Mechanical patterns of cervical injury influence postoperative neurological outcome: a verification of the allen system.

STUDY DESIGN

Retrospective clinical case study.

OBJECTIVE

To evaluate whether spinal column injury severity influences neurological outcome after cervical spine injury patterns of Allen's classification.

SUMMARY OF BACKGROUND DATA

Allen's classification is commonly used in cervical fracture/dislocation. Cervical spine injuries are classified into 6 common patterns by their mechanism. Each pattern is divided into stages according to spinal column damage severity, and these stages have been closely correlated with the neurological damage at injury. However, the validity of the relationship has not been adequately discussed. Moreover, only a few reports have assessed whether the injury pattern influences the neurological outcome.

METHODS

We selected 155 patients with unstable subaxial cervical spine injuries. Only 146 patients having more than 12-month postoperative follow-up were included. All were treated with posterior spinal arthrodesis. Supplemental anterior surgery was added in four patients. The injury patterns were graded using Allen's classification. The neurological status at injury and final follow-up was evaluated using the American Spinal Injury Association (ASIA) impairment scale.

RESULTS

Patients were categorized by using Allen's classification as follows: distractive flexion, 82; compressive flexion, 29; compressive extension, 21; vertical compression, 8; and distractive extension, 6. In distractive flexion cases, the ratios of ASIA A cases at final follow-up increased with advancing stage (27%, 18%, 63%, and 100% in stages 1-4; P < 0.001). Furthermore, in similar cases with neurological deficit, the ratio of postoperative improvement on the ASIA impairment scale (>1 level) decreased with advancing stage (62%, 67%, 27%, and 0% in stages 1-4; P < 0.01). With other patterns, neurological outcome was likely to be influenced by spinal column injury severity.

CONCLUSION

Injury patterns based on Allen's classification well-correlated with the neurological outcome and recovery rate. This was especially evident distractive flexion cases. Thus, Allen's classification can be a predictor of neurological outcome after cervical spine injury.