effectiveness of the parachutist ankle brace in reducing ankle injuries in an airborne Ranger battalion, The

Military Medicine, Dec 2000 by Pope, Richard W

In a study of the night combat parachute assault on Rio Hato Airfield during Operation Just Cause in 1989, it was found that the 2d Ranger Battalion sustained a significant number of ankle injuries. Data were collected on 486 of the 624 Rangers who participated in the parachute assault. A total 51 Rangers from the battalion sustained 55 ankle injuries (including 4 bilateral ankle injuries) during combat, and 92.7% of them occurred during the airborne infiltration. Nineteen injuries had no impact on combat effectiveness, 15 injuries limited combat effectiveness, and 21 injuries kept Rangers out of combat (10 fractures). The authors recommended development of an ankle brace for military parachuting.I The results of our study suggest that the PAB assists in reducing the frequency of ankle injuries in an operational airborne unit, answering the need for an acceptable brace for military use.

Like any brace, however, forces can be generated that exceed the capacity of the device. When the PAB fails, the posterior portion breaks, leaving the ankle relatively unsupported. We heard only anecdotal stories of brace failure without the Ranger sustaining a fracture. If an impact is profound enough, the brace will often cause a mild contusion or sprain rather than a debilitating sprain or fracture of the ankle. This occurs because the forces are spread throughout the contact area of the brace. Of note, two of the authors have experienced this type of injury. Mild ankle contusions such as these are often unreported and do not affect duty status for the Ranger.

The results of our study indicate that the PAB is successful at reducing eversion and inversion injuries. The ankle fracture pattern observed in parachuting is predominantly inversion or eversion.24,25 These are the movements that the PAB is designed to prevent. The braces will not prevent compression-type injuries such as tibial plafond fractures, which occur from axial loading of the ankle. This type of injury can be the result of falling the last 20 to 75 feet with little or no lift from the parachute canopy. The most frequent cause is when two jumpers come close together and the higher jumper's canopy moves directly over the lower jumper's canopy. The higher jumper has decreased lift, and as his air is "stolen" his canopy deflates, increasing his rate of decent until he falls past the lower jumper and his canopy reinflates. One common source of injury is when two jumpers begin to leapfrog in this manner. The jumper who strikes the ground with his chute partially deflated tends to suffer an injury. This falling past one another will also increase the jumper's oscillation from side to side, increasing the lateral impact with the ground.

On initial fielding of the PAB, many of the Rangers expressed concern that the brace would transfer forces to the proximal leg, causing an increase in tibial/fibular shaft fractures. Our results did not find this to be the case. However, tibial/fibular shaft fractures in parachuting account for a small number of all injuries. One study that reviewed 615 parachuting injuries, including 71 with positive radiographic findings, found that tibial/fibular shaft fractures accounted for only 8.5% of fractures, or 0.98% of all injuries. In the same study, the authors found that ankle fractures constituted 57.7% of all fractures and 6.7% of all injuries.24 In our study, there were six tibial/ fibular shaft fractures during the entire period. During the period of PAB use, we observed three patients with four fractures involving either the midshaft or the proximal tibia/fibula. Patient one had a fibular shaft fracture and a contralateral tibial plafond fracture as well as an axial load injury; the tibial plafond injury was counted among the ankle fractures. Patient two sustained bilateral tibial/fibular shaft fractures after his air was stolen, causing his parachute to deflate partially approximately 70 feet above the ground. Patient three had a fibular head fracture from a direct blow to the fibula when he struck a concrete runway. None of these injuries appear to be related directly to use of the PAB. Statistically, these leg injuries do not indicate that use of the PAB will increase tibial/fibular shaft fractures.