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Atlas: standard diagnostic tests for an unusual fracture
  1. S Leigh-Smith1,
  2. R Price2,
  3. D Summers3
  1. 1Defence Medical Services, Gosport, UK
  2. 2Department of Clinical Neurosciences, Western General Hospital, Edinburgh, UK
  3. 3Department of Neuroradiology, Western General Hospital
  1. Correspondence to:
 Mr S Leigh-Smith
 c/o Monckton House, Alverstoke, Gosport PO12 2DL, UK; simonlsukaol.com

Abstract

The case is reported of an unusual atlas fracture with no reports of such an injury in the literature. The diagnosis of this injury emphasises the importance of simple clinical decision instruments, and systematic interpretation of investigations.

  • imaging
  • fractures
  • diagnosticests

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A 28 year old man who was 5 feet 9 inches and 16 stone was playing rugby as a number 8. He ran head first into a tackle, causing an axial compression injury to his neck. This caused immediate, dull pain over the whole of his neck. He attempted to continue playing but found that merely running exacerbated the pain considerably. He later noticed the pain localising to the whole axial area along with his head “feeling heavy and loose”. He self treated with a soft collar for two days, before presenting to the accident and emergency (A&E) department, by which time the pain was persistent in the sub-occipital area. At no stage did he have any neurological symptoms.

Examination showed painful neck movements, with pronounced reduction of range in all directions.

Cervical spine radiography showed considerable retropharyngeal soft tissue swelling in the upper cervical spine (fig 1). The AP dens view showed subtle asymmetry of the atlantoaxial joints, with minor lateral displacement of the C1 lateral mass on the right (fig 2).

Figure 1

 Lateral cervical radiograph with considerable retropharyngeal soft tissue swelling anterior to the upper cervical vertebrae (arrowheads).

Figure 2

 AP open mouth radiograph of C1/C2 showing vertical lucency projected over peg (arrowheads).

His neck was immobilised, and he was transferred to the regional neurosurgical service. Review of the cervical spine radiograph showed an unusual vertical lucency projected over the dens, and computed tomography of this area was performed (fig 3). The appearances suggested a congenital midline cleft atlas, with diastasis of the anterior synchondrosis.

Figure 3

 Axial fine section CT through C1 ring showing C1 anterior arch midline cleft with diastasis (arrowheads). The streak artefact is due to dental amalgam.

The patient’s neck was immobilised in an Aspen collar cervical orthosis. Ten days after the injury, he was brought back for flexion and extension radiographs of his neck, which showed no abnormal movement. He remained neurologically intact and external bracing was continued for eight weeks. Follow up computed tomography showed persistence of the C1 cleft but resolution of the retropharyngeal swelling. The flexion and extension views were repeated and no abnormal movement was detected. Physiotherapy was started to rebuild his range of neck movements and treat residual discomfort. Given the developmental anomaly of C1, he was advised to stop taking part in contact sports.

DISCUSSION

Screening for potentially unstable cervical spine injury starts with the use of a proven clinical decision instrument to determine who needs a cervical spine radiograph.1 If radiography is required the ATLS system of cervical spine radiological interpretation or similar3,4 should be used.

In this case the patient clearly had a suggestive history and abnormal examination requiring radiography. The pronounced retropharyngeal swelling was sufficient to institute immobilisation and further specialist review.

Atlas fractures represent about 6% of cervical spine fractures.5 Different patterns were originally described by Jefferson,6 ranging from a fracture through one part of the ring to a complete burst fracture. Only 10 cases of paediatric atlas fractures have been reported,7 tending to pass through the fibrocartilagenous tissue between one of the three ossification centres.7,8–10 Ossification is usually complete by age 8 years,11 but incomplete ossification can occur (0.33%–5% of adults depending on position within the atlas) and lead to a persistent synchondrosis.7,9 Midline anterior atlas cleft is an unusual developmental anomaly, found in only 0.1% of adults in a necropsy study.12 It is usually associated with a midline posterior cleft. By analogy with the paediatric cases, a persistent synchondrosis in an adult may represent a weak point in the C1 ring and therefore be prone to disruption during axial compression loading. Although it is well known that congenital anomalies in the C1/2 region can be mistaken radiologically for new fractures we feel that the suggestive injury mechanism, symptomatology, prevertebral swelling, lateral mass displacement, apparent angulation at the anterior synchondrosis, and the subsequent improvement all point to an acute disruption of this patient’s anterior synchondrosis. The expectation was that this injury was stable and could be managed with external bracing. This was reinforced by the minimal lateral displacement of the right C1 lateral mass (more than 7 mm indicates potential instability5), the flexion-extension views, and the patient’s subsequent clinical course.

In both adult and paediatric age groups, neurological injury is unusual, because of the favourable proportions of the cord and canal in the upper cervical spine.

Most atlas injuries are considered stable and are managed conservatively with external bracing, although instability requiring internal fixation can occur if the transverse ligament of the dens is disrupted. Hence, A&E practitioners should consider all these injuries as unstable.

CONCLUSION

Significant cervical spine injury is a statistically unusual finding in A&E, but the thought of missing one is enough to bring most practitioners out in a cold sweat. This case shows that appropriate use of a clinical system of examination and radiological interpretation works. It also emphasises the importance of looking for retropharyngeal soft tissue swelling in cervical spine radiographs, which may be the only clue to significant cervical trauma.

REFERENCES

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