ABSTRACT
Background@#The use of translaminar screws may serve as a viable salvage method for complicated cases. To our understanding, the study of the feasibility of translaminar screw insertion in the actual entire subaxial cervical spine has not been carried out yet. The purpose of this study was to report the feasibility of translaminar screw insertion in the entire subaxial cervical spine. @*Methods@#Eighteen cadaveric spines were harvested from C3 to C7 and 1-mm computed tomography (CT) scans and three-dimensional reconstructions were created to exclude any bony anomaly. Thirty anatomically intact segments were collected (C3, 2; C4, 3; C5, 3; C6, 8; and C7, 14), and randomly arranged. Twenty-one segments were physically separated at each vertebral level (group S), while 9 segments were not separated from the vertebral column and left in situ (group N–S). CT measurement of lamina thickness was done for both group S and group N–S, and manual measurement of various length and angle was done for group S only. Using the trajectory proposed by the previous studies, translaminar screws were placed at each level. Screw diameter was the same or 0.5 mm larger than the proposed diameter based on CT measurement. Post-insertion CT was performed. Cortical breakage was checked either visually or by CT. @*Results@#When 1° and 2° screws of the same size were used, medial cortex breakage was found 13% and 33% of the time, respectively. C7 was relatively safer than the other levels. With larger-sized screws, medial cortex breakage was found in 47% and 46% of 1° and 2° screws, respectively. There were no facet injuries due to the screws in group N–S. @*Conclusions@#Translaminar screw insertion in the subaxial cervical spine is feasible only when the lamina is thick enough to avoid any breakage that could lead to further complications. The authors do not recommend inserting translaminar screws in the subaxial cervical spine except in some salvage cases in the presence of a thick lamina.
ABSTRACT
Although spinal fusion has been the definitive surgical management of symptomatic lumbar degenerative conditions, continued reports of adjacent level degeneration and suboptimal patient outcomes have prompted the advancement of motion-preserving technology. Posterior dynamic stabilization [PDS] devices are designed to maintain native motion while providing indirect foraminal decompression and off-loading of the facets and posterior anulus. Posterior dynamic stabilization systems relying on pedicle screws as vertebral anchors have the advantage of surgeon familiarity with screw placement technique and instrumentation. Interconnections between the screws serve as a tension band to resist posterior distractive forces during flexion and maintain foraminal height in extension. Short-term results of pedicle screw-based PDS systems show comparable pain relief to traditional fusion with the added advantage of retained motion and potential reduction of fusion-related morbidity and of the incidence of adjacent segment degeneration. As with most new technology, pedicle screw based PDS systems require further evaluation to determine their long-term clinical benefit