Individual Navigation Templates for Subcortical Screw Placement in Lumbar Spine.

Subcortical screw placement is currently performed using frontal view fluoroscopy or intraoperative O-arm navigation system. The emergence of a novel technique for spinal navigation based on individual navigation templates created using 3D printing technology determines the need to study their safety and effectiveness in subcortical implantation. The aim of the study was to evaluate and compare the efficacy of subcortical implantation of pedicle screws in the lumbar spine using individual navigation templates versus intraoperative fluoroscopy. Materials and Methods: The study was based on the analysis of treatment results in 39 patients who underwent surgery with subcortical implantation of 130 screws using the MidLIF technique. In group 1, navigation templates were used, in group 2 - intraoperative fluoroscopic control. Comparative analysis of implantation correctness and time, the total operation time, and radiation load was performed. Results: The mean distance between the screw and the cortical plate recorded in the groups ranged within 1.20-3.97 mm, without statistically significant difference (p>0.05). The mean time of pedicle screw implantation was 137.0 [115.25; 161.50] s in group 1 and 314.0 [183.50; 403.25] s in group 2. The total operation time was reduced from 173.0 [155.0; 192.25] min in group 2 to 119.0 [108.0; 128.75] min in group 1. The average of 1.0 [1.0; 2.0] X-ray image was performed to place one screw in group 1, while it was 12.0 [10.0; 13.25] in group 2. The differences between the groups in terms of implantation time and radiation load were statistically significant (p<0.05). Conclusion: Compared with intraoperative fluoroscopy, the use of individual navigation templates for subcortical implantation of pedicle screws provides their correct positioning with a significant reduction in both operation time and radiation load at similar safety.

[Assessment of the safety and accuracy of implantation of screws into the C2 vertebra using individual 3D-navigation matrices]. / Otsenka bezopasnosti i tochnosti implantatsii vintov v S2 pozvonok s primeneniem individual'nykh 3D-navigatsionnykh matrits.

INTRODUCTION: Individual 3D-navigation matrices are valuable to increase the safety of screw implantation into the axis. OBJECTIVE: To analyze safety and accuracy of screw deployment into the axis using individual 3D-navigation matrices compared to free hand technique. MATERIAL AND METHODS: A retrospective analysis included 23 patients (group 1) who underwent implantation of 44 screws into the axis using the «free hand¼ technique. The screws were installed along the transpedicular or pars trajectory. A prospective analysis enrolled 17 patients (group 2) who underwent installation of 34 screws using individual navigation matrices. 3D-printing technology was applied for manufacturing these matrices. Implantation results were evaluated considering postoperative CT data and SGT (Screw Guide Template) system. RESULTS: In the 1st group («free hand¼), grade 0 and 1 (no malposition or less than 50% of screw diameter) were recorded for 29 (65.91%) screws, grade 2 - for 13 (29.55%) screws, grade 3 - for 2 (4.45%) screws. Intraoperative injury of the vertebral artery without postoperative neurological deficit occurred in 4 (8.89%) patients. In the 2nd group, 97% of screws were implanted in accordance with grades 1 and 2. Deviation grade 2 was registered in 11 cases (32.35%). Mean deviation was 1.8 ± 1.0 mm. In the 2nd group, 28 (82.35%) out of 34 screws were completely within the bone structures (grade 0), 4 (11.76%) screws perforated pedicles for less than 50% of their diameter (grade 1). There were 2 cases of malposition grade 2 and 3 without vertebral artery injury. CONCLUSION: Individual 3D navigation matrix is an effective method for screw installation into the axis. This approach exceeds fluoroscopy-assisted "free hand" technique in terms of safety of implantation.

[The life cycle and fine morphology of the embryophores in Microsomacanthus paraparvula (Cestoda: Hymenolepididae), a parasite of diving ducks in Chukotka]. / Zhiznennyi tsikl i tonkaia morfologiia zarodyshevykh obolochek Microsomacanthus paraparvula (Cestoda: Hymenolepididae) parazita nyrkovykh utok Chukotki.

It was found out, that the cestode Microsomacanthus paraparvula Regel, 1994 being a common parasite of diving ducks in Chukotka uses a caddisfly Grensia praeteria (Trichoptera) as an intermediate host in its life cycle. Mature fragments of the cestode have been collected from droppings of the experimentally infected nestling of the kittiwake Rissa tridactyla (non-specific host) and used for the fine morphology study of embryonic shells and for an infection of intermediate hosts.

[Structure and differentiation of the inner egg membrane of Trichocephaloides megalocephala (Cestoda, Dilepididae)]. / Struktura i differentsirovka vnutrenni obolochki iaits Trichocephaloides megalocephala (Cestoda, Dilepididae).

Electron microscope studies of the inner membrane of developing eggs of T. megalocephala were carried out. At early developmental stages the inner membrane is a syncytial cytoplasmatic layer lying on the basal plate of the embryo. At the preoncosphere stage the division of the membrane into two zones (external and internal ones) takes place. Initially the differentiation manifests itself in the cytoplasm polarisation; at the end of the middle preoncosphere stage the zones are divided by the "oncosphere membrane". The formation of the "oncosphere membrane" is accomplished by the external part of the internal zone. Embryophore is a derivative of the external zone, at the final stages of the formation the embryophore material is transformed from granular into thin-fibrillary. The origin of the external integument of oncospheres of cyclophillids, which, as it has been shown for T. megalocephala, is a derivative of the inner membrane rather than of specialized epithelial oncosphere cells, is considered.