Interlaminar Fixation Using the Atlantoaxial Posterior Fixation System (3XS System) for Atlantoaxial Instability: Surgical Results and Biomechanical Evaluation

Abstract

This study evaluated the surgical results for patients with atlantoaxial instability due to various lesions treated using the atlantoaxial posterior fixation system (3XS system; Kisco DIR, Paris, France), together with a biomechanical study of this system. The strength of the 3XS system during torsion was examined using a biomechanical simulation model. The 3XS system consists of a transverse unit, hooks, and rods. The lower part of the biomechanical simulation machine was rigidly fixed and the upper part was movable, allowing torsion to be applied until the point of failure. The test was started at 1.5 newtonmeters, thought to be the maximum load on the upper cervical spine. The 3XS system tolerated torsion of up to 20 newton-meters, but became deformed. The instrument was fractured at 30 newton-meters. Fifteen patients, four with atlantoaxial instability, seven with os odontoideum, and four with odontoid fractures, underwent surgery using the 3XS system and an iliac bone fragment inserted between the C-1 and C-2 laminae. Postoperative rigid fixation of the lesion and optimal cervical alignment was obtained in all patients, and the patients were discharged within 2 weeks after surgery. Follow-up radiography showed bony fusion between C-1 and C-2 in all patients. Posterior fixations between C-1 and C-2 using the 3XS system were easy to perform and no surgical complications were encountered. The biomechanical study showed the 3XS system can tolerate torsions unlikely to occur during rotation movements in the atlantoaxial region in humans. The surgical use of the 3XS system for the treatment of atlantoaxial instability has several advantages.

Posterior Instrumentation Surgery for Craniocervical Junction Instabilities: an Update

“…Other posterior atlantoaxial fixation techniques have recently been reported, including atlantal translaminar screw, 18) atlantoaxial interlaminar hook/rod, 61) or intraarticular screw techniques combined with interlaminar clamps. 82) They have been Posterior Surgery for CCJ Instabilities used less frequently with a limited number of cases, and may have less biomechanical stability than transarticular screw fixation.…”

Pediatric Patient with Incidental Os Odontoideum Safely Treated with Posterior Fixation Using Rod-Hook System and Preoperative Planning Using 3D Printer: A Case Report

“…Biomechanically, the 3XS system has been proven to be capable of tolerating the rotational forces between C1 and C2. 6 To confirm whether the device fits the pediatric cervical spine correctly, we recreated a full-scale replica of the patient's C1-C2 preoperatively using a three-dimensional Fig. 3 At the 2-year follow-up, bone formation at the gap of the dens, which has been generally considered as pseudoarthrosis, was found after bony union of the posterior element of C1-C2 occurred.…”