OBJECTThe cause of irreducibility in irreducible atlantoaxial dislocation (AAD) appears to be the orientation of the C1–2 facets. The current management strategies for irreducible AAD are directed at removing the cause of irreducibility followed by fusion, rather than transoral decompression and posterior fusion. The technique described in this paper addresses C1–2 facet mobilization by facetectomies to aid intraoperative manipulation.METHODSUsing this technique, reduction was achieved in 19 patients with congenital irreducible AAD treated between January 2011 and December 2013. The C1–2 joints were studied preoperatively, and particular attention was paid to the facet orientation. Intraoperatively, oblique C1–2 joints were opened widely, and extensive drilling of the facets was performed to make them close to flat and parallel to each other, converting an irreducible AAD to a reducible one. Anomalous vertebral arteries (VAs) were addressed appropriately. Further reduction was then achieved after vertical distraction and joint manipulation.RESULTSAdequate facet drilling was achieved in all but 2 patients, due to VA injury in 1 patient and an acute sagittal angle operated on 2 years previously in the other patient. Complete reduction could be achieved in 17 patients and partial in the remaining 2. All patients showed clinical improvement. Two patients showed partial redislocation due to graft subsidence. The fusion rates were excellent.CONCLUSIONSComprehensive drilling of the C1–2 facets appears to be a logical and effective technique for achieving direct posterior reduction in irreducible AAD. The extensive drilling makes large surfaces raw, increasing fusion rates.
OBJECTIVEThe 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.METHODSNinety-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.RESULTSA 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.CONCLUSIONSBony 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.
The acute angulation of joint on one side and near normal on other side leads to differential vertical movement, further accentuated by splaying of bifid C1. The entity is seen in young patients and often present with neck tilt and spastic quadriparesis. Management requires reshaping the joints and facet manipulation. If the reshaping is inappropriate, the joint is likely to redislocate before fusion occurs.
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