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Erik E. Swartz, PhD, ATC, and Susan A. Norkus, PhD, ATC, contributed to conception and design; acquisition and analysis and interpretation of the data; and drafting, critical revision, and final approval of the article. Charles W. Armstrong, PhD, contributed to conception and design; acquisition and analysis and interpretation of the data; and critical revision and final approval of the article. Douglas M. Kleiner, PhD, ATC, contributed to analysis and interpretation of the data and critical revision and final approval of the article.
To quantify the amount of helmet movement, time for task completion, tool satisfaction, and overall efficiency for various face-mask removal tools during football helmet face-mask removal.
Each subject performed one trial with the anvil pruner (AP), Face Mask Extractor (FME), PVC pipe cutter (PVC), and Trainer's Angel (TA). Each subject cut through 4 loop straps and removed the face mask while kneeling behind the athlete's head.
Twenty-nine certified athletic trainers (age = 29.5 ± 6.2 years, athletic training experience = 6.3 ± 5.0 years).
Time to complete the task was recorded. Total range of motion and total movement of the helmet were assessed using a 6-camera, 3-dimensional motion-capture system. Satisfaction scores were measured for each subject for each tool. Efficiency scores were calculated using time and total helmet-movement data.
When using the FME, subjects were significantly faster than with all other tools (P < .05), and when using the AP and TA, they were significantly faster than with the PVC. No differences were noted between tools in either movement variable. Significant differences were noted for satisfaction (P < .05) for all comparisons except TA versus AP. Efficiency scores were FME, 11.6; AP, 14.3; TA, 14.5; and PVC, 22.9, with lower scores identifying increased efficiency.
In general, subjects using the FME were superior in all variables except the movement variables. Future researchers should assess the removal task using specific protocols to determine whether the tools truly differ in terms of the movement created.
Given the potentially catastrophic and life-altering result of cervical spine injury (CSI), much concern exists regarding the evaluation, prehospital management, and care of the cervical spine–injured athlete. Historically, research interest has centered on the mechanism and pathophysiology of the injured spinal cord subsequent to an axial load in the American football player.1–6
Other recent efforts in research have expanded to include a focus on the management of the cervical spine–injured football player.7–21 Any time the possibility of CSI is present, all equipment should be left on, except for the face mask.22 Radiographic studies of human subjects and cadaver models have shown that the cervical spine is taken out of its normal, neutral alignment when the football helmet is removed and the shoulder pads are left in place.7–10,21 By increasing the lordotic curvature and producing hyperextension in the cervical region, it is possible to further aggravate the athlete's injury by placing unnecessary stress on the spinal cord. Because obtaining access to the athlete's airway may be necessary, it has become the practice of sports medicine professionals to retract or remove the face mask from the helmet by cutting or unscrewing the plastic loop straps that hold the face mask in place. This is a challenging task, and it is recommended that multiple individuals participate in the prehospital care of the spine-injured athlete.22 However, there may be situations in which a certified athletic trainer (ATC) is the only qualified individual available to accomplish the task of face-mask removal.
The tool selected by the ATC to perform this vital task is extremely important for efficient on-the-field management of CSI. A tool that easily cuts through the loop straps is preferred. Additionally, the ATC hopes to remove the face mask without producing any undue motion to the cervical spine. Most ATCs have a tool they use expressly for this purpose.
Many tools have been used to cut the plastic loop straps that hold the face mask to the helmet. Two tools designed specifically for face-mask removal are the Face Mask Extractor (FME) (Sports Medicine Concepts, Inc, Rochester, NY) and the Trainer's Angel (TA) (Trainer's Angel, Riverside, CA). Inexpensive hardware or gardening tools such as the anvil pruner (AP) and the PVC pipe cutter (PVC) can also cut through the face-mask loop straps to allow airway access.
Previous research regarding the resultant helmet movement that occurs during the task of equipment removal from the spine-injured athlete is limited. Much of the literature has focused on the time to complete face-mask removal or retraction.12,14,15 Although researchers have not identified how much cervical spine movement after the initial injury could result in further injury, face-mask removal should not produce undue head or cervical spine movement. Limiting movement at the helmet and head during removal or retraction may be more critical than speed in preventing further injury. Swartz et al11 studied the 3-dimensional movement produced during face-mask retraction with 4 popular tools. Subjects were asked to cut the 2 lateral loop straps and retract the face mask. Since that investigation, the Inter-Association Task Force for the Appropriate Care of the Spine-Injured Athlete has recommended removal (cutting all 4 loop straps) over retraction.22 Therefore, the degree of helmet and resultant head movement during the removal task still needs to be quantified.
