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Screws, Facets, and Atlantoaxial Instability
Perspectives Commentary on: Atlantoaxial Fusion with Transarticular Screws: Meta-Analysis and Review of the Literature by Elliott et al. pp. 627-641.
Atul Goel, M.D. Professor and Head, Department of Neurosurgery King Edward Memorial Hospital and Seth Gordhandas Sunderdas Medical College
Screws, Facets, and Atlantoaxial Instability Atul Goel
L
ike elsewhere in the spine, screw fixation has become a popular mode of stabilization, even for atlantoaxial dislocation and has successfully challenged midline sublaminar wire and metal loop fixation techniques. The biomechanical strength of the screws and the relative ease of their insertion have made them attractive for the surgeon and effective for the patient. The facets of atlantoaxial region are the largest and strongest when compared to all other facets and are the most mobile and most stable regions of the spine. The strong purchase of screw in their largely “cortical” mass makes them ideally suited for such a method of treatment. After its initial description in 1986, the transarticular technique has found favor with many surgeons dealing with instability of the region (7). Transarticular screw fixation is a technically demanding and anatomically precise operation. The anatomy of the vertebral artery in general and in its relationship to the facet of C2, in particular, needs to be understood in an exact three-dimensional configuration before attempting the procedure. The analysis of Elliot et al. from an elaborate literature survey confirms the effectiveness of the Magerl’s transarticular screw method of fixation. The fusion rates were high and the complications were few. The outcome of the patients evaluated in the analysis does suggest that transarticular method of fixation can be a recommended operation for a select group of patients having atlantoaxial instability. The movements of the atlantoaxial region primarily occur at their facets. Any method that involves fixation at the point of fulcrum of all movements is superior to that which involves fixation of bone elements remote from this site. Transarticular method of fixation involves placement of one screw that traverses from C2 facet to the facet of C1 through the articular joint cavity. The site of insertion and direction of the placement of screw needs to be
Key words 䡲 Arthrodesis 䡲 Atlantoaxial 䡲 C1-2 䡲 C1-C2 䡲 Transarticular screw 䡲 Vertebral artery
514
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precise and essentially under fluoroscopic or neuronavigational control. The position of the head and the inclination of the facets of atlas and axis should be suitable for the conduct of the operation. The alignment of the facets during the process of screw insertion has to be in the reduced position of the dislocation. As the operation is extraspinal and away from the dural tube, it is safer than techniques that involve sublaminar wire insertion. The high riding vertebral artery can be a major contraindication for the surgery. Considering the acute angulation of the screw that is necessary an additional skin incision is frequently necessary for screw insertion. The insertion of screw in the facet of C1 is essentially blind. The extent of purchase of the screw in the facet of the atlas has to be determined by fluoroscopy. During operation, reinsertion and repositioning of a failed screw is relatively difficult. The quality of bone of the facets determines the strength of fixation. Osteoporosis of bone and affection of the facets by conditions like tuberculosis and rheumatoid arthritis can challenge the conduct of the procedure. Several investigators advocate a supplementary midline sublaminar wire fixation to make the stabilization biomechanically appropriate and comparable to atlantoaxial screw-plate/rod constructs. The technique of transarticular fixation enjoyed its reign for about two decades. The introduction of atlantoaxial screw-plate/rod technique that involves insertion of screws (monoaxial or polyaxial) into the facet of C1 and pars/pedicle/facet/body of C2 individually and stabilized with plates or rods has presented a firm competition (3, 5). The latter technique is finding an increasing favor. Although technically more demanding, there are clear advantages of the atlantoaxial screw-plate/rod technique over transarticular method of fixation. The technique is relatively safer for the vertebral artery during its course in relationship to the facet of C2, as the site of screw insertion can be more superior and the direction of the screw insertion can be more medial.
