Is Transoral Surgery Still a Relevant Procedure in Atlantoaxial Instability?

Abstract

Background: The treatment of atlantoaxial instability (AAI) involves stable fixation and fusion with adequate decompression of spinal cord. After the advent of the Goel posterior joint manipulation technique, most of the once irreducible atlantoaxial dislocations (AAD) could be reduced and the need for transoral odontoidectomy became almost nil. Here we tried to iterate the indications of anterior transoral odontoid surgery for AAI in the current scenario.

Methods: A retrospective study compiling the clinical, radiological, and surgical characteristics of 6 cases (5 scenarios). These patients underwent anterior transoral surgery alone or in combination with a posterior approach.

Results: Two patients had a well-formed occipito-cervical fusion mass, with a displaced odontoid and unreduced C1-C2 joint causing cervical myelopathy. A middle-aged woman presented with unreduced AAD following failed C1-C2 joint distraction technique. A displaced dystopic os odontoideum ossicle was found in an adolescent boy, prohibiting the reduction of AAD. A young man had displacement of the fractured odontoid segment with intact transverse alar ligament and C1-C2 joint complex. One patient had a rare scenario of abnormal orientation of the C1-C2 joint. All 6 patients were successfully treated with adequate spinal cord decompression achieved by the anterior transoral route and stabilization by either the anterior approach itself or in combination with posterior surgery. All had significantly better postoperative outcomes except for 1 patient who expired due to poor respiratory reserve.

Conclusion: We tried to emphasize the indications for using transoral anterior odontoid surgery over the posterior approach in the management of AAI. This will prevent the surgical technique of anterior odontoidectomy from becoming an obsolete procedure in the current practice.

Keywords: AAD; atlantoaxial instability; odontoidectomy; transoral surgery.

Figure 1

(A–G) Scenario 1: (A) X-ray of 67-year-old woman with occipito-cervical wiring and bone grafting done outside. (B–D) Preoperative computed tomography of the spine shows well-fused C1-C2 (arrows), making a posterior approach practically impossible. Atlantoaxial dislocation with narrowing of the spinal canal is also observed. (E) T2 MRI sagittal section of cervical spine with high cervical cord compression, myelomalacia, and signal changes. (F) Preoperative image showing decompressed spinal cord after excising odontoid and C1 arch by the transoral approach. (G) Postoperative x-ray shows removal of wires with absent resected odontoid.

Figure 2

(A–E) Scenario 3: (A, B) Flexion and extension x-ray revealing unstable atlantoaxial dislocation secondary to os odontoideum (C) Preoperative computed tomography of the spine shows dystopic os odontoideum ossicle lying between C1 arch and C2 vertebra, making the joint irreducible (arrows). (D) T2 MRI sagittal section of cervical spine with high cervical cord compression. (E) Postoperative x-ray shows occipito-cervical fusion with wires and iliac bone grafting.

Figure 3

(A–F) Scenario 4: (A, B) Preoperative computed tomography of the spine (sagittal and coronal) demonstrates normal joint C1-C2 joint space, but the odontoid process is hitching against C1, making it irreducible (arrow). (C) T2 MRI of the sagittal section of cervical spine shows a fractured odontoid with mild hemorrhage (arrow) and normal cerebrospinal fluid space and cord. (D, E) eIntra-operative images demonstrating double incision; transoral approach for reduction of the fragment and transcervical approach through C5-C6 for the screw placement. (F) Follow-up computed tomography scan shows well-reduced and united odontoid with screw in situ (arrow).

Figure 4

(A–D) Scenario 5: (A, B) Flexion and extension x-ray showing unstable atlantoaxial dislocation. (C) Preoperative computed tomography of the spine shows vertical alignment of C1-C2 joint space (arrows), assimilated C1, and basilar invagination of the bone. (D) T2 MRI of the sagittal section of cervical spine pinching the brain stem and high cervical cord (arrow).