The purposes of this investigation were to (1) quantify movement produced by various tools when cutting loop straps in a sampled amount of time during face-mask removal, (2) evaluate the amount of time it takes to remove a face mask using various tools, and (3) identify which of 4 tools ATCs preferred (ie, were most satisfied with). The results from this study may help to identify a single tool as superior in speed and movement created during face-mask removal.
Twenty-nine ATCs (n = 29: 13 men, 16 women) from among local sports medicine professionals voluntarily agreed to participate in this investigation (age = 29.5 ± 6.2 years, years certified = 6.3 ± 5.0, hand length = 17.64 ± 1.34 cm, hand width = 8.08 ± 0.62 cm, grip strength = 41.65 ± 11.29 kg). Subjects with any significant orthopaedic or neural abnormalities of the upper extremities were excluded from the study. Subjects were accepted for participation after signing the informed consent form approved by the university's institutional review board, which also approved the study.
The face-mask removal tools used in this investigation were the AP (Scotts, Columbus, OH), FME, PVC (Sears, Chicago, IL), and TA. These tools have been used in previous research and are commonly used by ATCs.12–19 Although the screwdriver has been included in previous studies,17,23 it was not included in this investigation because the screws and T-nuts of football helmets may fail owing to rust, corrosion, spinning, or shredding of the screw face. Furthermore, the mechanism of unscrewing the hardware differs from cutting the loop straps.
We used a 6-camera, EVa Hi-Res 3-D kinematic motion-capture system (Motion Analysis Corp, Santa Rosa, CA) to collect the movement data for this investigation. A research assistant was fitted with a Riddell football helmet (Elyria, OH) and positioned supine in the center of the data-collection area. The same research assistant was used throughout the entire data collection. Three 2.54-cm (1-in) retroreflective markers were placed on the helmet of the model in a triangular fashion. Movement of the helmet segment was referenced to the horizontal plane. The motion-capture system is designed to track the movement of these markers in 3 planes, and associated software was used to measure the movement produced during the task. Marker accuracy has been determined to be less than 0.5 mm according to cube and wand calibration techniques.24 The face mask was held in place with 4 Armourguard loop straps (Schutt, Inc, Litchfield, IL). Total time to remove the face mask was measured using a standard stopwatch.
Each subject was then asked to rank each tool independently as to how well the tool completed the task of face-mask removal. Tool satisfaction was determined using a simple Likert scale (1–10), with 1 indicating the lowest degree of satisfaction and 10 indicating the highest degree of satisfaction.
Subjects reported to the Applied Biomechanics Laboratory for familiarization with the methods and protocol of the investigation approximately 2 to 4 days before data collection. At this time, written consent was obtained, and the exact instructions were given to each subject. Each subject was instructed on the proper use of all 4 tools and practiced face-mask removal with each of the 4 tools at least one time. Subjects were then encouraged to practice the task until they felt comfortable with their ability to remove the face mask with each tool.
On the day of data collection, the subject removed the face mask 4 times, once with each tool. The protocol used for face-mask removal required the subject to cut through all 4 face-mask loop straps, in any order, and physically remove the face mask from the helmet. To simulate a worst-case scenario, subjects were positioned behind the model's head and instructed to provide stabilization with both knees. Additionally, subjects were encouraged to place their free hand on the helmet to provide further stabilization. Subjects were to cut the loop straps as quickly as possible while maintaining the head and cervical spine as motionless as possible. Each subject was given a new tool for each trial, and the order of face-mask removal tools was counterbalanced using a Latin square. The subject started in a position of stabilization with the tool resting on the floor. Timing began when the subject picked up the tool and ended when the face mask was placed on the floor.
