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The Difference in Head and Helmet Motion during an Emergency Management Maneuver: Does the Helmet Immobilize the Head?

Silva KJ, Cohen MR, Decoster LC, Tucker WS*, Hollingworth AT, Swartz EE†: New Hampshire Musculoskeletal Institute, Manchester, NH, *University of Central Arkansas, Conway, AR, †University of New Hampshire, Durham, NH

Context: In a supine football player, the helmet and shoulder pads maintain neutral cervical alignment. Current guidelines for managing a potential spine injury recommend leaving the helmet in place, assuming that stabilizing the helmet will also immobilize the head.  Guidelines further recommend facemask removal to allow access to the airway. New research suggests that the chinstrap’s chin cup prohibits proper mask seal, interfering with ventilation, suggesting the chinstrap may need to be removed. The current recommendation for chinstrap removal calls for cutting the chinstrap off. There is no evidence regarding whether the head is immobilized during this emergency management approach.

Objective: To determine the difference between helmet and head motion during chinstrap removal.

Design: Repeated Measures.

Setting: Controlled laboratory.

Participants: Thirty-four certified athletic trainers (males=17; age=29.35±8.57yrs, height=180.19±5.51cm, weight=85.33±14.88kg, experience=6.91±8.58yrs), (females=17; age=26.18±3.11yrs, height=163.64±6.83cm, weight=74.63±16.48kg, experience=2.80±2.42yrs).

Interventions: A healthy male model was positioned supine wearing a properly-fitted Riddell 360 helmet with the facemask removed and Riddell Power CPX shoulder pads. Two biaxial (transverse (x), sagittal (y)) inclinometers were used. One was secured to the model’s goggles. The other was secured to the helmet. Participants worked in pairs; one stabilized the head, while the other cut the chinstrap off. Trials were complete when the cut portion of the chinstrap was placed on the floor. A new pair of 7.5” scissors was issued to each pair. Each participant performed one trial in each role (stabilization and removal) in random order.  Helmet and head motion data were integrated over each trial to allow comparison of the motion over the length of the trial. Paired samples t-tests were used to compare helmet and head motion in each plane.

Main Outcome Measures: The dependent variables were the integrated motion of the helmet and head in the transverse and sagittal planes.  The independent variable was the chinstrap removal perturbation.

Results: The mean time per trial was 39.5±9.7 seconds. In the sagittal plane, the head experienced significantly more motion (26.7±13.0°) than the helmet (12.7±5.3°, t(16)=5.5, p<0.001).  In the transverse plane, there was no difference between head (15.02±5.6°) and helmet motion (14.9±6.9°, t(16)=.234, p=0.818).  The 95% confidence interval (CI) for the difference between head and helmet motion was -1.4–1.7 in the transverse plane and 8.6–19.3 in the sagittal plane.

Conclusions:  Despite a rescuer’s manual stabilization of the helmet, the head experienced sagittal movement inside the helmet during the trials.  These results call into question the assumption that stabilizing the helmet immobilizes the head. This work should be repeated studying other helmet types, different perturbations and multiple models. If confirmed, guidelines may require updating to allow manual stabilization of the head instead of the helmet.