at which operative stabilization should be considered ( Table 2 ). 3, 4, 11, 12, 17, 24, 25 TABLE 2 Criteria for atlantoaxial stabilization in patients without neurological symptoms Authors & Year Subluxation Ranawat, et al. , 1979 > 8 mm Conaty & Mongan, 1981 > 6 mm Heywood, et al. , 1988 > 10 mm Kourtopoulos & von Essen, 1988 > 6 mm McCarron & Robertson, 1988 > 8 mm Santavirta, et al. , 1988 > 9 mm Clark, et al. , 1989 > 8 mm The decision regarding operative
Stephen M. Papadopoulos, Curtis A. Dickman and Volker K. H. Sonntag
Eric M. Horn, Jonathan S. Hott, Randall W. Porter, Nicholas Theodore, Stephen M. Papadopoulos and Volker K. H. Sonntag
atlantoaxial stabilization. In this technique the lateral masses of C-1 to C-3 were fixated using polyaxial screws and rods, which were then connected to the axis using sublaminar wires and coupled with a standard posterior atlantoaxial wiring of an autologous bone graft. This technique was safe and provided excellent fixation and fusion. This technique is most appropriate for patients who are not suitable to undergo traditional transarticular screw fixation for atlantoaxial instability because it presents no risk of injury to the VA. References 1 Dickman CA
Michael B. Donnellan, Ioannis G. Sergides and William R. Sears
The authors present a novel technique of atlantoaxial fixation using multiaxial C-1 posterior arch screws. The technique involves the insertion of bilateral multiaxial C-1 posterior arch screws, which are connected by crosslinked rods to bilateral multiaxial C-2 pars screws. The clinical results are presented in 3 patients in whom anomalies of the vertebral arteries, C-1 lateral masses, and/or posterior arch of C-1 presented difficulty using existing fixation techniques with transarticular screws, C-1 lateral mass screws, or posterior wiring. The C-1 posterior arch screws achieved solid fixation and their insertion appeared to be technically less demanding than that of transarticular or C-1 lateral mass screws. This technique may reduce the risk of complications compared with existing techniques, especially in patients with anatomical variants of the vertebral artery, C-1 lateral masses, or C-1 posterior arch. This technique may prove to be an attractive fixation option in patients with normal anatomy.
John K. Stokes, Alan T. Villavicencio, Paul C. Liu, Robert S. Bray and J. Patrick Johnson
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.
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.
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.
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.
Case report and review of the literature
Domagoj Coric, Charles L. Branch Jr., John A. Wilson and James C. Robinson
– S16 , 1991 Montesano PX, Juach EC, Anderson PA, et al: Biomechanics of cervical spine internal fixation. Spine 16 (Suppl 3): S10–S16, 1991 16. Papadopoulos SM , Dickman CA , Sonntag VKH : Atlantoaxial stabilization in rheumatoid arthritis. J Neurosurg 74 : 1 – 7 , 1991 Papadopoulos SM, Dickman CA, Sonntag VKH: Atlantoaxial stabilization in rheumatoid arthritis. J Neurosurg 74: 1–7, 1991 17. Sherk HH , Snyder B : Posterior fusions of the upper cervical spine: indications, techniques
Masashi Neo, Mutsumi Matsushita, Tadashi Yasuda, Takeshi Sakamoto and Takashi Nakamura
biomechanical analysis of atlantoaxial stabilization methods using a bovine model. C1/C2 fixation analysis. Clin Orthop 290 : 285 – 295 , 1993 Smith MD, Kotzar G, Yoo J, et al: A biomechanical analysis of atlantoaxial stabilization methods using a bovine model. C1/C2 fixation analysis. Clin Orthop 290: 285–295, 1993 22. Song GS , Theodore N , Dickman CA , et al : Unilateral posterior atlantoaxial transarticular screw fixation. J Neurosurg 87 : 851 – 855 , 1997 Song GS, Theodore N, Dickman CA, et al
Curtis A. Dickman and Volker K. H. Sonntag
: Experimental study of atlas injuries I. Biomechanical analysis of their mechanisms and fracture patterns. Spine (Suppl 10) 16 : S460 – S465 , 1991 Panjabi MM, Oda T, Crisco JJ III, et al: Experimental study of atlas injuries I. Biomechanical analysis of their mechanisms and fracture patterns. Spine (Suppl 10) 16: S460–S465, 1991 35. Papadopoulos SM , Dickman CA , Sonntag VKH : Atlantoaxial stabilization in rheumatoid arthritis. J Neurosurg 74 : 1 – 7 , 1991 Papadopoulos SM, Dickman CA, Sonntag VKH
Daryl R. Fourney, Julie E. York, Zvi R. Cohen, Dima Suki, Laurence D. Rhines and Ziya L. Gokaslan
subperiosteal exposure of the occipital region and cervical spine were performed. Decompression of the spinal cord by means of laminectomies, and posterior tumor debulking was performed in selected cases ( Table 3 ). An instrumentation-augmented occipitocervical fusion was performed in all patients. We avoided the use of shorter (that is, atlantoaxial) stabilization, even in the few patients with relatively localized osseous involvement, because progression of the destructive neoplastic process to adjacent vertebral segments is unpredictable and may be detrimental to the
Richard C. E. Anderson, Brian T. Ragel, J Mocco, Leif-Erik Bohman and Douglas L. Brockmeyer
requiring unusual constructs that have been emphasized in this report. Treatment of atlantoaxial and occipitocervical instability in children has traditionally been achieved with a combination of posterior wiring techniques and an external halo or-thosis. 17 , 18 , 28 Many neurosurgeons have been reluctant to adopt rigid internal fixation for occipitocervical and atlantoaxial stabilization in children because of the combination of the smaller physical size and variable anatomy in this population, as well as the practitioners' unfamiliarity with the use and availability
Jae Taek Hong, Sang Won Lee, Byung Chul Son, Jae Hoon Sung, Il Sub Kim and Chun Kun Park
VKH , Dickman C : Biomechanical comparison of C1-C2 posterior fixations: cable, graft, and screw combinations . Spine 23 : 1946 – 1955 , 1998 18 Reilly TM , Sasso RC , Hall PV : Atlantoaxial stabilization: clinical comparison of posterior cervical wiring technique with trans-articular screw fixation . J Spinal Disord Tech 16 : 248 – 253 , 2003 19 Ryken TC , Goel VK , Clausen JD , Traynelis VC : Assessment of unicortical and bicortical fixation in a quasistatic cadaveric model. Role of bone mineral density and screw torque