As a chiropractor, I have noticed that the frustrating truth behind
flying helicopters is the great number of potential neck and back
injuries that can be sustained by active aviators.
As a chiropractor, I have noticed that the frustrating truth behind flying helicopters is the great number of potential neck and back injuries that can be sustained by active aviators. Military helicopter pilots from various backgrounds – however well intentioned – are often not able to operate at their optimum level without access to chiropractic care. Basic training for helicopter pilots should address the danger of back injuries due to poor posture and vibration. Chiropractors can assist in education and preventing such injuries from occurring.
|Two Canadian air force helicopter pilots in their cockpit.
Previous medical reports submitted on behalf of a 45-year-old male veteran helicopter pilot revealed a lateral curvature of the spine (a.k.a. mild “C” shape scoliosis). Since scoliosis is common within the general population, it was unlikely that having a lateral curvature of the spine by itself would indicate any evidence of a pathological change due to aging. It was also reported that the pilot had been experiencing front and side chest pain from the thoracic spine since 2002. That same year, he had received physiotherapy treatments for his neck, an action that, in the short term, appeared to have helped decrease his physical discomfort. The musculoskeletal structures of the thoracic wall and neck are common sources of chest pain. However, in this pilot’s case, the musculoskeletal chest wall disorder stemmed from arthritis, which further complicated the articulations of the sternum, ribs and thoracic spine.
THE GOOD, THE BAD AND THE UGLY
According to Greth (1994), a substantial percentage of army helicopter pilots have encountered back pain, a condition commonly caused by poor posture during flight. A typical seating posture described as the “helicopter hunch” (in which the spine is bent forward) was a contributing factor in the back pain diagnosis of our case study pilot. The primary reason this pilot maintained this particular posture was that he needed to ensure the stability and operation of the aircraft’s cyclic control. By sitting with the body hunched forward, pilots are able to bring their arms closer to the instrument panel to manoeuvre the controls more efficiently. Unfortunately, this slouched position is further exacerbated by pilots using their right thigh as an armrest to support and stabilize the forearm. Since the elbow rest position is three to five inches above the thigh, pilots must lean forward and slightly to the right, to make contact. At the same time, they need to tilt their torso to the left to 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 displacement 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 degeneration 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. Hadjipavlou 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 surrounding 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 researchers, 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 mechanical stress on the spine and intervertebral disc degeneration, which was considered to be the most likely cause of back pain. His findings disclosed that mechanical stress hastens degenerative 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.
It is impossible to review all of the congenital and acquired malformations or diseases of the thoracic and lumbar spine. However, the most common malformations and/or diseases are disc degeneration and disc herniation. It is normal for the discs between 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 predisposes 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 condition normally increases with age. The cumulative effects and repetitive loading of the spine due to an awkward body posture (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 chiropractor, 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 helicopters. Furthermore, the helicopter pilot in this case study appeared not to have made any significant improvement while participating 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 incorporate postural exercises, nutrition, chiropractic, massage therapy, acupuncture and aircraft ergonomic advice. I would further advocate mandatory MRI scans and aviation medical examinations at regular intervals – designed and implemented for helicopter pilots – based on their cumulative flying hours.
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-Garrison Military Base, Edmonton, Alberta, in January 2011. Approximately 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 problems at high altitudes. Dehydration tends to lower blood pressure, 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, pilots were advised to stretch and improve their core muscle endurance 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 flying 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 themselves, 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.
Dr. Emily Roback is a chiropractor with Chiroback Trekker, practising in aviation chiropractic. Her aviation patients have inspired her to pursue a mountain ski guide certificate and private pilot licence to work in the heli-ski industry. In April 2011, she presented a spinal health seminar for the Calgary Police and STARS-Calgary base helicopter pilots. Her next presentation for STARS-Calgary helicopter pilots is scheduled for September 2011. Dr. Roback can be contacted at firstname.lastname@example.org or 1-866-233-8242.
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