The Clinical Study Of The Percutaneous Anterior Transarticular Screw Fixation And Fusion By Microendoscopy For Atlantoaxial Instability

Objective：To improve the safety of the PATSF (percutaneous anterior transarticularscrew fixation) by measuring parameters related to PATSF, and to retrospectively analyze theclinical results and complications of the patients with atlantoaxial instability treated by usingPATSF and fusion under microendoscopy.Methods:1. Fifty helical computerized tomography (helical CT) scans with volumetric acquisitionwere studied, including the atlanto-axis. The section of inner margin of atlantal supueriorarticular facet,the coronal plane of vertebral artery cavity in axis and the sagittal plane ofatlano-axis were obtained with MPR (muhiplanar reconstruction)on helical CT．The directionof vertebral artery cavity and the atlantoaxial vertebral structure were observed. Theparameters of PATSF were obtained．2. From May2007to December2010,13patients (2F，11M) with atlantoaxial instabilitywere treated by using PATSF and fusion under endoscopy and followed up. All cases included5with odontoid fracture,2with free den and6patients with Jefferson fracture. The mean agewas41.3years (range,17-61years). The blood loss, operative time,X-ray exposure time andcomplications were collected and analyzed. Clinical outcome was assessed by using theFrankel method. Fusion rates were determined by using CT scan reconstruction and dynamiccervical radiography in last fellow up.Results:1. The suitable position was4.0mm away from the midpoint of the atlantoaxialanteroinferior margin, where the screw was inserted.The maximum external angle of the PATSF was (29.89±1.41)°，the minimum external angle (4.37±0.87)°, the optimal externalangle (17.13±0.88)°, the maximum backward angle (32.41±1.66)°,the optimal backwardangle (17.62±1.03)°, and the optimal screw length (41.57±0.79) mm. The diameter ofatlantoaxial articular surface was (16.71±1.61)mm,the maximum distance of the atlantallateral displacement was (6.96±1.09) mm，and the ratio of which to the atlantoaxialarticular facial diameter was (41.80±5.69)%.2.The average follow-up duration was25.9months （range of12-47months）. The meanoperative time was (124±17) minutes, The mean intra-operative blood loss was (65±10) ml.The average radiation time was (41±16) s. The neurological function improved from grade Dto E in2patients after surgery. Other remained normal. The fusion rate at final follow-up was84.6%（11/13）. Postoperative dysphagia occurred and disappeared in five cases within oneweek. No nerve injury and implant failure occurred.Conclusion：1. The PATSF was reliable and safe by the optimal screw insertion.The screw can beinserted when the atlantal lateral mass was separated in a limited degree.2. PATSF and fusion under microendoscopy is a safe and effective procedure fortreatment of atlantoaxial instability, which has potential advantage and is minimally invasivetechnique.