Introduction: Allen and Ferguson in 1982 described five stages of compression extension injury to the cervical spine; the first stage that was considered as a stable injury involves fracture of the articular process, pedicle or lamina which may be associated with a rotary spondylolisthesis. This fracture pattern, which is not uncommonly missed on the initial X-rays, can be diagnosed using CT scanning especially if patients present with root symptoms. This fracture will be usually treated conservatively as a stable injury. In practice we found out that this type of bony fracture might present later on with subluxation and/or persistence of symptoms even if treated in rigid immobilisation devices including halo jacket. The hypothesis around this fracture pattern will be a hyperextension mechanism combined with a degree of lateral tilt and rotation producing an anterior annular disruption under tension and a unilateral posterolateral mass or laminar fracture under compression with a resultant rotational instability around the intact lateral mass.

Material and Methods: Ten patients with stage I compression extension injury who presented with subluxation were studied prospectively aiming for addressing the patho-anatomy and define a method for treatment. All the cases presented with neurological manifestations, nine cases with root symptoms and one case with incomplete cord injury. The treatment consisted of early closed reduction followed by anterior fusion and fixation.

Results and Conclusion: All patients showed neurological improvement. Radiological union was achieved in all the patients with maintenance of the alignment. In conclusion, extension compression injury type I (fracture of the bony posterior elements) is usually a stable injury but if there is additional failure of the disc this segment will be rendered rotationally unstable. Despite the limited number of patients in this series the results of early anterior fusion with fixation were very satisfactory encouraging the recommendation for using this type of treatment.