Posterior atlantoaxial stabilization: new alternative to C1–2 transarticular screws

Abstract

<jats:sec> <jats:title>Object</jats:title> <jats:p>Surgical treatment of atlantoaxial instability has evolved to include various posterior wiring techniques including Brooks, Gallie, and Sonntag fusions in which success rates range from 60 to 100%. The Magerl–Seemans technique in which C1–2 transarticular screws are placed results in fusion rates between 87 and 100%. This procedure is technically demanding and requires precise knowledge of the course of the vertebral arteries (VAs). The authors introduce a new C1–2 fixation procedure in which C-1 lateral mass and C-2 pedicle screws are placed that may have advantages over C1–2 transarticular screw constructs.</jats:p></jats:sec> <jats:sec> <jats:title>Methods</jats:title> <jats:p>A standard posterior C1–2 exposure is obtained. Polyaxial C-2 pedicle screws and C-1 lateral mass screws are placed bilaterally. Rods are connected to the screws and secured using locking nuts. A cross-link is then placed. Fusion can be performed at the atlantoaxial joint by elevating the C-2 nerve root.</jats:p> <jats:p>The technique for this procedure has been used in four cases of atlantoaxial instability at the author's institution. There have been no C-2 nerve root– or VA-related injuries. No cases of construct failure have been observed in the short-term follow up period.</jats:p></jats:sec> <jats:sec> <jats:title>Conclusions</jats:title> <jats:p>Atlantoaxial lateral mass and axial pedicle screw fixation offers an alternative means of achieving atlantoaxial fusion. The technique is less demanding than that required for transarticular screw placement and may avoid the potential complication of VA injury. The cross-linked construct is theoretically stable in flexion, extension, and rotation. Laminectomy or fracture of the posterior elements does not preclude use of this fixation procedure.</jats:p></jats:sec>

Posterior atlanto-axial fixation with polyaxial C1 lateral mass screws and C2 pars screws

“…However, correct C1 screw position is documented in the series by Harms and Melcher [9], Stulik et al [20] and Goel et al [5]. No evaluation of C1 screw positioning is indicated in the reports of Fiore et al [3] and Stokes et al [19]. Correct C1 screw placement within the lateral masses was shown in all 24 C1 screws in the current series, with 23 bi-cortical and one mono-cortical position.…”

“…The average estimated blood loss was 480 ml (range: 150-800). The mean length of the C1 lateral mass screws was 32 mm (range: 30-34) and 17 mm (range: [14][15][16][17][18][19][20] for the C2 pars screws (Table 2).…”

“…In 2001, Harms and Melcher [9] described a posterior C1-C2 fixation with polyaxial C1 lateral mass and C2 pars screws, connected with posterior rods. C2 pars screw placement remains technically demanding, but is more widely applicable than trans-articular screws, as the screw trajectory is directed 20-25°medially and thus passes medial of even an enlarged vertebral artery foramen [3,7,9,14,19,20]. Additionally, better direct visual control during drilling and insertion of a pars screw has been argued to enhance safety over trans-articular screw placement [7,9].…”

“…The posterior approach is by far the most common approach for C1-C2 fixation and dorsal wiring techniques have increasingly been replaced by newer screw fixation techniques [3,9,10,12,14,15,[18][19][20].…”

C1 lateral mass screw-induced occipital neuralgia: a report of two cases

“…The Magerl transarticular technique provides significant fixation advantages over wiring techniques and up to a 100% fusion rate [5,[7][8][9]11]. However, anatomical reduction of C1 on C2 prior to screw insertion is required and there is potential for inadvertent vertebral artery injury [12]. Various anatomical factors such as an increased thoracic kyphosis may interfere with transarticular screw insertion.…”