Biomedical Engineering Reference
In-Depth Information
Atlas (C1)
Axis (C2)
Cervical
Vertebra
C1-C7
C7
T1
oracic
Vertebra
T1-T12
T12
L1
Lumbar
Vertebra
L1-L12
L5
Sacrum
S1-S5
Coccyx
FIgure 18.1
(See color insert.)
Anatomical structure of the human spine.
Aircraft occupants, especially military aircrew, subjected to complex dynamic impacts are prone
to developing spinal complications or disabilities. For example, the firing of the ejection gun applies
an accelerative impact of more than 15 G on the aviator along the long axis of the spine. The tre-
mendous thrust force can lead to large flexion compression of vertebrae and thus induce a high risk
of vertebral fracture or disc rupture. Although the ejection seat and restraint system have been in
use for many years, the incidence of ejection-associated spinal injury remains high. According to
an investigation by Lewis (2006), the overall percentage of ejection survivals who sustained spinal
fractures was 29.4% and the majority of fractures were located around the thoracolumbar region.
It is worth mentioning that landing on the ground after ejection is also an important event that
may cause spinal injury or aggravate the level of lesions produced during ejection (Sturgeon, 1987).
Sturgeon also compared the distribution pattern of vertebral fractures occurring during ejection with
landing-induced vertebral fracture and found that ejection vertebral fractures tended to be broadly
distributed between T3 and L1, while landing fractures were more commonly located below L1.
Despite advancements in the crashworthiness of helicopters, both the rate and severity of injuries
sustained in helicopter accidents remain relatively high. An analysis of medical records showed
that 86.5% of aircrew involved in helicopter accidents suffered injury (Sasirajan, Narinder, and
Dahiya, 2007). Of these, 43.4% were spinal lesions, the leading cause of injury, followed by injury
to the head and face (22.6%). Similar to ejection injuries, the thoracolumbar junction was the most
common site of injury and compression fractures represented the majority of injury patterns.
Developments in engine performance and aerodynamics have given modern fighter pilots
increased agility in the air, which can potentially lead to cervical spine injury. Such agile fight
maneuvers are capable of exposing pilots to multiaxial forces and the unrestrained head-neck com-
plex may bear the brunt of these forces. In such instances, several types of injury may occur, such
as compression fractures, ligament tearing (Schall, 1989), and muscle pain (Green, 2003; Lecompte
et al., 2008; De Loose et al., 2009). The weight of the helmet and oxygen mask worn by the pilot will
accentuate the strain on the neck muscles and induce further flexion compression to the cervical
spine (Hamalainen, 1993). In addition, the increasing number of display and sighting systems adds
to the complexity of the acceleration environment and the potential for injury (Newman, 2006).
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