The influence of various factors on high school football helmet face mask removal: a retrospective, cross-sectional analysis.

CONTEXT Most research on face mask removal has been performed on unused equipment. OBJECTIVE To identify and compare factors that influence the condition of helmet components and their relationship to face mask removal. DESIGN A cross-sectional, retrospective study. SETTING Five athletic equipment reconditioning/recertification facilities. PARTICIPANTS 2584 helmets from 46 high school football teams representing 5 geographic regions. INTERVENTION(S) Helmet characteristics (brand, model, hardware components) were recorded. Helmets were mounted and face mask removal was attempted using a cordless screwdriver. The 2004 season profiles and weather histories were obtained for each high school. MAIN OUTCOME MEASURE(S) Success and failure (including reason) for removal of 4 screws from the face mask were noted. Failure rates among regions, teams, reconditioning year, and screw color (type) were compared. Weather histories were compared. We conducted a discriminant analysis to determine if weather variables, region, helmet brand and model, reconditioning year, and screw color could predict successful face mask removal. Metallurgic analysis of screw samples was performed. RESULTS All screws were successfully removed from 2165 (84%) helmets. At least 1 screw could not be removed from 419 (16%) helmets. Significant differences were found for mean screw failure per helmet among the 5 regions, with the Midwest having the lowest failure rate (0.08 +/- 0.38) and the Southern (0.33 +/- 0.72), the highest. Differences were found in screw failure rates among the 46 teams (F(1,45) = 9.4, P < .01). Helmets with the longest interval since last reconditioning (3 years) had the highest failure rate, 0.47 +/- 0.93. Differences in success rates were found among 4 screw types (chi(2) (1,4) = 647, P < .01), with silver screws having the lowest percentage of failures (3.4%). A discriminant analysis (Lambda = .932, chi(2) (14,n=2584) = 175.34, P < .001) revealed screw type to be the strongest predictor of successful removal. CONCLUSIONS Helmets with stainless steel or nickel-plated carbon steel screws reconditioned in the previous year had the most favorable combination of factors for successful screw removal. T-nut spinning at the side screw locations was the most common reason and location for failure.