Case 1

THE NAVIGATOR OF THE FIRST AIRCRAFT (35 YEARS)

His Glasgow Coma Score (GCS) was 13/15 (E4M6V3) at the scene but on arrival at the accident and emergency (A&E) department, it had dropped to 10/15 (E4M3V3). The right pupil was noted to be larger than the left and both pupils reacted briskly. The pulse, blood pressure and respiratory rate were within normal limits.

Radiographs of the cervical spine showed evidence of C1-C2 subluxation with 1 cm forward displacement of C1 on C2. The patient was kept immobilised on the spinal board and intubated, paralysed and his lungs ventilated. Computed tomography (CT) of the brain showed a left frontal haematoma, with no mass effect. The patient was then airlifted to the regional neurosurgical centre for further management. He was managed conservatively in the intensive treatment unit and extubated after 24 hours.

It was then noted that the patient had left upper extremity weakness. Further investigation by CT and magnetic resonance imaging (MRI) (figs 1 and 2) showed atlantoaxial dislocation with avulsion of the transverse ligament and gross posterior soft tissue disruption.²

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Figure 1

Lateral radiograph of the cervical spine showing widened atlantodental interval.

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Figure 2

Axial CT at C1. The widening of the atlantodental interval is shown.

Six days after admission, the patient underwent C1 to C2 modified Gallie and transarticular C1/C2 fusion and fixation. His postoperative course was uneventful and on discharge to his local hospital for rehabilitation, the patient was walking with a frame and able to converse. At six months after the operation, he had complete recovery of motor power in the right arm. Unfortunately weakness in the left arm has persisted. This is thought to be attributable to brachial plexus injury, based on clinical examination findings; unfortunately this has prevented his return to flying.

Case 2

THE PILOT OF THE FIRST AIRCRAFT (35 YEARS)

There was loss of consciousness from the time of ejection and the first thing he remembered was lying on the ground at the scene. He was then able to get up and walk around; however on doing so he developed paraesthesia of both upper limbs below the elbow. This was his only symptom and in particular he did not complain of any neck or chest pain.

On examination he had a GCS of 15 and was alert and orientated. Vital signs were normal. Examination of the neck was normal except that extension of the cervical spine worsened the patient's symptoms. The power in his upper and lower limbs was noted to be globally reduced and was graded at 3/5 (MRC grading)

Though the patient continued to complain of paraesthesia below both elbows, there was no objective sensory abnormality on testing. Plain radiographs of the cervical spine showed no bony abnormality but there was some soft tissue fullness at the level of C6/C7.

MRI was arranged and this showed central disc protrusion at C5/C6 with an increase in T2 signal in the cord suggestive of a contusion (fig 3).

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Figure 3

T2 weighted MRI showing central disc protrusion at C5/C6, with an increase in T2 signal in the cord suggestive of a contusion.

As the patient was intent on returning to active flying, he was referred to the spinal unit where he underwent an elective C5/C6 discectomy and interbody fusion.

He made an uneventful postoperative recovery and returned to active flying within six months.

Case 3

PILOT OF THE SECOND AIRCRAFT (30 YEARS)

This man did not lose consciousness and he walked around helping with the rescue after the crash. He complained of lower back pain but there was no neck pain. On examination his vital signs were normal with GCS of 15. On examination, there was some tenderness over the lower cervical spine only with no distal neurology. Radiographs of the spine raised the suspicion of C6 compression. CT confirmed slight anterior compression of C6 but there was no derangement in mechanical alignment. He was treated conservatively and made a good recovery. He was able to return to active flying duties.

Case 4

THE NAVIGATOR OF THE SECOND AIRCRAFT (34 YEARS)

There was no history of loss of consciousness and he had recall of the ejection. On arrival at hospital, he complained of left facial pain only. There were no neck symptoms.

