Occipitocervical fusion by using inter-diploe screw fixation for basilar invagination associated with occipitalisation of atlas and atlantoaxial dislocation

English Keywords:asilar invagination  Occipitalisation of atlas  Atlantoaxial dislocation  Inter-diploe screw fixation  Occipitocervical fusion

English Abstract:

  【Abstract】 Objectives: To study the safety and reliability of occipitocervical fusion by using inter-diploe screw fixation for basilar invagination associated with occipitalisation of atlas and atlantoaxial dislocation. Methods: From January 2004 to June 2012，9 patients(6 males, 3 females) were diagnosed with basilar invagination associated with occipitalisation of atlas and atlantoaxial dislocation. The ages ranged from 36 to 58 years(45.4±7.8 years)． All the patients had symptoms of spinal medulla compression． The JOA scores of preoperation ranged from 7 to 12(9.6±1.9). The atlas dens index(ADI), distance from tip of dens to Chamberlain line(DDCL), cervical medullary angle(CMA) and space available for the cord(SAC) of preoperation was 3.5-14.2mm(8.4±3.2mm), 4.5-14.2mm(8.9±3.3mm), 118°-152°(135.4°±11.3°) and 4.3-9.2mm(6.3±1.7mm) respectively. All the patients received head traction by modified Halo-vest for 1-2 weeks. All cases received occipitocervical fusion by using inter-diploe screw-rod-pedicel screw system. The operation time and blood loss were recorded, and the complications were observed after operation. The atlanto-axial dislocation and spinal cord compression were evaluated by postoperative radiography. All the patients were followed up every 3 months after surgery. Lateral X-ray and CT scan were used to evaluate bone graft fusion, and the JOA score was used to evaluate the improvement of spinal cord function. Results: All the patients underwent surgery successfully. The operation time was 90-195min( 132.2±33.9min), and the blood loss was 80-200ml(122.2±43.4ml)． 1 patient suffered from soft tissue infection after operation and was cured by local dressing. 1 patient with cerebrospinal fluid leakage was cured lumbar subarachnoid drainage for one week. Postoperative CT scan and MRI image showed the ADI 2.5±1.5mm, DDCL 0.9±1.7mm, CMA 154.4°±9.2° and SAC 16.3±1.98mm, which had statistical differences compared with the preoperative ones(P<0.05). All the inter-diploe screws were placed well, with no screw penetrating into inner occipital plate. 2 C2 pedicle screws were found violating into vertebral artery foramen with no vertebral artery injury. All the cases were followed up for 6-18 months(11.7±4.7 months), and all had neurofunction improved more significantly than preoperation. The JOA score at last follow-up was 12-16(14.3±1.4). Bone graft fusion was achieved in 3-9 months(5.0±2.1 months). There was no internal fixation breakage or loosening. Conclusions: Occipitocervical fusion by using inter-diploe screw-rod-pedicel screw system is an effective for basilar invagination associated with occipitalisation of atlas and atlantoaxial dislocation due to its rigid fixation, simple operation and easy bone graft.