Revisiting the differences between irreducible and reducible atlantoaxial dislocation in the era of direct posterior approach and C1–2 joint manipulation

Abstract

<jats:sec> <jats:title>OBJECTIVE</jats:title> <jats:p>The current management of atlantoaxial dislocation (AAD) focuses on the C1–2 joints, commonly approached through a posterior route. The distinction between reducible AAD (RAAD) and irreducible AAD (IrAAD) seems to be less important in modern times. The roles of preoperative traction and dynamic radiographs are questionable. This study evaluated whether differentiating between the 2 groups is important in today's era.</jats:p></jats:sec> <jats:sec> <jats:title>METHODS</jats:title> <jats:p>Ninety-six consecutive patients with congenital AAD (33 RAAD and 63 IrAAD), who underwent surgery through a posterior approach alone, were studied. The preoperative and follow-up clinical statuses for both groups were studied and compared using Japanese Orthopaedic Association (JOA) scores. The radiological findings of the 2 groups were compared, and the intraoperative challenges described.</jats:p></jats:sec> <jats:sec> <jats:title>RESULTS</jats:title> <jats:p>A poor preoperative JOA score (clinical status) was seen in one-fifth of patients with IrAAD, although the mean JOA score was nearly similar in the RAAD and IrAAD groups. There was significant improvement in follow-up JOA score in both groups. However, segmentation defects (such as an assimilated arch of the atlas and C2–3 fusion) and anomalous vertebral arteries were found significantly more often in cases of IrAAD compared with those of RAAD. Os odontoideum was commonly seen in the RAAD group. The C1–2 joints were acute in IrAAD compared with RAAD. Preoperative traction in IrAAD resulted in vertical distraction and improvement in clinical and respiratory status. Surgery for IrAAD required much more drilling and manipulation of the C1–2 joints while safeguarding the anomalous vertebral artery.</jats:p></jats:sec> <jats:sec> <jats:title>CONCLUSIONS</jats:title> <jats:p>Bony and vascular anomalies were much more common in patients with IrAAD, which made surgery more challenging than it was in RAAD despite similar approaches. An irreducible dislocation seen on preoperative radiographs made surgeons aware of difficulties that were likely to be encountered and helped them to better plan the surgery. Distraction achieved through preoperative traction reaffirmed the feasibility of intraoperative reduction. This made the differentiation between the 2 groups and the use of preoperative traction equally important.</jats:p></jats:sec>

C1C2 Distraction and Compression Technique for Craniovertebral Junction Anomalies with Basilar Invagination and Irreducible Atlantoaxial Dislocation

“…The recent reports by Chandra et al and Saluke et al advocated the drilling of joints to insert cages. 6,[17][18][19] Though this is a small series, the authors demonstrated achieving the alignment without the need for drilling the joint. In addition, drilling the joint is technically more cumbersome and also theoretically it carries the prospect of subsidence of the cage into the lateral mass of the C1 keeping in view the fact that the strong cortical surface is rendered weak by drilling.…”

Congenital atlantoaxial dislocation: Nature’s engineering gone wrong and surgeon’s attempt to rectify it

“…Often, the C1-2 joints are normal in such cases and dislocation reduces with neck extension. [ 6 ] Hyperextension may lead to retrolisthesis in the canal. Multiple trauma due to repeated reduction and dislocation leads to deficits.…”

“…Os odontoideum may coexist with deformed C1-2 joints, and the dislocation in such cases may be more complex. [ 6 ] The anteroposterior and vertical dislocation progresses and the os is seen anterior to the C2 body. The lax capsules may lead to excessive lateral translation in the presence of os odontoideum.…”

Evaluation and Surgical Planning for Craniovertebral Junction Deformity

“…[1][2][3][4] The stability of CVJ is dependent on a robust ligamentous complex and the shape of the bony structures, which are also responsible for much of the axial rotation (C1-2 joint) and flexion-extension movements (C0-1 and C1-2 joint). [5][6][7] Although deformity or malalignment around CVJ is a rare, CVJ deformity results in sagittal and coronal imbalances, which causes significant pain due to arthritis, instability, and C2 foraminal stenosis. Moreover, malalignment can be a potentially life-threatening due to swallowing difficulty and cervicomedullary compressive myelopathy.…”