Treating irreducible atlantoaxial dislocation by transoral bony deformity osteotomy and releasing combined with plate fixation

English Keywords:Irriducible atlantoaxial dislocation  Basilar invagination  Transoral osteotomy releasing and plate fixation  Curative effect

English Abstract:

  【Abstract】 Objectives: To investigate a novel method for treating irreducible atlantoaixal dislocation (IAAD) by transoral bony deformity osteotomy and releasing combined with plate fixation. Methods: A retrospective analysis was conducted on the data of 213 consecutive patients diagnosed as IAAD associated with bony obstruction factors, who underwent a novel method by transoral bony deformity osteotomy and releasing combined with plate fixation from March 2015 to December 2018 in our hospital. There were 15 cases of old odontoid fractures with atlantoaxial dislocation, 5 cases of free odontoids with atlantoaxial dislocation, and 193 cases of basilar invagination (BI) with atlantoaxial dislocation. The period from the onset of clinical symptoms to surgery was 6 months to 3 years, averaged 1.5 years. The skeletal factors affecting IAAD were categorized into two types and 8 subgroups: type A1 [clivus of superior articular facet of axis in 118 cases (55.4%) with 178 sides (41.8%)], type A2 [labial hyperosteogeny of lateral mass joint in 19 cases (8.9%) with 31 sides (7.3%)], and type A3 [lateral mass joint ball and socket deformity in 15 cases (7.1%) with 21 sides (4.9%)], type A4 [lateral mass joint vertical interlocking deformity, 13 cases (6.1%) with 20 sides (4.7%)] and type A5 [dot like bone fusion between lateral mass joints in 6 cases (2.8%) with 9 sides(2.1%)]; and type B1 (bony structures hindering reduction between the atlas-dens gap in 30 cases, 14.1%), type B2 (5 cases of uncinate odontoid deformity, 2.3%), and type B3 (7 cases of hypertrophic odontoid deformity, 3.3%). After soft tissue releasing, the bony structures were eliminated by osteotomy and remodeling to transform the irreducible atlantoaxial dislocation (IAAD) into reducible type, which was fixed with plate after bone implantation between the lateral mass joints. The atlas-dens interval(ADI), vertical distance fromodontoid process to Chamberlain′s line(DOCL) and the clivus axis angle(CAA) were measured on CT films of the mid-sagittal reconstruction of the cervical spine before and after operation. The cervical medulla angle(CMA) was measured on the MRI film before and after operation, and the Japanese Orthopaedic Association(JOA) scores were recorded before operation and at half-year follow-up. Results: Of the 213 patients, the average operation time was 148±38min and the intra operative blood loss was 150±35ml. After operation, the symptoms of numbness, weakness and walking instability were improved to varying degrees, and the symptoms of headache and neck pain were alleviated significantly. The average preoperative ADI was 6.5±3.2mm, and the postoperative ADI was improved to 2.5±1.5mm on average(P<0.05). The average value of VDI before operation was 10.3±4.8mm, and was improved to 3.3±2.1mm postoperatively(P<0.05). The average preoperative CMA was 115°±25°, and the postoperative CMA was 158°±21°(P<0.05); the preoperative CAA averaged 101°±28°, and the postoperative CAA was 141°±10°(P<0.05). The follow-up time was 18±13 months and the JOA score improved from 9.3±2.8 preoperatively to 13.9±2.5 half year after operation(P<0.05). During the process of plate fixation, 3 reverse pedicle screws entered the vertebral artery foramen inwardly, all of which were on non-dominant sides and did not cause serious consequences. In this group of cases, excepted 1 patient experienced screw loosening due to osteoporosis, the rest achieved bone fusion within half a year to 1 year after operation. One case of incision infection occurred 1 week after operation. The wound was immediately debrided, the steel plate was removed, and the posterior fixation was adopted. The follow-up at 2 years after operation showed the wound healed well. Conclusions: In addition to soft tissue factors, bone obstruction is an important factor affecting atlantoaxial reduction. Transoral bony deformity osteotomy and releasing combined with plate fixation is effective in dealing with IAAD with bone obstruction factors.