Treatment of Irreducible Atlantoaxial Dislocation with C1-2 Sublaminar Cable-Dragged Reduction and Screw Fixation

Abstract

Introduction Irreducible atlantoaxial dislocation (IAAD) is defined as the fixed displacement of C1-2 which is difficult to reach anatomic reduction, even with strong cranial skeletal traction under general anesthesia. The most frequently used method to treat symptomatic IAAD is transoral decompression or release combined with posterior fixation following preoperative cranial traction. However, those procedures are accompanied with high morbidity and mortality. We assumed that the inability to be reduced through cranial traction does not necessarily mean an irreducible dislocation, for the force exerted by cranial traction is oriented mainly upward, leading to an indirect reducing effect. Therefore, a new reduction strategy, called C1-2 sublaminar cable-dragged technique, has been developed to exert a straight backward force on the atlas to achieve an anatomic reduction followed by C1-2 screw fixation in a single stage via a posterior approach. The purpose of the present article is to report the early results of application of this method. Materials and Methods Thirty-two consecutive patients with IAAD, who underwent C1-2 posterior cable-dragged reduction and fixation, were retrospectively reviewed with minimum 2-year follow-up. Patient's mean age was 43.6 ± 19.4 years (range, 31-68). Anatomic reduction was achieved by passing a double 18-gauge titanium cable through the arch of C1 and lamina of C2. The cable was then retracted and tightened temporarily with a cable tensioner. Once satisfactory reduction was achieved and confirmed by C-arm radiography, fixation with C1 lateral mass screw and C2 pedicle screw was routinely performed. Then an autologous cancellous bone was grafted between the posterior arch of C1 and lamina of C2 using a modified Brooks-Jenkins procedure (Fig. 1). Lateral radiograph, 3D-CT, and MRI were obtained before surgery and at 3, 6, 12, and 24 months after surgery. Bony fusion was evaluated in flexion and extension lateral radiographs. Clinical symptoms were assessed with NDI and Frankel classification. Results The average follow-up period was 16.4 months. Radiographic evaluation of the group at follow-up showed 30 complete and 2 partial reductions, and satisfactory decompression in all cases (Fig. 2). Surgical complications, such as dural tear, laminar fracture, and spinal cord injury did not occur in any cases. The relief of occipital pain showed in 29 patients (90.6%). With regard to neurological recovery after surgery, 24 patients (75.0%) showed improvement by at least one level of Frankel criteria. Bony union was achieved in 31 patients (96.9%). Subaxial lesion occurred in four cases (12.5%), but additional surgery was not required in any cases. Conclusion Cable-dragged reduction and screw fixation are almost as effective for reduction as anterior release but is less invasive and risky. It could provide a high fusion rate and relief of pain. We suggest the use of a braided cable wire because it is soft and relatively safe to pass, resists fatigue well, and provides excellent fixation. However, there is little risk of vertebral artery and spinal cord injury. In conclusion, we recommend this new technique for IAAD patients with intact posterior arch of atlas. Disclosure of Interest None declared