During pilot testing, we observed that when the subject began the task of face-mask removal, some initial movement was produced from the body and tool positioning. Because our focus was on tool performance only, we chose to begin data collection 5 seconds after the subject picked up the tool. This allowed the subject the necessary time to “settle in” to the task. Also during familiarization, numerous subjects demonstrated that they could cut through all 4 loop straps and completely remove the face mask in as little as 35 seconds. This necessitated ending the movement analysis after 25 seconds to avoid any potential movement created after the loop straps were cut. Again, our purpose was not to assess total movement (TMT) produced during face-mask removal but rather movement produced by each tool during cutting of the face-mask loop straps. A longer window of data collection might have introduced additional movement variables, such as subjects attempting to manipulate loop-strap remnants or actually attempting to pry the face mask away from the helmet. Although we acknowledge that these are very important factors and indeed contribute to overall movement, this investigation focused on tool performance as opposed to subject or ATC performance. Therefore, to collect movement produced solely from the cutting of the loop straps, we chose to analyze a sample of the movement data.
Five dependent measures were assessed in this investigation: time, TMT, total range of motion (ROM), user satisfaction, and overall efficiency score. As described earlier, time was defined as the length of time between the subject's picking the tool up and placing the removed face mask on the floor. The total degree of movement the helmet experienced during the data-collection session is TMT. This variable is a combination of the movements produced in all 3 planes (flexion-extension, lateral flexion left-right, and rotation left-right) and can be described as the sum of the path of motion the helmet traveled. Total ROM produced was a combination of maximal range of movement in all 3 planes and was calculated as the difference between maximum and minimum angles produced during data collection. User satisfaction is a subjective measure of how well the subjects felt each tool performed the task. The efficiency score provides an overall variable in which both movement and time are represented. Previous researchers have used an efficiency score to provide the clinician with applicable information. The formula we used to identify efficiency was TMT × time/1000. A lower score indicates that overall, the tool performed more quickly and with less movement.11,17
Four separate, repeated-measures multivariate analyses of variance were calculated to identify significant differences among tools for time, TMT, ROM, and satisfaction. The 4 tools served as the independent variables. If any significant findings were identified (P < .05), paired t tests were computed as a post hoc measure. All statistical analyses were performed using SPSS (version 11.0 for Windows, SPSS Inc, Chicago, IL).
Data for time, TMT, ROM, and satisfaction are provided in the Table. Figures Figures11 and and22 present graphic representations of the movement variables. A significant main effect was detected for time (F3,26 = 17.962, P = .000) and preference (F3,26 = 34.540, P = .000). When using the FME, subjects were significantly faster than with all other tools (for AP versus FME, t28 = 2.398, P ≤ .023; for FME versus PVC, t28 = −7.334, P ≤ .000; for FME versus TA, t28 = −3.527, P ≤ .001) and when using the AP and TA, subjects were significantly faster than when using the PVC (for AP versus PVC, t28 = −5.387, P ≤ .000; for AP versus TA, t28 = −0.560, P = .580; for PVC versus TA, t28 = 4.575, P ≤ .000). Significant differences were noted for subject satisfaction for all comparisons except TA versus AP (for AP versus FME, t28 = −2.544, P ≤ .017; for FME versus TA, t28 = 4.662, P ≤ .000; for AP versus PVC, t28 = 7.035, P ≤ .000; for AP versus TA, t28 = 1.498, P = .145; for FME versus PVC, t28 = 8.081, P ≤ .000; for PVC versus TA, t28 = −3.771, P ≤ .001). No significant differences were noted in the ROM (F3,26 = 0.343, P > .05) or TMT (F3,26 = 0.357, P > .05) variables. The FME had the highest degree of efficiency (tool efficiency: FME 11.6, AP 14.3, PVC 22.9, TA 14.5).
Time has been the most common variable measured in previous investigations of face-mask removal.11,12,16–19 Our results indicate that the FME was significantly faster than the AP, TA, and PVC during face-mask removal. Our results are consistent with previous findings in which either the AP or the FME has consistently been identified as allowing subjects to perform face-mask removal or retraction fastest.11,12,15,17–18 The screwdriver has also been shown to perform face-mask removal faster than the TA and AP;17 however, it was not included as a tool in this study.
