Kathryn L. O’Connor

Head impact measurement devices: a clinical review

Context: Concussive injuries are at the forefront of sports medicine research. Recently, researchers have used a variety of head- and helmet-based impact-monitoring devices to quantify impacts sustained during contact sport participation. This review provides an up-to-date collection of head accelerometer use at the youth, high school, and collegiate levels. Evidence Acquisition: PubMed was searched for articles published between 1980 and 2015 using the terms accelerometer and concussion, impact sensor and concussion, head impact telemetry system, head impact telemetry, and linear acceleration and concussion. An additional Google search was performed to capture devices without publications. Study Design: Clinical review. Level of Evidence: Level 4. Results: Twenty-four products track and/or record head impact for clinical or research use. Ten of these head impact devices have publications supporting their utility. Conclusion: Head impact measuring devices can describe athlete exposure in terms of magnitude and/or frequency, highlighting their utility within a multimodal approach for concussion assessment and diagnosis.

Descriptive Analysis of a Baseline Concussion Battery Among U.S. Service Academy Members: Results from the Concussion Assessment, Research, and Education (CARE) Consortium

Introduction The prevalence and possible long-term consequences of concussion remain an increasing concern to the U.S. military, particularly as it pertains to maintaining a medically ready force. Baseline testing is being used both in the civilian and military domains to assess concussion injury and recovery. Accurate interpretation of these baseline assessments requires one to consider other influencing factors not related to concussion. To date, there is limited understanding, especially within the military, of what factors influence normative test performance. Given the significant physical and mental demands placed on service academy members (SAM), and their relatively high risk for concussion, it is important to describe demographics and normative profile of SAMs. Furthermore, the absence of available baseline normative data on female and non-varsity SAMs makes interpretation of post-injury assessments challenging. Understanding how individuals perform at baseline, given their unique individual characteristics (e.g., concussion history, sex, competition level), will inform post-concussion assessment and management. Thus, the primary aim of this manuscript is to characterize the SAM population and determine normative values on a concussion baseline testing battery. Materials and Methods All data were collected as part of the Concussion Assessment, Research and Education (CARE) Consortium. The baseline test battery included a post-concussion symptom checklist (Sport Concussion Assessment Tool (SCAT), psychological health screening inventory (Brief Symptom Inventory (BSI-18) and neurocognitive evaluation (ImPACT), Balance Error Scoring System (BESS), and Standardized Assessment of Concussion (SAC). Linear regression models were used to examine differences across sexes, competition levels, and varsity contact levels while controlling for academy, freshman status, race, and previous concussion. Zero inflated negative binomial models estimated symptom scores due to the high frequency of zero scores. Results Significant, but small, sex effects were observed on the ImPACT visual memory task. While, females performed worse than males (p < 0.0001, pη2 = 0.01), these differences were small and not larger than the effects of the covariates. A similar pattern was observed for competition level on the SAC. There was a small, but significant difference across competition level. SAMs participating in varsity athletics did significantly worse on the SAC compared to SAMs participating in club or intramural athletics (all ps < 0.001, η2 = 0.01). When examining symptom reporting, males were more than two times as likely to report zero symptoms on the SCAT or BSI-18. Intramural SAMs had the highest number of symptoms and severity compared to varsity SAMs (p < 0.0001, Cohens d < 0.2). Contact level was not associated with SCAT or BSI-18 symptoms among varsity SAMs. Notably, the significant differences across competition level on SCAT and BSI-18 were sub-clinical and had small effect sizes. Conclusion The current analyses provide the first baseline concussion battery normative data among SAMs. While statistically significant differences may be observed on baseline tests, the effect sizes for competition and contact levels are very small, indicating that differences are likely not clinically meaningful at baseline. Identifying baseline differences and significant covariates is important for future concussion-related analyses to inform concussion evaluations for all athlete levels.

