The medial window technique as a salvage method to insert C2 pedicle screw in the case of a high-riding vertebral artery or narrow pedicle: a technical note and case series

Application of C2 subfacetal screws for the management of atlantoaxial dislocation in patients with Klippel-Feil syndrome characterized by a narrow C2 pedicle and high-riding vertebral artery

“…Du et al and Lee et al have reported the medial “in–out-in” technique, which prevents VA injury by opening a window through the wall of the spinal canal to achieve multi-cortical tri-column fixation. Although no spinal cord injury has been reported, the screw entering the spinal canal poses a certain threat to the spinal cord [ 3 , 13 ]. Additionally, Goel performed the VA transposition technique, using two smaller screws for fixation.…”

“…Although no spinal cord injury has been reported, the screw entering the spinal canal poses a certain threat to the spinal cord [3,13]. Additionally, Goel performed the VA transposition technique, using two smaller screws for fixation.…”

“…The pedicle width was measured using axial CT. Narrow pedicle was considered when the maximum width of the pedicle did not exceed 4.0 mm [ 13 ]. HRVA was defined when the isthmus height did not exceed 5 mm and/or the internal height did not exceed 2 mm [ 16 ].…”

Feasibility of C2 Pedicle Screw Fixation With the “in-out-in” Technique for Patients With Basilar Invagination

“…Therefore, a breach of the medial wall of the pedicle up to 50% of the screw diameter is usually safe, similar to the expressed by Sciubba et al 17 However, the MPD of 3.53 mm measured by Bydon et al and 2.9 mm by Lee et al and the MPD and MPSC of 5.6 mm and 10.1 mm, respectively measured by Chiapparelli et al, are larger than the measures made for our cohort. 13,20,24 We believe that such differences are due to the following: BI patients often have Chiari malformation, which may enlarge the dura and spinal cord, leading to a reduction in MPD and MPSC; the anteroposterior diameter of the spinal canal is smaller than normal in BI patients, 3 which may cause the dura to expand laterally, leading to a reduction in MPD; compared with the studies of Bydon et al and Chiapparelli et al, the results of Lee et al are closer to this study, indicating that racial differences may also be an important factor. 13,20,24 Based on the above results, the morphologic structure around the C2 pedicle of the BI patient was sufficient to accommodate a portion of the screw that breached the cortex, and both the medial safe and limit zones are larger than the lateral.…”

“…[19][20][21] Another viable option can consist of C2PS fixation with a medial/lateral "in-out-in" technique, deliberately breaching the pedicle cortex to apply screws to patients with narrowed pedicles and provide three-column fixation. [22][23][24] However, the anatomic parameters associated with the application of this technique in patients with basilar invagination (BI) are unclear. The purpose of this study was to describe the average anatomic distances between the C2 pedicle and the dura or the VA in BI patients and evaluate the feasibility of C2PS fixation with "in-out-in" technique in BI patients.…”