In general, subjects performed the removal task faster for all tools than the retraction task in our previous investigation,11 yet slower for the TA and AP compared with another study.17 Faster times are certainly warranted in these situations, especially in the worst-case scenario of an athlete who has stopped breathing. Yet, an exact amount of time has not been quantified and deemed to be an acceptable amount of time for this task. The ATC should practice spine-management techniques in equipment-intensive sports to ensure access to the airway in a timely manner.
Previous researchers have found that movement at the head results in movement of the cervical spine.19–21 In a recent investigation, using radiographic techniques to analyze the amount of cervical spine movement associated with head movement,20 4.5 and 9.0 cm of lateral flexion of the head produced 7.5° and 11.5° change, respectively, at the C5 spinal segment. However, this investigation only included 1 subject and focused on movement that occurred at 1 level of the cervical spine.
Tierney et al21 used magnetic resonance imaging to assess spinal-cord space, spinal-cord diameter, and cervical-thoracic angle in 12 subjects. Each subject was imaged while wearing both a helmet and shoulder pads and then with only shoulder pads.21 The sagittal space in the spinal canal was significantly changed, increasing at the occiput level from 0 to 4 cm after both immobilization and a change in head position.21
In another investigation,19 the movement created at the head within helmets worn by football, lacrosse, and hockey players was identified using 3-dimensional techniques.21 Movement was assessed during backboard immobilization, and the focus was specifically on how much movement the head was subjected to in relation to movement at the helmet. A bite-stick marker allowed the identification of rotational head movement versus movement of helmet markers. Although the results suggested that the head moved less within the football helmet compared with lacrosse and hockey helmets, the findings were not statistically significant. It is important to note that helmet movement as well as movement of the head within the helmet both occurred.
These studies demonstrate that the cervical spine is affected by the movement created at the head through helmet movement and that the space in a spinal canal constricted by a bone fragment or dislocation may not be safe for an injured spinal cord. An exact predictor of how much face-mask, helmet, or head movement produces cervical spine movement has not been established. Furthermore, how much movement at the cervical spine results in injury to the spinal cord and how much cervical spine motion is acceptable during the face-mask removal task are unknown. Therefore, movement in this study is described as head movement, not helmet or cervical spine movement. We do, however, assume that movement of the helmet results in some movement at the cervical spine.
To our knowledge, the only published report using 3-dimensional motion capture to assess movement at the head during face-mask retraction is that of Swartz et al.11 Yet, comparison of our results with this previous study is difficult because the tasks performed by the subjects differed, and only total ROM was reported.11
In the earlier investigation,11 no significant differences in ROM were identified between tools. However, although they were not significantly different from one another, the FME produced the least movement, followed by the TA, AP, and PVC. In our current study, the tools were nearly identical to one another in the total ROM produced during face-mask removal (see Figure Figure1).1). The TMT findings identified the FME as producing more movement than the other 3 tools (see Figure Figure2),2), which is contradictory to the previous study.11 These differences may be explained by the subjects completing 2 different tasks, and therefore, caution should be taken when making comparisons between studies.
Knox and Kleiner17 determined TMT of the head in a study of face-mask retraction through deviation of the center of pressure of the helmet on a force platform. The TA produced significantly more movement of the center of pressure than the screwdriver or AP.17 These results are not consistent with our results. It is difficult to relate the results from both studies, considering the differences in methods, tools, and instrumentation. The deviation of the center of pressure has not been shown to correlate with movement at the head as determined by other techniques such as 3-dimensional video, nor has deviation in the center of pressure been shown to correlate with movement in the cervical spine.
A limitation in this study was the 25-second sample used to assess movement while the tools were cutting the loop straps. Specifically, the length of time the tools took to complete the task and how much of that task was analyzed for movement differed for each tool. It is important to remember that the purpose of the investigation was to analyze movement created by the tool's cutting the loop straps, so all samples contained only movement data derived from the tool cutting the straps. However, it is logical to conclude that more movement occurred during the remainder of the task after the 25-second movement sample was completed.
For example, the PVC took an average of 155.9 seconds to complete the task (Figure (Figure3).3). Theoretically, because the 25-second sample only represents approximately 16% of the entire task for the PVC, potentially more than 900° of motion might be seen if movement data were collected throughout the entire trial. Although the degree of movement required to cause further injury to the spinal cord has not been established, the clinician who hopes to create little to no movement during the face-mask removal process would be far from achieving this goal, even with the movement captured during the 25-second sample.
