Comparison of Outcomes after Atlantoaxial Fusion with Transarticular Screws and Screw-Rod Constructs

OBJECTIVE: The purpose of this study was to compare the radiological and neurological outcomes between two atlantoaxial fusion method for atlantoaxial stabilization; C1 lateral mass-C2 pedicle screws (screw-rod constructs, SRC) versus C1-2 transarticular screws (TAS). METHODS: Forty-one patients in whom atlantoaxial instability was treated with atlantoaxial fixation by SRC group (27 patients, from March 2005 to May 2011) or TAS group (14 patients, from May 2000 to December 2005) were retrospectively reviewed. Numeric rating scale (NRS) for pain assessment, Oswestry disability index (ODI), and Frankel grade were also checked for neurological outcome. In radiologic outcome assessment, proper screw position and fusion rate were checked. Perioperative parameters such as blood loss during operation, operation time, and radiation exposure time were also reviewed. RESULTS: The improvement of NRS and ODI were not different between both groups significantly. Good to excellent response in Frankel grade is shown similarly in both groups. Proper screw position and fusion rate were also observed similarly between two groups. Total bleeding amount during operation is lesser in SRC group than TAS group, but not significantly (p=0.06). Operation time and X-ray exposure time were shorter in SRC group than in TAS group (all p<0.001). CONCLUSION: Both TAS and SRC could be selected as safe and effective treatment options for C1-2 instability. But the perioperative result, which is technical demanding and X-ray exposure might be expected better in SRC group compared to TAS group.

Targeting a Safe Entry Point for C2 Pedicle Screw Fixation in Patients with Atlantoaxial Instability

OBJECTIVE: This investigation was conducted to evaluate a new, safe entry point for the C2 pedicle screw, determined using the anatomical landmarks of the C2 lateral mass, the lamina, and the isthmus of the pars interarticularis. METHODS: Fifteen patients underwent bilateral C1 lateral mass-C2 pedicle screw fixation, combined with posterior wiring. The C2 pedicle screw was inserted at the entry point determined using the following method : 4 mm lateral to and 4 mm inferior to the transitional point (from the superior end line of the lamina to the isthmus of the pars interarticularis). After a small hole was made with a high-speed drill, the taper was inserted with a 30 degree convergence in the cephalad direction. Other surgical procedures were performed according to Harm's description. Preoperatively, careful evaluation was performed with a cervical X-ray for C1-C2 alignment, magnetic resonance imaging for spinal cord and ligamentous structures, and a contrast-enhanced 3-dimensional computed tomogram (3-D CT) for bony anatomy and the course of the vertebral artery. A 3-D CT was checked postoperatively to evaluate screw placement. RESULTS: Bone fusion was achieved in all 15 patients (100%) without screw violation into the spinal canal, vertebral artery injury, or hardware failure. Occipital neuralgia developed in one patient, but this subsided after a C2 ganglion block. CONCLUSION: C2 transpedicular screw fixation can be easily and safely performed using the entry point of the present study. However, careful preoperative radiographic evaluation, regardless of methods, is mandatory.

Inferolateral Entry Point for C2 Pedicle Screw Fixation in High Cervical Lesions

OBJECTIVE: The purpose of this retrospective study was to evaluate the efficacy and safety of atlantoaxial stabilization using a new entry point for C2 pedicle screw fixation. METHODS: Data were collected from 44 patients undergoing posterior C1 lateral mass screw and C2 screw fixation. The 20 cases were approached by the Harms entry point, 21 by the inferolateral point, and three by pars screw. The new inferolateral entry point of the C2 pedicle was located about 3-5 mm medial to the lateral border of the C2 lateral mass and 5-7 mm superior to the inferior border of the C2-3 facet joint. The screw was inserted at an angle 30degrees to 45degrees toward the midline in the transverse plane and 40degrees to 50degrees cephalad in the sagittal plane. Patients received followed-up with clinical examinations, radiographs and/or CT scans. RESULTS: There were 28 males and 16 females. No neurological deterioration or vertebral artery injuries were observed. Five cases showed malpositioned screws (2.84%), with four of the screws showing cortical breaches of the transverse foramen. There were no clinical consequences for these five patients. One screw in the C1 lateral mass had a medial cortical breach. None of the screws were malpositioned in patients treated using the new entry point. There was a significant relationship between two group (p=0.036). CONCLUSION: Posterior C1-2 screw fixation can be performed safely using the new inferolateral entry point for C2 pedicle screw fixation for the treatment of high cervical lesions.

Safety Issues and Neurological Improvement following C1 C2 Fusion using C1 Lateral Mass and C2 Pedicle Screw in Atlantoaxial Instability

The evolution of instrumentation methods for C1 C2 fusion from the use of posterior wiring methods to transarticular screws and C1 lateral mass with C2 pedicle screw construct have improved fusion rates to almost 100%. However, the C1 lateral mass and C2 pedicle screw technique is technically demanding. This is a prospective review of a series of ten patients who was planned for C1 C2 fusion using C1 lateral mass and C2 pedicle screw technique between January 2007 and June 2009. The procedure was converted