be able to look out the side window. This asymmetric hunching has resulted in a “hunched-back” curvature, which has further increased the loading of the mid-back due to the forward dis-placement of the upper torso and head. Helicopter vibration and discs Research has shown that helicopter vibrations (pressure waves caused by imbalances in rotating aircraft parts) have a peak power frequency of approximately 5 Hz, which is within the range where a human’s upper body presents resonance frequency (De Oliveira CD and Nadal J, 2005). Previous researchers have studied whole-body vibration and the pathogenesis of disc de-generation in animals. The results have suggested that vibration can adversely affect the nutrition and metabolism of the disc, especially if the vibration matches the resonant frequency of the spine (4 Hz to 6 Hz). Therefore, people exposed to whole-body vibration in the same resonant range, such as helicopter pilots, are significantly more prone to experiencing back pain. Hadji-pavlou et al. (2008) further explained that when the spine is flexed the joints offer less constraint to rotation, a situation that leads to tears in the discs, yet does not damage the joints. According to Hadjipavlou et al. (2008), the intervertebral discs (spine shock absorbers) are the largest avascular tissues in the body; furthermore, cells in the centre of an adult thoracic disc are approximately eight millimetres away from the nearest supply of blood. The cells, which are located on the outer edges of the disc, obtain nutrients from large blood vessels in the sur-rounding muscles and from a sparse diffusion of capillaries in the muscle’s outermost region. The capillary network is regulated by noradrenalin and acetylcholine, and by mechanical stimuli such as vibration. Each disc relies on a distribution system to pump water and nutrients into the disc. According to some research-ers, sustained compression or an immobilization of the spine can become a base for impairing the flow of nutrition to the disc. The reduced supply of nutrients leads to an increase in stress and cell death at the centre of the disc that eventually spreads throughout the entire disc with increased age and degeneration. Sandover (1981) reviewed the relationship between me-chanical stress on the spine and intervertebral disc degenera-tion, which was considered to be the most likely cause of back pain. His findings disclosed that mechanical stress hastens de-generative changes in the spine via microscopic injuries to the uppermost and/or lower-end surfaces of the vertebrae – regions through which the discs between the vertebrae are nourished. (static work, bending and twisting) and whole-body vibration does, in fact, contribute to expediating the degeneration and general fatigue failure of the spine in these aviators. Based on research and experience as a practising chiroprac-tor, it is my belief the duties of a helicopter pilot have been found to actually accelerate and amplify the level of spinal degeneration originating primarily in the thoracic and low-back region. The signs and symptoms of osteoarthritis due to induced vibration and postural stresses appear to be directly related to both back pain and the unique after-effects of having flown heli-copters. Furthermore, the helicopter pilot in this case study ap-peared not to have made any significant improvement while par-ticipating in his physiotherapy treatments in 2002 at a local base hospital. Although the physiotherapy program was extensive, it would be a problematic task to ascertain whether or not it would be therapeutically beneficial. With this in mind, I recommend that this veteran pilot would be an excellent candidate for an integrative health-care program – a platform that would incorpo-rate postural exercises, nutrition, chiropractic, massage therapy, acupuncture and aircraft ergonomic advice. I would further ad-vocate mandatory MRI scans and aviation medical examinations at regular intervals – designed and implemented for helicopter pilots – based on their cumulative flying hours. THE RUNDOWN It is impossible to review all of the congenital and acquired mal-formations or diseases of the thoracic and lumbar spine. How-ever, the most common malformations and/or diseases are disc degeneration and disc herniation. It is normal for the discs be-tween the vertebrae to deteriorate with age. Harrison, D et al. (2000) studied the optimal driver’s seat and spine position and established that piloting a helicopter predis-poses a flight operator to mid-back pain and degenerative joint disease. In spinal osteoarthritis, it has been reported that there is an accelerated and increased level of deterioration (especially in workers 45 to 50 years of age) and the prevalence of this con-dition normally increases with age. The cumulative effects and repetitive loading of the spine due to an awkward body posture 36 • CANAdiAN CHiROpRACTOR | MAY 2011 AIR FORCE 2011 This case was presented by the author to a group of Canadian air force helicopter pilots as a testimonial at the end of a spinal health seminar at the 408 Helicopter Squadron, Edmonton-Gar-rison Military Base, Edmonton, Alberta, in January 2011. Ap-proximately 90 per cent of the pilots in the audience reported experiencing back pain at the time of the presentation, with the remainder claiming to have suffered back issues in the past. The seminar focused on seat and spine position, spine hydration and back stabilization in aviators. Understanding the positioning of the pilot’s form, the spine was identified as being near an extreme point of the body’s range of motion; therefore, the ligaments and discs were more prone to injury. Secondly, lack of water intake was discussed as a factor that may predispose the pilot to having to endure back prob-lems at high altitudes. Dehydration tends to lower blood pres-sure, which in turn leads to a decrease in “G” tolerance. The high cockpit altitudes and breathing in of what could be extremely dry oxygen, can lead to additional water loss in flight. Next, pi-lots were advised to stretch and improve their core muscle en-durance and/or strength and to avoid shifting their bodies about to minimize discomfort while seated. The helicopter pilots were advised to follow through with having their back checked by an aviation chiropractor and a medical doctor, practise good flight posture, exercise proper fly-ing techniques and drink two litres of water daily. One added suggestion was for the aviators to use a cushion, as it can dampen the long-term, negative after-effects of vibrations occurring while in flight. The health of pilots is important, both to the pilots them-selves, for obvious reasons, and to the army, because they are the most expensive part of the helicopter. Without the proper funding for integrative health care for our active pilots, we will be converting more pilots into veterans. • For article with references, visit www.canadianchiropractor.ca. www.canadianchiropractor.ca
Chiropractic + Naturopathic Doctor May 2011: Page 36
