ABSTRACT
Objective:To subdivide clinical classification of refractory atlantoaxial dislocation, and evaluate the reliability of new subdivide clinical classification of refractory atlantoaxial dislocation.Methods:From January 2010 to December 2018, 48 patients with refractory atlantoaxial dislocation were treated, including 19 males and 29 females, aged 16 to 65 years, with an average of 39.2±13.3 years. According to the changes of relative anatomical position of C 1 and C 2 under general anesthesia with heavy traction of 1/6 body weight, subdivide clinical classification of refractory atlantoaxial dislocation were proposed, and refractory atlantoaxial dislocation was divided into traction loosening type (atlantoaxial angle≥5°) and traction stabilization type (atlantoaxial angle<5°). The traction loosening type was directly reduced by posterior atlantoaxial screw-rod fixation and fusion without anterior or posterior soft tissue release. For traction stabilization type, transoral soft tissue release was performed first, and then transoral anterior reduction plate fixation and fusion or posterior atlantoaxial screw-rod fixation and fusion were performed. Atlantodental interval (ADI) and atlantoaxial angle (AAA) were measured and collected before and after surgery to evaluate atlantoaxial reduction. The space available for the spinal cord (SAC) were measured to evaluate spinal cord compression. Visual analogue score (VAS) was used to evaluate the neck pain levels, and Japanese Orthopaedic Association (JOA) scores was used to evaluate the neurological function. American Spinal Cord Injury Association impairment scale (AIS) was used to evaluate the degree of spinal cord injury. One week, 3, 6, 12 months postoperatively and the annual review of the X-ray and CT scan were checked, in order to evaluate the reduction, internal fixation and bone graft fusion. Results:Among all 48 cases, 22 cases were traction loosening type, of which posterior atlantoaxial screw-rod fixation and fusion were performed in 16 cases and occipitocervical fixation and fusion in 6 cases. 26 cases were traction stabilization type, and they all underwent anterior transoral release, and then, anterior TARP fixation and fusion were performed in 24 cases and posterior screw-rod fixation and fusion in the other 2 cases. X-ray, CT and MRI images and of all patients 1 week after surgery showed good atlantoaxial reduction and decompression of spinal cord. In each of the two types, there was one case lost to follow-up. For 46 cases in follow-up, the follow-up time ranged from 6 to 72 months, with an average of 38.0±17.2 months. Among 46 cases, 21 cases of traction loosening type showed that, ADI reduced from preoperative 9.9±2.2 mm to 2.3±0.9 mm at 3 months after surgery and 2.3±1.0 mm at the last follow-up, AAA increased from preoperative 57.9°±12.3° to 91.0°±2.2° at 3 months after surgery and 90.9°±2.2° at the last follow-up, SAC increased from preoperative 9.8±1.3 mm to 15.1±0.7 mm at 3 months after surgery and 14.9±0.7 mm at the last follow-up, VAS score reduced from preoperative 1.5±2.1 to 0.7±1.0 at 3 months after surgery and 0.3±0.6 at the last follow-up, and JOA score increased from preoperative 10.2±1.7 to 13.3±1.3 at 3 months after surgery and 14.9±1.5 at the last follow-up. Twenty-five cases of traction stabilization type presented that, ADI reduced from preoperative 9.7±2.0 mm to 2.1±1.4 mm at 3 months after surgery and 2.1±1.3 mm at the last follow-up, AAA increased from preoperative 55.8°±9.2° to 90.9°±1.4° at 3 months after surgery and 90.9°±1.3° at the last follow-up, SAC increased from preoperative 10.5±1.0 mm to 15.4±0.5 mm at 3 months after surgery and 14.8±2.8 mm at the last follow-up, VAS score reduced from preoperative 1.7±2.1 to 0.7±0.9 at 3 months after surgery and 0.3±0.5 at the last follow-up, and JOA score increased from preoperative 10.1±1.3 to 12.9±1.5 at 3 months after surgery and 14.4±1.3 at the last follow-up. In the traction loosening type, all the 10 grade D patients were improved to grade E at the last follow-up. In the 2 grade C patients of traction stabilization type before surgery, 1 patient was improved to grade E, 1 patient was improved to grade D, and all 11 patients with grade D were improved to grade E at the last follow-up. Bony fusion was obtained in all patients from 3 to 6 months, with an average of 4.4±1.5 months. During follow-up period, no looseness of internal fixation or redislocation happened.Conclusion:Refractory atlantoaxial dislocation can be divided into traction loosening type and traction stabilization type. For traction loosening type, satisfactory reduction can be achieved by using posterior atlantoaxial screw-rod system without soft tissue release. For traction stabilization type, anterior release is preferable, and then anterior TARP or posterior screw-rod can be used to achieve satisfactory reduction.