Department of Neurosurgery, Seth Gordhandas Sunderdas Medical College and King Edward Memorial Hospital, Parel, Mumbai, India To whom correspondence should be addressed: Atul Goel, M.D. [E-mail: [email protected]] Citation: World Neurosurg. (2013) 80, 5:514-515. http://dx.doi.org/10.1016/j.wneu.2012.05.020
WORLD NEUROSURGERY, http://dx.doi.org/10.1016/j.wneu.2012.05.020
PERSPECTIVES
There is a possibility of medially directing the C2 screw through the pedicle into the facet and even toward the vertebral body to avoid the location of a “high riding” vertebral artery. Elliot et al. have identified from the literature that 10%–20% patients are unsuitable for conduct of transarticular screw implantation due to the high riding vertebral artery. From the experience with our technique, the incidence of inability to complete the operation due to the location of vertebral artery is less than 4%.The screw insertion in the facet of the atlas is under vision and it can be placed in the entire length of the facet. Several studies that have assessed the biomechanical properties of transarticular and atlantoaxial screw-plate/rod fixation techniques have found the latter technique superior. Some investigators opine that external arthrosis may even be avoided when this technique is used. In 2007 we described a “double insurance” technique of atlantoaxial fixation (2). The technique involves placement of a C1 facet screw and placement of C2 screw in a transarticular fashion (Figure 1). The technique enjoys advantages of both transarticular and interarticular techniques. The conduct of the transarticular or even atlantoaxial polyaxial screw/rod operative techniques are relatively simpler and quicker when compared with the techniques that involve opening of the joint and direct insertion of the screws into the facets of the atlas and the axis individually. Dissection in the lateral gutter of the region is wrought with difficulties in handling venous bleeding due to the presence of large venous plexuses in the region. The issue of violation of articular surface and attempts at preservation of joint is much discussed. In atlantoaxial dislocation, fusion of the atlantoaxial vertebrae in general and atlantoaxial joint, in particular, is the primary goal. However, in cases with trauma with fracture of spinal segments or where fusion of the bone is possible, joint preservation can be attempted. Joint is always violated in transarticular method of fixation, but can be possibly saved in the atlantoaxial screw-plate/rod technique. In general, we do not recommend attempts at saving the joint in cases where an atlantoaxial fixation is carried out. “Joint treatment”
REFERENCES 1. Goel A: Treatment of basilar invagination by atlantoaxial joint distraction and direct lateral mass fixation. J Neurosurg Spine 1:281-286, 2004. 2. Goel A: Double insurance atlantoaxial fixation. Surg Neurol 67:135-139, 2007. 3. Goel A, Desai K, Muzumdar D: Atlantoaxial fixation using plate and screw method: a report of 160 treated patients. Neurosurgery 51:1351-1357, 2002.
Figure 1. Line drawing showing double insurance fixation. The C1 screw is placed directly into the facet of C1, whereas the C2 screw is transarticular. The two screws are connected with a plate (or rod).
forms an essential component of our technique (3, 5). Joint treatment involves opening up of the joint, denuding of the articular cartilage, and stuffing of bone graft pieces within the articular cavity. The procedure provides additional stability to the fixation and to the implant, an additional ground for bone fusion, besides obstructing movements at the center point of instability. Sectioning of the C2 ganglion is necessary in most cases where joint treatment is contemplated (3, 5). Manipulation and distraction of facets can be effectively used in the treatment of irreducible atlantoaxial dislocation, rotatory dislocation, basilar invagination, and basilar impression (1, 4, 6). Such procedures have opened newer scope of mending the issues related to craniovertebral junction instability.
4. Goel A, Kulkarni AG, Sharma P: Reduction of fixed atlantoaxial dislocation in 24 cases: technical note. J Neurosurg Spine 2:505-509, 2005.
7. Magerl F, Seeman P: Stable posterior fusion of the atlas and axis by transarticular screw fixation. In: Kehr P, Weidner A, eds. Cervical spine I. New York: Springer-Verlag; 1987: 217-221.
5. Goel A, Laheri VK: Plate and screw fixation for atlanto-axial dislocation (technical report). Acta Neurochir (Wien) 129:47-53, 1994.
Citation: World Neurosurg. (2013) 80, 5:514-515. http://dx.doi.org/10.1016/j.wneu.2012.05.020
6. Goel A, Shah A: Atlantoaxial facet locking: treatment by facet manipulation and fixation. Experience in 14 cases. J Neurosurg Spine 14:3-9, 2011.