Perhaps the most striking and clinically pertinent finding from our study was the large amount of TMT created during a 25-second sample during face-mask removal (see Figure Figure2).2). These average values ranged between 142° and 152° of combined movement from all 3 planes of motion. This is clearly unacceptable when managing a potential CSI. Interpretation of these results might suggest that subjects did not sustain adequate cervical spine stabilization during this study, which allowed for inflated movement during the trial. Yet, the ROM was consistently between 9° and 10° for each tool, showing a restriction to excessive ranges of motion of the helmet by the subjects across all tools. Clinically, however, 9° to 10° of movement may be detrimental.
An efficiency score has been used in previous research.11,17 This score can be important in the overall assessment of each tool by combining the movement and time variables. However, although this score combines the 2 variables of movement and time, which variable is more important or whether they are equally important is yet to be determined. Furthermore, either of the variables could change in their priority depending on the situation. Knox and Kleiner17 used a TMT variable from ground reaction force data combined with time and found the AP to be more efficient than the TA or a screwdriver. Their study did not include the FME.17 Swartz et al11 used a total ROM variable and found the FME to have the best efficiency score.11 Our current study identifies the FME as the most efficient tool according to the combined time and TMT. Still, because of the differences in techniques, instrumentation, and measurements, we did not compare the results of the efficiency scores among studies. Knox and Kleiner17 looked at efficiency ratings with an analysis of variance and found no significant differences. Even though this rating can provide the clinician with an important overall assessment of tools, until the relative importance of time and movement have been established, this value should be treated appropriately. Therefore, we did not attempt to analyze the efficiency score results statistically other than to report the final scores obtained by including the overall averages in the formula.
Tool preference, or satisfaction, among subjects has also been investigated extensively, and the results have been consistent.11,13–15,17–18 Subjects in our study expressed the greatest degree of satisfaction with the FME, a finding that was significantly different from all other tools. The AP was second to the FME in satisfaction ratings, with subjects being the least satisfied with the PVC. These findings are in general agreement with other research.13–15,17–18
Why subjects are more satisfied with or prefer one tool over another has not been established. It is logical to assume that the most preferred tools, or the tools gaining the highest satisfaction among users, would be those performing the best in the time and movement variables. This appears to be the case when comparing the findings from the literature but has not yet been demonstrated scientifically.
The FME allowed subjects to perform face-mask removal with superior performance for time to complete the task and provided more subject satisfaction and was the most efficient tool when combining TMT and time. A high degree of TMT may be created during the removal process, but how much movement is acceptable is unknown. Our movement data were limited to the 25-second sample of movement analyzed and cannot be generalized to the entire face-mask removal task.
Future research is necessary to identify how much movement is occurring during the entire face-mask removal task, while controlling for external factors. We believe the only way to assess movement between tools is to have each tool perform the task in the same amount of time using specific protocols so that an equal sample from each tool can be compared. Investigators should compare the movement created during face-mask removal and retraction to scientifically support one technique versus another and should attempt to identify subsets that may begin to explain what a subject considers when asked to rate a tool on its satisfaction. Face-mask removal from athletes in other helmeted sports, such as hockey and lacrosse, should also be addressed.
On the basis of our findings, we recommend use of the FME to remove the face mask when it is attached with Armourguard loop straps because of its performance in time, satisfaction rating, and efficiency. These results pertain to the FME in its original design. However, it is important to note that the FME is no longer available in its original design. The new version is expected to be available in the spring of 2003 and to offer additional beneficial features. Furthermore, recent design changes in helmets, face masks, and loop fasteners should be studied so that we can determine which work best for the clinician and the athlete.
Additionally, because we did identify movement during the removal process with all tools, ATCs should be extremely cautious when performing this task, focusing not only on removing the face mask but also on effectively stabilizing the cervical spine. We also recommend that any ATC who may have to remove a face mask practice the skill often.
We thank the National Athletic Trainers' Association Research and Education Foundation for funding this project. We also thank Laura Decoster, ATC, of The New Hampshire Musculoskeletal Institute (Manchester, NH), for her contributions to data collection and manuscript review.