Comparison of Head Impact Exposure Between Male and Female High School Ice Hockey Athletes

Background: Concussion incidence rates are higher among female than male athletes in sports played by both sexes. Biomechanical factors may play a role in observed sex-based differences in concussion incidence. Purpose: To compare head impact counts and magnitudes during sports participation between male and female high school ice hockey athletes. Study Design: Cohort study; Level of evidence, 2. Methods: Over 2 seasons, a total of 21 male and 19 female ice hockey athletes from a single high school were instrumented with impact-sensing adhesive skin patches worn over the mastoid process while participating in games and practices. The impact sensors recorded the number, magnitude (peak linear acceleration [PLA, g] and peak angular acceleration [PAA, rad/s2] of the head; Head Impact Telemetry severity profile [HITsp]), and location of impacts sustained during each instrumented session. Head impact counts, magnitudes, and locations were compared between the sexes. Results: Males experienced more head impacts than females during games (mean ± SD: 7.7 ± 3.0 vs 5.3 ± 2.0, P < .001) as well as practices (4.3 ± 1.6 vs 3.8 ± 1.1, P = .002). Mean impact magnitudes were greater for females for PLA (18.8g ± 1.7g vs 17.1g ± 1.6g, P < .001) and HITsp (19.7 ± 1.5 vs 17.7 ± 1.4, P < .001), while mean PAA was greater for males (3057.6 ± 2.0 rad/s2 vs 2778.3 ± 2.7 rad/s2, P < .001). Female athletes experienced higher PLA, PAA, and HITsp magnitudes for the top 10%, 5%, and 1% of impacts (all P < .050). Males experienced more impacts to the front (34.3%) and back (31.7%) of the head, while females experienced more impacts to the side (43.1%) and top (4.1%) (χ2 = 295.70, df = 3, P < .001). Conclusion: While male high school ice hockey athletes experienced more head impacts than females, impact magnitudes tended to be higher for females.

The prevalence of concussion within the military academies: findings from the concussion assessment, research, and education (care) consortium

Objective Describe prevalence and risk factors for concussion among USA Service Academy cadets. Design Prospective. Setting Three USA Service Academies. Participants NCAA and non-NCAA athlete cadets (n=7636, 22% female) enrolled in the CARE Consortium (2014–2015). Assessment of risk factors NCAA status, contact-sport, gender, and brief sensation seeking scale (BSSS) were examined as risk factors for previous concussion. Outcome measures Number of previous concussions. Main results 21% of cadets reported a previous concussion with median time from injury being 2.5 years (IQR 0.99–4.57). At least one previous concussion occurred in 18% of freshman prior to Service Academy enrollment and 12% of sophomore through senior cadets sustained a concussion during their time at the academy. Cadets who are NCAA athletes had a 1.57 (95% CI: 1.12–2.19) greater odds of sustaining a concussion at the academy than non-NCAA cadets. Poisson regression modelling the number of previous concussions revealed significant main effects for contact-sport and BSSS. Controlling for BSSS, contact-sport cadets had 1.82 (95% CI: 1.69–1.95) times the prevalence rate of previous concussion compared to non-contact sport athletes. Additionally, controlling for contact-sport, higher BSSS scores increased prevalence of previous concussions by 1.17 (95% CI: 1.10–1.24) times. Conclusions Overall concussion prevalence among all service academy cadets is similar to prevalence of concussion previously reported for NCAA athletes. Within the academies, cadets who are also NCAA athletes have greater odds of concussion, likely due to increased risk exposure. Contact-sport status and increased sensation seeking is associated with increased number of previous concussions. Competing Interests/ Acknowledgements This project was supported, in part, with support from the Grand Alliance Concussion Assessment, Research, and Education (CARE) Consortium, funded, in part by the National Collegiate Athletic Association (NCAA) and the Department of Defense (DOD). The U.S. Army Medical Research Acquisition Activity, 820 Chandler Street, Ford Detrick MD 21702–5014 is the awarding and administering acquisition office. This work was supported by the Office of the Assistant Secretary of Defense for Health Affairs through the Psychological Health and Traumatic Brain Injury Program under Award NO W81XWH-14-2-0151. Opinions, interpretations, conclusions and recommendations are those of the author and are not necessarily endorsed by the Department of Defense (DHP funds.)