Parachute ankle brace and extrinsic injury risk factors during parachuting.

INTRODUCTION This study examined the injury prevention effectiveness of the parachute ankle brace (PAB) while controlling for known extrinsic risk factors. METHODS Injuries among airborne students who wore the PAB during parachute descents were compared with injuries among those who did not. Injury risk factors from administrative records included wind speed, combat loads, and time of day (day/night). Injuries were collected in the drop zone. RESULTS A total of 596 injuries occurred in 102,784 parachute descents. In univariate analysis, students not wearing the PAB (Controls) were 2.00 [95% confidence interval (95% CI) = 1.32-3.02] times more likely to experience an ankle sprain, 1.83 (95% CI = 1.04-3.24) times more likely to experience an ankle fracture, and 1.92 (95% CI = 1.38-2.67) times more likely to experience an ankle injury of any type. PAB wearers and Controls had a similar incidence of lower body injuries exclusive of the ankle [risk ratio (Control/PAB) = 0.92, 95% CI = 0.65-1.30]. After accounting for known extrinsic injury risk factors, Controls were 1.90 (95% CI = 1.24-2.90) times more likely than PAB wearers to experience an ankle sprain, 1.47 (95% CI = 0.82- 2.63) times more likely to experience an ankle fracture, and 1.75 (95% CI = 1.25-2.48) times more likely to experience an ankle injury of any type. The incidence of parachute entanglements that persisted until the jumpers reached the ground were similar among PAB wearers and Controls IRR (Control/PAB) = 1.17, 95% CI = 0.61-2.29]. CONCLUSION After controlling for known injury risk factors, the PAB protected against ankle injuries, and especially ankle sprains, while not influencing parachute entanglements or lower body injuries exclusive of the ankle.