Screw placement strategy of transoral occipitoatlantoaxial instrumentation for craniocervical junction diseases

English Keywords:Craniocervical junction disease  Atlantoaxial joints  Transoral surgery  Screw placement strategy

English Abstract:

  【Abstract】 Objectives: To study the screw placement strategy of transoral occipitoatlantoaxial instrumentation for craniocervical junction diseases. Methods: 30 patients with craniocervical disease (including 12 atlantoaxial dislocation, 15 basilar invagination, and 3 congenital deformity of craniocervical junction) were treated surgically with transoral atlantoaxial reduction plate-Ⅲ(TARP-Ⅲ) from January to December of 2010. All the patients presented with neck pain and extremity weakness and numbness in different degrees. Preoperative imaging of all cases showed the obvious ventral spinal cord compression. According to ASIA score, 5 cases were in grade C and 25 were in grade D. The motorscore was averagely 77.2±14.4(range, 42-96). Three-dimensional craniocervical models of all cases were established according to the technique of CAD-RP with the proportion of 1∶1. Preoperational screw-insertion simulation was performed on the models of 13 cases. 4 techniques of screw placement for transoral occipitoatlantoaxial internal fixation were adopted as follows: A, C1 lateral mass/occipital condyle complex screw(indicated for C0/C1 fusion); B, lateral mass screw of C1 (indicated for C0/C1 non-fusion); C, transoral transpedicular screw of C2(indicated for normal pedicle without basilar invagination); D, transoral articular mass screw of C2(indicated for basilar invagination, slim pedicle of C2, or elevatus vertebral artery of C2, etc.). The screw combination of AC or AD was chosen based on the presence of basilar invagination, that of BC or BD was chosen based on atlantoaxial dislocation or congenital craniocervical malformation. As a result, the combination of the screw placement for TARP fixation included: AC, AD, BC, and BD. Results: All 30 cases had neck pain and extremity weakness and numbness improved to some degree after operation. Infection, neurological or vascular injury, or screw-loosening was not noted. Some cases presented with light dizziness, which was resolved 2-4 weeks later maturely. Postoperative imaging showed the ideal position of internal fixation and complete decompression. 8 cases had neurofuntion improved from D to E according to ASIA standard; while the other 17 cases remained unchanged, but their motor scores increased to 96.4±4.2(range, 87-100). 5 cases had ASIA score improved from C to D. During an average follow-up of 7.2 months, all cases obtained bony fusion, and all 120 screws(including 30 in C1 lateral mass/occipital condyle complex screw, 30 in lateral mass screw of C1, 16 in transoral transpedicular screw of C2, and 44 in transoral articular mass screw of C2) were in good position. Conclusions： For craniocervical junction diseases necessitating transoral procedure, the screw placement should be decided individually. Multiple combinations of the occipitoatlantoaxial screws are available.