Treatment of irreducible atlantoaxial dislocation by bony deformity osteotomy, remodeling, releasing, and plate fixating through transoral approach

Objective Investigate a novel method for treating irreducible atlantoaxial dislocation (IAAD) or with basilar invagination (BI) by bony deformity osteotomy, remodeling, releasing, and plate fixating through transoral approach. Method From March 2015 to December 2019, 213 consecutive patients diagnosed as IAAD/BI were treated with transoral bony deformity remodeling and releasing combined with plate fixation. The main clinical symptoms include neck pain, headache, numbness of the limbs, weakness, unstable walking, inflexible hand-held objects, and sphincter dysfunction. The bony factors that impact reduction were divided into as follows: type A1 (sloping of upper facet joint in C2), type A2 (osteophyte in lateral mass joints between C1 and C2), type A3 (ball-and-socket deformity of lateral mass joint), type A4 (vertical interlocking between lateral mass joints of C1–C2), type A5 (regional bone fusion in lateral mass joints), type B1 (bony factor hindering reduction between the atlas-dens gap), type B2 (uncinate odontoid deformity), and type B3 (hypertrophic odontoid deformity). All of them were treated with bony deformity osteotomy, remodeling, and releasing techs. Result The operation time was 144 ± 25 min with blood loss of 102 ± 35 ml. The average pre-operative ADI improved from 7.5 ± 3.2 mm pre-surgery to 2.5 ± 1.5 mm post-surgery ( p < 0.05). The average VDI improved from 12.3 ± 4.8 mm pre-surgery to 3.3 ± 2.1 mm post-surgery ( p < 0.05). The average pre-operative CMA improved from 115 ± 25° pre-surgery to 158 ± 21° post-surgery ( p < 0.05); the pre-operative CAA changed from 101 ± 28° pre-surgery to 141 ± 10° post-surgery. After the operation, the clinic symptoms improved, and the JOA score improved from 9.3 ± 2.8 pre-operatively to 13.8 ± 2.5 in the sixth months of follow-up. Conclusion In addition to soft tissue factors, bony obstruction was another important factor impeding atlantoaxial reduction. Transoral bony deformity osteotomy, remodeling, releasing combined with plate fixating was effective in treating IAAD/BI with bony obstruction factors.