sports injuries with upwards of 3.8 million traumatic brain injuries (TBI), predominantly mild TBI/concussion, occurring annually in the United States (US) (Langlois, 2006). In the US military, annual concussion incidence is variable, depending on engagement in combat, branch of the military, and specific duties (Armistead-Jehle et al., 2017). Mechanisms of injury in military environments for concussion comprise very different types of etiologies, including those from blunt forces and high-explosive blast forces (Greer et al., 2016). According to data from the National Collegiate Athletic Association Injury Surveillance Program in the US (NCAA-ISP), aside from concussion, ankle sprains and anterior-cruciate ligament injuries are the most common orthopedic conditions occurring each year as a result of sports participation (Hootman et al., 2007). Musculoskeletal injuries also commonly befall US service members, significantly contributing to the 1.6 million injuries occurring each year (Hauret et al., 2010). Foot and ankle, knee, and low back injuries are the most commonly reported musculoskeletal injuries in service members (Teyhen et al., 2018).

When a concussion or musculoskeletal injury occurs in athletes or service members, a primary goal is to return to play or military activity, respectively. Generally speaking for concussion, recovery is established once there is dissipation of self-reported symptoms (including headaches, dizziness, noise and light sensitivity, emotional concerns, sleep disturbances, etc.) at rest and with activity (McCrory et al., 2017). For other injuries, the absence of pain and return of normalized movement patterns needed for function are key indicators of recovery. In order for musculoskeletal injuries to be appropriately yet safely challenged, physical therapy intervention is routinely utilized to provide treatment as well as guidance related to return to activity. Research evidence only recently emerged to support physical therapy utilizing multi-modal (i.e. cervical, vestibular, and oculomotor interventions) as a treatment directly following concussion (Reneker et al., 2017). At this time, physical therapy is not routinely utilized after a concussion to establish fitness for return to play or duty.

A key concern with return to activity is the risk of re-injury. In sports, it is believed that athletes who have suffered one concussion are at a higher risk for another concussion (McCrory et al., 2017). The risk of this phenomenon has not been quantified across studies in athletes and there is little research describing secondary concussion risk in military contexts. Subsequent musculoskeletal injuries are also common after experiencing a primary musculoskeletal injury for both athletic and military populations (Wiggins et al., 2016; Schneider et al., 2000; Fulton et al., 2014). It has been reported that military personal who have experienced a traumatic injury, as opposed to an overuse or unspecified injury, have an 83% increased likelihood of experiencing a subsequent injury (Schneider et al., 2000). One systematic review reported that among professional soccer players, those who have experienced an ankle sprain were 50% more likely to experience a repeated ankle sprain than those who had not experienced a previous injury (Fulton et al., 2014).

Recently there has been an emergence of research reporting risk of musculoskeletal injury after a concussion. It is hypothesized that despite clinical recovery after a concussion, residual deficits in motor control remain, which increases risk of musculoskeletal injury (Brooks et al., 2016; Kardouni et al., 2018). A recent systematic review and meta-analysis was published on the risk of musculoskeletal injury in athletes after a sport-related concussion (McPherson et al., 2018), but the overall phenomenon describing the association between history of any concussion/mild TBI (not just sport-related concussion) and any type of subsequent injury, including estimates for secondary concussion, and using additional metrics of risk has not been reported in athletes. In addition, we are not aware of any previously reported meta-analyses to approximate risk of injury in service members after a concussion.

The purpose of this systematic review and meta-analysis was to provide an evidence synthesis describing risk of injury in athletic and military populations with and without a history of concussion. The objective was to provide summary estimates, utilizing any type of risk data (i.e. odds ratio, hazard ratio, and rate ratio), for overall risk of any type of injury followed by the subsets of concussion risk; extremity injury risk; and lower extremity risk.