ABSTRACT
Objective To investigate the clinical effect of posterior screw-rod fixation fusion for the treatment of atlantoaxial dislocation due to rheumatoid arthritis.Methods From January 2011 to December 2015,15 patients with atlantoaxial dislocation due to rheumatoid arthritis were treated,including 6 males and 9 females,aged 35 to 75 years (mean 55 years).All cases were evaluated about the difficulty of relocation by extension-flexion X-ray and treated with posterior screw-rod reduction,fixation and autogenous bone grafting under general anesthesia.Atlantodental interval (ADI) was measured and collected before and after surgery.Visual Analogue Scale/Score (VAS),American Spinal Cord Injury Association (ASIA) and Japanese Orthopaedic Association (JOA) scores were comprehensively used to evaluate the clinical effect.1 week,3,6,12 months postoperatively and the annual review of the X-ray and CT were checked,in order to evaluate the reduction,internal fixation and bone graft fusion.Results All patients were reducible dislocation and successfully performed the posterior screw-rod fixation fusion surgery.The patients were followed up for 3 to 24 months (average,15 months).Atlantoaxial solid bony fusion was obtained from 3 to 6 months.ADI reduced from preoperative 6.3±1.7 mm to postoperative 2.2±0.8 mm,VAS score reduced from preoperative 5.4±2.7 to postoperative 1.7±1.0,ASIA motor score improved from preoperative 82.3±15.6 to 95.3±4.5 at 6 months after the surgery,JOA score increased from preoperative 13.8±2.9 to 15.5±1.4 at 6 months after the surgery,and the statistical significance was revealed between preoperation and postoperation.Nine cases were in D grade of ASIA,3 cases improved from D to E grade after surgery,2 cases reached E grade in the other 6 cases after 6 months,2 cases recovered to E grade after 12 months and other 2 cases in D grade got uniformity after surgery.Well internal fixation and no redislocation were found on X-ray and CT during follow-up period.Conclusion Atlantoaxial dislocation because of rheumatoid arthritis was numerously reducible genre.Posterior screw-rod fixation and autogenous bone grafting can gain satisfying clinical efficacy.
ABSTRACT
BACKGROUND: Atlantoaxial posterior approach is currently the main surgical treatment for atlantoaxial instability and/or dislocation, but the shape of rod in normal screw-rod device system is cylindrical. To obtain satisfactory reduction of atlantoaxis, the rod will be pre-bent obviously before fixation; however, the cylindrical rod will be rotated when tighten the nuts. Extra devices will be required to adjust and maintain the direction of the rod, thereafter, the surgical field will be blocked by the device, and spinal injury will occur once the devices are not held tightly. While the novel automatic anti-rotation rod has the function of anti-rotation during nut-tightening process, and also holds all the advantages of normal rod. Further research should be performed for the differences in biomechanical characteristics between two methods.OBJECTIVE: To investigate the biomechanical properties of the novel automatic anti-rotation rod for internal fixation system of atlantoaxial posterior approach based on three-dimensional finite-analysis model of upper cervical spine.METHODS: The three-dimensional finite element model of upper cervical spine with internal rod fixation system was developed. The biomechanical characteristics of the internal fixation system were analyzed. RESULTS AND CONCLUSION: The traditional and novel three-dimensional finite element model with realistic and geometric similarity contained 198330 elements, 964747 nodes and 246788 elements, 996069 nodes,correspondingly. There was no obvious stress concentration in both two systems, stress was concentrated mainly in the screw-bone and screw-rod interfaces. The stress values of the novel system were higher than those of the traditional system, but the maximum Von Misses Stress of two systems was lower than the yield (795-827 MPa ) and ultimate (860-896 MPa) strength of titanium alloys. These results show that the design of the novel automatic anti-rotation rod-screw fixation system has matched the biomechanical requirements for new internal fixation instruments, and is one safe, effective and practical device for atlantoaxial posterior procedure showing promising application prospect.