WORLD NEUROSURGERY 80 [5]: 514-515, NOVEMBER 2013
Journal homepage: www.WORLDNEUROSURGERY.org Available online: www.sciencedirect.com 1878-8750/$ - see front matter © 2013 Published by Elsevier Inc.
www.WORLDNEUROSURGERY.org
515
Atul Goel, M.D. Professor and Head, Department of Neurosurgery King Edward Memorial Hospital and Seth Gordhandas Sunderdas Medical College
Screws, Facets, and Atlantoaxial Instability Atul Goel
L
ike elsewhere in the spine, screw fixation has become a popular mode of stabilization, even for atlantoaxial dislocation and has successfully challenged midline sublaminar wire and metal loop fixation techniques. The biomechanical strength of the screws and the relative ease of their insertion have made them attractive for the surgeon and effective for the patient. The facets of atlantoaxial region are the largest and strongest when compared to all other facets and are the most mobile and most stable regions of the spine. The strong purchase of screw in their largely “cortical” mass makes them ideally suited for such a method of treatment. After its initial description in 1986, the transarticular technique has found favor with many surgeons dealing with instability of the region (7). Transarticular screw fixation is a technically demanding and anatomically precise operation. The anatomy of the vertebral artery in general and in its relationship to the facet of C2, in particular, needs to be understood in an exact three-dimensional configuration before attempting the procedure. The analysis of Elliot et al. from an elaborate literature survey confirms the effectiveness of the Magerl’s transarticular screw method of fixation. The fusion rates were high and the complications were few. The outcome of the patients evaluated in the analysis does suggest that transarticular method of fixation can be a recommended operation for a select group of patients having atlantoaxial instability. The movements of the atlantoaxial region primarily occur at their facets. Any method that involves fixation at the point of fulcrum of all movements is superior to that which involves fixation of bone elements remote from this site. Transarticular method of fixation involves placement of one screw that traverses from C2 facet to the facet of C1 through the articular joint cavity. The site of insertion and direction of the placement of screw needs to be
Key words 䡲 Arthrodesis 䡲 Atlantoaxial 䡲 C1-2 䡲 C1-C2 䡲 Transarticular screw 䡲 Vertebral artery
514
www.SCIENCEDIRECT.com
precise and essentially under fluoroscopic or neuronavigational control. The position of the head and the inclination of the facets of atlas and axis should be suitable for the conduct of the operation. The alignment of the facets during the process of screw insertion has to be in the reduced position of the dislocation. As the operation is extraspinal and away from the dural tube, it is safer than techniques that involve sublaminar wire insertion. The high riding vertebral artery can be a major contraindication for the surgery. Considering the acute angulation of the screw that is necessary an additional skin incision is frequently necessary for screw insertion. The insertion of screw in the facet of C1 is essentially blind. The extent of purchase of the screw in the facet of the atlas has to be determined by fluoroscopy. During operation, reinsertion and repositioning of a failed screw is relatively difficult. The quality of bone of the facets determines the strength of fixation. Osteoporosis of bone and affection of the facets by conditions like tuberculosis and rheumatoid arthritis can challenge the conduct of the procedure. Several investigators advocate a supplementary midline sublaminar wire fixation to make the stabilization biomechanically appropriate and comparable to atlantoaxial screw-plate/rod constructs. The technique of transarticular fixation enjoyed its reign for about two decades. The introduction of atlantoaxial screw-plate/rod technique that involves insertion of screws (monoaxial or polyaxial) into the facet of C1 and pars/pedicle/facet/body of C2 individually and stabilized with plates or rods has presented a firm competition (3, 5). The latter technique is finding an increasing favor. Although technically more demanding, there are clear advantages of the atlantoaxial screw-plate/rod technique over transarticular method of fixation. The technique is relatively safer for the vertebral artery during its course in relationship to the facet of C2, as the site of screw insertion can be more superior and the direction of the screw insertion can be more medial.
