Computed tomography morphometric analysis for axial and subaxial translaminar screw placement in the pediatric cervical spine

Abstract

<jats:sec> <jats:title>Object</jats:title> <jats:p>The management of upper cervical spinal instability in children continues to represent a technical challenge. Traditionally, a number of wiring techniques followed by halo orthosis have been applied; however, they have been associated with a high rate of nonunion and poor tolerance for the halo. Alternatively, C1–2 transarticular screws and C-2 pars/pedicle screws allow more rigid fixation, but their placement is technically demanding and associated with vertebral artery injuries. Recently, C-2 translaminar screws have been added to the armamentarium of the pediatric spine surgeon as a technically simple and biomechanically efficient means of fixation. However, the use of subaxial translaminar screws have not been described in the general pediatric population. There are no published data that describe the anatomical considerations and potential limitations of this technique in the pediatric population.</jats:p></jats:sec> <jats:sec> <jats:title>Methods</jats:title> <jats:p>The cervical vertebrae of 69 pediatric patients were studied on CT scans. Laminar height and thickness were measured. Statistical analysis was performed using unpaired Student t-tests (p &lt; 0.05) and linear regression analysis.</jats:p></jats:sec> <jats:sec> <jats:title>Results</jats:title> <jats:p>The mean laminar heights at C-2, C-3, C-4, C-5, C-6, and C-7, respectively, were 9.76 ± 2.22 mm, 8.22 ± 2.24 mm, 8.09 ± 2.38 mm, 8.51 ± 2.34 mm, 9.30 ± 2.54 mm, and 11.65 ± 2.65 mm. Mean laminar thickness at C-2, C-3, C-4, C-5, C-6, and C-7, respectively, were 5.07 ± 1.07 mm, 2.67 ± 0.79 mm, 2.18 ± 0.73 mm, 2.04 ± 0.60 mm, 2.52 ± 0.66 mm, and 3.84 ± 0.96 mm. In 50.7% of C-2 laminae, the anatomy could accept at least 1 translaminar screw (laminar thickness ≥ 4 mm).</jats:p></jats:sec> <jats:sec> <jats:title>Conclusions</jats:title> <jats:p>Overall, the anatomy in 30.4% of patients younger than 16 years old could accept bilateral C-2 translaminar screws. However, the anatomy of the subaxial cervical spine only rarely could accept translaminar screws. This study establishes anatomical guidelines to allow for accurate and safe screw selection and insertion. Preoperative planning with thin-cut CT and sagittal reconstruction is essential for safe screw placement using this technique.</jats:p></jats:sec>

Variations in the Dimensions of Sub Axial Vertebrae and Its Clinical Significance

“…In The morphometry of cervical vertebra which was studied by Gajendran Prabavathy et al [11] where maximum pedicle length was noted at C3, Minimum pedicle length was noted at C5, This was in variance with our present study. The Lamina dimensions are very important for laminotomy (where making hole in lamina to create more space for spinal cord), laminectomy where removal part or all of lamina to reduce pressure on spinal cord & also in laminoplasty procedure [15,16,19,20]. These are all decompression procedures frequently used for the treatment of cervical spondylosis, mylopathy, tumors of spinal medulla (wang et al [16]).…”

Feasibility of CT-based intraoperative 3D stereotactic image-guided navigation in the upper cervical spine of children 10 years of age or younger: initial experience

“…These differences include ligamentous laxity, increased mobility, incomplete ossification, potential congenital anomalies, and relatively small bone size. 4,12 Screw fixation in younger children may be technically difficult for these reasons. Improperly placed screws may injure vital structures or may have less mechanical stability compared with properly placed screws.…”

“…27,32 Rigid screw fixation provides superior mechanical stability and improved fusion rates compared with nonrigid techniques. 4,9,10,14,21 Rigid screw fixation often obviates the need for postoperative halo fixation. There are anatomical studies evaluating the feasibility of commercially available screws in the pediatric population.…”

“…However, placement of 2 translaminar screws is generally not feasible in children younger than 16 years of age. 4 Therefore, we prefer a construct with a translaminar screw coupled with either a contralateral C-2 pars or pedicle screw. An additional advantage of this construct is that only 1 vertebral artery is at risk from screw placement.…”

Posterior fusion of the occipital axis in children with upper cervical disorder using both C2 pedicle and laminar screws (C2 hybrid screws)

“…Several reports have described the use of a C2 laminar screw (LS) without a pedicle screw (PS) for occipitalcervical fusion in pediatric patients [5][6][7] . However, the fusion area expands to C3 or more caudally.…”