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Flying Against the Odds

When it comes to understanding how the long-term effects of piloting a helicopter can affect your spinal health, few people have as much knowledge as Dr. Emily Roback.

Military pilots are particularly susceptible to back problems over the course of their careers. (Photo courtesy Canadian Armed Forces Combat Camera)

A practising aviation chiropractor with Alberta sports rehabilitation firm Chiroback Trekker, Dr. Roback recently produced a case study focused on seat and spine position, spine hydration and back stabilization in aviators. She presented the report to a group of Canadian Air Force helicopter pilots at the end of a spinal health seminar in January at the 408 Helicopter Squadron, Edmonton-Garrison Military Base. The premise of the study hit home with the vast majority of attendees, as approximately 90 per cent of the pilots in the audience reported experiencing back pain, with the remainder claiming to have suffered back issues in the past.

The premise of Roback’s case study is clear: one of the realities of being a helicopter pilot is the risk of neck and back injuries due to poor posture and helicopter vibration. Helicopter pilots from various backgrounds – however well-intentioned – often succumb to these injuries and are not able to operate at their optimum level. As Roback chronicles in her report, chiropractors can be invaluable in the education, treatment and prevention of such injuries.

Case in point: recent medical reports submitted on behalf of a 45-year-old male veteran helicopter pilot revealed a lateral curvature of his spine (a.k.a. mild “C” shape scoliosis). Since scoliosis is common within the general population, it is unlikely that having a lateral curvature of the spine by itself would indicate any evidence of a pathological change due to aging. The reports also showed that the pilot had been experiencing front and side chest pain from the thoracic spine (mid-back) since 2002. That same year, he had received physiotherapy treatments for his neck that in the short term appeared to decrease his physical discomfort. The musculoskeletal structures of the thoracic wall and neck are common sources of chest pain; however, in this 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
Roback’s case study is based on more than 17 years of research into the effects of prolonged flying and back injuries – and highlights a number of conditions pilots may experience. For example, according to a 1994 report by R. Greth of the U.S. Army Aviation and Troop Command (see reference sidebar), “helicopter hunch” is one such condition that may inflict pilots. This condition is generally caused by poor posture during flight. It occurs when the spine is bent forward and is a contributing factor in the back pain diagnosis of a pilot. The need to ensure the stability and operation of the aircraft’s cyclic control is the primary reason the pilot in this study maintained this particular posture. By sitting with the body hunched forward, pilots are able to bring their arms closer to the dashboard to manoeuvere the controls more efficiently.

Research confirms that helicopter vibrations can seriously damage the discs in a pilot's back. (Photo courtesy Canadian Armed Forces).

Unfortunately, this slouch position is further exacerbated as pilots use 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 (ie. flattening of the lower back, increased mid-back curvature, and straightening of neck) which further increases the loading of the mid-back because of the forward displacement of the upper torso and head.

A Vibration Across the Industry
Research has shown that helicopter vibrations (pressure waves caused by imbalances in rotating aircraft parts) have a peak power frequency of approximately five hertz, which is within the range where a human’s upper body presents resonance frequency (see references sidebar: De Oliveira, Nadal). Other 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 (four to six hertz). With this in mind, people exposed to whole-body vibration in the same resonant range, such as helicopter pilots, are significantly more prone to experiencing back pain. Further, according to a 2008 report on the pathophysiology of disc degeneration by A.G. Hadjipavlou (see references sidebar), 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 to the joints.

Dr. Emily Roback recently presented the findings of her detailed back study to a group of Canadian Air Force helicopter pilots at the 408 Helicopter Squadron, Edmonton-Garrison Military Base. (Photo courtesy Dr. Roback)

According to Hadjipavlou, the intervertebral discs (spine shock absorbers) are the largest avascular tissues in the body, which suggests the conclusion that cells in the centre of an adult thoracic disc are approximately eight millimetres away from the nearest supply of blood. The cells that 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 (tiny blood vessels) in the muscle’s outermost region. The capillary network is regulated by noradrenalin and acetylcholine (vessel constrictors and dilators), 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, and eventually spreads throughout the entire disc with increased age and degeneration.

A 1981 report on the effects of vibration, posture and low-back disorders of professional drivers by J. Sandover of the University of Technology, Loughborough, England, reviewed the relationship between mechanical stress on the spine and intervertebral disc degeneration, considered to be the most likely cause of the back pain in Roback’s case study. Sandover’s 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.

The Rundown
It is impossible to review all of the congenital and acquired malformations or diseases of the thoracic (mid-back) and lumbar (low-back) spine. However, the most common malformations and/or diseases are disc degeneration (also known as spinal osteoarthritis) and disc herniation (slipped disc). It is normal for the discs between the vertebrae to deteriorate with age. Herniation of a disc may be the result of degeneration accompanied by severe loading. The herniated disc can bulge or rupture into the spinal canal through the back end of the spine. This bulge can subsequently entrap the nerves of the upper and/or lower body, causing intense pain in the area served by the nerves, paralysis, or a parenthesis – a tingling, or “pins and needles” sensation.

Many pilots feel their spines are perfectly fine; however, they need to have routine checkups just to be sure. (Photo courtesy Canadian Armed Forces Combat Camera).

In addition, D. Harrison of the Journal of Manipulative & Physiological Therapeutics, studied the optimal driver’s seat and spine position and established that piloting a helicopter predisposes a flight operator to mid-back pain and a degenerative joint disease (spinal osteoarthritis). In spinal osteoarthritis, it has been reported that there is an accelerated and increased level of deterioration (especially in workers in the 45-50 age range) 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 expediting the degeneration and general fatigue failure of the spine.

Based on research and experience as a practice chiropractor, Roback concludes that the duties of a helicopter pilot 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 difficult to ascertain whether or not if it would be therapeutically beneficial.

With this in mind, 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. Furthermore, mandatory MRI scans and aviation medical examinations at regular intervals – designed and implemented for helicopter pilots based on their cumulative flying hours – would be a recommended course of action.

Air Force 2011
Looking at Roback’s case study and 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. The pilot’s back muscles became fatigued by experiencing stress in a constrained posture, and the pilot was less able to protect his spine against the effects of vibration.

Repeated or persistent loading (vibrations) of the joints was suspect in causing inflammation or degeneration of the affected joints.

Another important factor to consider is dehydration. Lack of water intake may predispose a pilot to back problems at high altitudes.

Dehydration tends to lower blood pressure which in turn leads to a decrease in ‘G’ tolerance. The combination of high cockpit altitudes and breathing in what could be extremely dry oxygen can lead to additional water loss in flight.

Moreover, spine instability is a condition in which the bones positioned in the back are unable to remain in their proper setting while the body is in motion. Prolonged, unsupported sitting will lead to reduced flexibility in the lower back and hip joints. Pilots who do not stretch and improve their core muscle endurance and/or strength usually find themselves shifting their bodies to minimize discomfort while seated.

Flying Upstream
Roback maintains it is a misconception for helicopter pilots to assume they have a healthy spine. Her advice is simple – have your back checked over by an aviation

chiropractor and a medical doctor. Practise good flight posture, exercise proper flying techniques and drink two litres of water daily. Also, consider using a cushion as it can dampen the long-term, negative after-effects of in-flight vibrations.

Pilot health is of paramount importance to the safe operation of all flights. Both to the pilots themselves, for obvious reasons, and to the military, as pilots are the most expensive part of the helicopter. Basic training for helicopter pilots should address the risks associated with posture and vibration. 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. Dr. Emily Roback can be contacted at roback@doctor.com or 1-866-233-8242.