Department of Neurosurgery, Seth Gordhandas Sunderdas Medical College and King Edward Memorial Hospital, Parel, Mumbai, India To whom correspondence should be addressed: Atul Goel, M.D. [E-mail: [email protected]] Citation: World Neurosurg. (2013) 80, 5:514-515. http://dx.doi.org/10.1016/j.wneu.2012.05.020
WORLD NEUROSURGERY, http://dx.doi.org/10.1016/j.wneu.2012.05.020
PERSPECTIVES
There is a possibility of medially directing the C2 screw through the pedicle into the facet and even toward the vertebral body to avoid the location of a “high riding” vertebral artery. Elliot et al. have identified from the literature that 10%–20% patients are unsuitable for conduct of transarticular screw implantation due to the high riding vertebral artery. From the experience with our technique, the incidence of inability to complete the operation due to the location of vertebral artery is less than 4%.The screw insertion in the facet of the atlas is under vision and it can be placed in the entire length of the facet. Several studies that have assessed the biomechanical properties of transarticular and atlantoaxial screw-plate/rod fixation techniques have found the latter technique superior. Some investigators opine that external arthrosis may even be avoided when this technique is used. In 2007 we described a “double insurance” technique of atlantoaxial fixation (2). The technique involves placement of a C1 facet screw and placement of C2 screw in a transarticular fashion (Figure 1). The technique enjoys advantages of both transarticular and interarticular techniques. The conduct of the transarticular or even atlantoaxial polyaxial screw/rod operative techniques are relatively simpler and quicker when compared with the techniques that involve opening of the joint and direct insertion of the screws into the facets of the atlas and the axis individually. Dissection in the lateral gutter of the region is wrought with difficulties in handling venous bleeding due to the presence of large venous plexuses in the region. The issue of violation of articular surface and attempts at preservation of joint is much discussed. In atlantoaxial dislocation, fusion of the atlantoaxial vertebrae in general and atlantoaxial joint, in particular, is the primary goal. However, in cases with trauma with fracture of spinal segments or where fusion of the bone is possible, joint preservation can be attempted. Joint is always violated in transarticular method of fixation, but can be possibly saved in the atlantoaxial screw-plate/rod technique. In general, we do not recommend attempts at saving the joint in cases where an atlantoaxial fixation is carried out. “Joint treatment”
REFERENCES 1. Goel A: Treatment of basilar invagination by atlantoaxial joint distraction and direct lateral mass fixation. J Neurosurg Spine 1:281-286, 2004. 2. Goel A: Double insurance atlantoaxial fixation. Surg Neurol 67:135-139, 2007. 3. Goel A, Desai K, Muzumdar D: Atlantoaxial fixation using plate and screw method: a report of 160 treated patients. Neurosurgery 51:1351-1357, 2002.
Figure 1. Line drawing showing double insurance fixation. The C1 screw is placed directly into the facet of C1, whereas the C2 screw is transarticular. The two screws are connected with a plate (or rod).
forms an essential component of our technique (3, 5). Joint treatment involves opening up of the joint, denuding of the articular cartilage, and stuffing of bone graft pieces within the articular cavity. The procedure provides additional stability to the fixation and to the implant, an additional ground for bone fusion, besides obstructing movements at the center point of instability. Sectioning of the C2 ganglion is necessary in most cases where joint treatment is contemplated (3, 5). Manipulation and distraction of facets can be effectively used in the treatment of irreducible atlantoaxial dislocation, rotatory dislocation, basilar invagination, and basilar impression (1, 4, 6). Such procedures have opened newer scope of mending the issues related to craniovertebral junction instability.
4. Goel A, Kulkarni AG, Sharma P: Reduction of fixed atlantoaxial dislocation in 24 cases: technical note. J Neurosurg Spine 2:505-509, 2005.
7. Magerl F, Seeman P: Stable posterior fusion of the atlas and axis by transarticular screw fixation. In: Kehr P, Weidner A, eds. Cervical spine I. New York: Springer-Verlag; 1987: 217-221.
5. Goel A, Laheri VK: Plate and screw fixation for atlanto-axial dislocation (technical report). Acta Neurochir (Wien) 129:47-53, 1994.
Citation: World Neurosurg. (2013) 80, 5:514-515. http://dx.doi.org/10.1016/j.wneu.2012.05.020
6. Goel A, Shah A: Atlantoaxial facet locking: treatment by facet manipulation and fixation. Experience in 14 cases. J Neurosurg Spine 14:3-9, 2011.
WORLD NEUROSURGERY 80 [5]: 514-515, NOVEMBER 2013
Journal homepage: www.WORLDNEUROSURGERY.org Available online: www.sciencedirect.com 1878-8750/$ - see front matter © 2013 Published by Elsevier Inc.
www.WORLDNEUROSURGERY.org
515