Laboratory tests in which dummy headforms are used to evaluate helmet performance must be representative of real-world conditions to ensure helmets perform well in the field. The objective of this study was to quantify shape differences that may affect helmet fit between two dummy headforms commonly used for football helmet testing. Point-cloud models of a 50th percentile male Hybrid III headform and a medium NOCSAE headform were generated using a coordinate measuring machine. The headforms were optimally aligned and shape comparisons were made in the mid-sagittal plane, three coronal planes, and 3D. Planar and 3D differences were quantified by comparing maximum (MRD) and root-mean-square (RMSD) radial deviations. Minor differences were observed in the upper skull contours of all planar cross-sections, where MRDs were less than 3.5 mm and RMSDs were less than 1.7 mm. Larger deviations were observed in other regions including the jaw in the anterior coronal plane, where the MRD was 6.6 mm and the RMSD deviation was 4.5 mm. Substantial differences were noted between the Hybrid III and NOCSAE at the base of the skull, cheeks, jaw and chin. The headforms were also compared to a head model based on medical imaging of a human subject, which the NOCSAE matched more closely than the Hybrid III. The data presented in this study show that the Hybrid III and NOCSAE headforms have substantial shape differences in several regions that are important for helmet fit, possibly making the NOCSAE a better option for realistic helmet fit.

These data are a further step toward developing effective strategies to reduce the incidence of concussion in youth football and have applications toward youth-specific football helmet designs.

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OBJECTIVE Adolescent participation in athletics continues to grow, leading to an increasing incidence of sports-related concussion (SRC). The current literature suggests that a greater number of prior concussions positively correlates with a greater number of total symptoms, but the specific concussion-related symptoms are not as well defined. The current study investigated the effects of prior recurrent head injury on the symptom profiles of student-athletes after another suspected concussion. METHODS A multicenter database consisting of 25,815 Immediate Post-Concussion Assessment and Cognitive Testing (ImPACT) results was filtered for student-athletes aged 12–22 years old who competed in 21 different sports. Patients were separated into 2 cohorts: athletes reporting a single prior concussion (SRC1) and athletes reporting 2 or more prior concussions (SRC2+). Comparisons were assessed for differences in 22 symptoms and 4 symptom clusters at baseline, first postinjury test (PI1), and second postinjury test (PI2) by using univariate and multivariate analyses. RESULTS No differences were seen between SRC1 (n = 2253) and SRC2+ (n = 976) at baseline. At PI1, the SRC2+ group (n = 286) had lower severity of headaches (p = 0.04) but increased nervousness (p = 0.042), irritability (p = 0.028), sadness (p = 0.028), visual problems (p = 0.04), and neuropsychiatric symptoms (p = 0.009) compared with SRC1 (n = 529). Multivariate analysis revealed decreased headache severity with increased prior concussion (β = −0.27,95% CI −0.45 to −0.09, p = 0.003). Multivariate analysis at PI2 demonstrated the SRC2+ cohort (n = 130) had increased cognitive (β = 1.22, 95% CI 0.27–2.18, p = 0.012), sleep (β = 0.63, 95% CI 0.17–1.08, p = 0.007), and neuropsychiatric (β = 0.67,95% CI 0.14–1.2,0.014) symptoms compared with SRC1 (n = 292). CONCLUSIONS At longitudinal follow-up, patients with a history of recurrent concussions reported greater symptom burden in cognitive, sleep, and neuropsychiatric symptom clusters but not migraine symptoms. This is an important distinction because migraine symptoms are often more easily distinguishable to patients, parents, and physicians. Careful assessment of specific symptoms should be considered in patients with a history of recurrent head injury prior to return to play.