Human and behavioral factors contibuting to spine-based neurological cockpit injuries in pilots of high-performance aircraft: Recommendations for management and prevention

Military Medicine, Jan 2000 by Jones, Jeffrey A

In high-performance aircraft, the need for total environmental awareness coupled with high-g loading (often with abrupt onset) creates a predilection for cervical spine injury while the pilot is performing routine movements within the cockpit. In this study, the prevalence and severity of cervical spine injury are assessed via a modified cross-sectional survey of pilots of multiple aircraft types (T-38 and F-14, F-16, and F/A-18 fighters). Ninety-five surveys were administered, with 58 full responses. Fifty percent of all pilots reported in-flight or immediate post-flight spine-based pain, and 90% of fighter pilots reported at least one event, most commonly (>90%) occurring during high-g (>5 g) turns of the aircraft with the head deviated from the anatomical neutral position. Pre-flight stretching was not associated with a statistically significant reduction in neck pain episodes in this evaluation, whereas a regular weight training program in the F/A-18 group approached a significant reduction (mean = 2.492; p

Introduction

The health and welfare of aviators in the U.S. Department of Defense present a challenge for military occupational health care workers because of the unique and physically taxing environment in which the aviators work and live. Aviation and aerospace represent a large component of the U.S. military budget, and pilots controlling and protecting extremely costly federal assets must be in top physical condition to perform their mission safely. The responsibility of maintaining the pilot's health and performance conditions Res with the squadron flight surgeon. The health of the pilots extends beyond their military careers, because these individuals become the core of aviation operations for the entire U.S. aerotransportation industry.

Technological advances have produced improvements in U.S. fighter airframe composite materials, flight controls, propulsion systems, and avionics, allowing the warplane to fly farther, faster, higher, and longer. These aircraft characteristics are pushing beyond the limits of current human capability and endurance. As a result, the fighter pilot, more than ever, is at risk for injury and adverse health outcomes as a result of the occupational hazards of the profession.

The current operational fighter/attack aircraft in the U.S. inventory include the F- 14, F- 15, F- 16, F/A- 18, and AV813 (Harrier). These aircraft possess 7.5- 10 X gravity (g) limitations for structural integrity. Future high performance aircraft, like the F-22, a new air-superiority fighter, or possibly the Joint Strike Fighter, may possess airframes capable of withstanding greater than 10 X g. The USAF Combat Edge Program with g-suit vest, helmet, and mask modifications ATAGS (advanced technology anti-g suit) are designed to push the pilot's cardiovascular gtolerance to 12 '1.2 Soon to follow, if funding allows, will be the Joint Strike Fighter. By the year 2020, the United States may also have a small fleet of military space planes, with even greater load-bearing limits for reentry and cross-range maneuvering, If piloted, these vehicles are bound to possess increased electronic reconnaissance and control capability, which usually translates into more intense task saturation, on top of the added physical stresses of operating at extremely high speed and g-loads. Additionally, reduced military budgets have meant a higher operations tempo with diminished manpower (getting more out of fewer personnel). This adds fatigue to increased tasking and higher physical stresses, creating conditions ripe for pilot error and injury.

During the past 15 years, there have been increasing numbers of reports of neck injury as a result of the g-forces experienced in modem fighter aircraft. These reports began appearing in the literature in the late 1970s,',' with a specific case report of a backseat injury in the F- 16B appearing in 1988.1 The injury issue has since been evaluated with more scrutiny by both U.S. Air Force and Navy flight surgeons, first epidemiologically in 1988 '6, 1 and then mechanistically by a North Atlantic Treaty Organization ally, the Finnish Air Force, in the mid 1990s.1-11 The results of these evaluations pointed to a number of potential contributory factors, including (1) the load onto the cervical spine from the weight of the head and helmet with or without night vision goggles (head, 3.5-5.0 kg; helmet, visor, and communication combo [without night vision goggles], 1. 1-2 kg, depending on the type of helmet [AF:HGU-55P 11. 1 kg vs. HGU26P 11.6 kg)]),9 e.g., the relative load of head plus helmet on the cervical spine at 9 g = 48 to 65 kg (105-143 pounds); (2) other forces on the spinal column, including type of force-compressive (Gz), torsional, and translational-and direction of forceGx, Gy, etc.; and (3) type and orientation of ejection seat (upright vs. reclined).

The flight equipment that has been developed to support the cardiovascular system, to prevent g-induced loss of consciousness includes g-suit and combat edge. Also, there is equipment in the cockpit to support the pulmonary/oxygen transport system: either onboard oxygen-generating system or liquid oxygen to increase fraction of inspired oxygen near 100%, if required, and positive pressure supply to a tight-fitting aviator's mask. However, to date, there has been no equipment developed to support the musculoskeletal system.

One flight surgeon, in a recent report, has begun an inquiry into possible prevention strategies. 14 Prevention strategies are felt to be critical to slow the alarming number of pilot spine injuries observed during the past few years. During joint service medical responsibility situations, such as dissimilar aircraft combat training, flight surgeons have observed an increased number of cervical neck injuries in F-16 and F/A-18 pilots. Conditions that we felt were important to evaluate, in terms of both understanding etiologic factors and developing a concrete prevention strategy, were as follows: ergonomics of airframe, flight characteristics of airframe, rapid-onset turning capability, location of the flight control stick, and rafls/handles in the cockpit to brace/support the pilot's upper body during high-g turning. We also felt it was important to evaluate a number of behavioral issues that may contribute to these injuries, including (1) pre-flight behavior issues: exercise (resistive and aerobic), conditioning, stretching, warm-up, general health factors, sleep patterns, smoking, ethanol ingestion; (2) in-flight behavior issues: head and body position during bracing for turns, onset rate of pull for high-g turns; and (3) post-flight behavior issues: stretching, exercise, use of analgesics, use of ancillary therapeutic aids (heating pads, etc.). Therefore, a more in-depth evaluation of pilots was conducted to examine the issues felt to be important in the production of spinal injury.