Abstract
BackgroundBilateral C1-2 transarticular screw and C1 laminar hook fixation was developed on the basis of transarticular screws fixation. The modified technique has showed a better biomechanical stability than established techniques in previous study. However, long-term (minimum follow-up 7 years) outcomes of patients with reducible atlantoaxial dislocation who underwent this modified fixation technique have not still been reported.MethodsA retrospective study was conducted to evaluate the outcome of 36 patients who underwent this modified technique. Myelopathy was assessed using the Ranawat myelopathy score and Myelopathy Disability Index. Pain scores were assessed using Visual Analogue Scale. Radiological imaging was assessed and the following data were extracted: the atlantodental intervals, the space available for cord, presence of spinal cord signal change on T2 weighted image, C1–C2 angle, C2–C7 angle and fusion rates.FindingsAll patients achieved a minimum seven-year follow up. 95% patients with neck and suboccipital pain improved after surgery; in their Visual Analogue pain scores, there was a greater than 50% improvement in their VAS scores with a drop of 5 points on the VAS (P<0.05). 92% of patients improved in the Ranawat myelopathy grade; the Myelopathy Disability Index assessment showed a preoperative mean score of 35.62 with postoperative mean 12.75(P<0.05). There was not any significant atlantoaxial instability at each follow-up time. The space available for cord increased in all patients. Postoperative sagittal kyphosis of the subaxial spine was not observed. After six months after surgery, bone grafts of all patients were fused. No complications related to surgery were found in the period of follow-up.ConclusionsThe long-term outcomes of this case series demonstrate that under the condition of thorough preoperative preparations, bilateral C1–C2 transarticular screw and C1 laminar hook fixation and bone graft fusion is a reliable posterior atlantoaxial fusion technique for reducible atlantoaxial dislocation.
Highlights
Atlantoaxial dislocation caused by fractures, rheumatoid arthritis, congenital deformities or traumatic lesions of the transverse ligament [1], often results in acute or chronic spinal cord compression, a possible threat to a patient’s life if immediate reduction has not been achieved
Even though conservative management, including halo brace or cast, could be appropriate for few patients, such as atlantoaxial rotatory subluxation or avulsing fracture of the tubercle for insertion of the transverse ligament, surgical intervention is usually necessary for most patients who suffer from atlantoaxial dislocations
Two-point fixation stabilizes the articulation with C1-2 transarticular screws laterally placed into C1-2 lateral mass or bilateral C1 lateral mass screws combined with C2 isthmic screws
Summary
Atlantoaxial dislocation caused by fractures, rheumatoid arthritis, congenital deformities or traumatic lesions of the transverse ligament [1], often results in acute or chronic spinal cord compression, a possible threat to a patient’s life if immediate reduction has not been achieved. Conventional posterior atlantoaxial fixation techniques, such as Gallie wiring and C1-2 transarticular screw, considered to be successful for a long time, are frequently associated with high rates of pseudoarthrosis and internal fixation breakage [2,3]. From a biomechanical point of view, fixation techniques of the atlantoaxial articulation can be divided into three different types. One-point fixation stabilizes the motion segment merely from posterior with a structural bone graft (e.g. Gallie wiring, Halifax clamps). Two-point fixation stabilizes the articulation with C1-2 transarticular screws laterally placed into C1-2 lateral mass or bilateral C1 lateral mass screws combined with C2 isthmic screws. Three-point fixation consists of the combination of the two previous types, such as transarticular screw combined with Gallie wiring, stabilizing the C1–C2 motion segment both laterally and posteriorly. Long-term (minimum follow-up 7 years) outcomes of patients with reducible atlantoaxial dislocation who underwent this modified fixation technique have not still been reported
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