Management of traumatic atlanto-axial instability: A retrospective study of eight cases

Factors influencing feasibility of direct posterior reduction in irreducible traumatic atlantoaxial dislocation secondary to isolated odontoid fracture

INTRODUCTION

Direct posterior reduction by intraoperative manipulation of joints for irreducible traumatic atlantoaxial dislocation (IrTAAD) has gained acceptance in the recent past. However, factors determining its feasibility have not been elucidated. Our study aims to examine the clinico-radiological factors predicting feasibility of direct posterior reduction in IrTAAD secondary to isolated odontoid fracture, in an attempt to differentiate the "truly irreducible" from those "deemed irreducible."

MATERIALS AND METHODS

The onset and progression of neck pain and myelopathy was studied in 6 patients of IrTAAD with fracture odontoid, which failed to reduce despite traction. The dynamic X-rays and computed tomography (CT) scans of craniovertebral junction, along with the vertebral artery angiogram were studied to look for the slightest mobility, interface of fractured fragments, malunion, callous, and relationship of the C1-2 facets and vertebral artery.

RESULTS

All 6 patients had progressive worsening of neck pain. Three patients had progressive myelopathy. Three patients presented 6 months after trauma. Radiology showed type-II fracture with IrTAAD (anterolisthesis in 5 and retrolisthesis with lateral dislocation in 1) and locked facets in all. X-rays showed doubtful callous formation in 3 patients and CT confirmed non-union. Three patients showed angular movement on dynamic X-rays despite irreducibility and locked facets. Angiogram showed thrombosis of vertebral artery in one patient. Intraoperative reduction could be achieved in all 6 patients with good clinico-radiological outcome.

CONCLUSION

Worsening pain, progression of myelopathy, some movement on dynamic X-rays, a malunion ruled out on CT scan, and the presence of locked facets make direct posterior reduction feasible in patients with IrTAAD. The difficulty increases in remote fractures due to fibrosis around the dislocated joints. The role of the CT angiogram, in defining the relationship of Vertebral artery (VA) to the dislocated facets, and in determining the extent of VA injury, is vital. Preoperative detection of VA injury reduces the chance of intraoperative reduction, especially if only unilateral joint approach is planned.

Reduction techniques in the management of atlantoaxial subluxation

BACKGROUND

The traditional approach to atlantoaxial subluxation which is irreducible after traction is transoral decompression and reduction or odontoid excision and posterior fixation. Transoral approach is associated with comorbidities. However using a posterior approach a combination of atlantoaxial joint space release and a variety of manipulation procedures, optimal or near optimal reduction can be achieved. We analysed our results in this study based on above procedure.

MATERIALS AND METHODS

66 cases treated over a 5 year period were evaluated retrospectively. Three cases treated by occipito cervical fusion were not included in the study. The remaining 63 cases were classified into three types. All except two cases were subjected to primary posterior C1-C2 joint space dissection and release followed by on table manipulation which was tailored to treat the type of atlantoaxial subluxation. Optimal or near optimal reduction was possible in all cases. An anterior transoral decompression was needed only in two cases where a bony growth (callus) between the C1 anterior arch and the odontoid precluded reduction by posterior manipulation. All cases then underwent posterior fusion and fixation procedures. Patients were neurologically and radiologically evaluated at regular followups to assess fusion and stability for a minimum period of 6 months.

RESULTS

Of the 63 cases who underwent posterior manipulation, 49 cases achieved optimum reduction and the remaining 14 cases showed near optimal reduction. Two cases expired in the postoperative period. None of the remaining cases showed neurological worsening after the procedure. Evaluation at 6 months after surgery revealed good stability and fusion in all except three cases.

CONCLUSION

Atlantoaxial joint release and manipulation can be used to achieve reduction in most cases of atlantoaxial subluxation, obivating the need of transoral odontoid excision.