On examination he was alert and orientated. His vital signs were within normal limits. He had a minor facial laceration. He was mildly tender over the paraspinal muscles of the neck and lower thoracic spine. There was no distal neurology. Cervical and thoracic spine radiographs were normal but there was a suggestion of slight loss of height at the level of T9. The patient was admitted for observation. He remained stable and he was well enough to be discharged the next day, to be reviewed in the fracture clinic. He was referred for a course of physiotherapy but as he had persistent localised tenderness over the lower thoracic spine, a bone scan was arranged. It confirmed an increased uptake at the level of T9.

The patient progressed well with physiotherapy to strengthen his back muscles and was then discharged from the clinic. He returned to flying duties.

Discussion

The ejection seat has been responsible for saving the lives of thousands of pilots around the world since its introduction in the late 1940s. Typical survival rates quoted in the literature vary from 80–97%.³

On most modern seats escape is initiated by pulling a seat firing handle. This fires a cartridge and gas from this is then piped around the seat to initiate⁴:

1. Powered shoulder retraction

2. Canopy jettison or fragmentation by miniature detonating cord (MDC)

3. Firing of ejection gun to propel seat from aircraft

4. Firing of rocket pack to propel seat away from aircraft

The medical problems encountered with ejection can be classified as follows:

1. Injuries from the emergency that causes ejection—fire or collision.

2. Canopy jettison: burns from “MDC splatter” and cuts from fragmented plastic. For these reasons, aircrew are always advised to wear their visors down, to protect the face.

3. Firing of ejection gun: spinal injuries.

4. Entering airflow: wind blast may cause lung damage; seat tumbles at variable speed, which may be as high as 180 rpm. (All seats have a drogue parachute or deployable aerodynamic panels to prevent tumbling); flail injuries to extremities.

5. Parachute deployment: snatch injuries.

6. Landing: lower limb injuries.

Probably the most serious injuries are those of the head and spinal column. There are many factors that influence whether aircrew who eject sustain a spinal fracture or not. These include: the design of the seat, aircraft speed and attitude at time of ejection and age of the patient.

It is generally accepted that radiographic evidence of vertebral fracture can be found in 30%–70% of aircrew after ejection.^{5, 6} To avoid excessively high acceleration rates, the ejection gun fires in three stages with a short delay between each (a few milliseconds). Individual vertebrae are able to withstand large compressive loads if applied at right angles to the plane of the intervertebral disc. However, because of engineering constraints the initial thrust is an impulsive load that is experienced at an angle to the long axis of the spine. In our case, the navigator who was severely injured was given no warning of the ejection as there was not enough time. This is called a command ejection. The ejection seat had a power retraction unit fitted, however, which would have ensured his spine was aligned in the correct position before any seat movement occurred.

The lower thoracic spine is especially prone to injury.⁷ This part of the spine is subjected to the static load of the trunk and head transmitted through the vertebrae above it. At this region of the spinal column the vertebral end plate has the highest loading per unit area.⁴ The vertebral bodies act as dampers, the blood within them being squeezed out under compression, before vertebral collapse or fracture.⁸

Spinal injuries from ejection do occur at other sites, as demonstrated in the cases that have been described here. The mechanism of the injuries we have described is complex and includes several factors such as aerodynamic helmet lift, head flail, impact of the head on the ejection seat head box.

After the accident referred to in this report, the Royal Air Force now sends all of its aircrew who have ejected from aircraft for a complete spinal MR scan (personal communication).

Conclusions

A&E physicians may be called to see aircrew who have ejected from their aeroplanes. The RAF aircraft accident rate amounts to approximately 7–9 per year, not all of which involve ejection. The ejection rate for 1998 was 0.17 per 10 000 flying hours (personal communication). It is the fact that ejectees are seen so infrequently that leads to relative ignorance by receiving hospitals of the forces involved and the possible injury patterns. After initial resuscitation it is essential that particular attention be paid to examination of the spine and peripheral nervous system. To avoid missing potential injury further imaging of the spinal column with either CT, or ideally MRI should be considered mandatory in all patients who have ejected from aircraft.