Study Design:Retrospective cohort study.Objective:To determine risk factors that may affect the rate of pedicle screws loosening in patients with degenerative diseases of the lumbar spine.Methods:A total of 250 patients with a low-grade spondylolisthesis and lumbar instability associated with degenerative diseases were enrolled. Preoperatively patients underwent computed tomography (CT) and cancellous bone radiodensity of a vertebral body was measured in Hounsfield units (HU). Pedicle screw fixation was used to treat patients either with a posterior fusion only or in combination with transforaminal lumbar interbody fusion (TLIF), anterior lumbar interbody fusion (ALIF), and direct lateral interbody fusion (D-LIF). Minimal follow-up period accounted for 18 months. Cases with screw loosening were registered assessing association with risk factors using logistic regression.Results:The rate of screw loosening was in positive correlation with the number fused levels and decreasing bone radiodensity. Fusion with a greater load-bearing surface cage was associated with the decrease in rate of pedicle screws loosening. Incomplete reduction in case of spondylolisthesis, bilateral facet joints removal, and laminectomy performed without anterior support favored pedicle screws loosening development. The estimated model classifies correctly 79% of cases with the specificity and sensitivity accounting for 87% and 66% respectively.Conclusions:The decreasing bone radiodensity in Hounsfield units has a considerable correlation with the rate of pedicle screws loosening. On the other hand, the length of fixation and applied surgical technique including fusion type also have a significant impact on complication rate. Spinal instrumentations should be planned by taking into account all potential risk factors and not characteristics relevant to bone quality assessment alone.

The aim of the study is to evaluate biocompatibility of a novel hybrid polyoligomer in in vitro and in vivo models. Materials and Methods. Cytotoxicity of the material was investigated using the MTT assay with human dermal fibroblasts as test cultures. To study direct interaction of the hybrid polyoligomer with cells, the fibroblasts were cultured on the polymer samples for 96 h, the cultures were assessed every 24 h using fluorescence microscopy. To study the tissue reaction in the area of contact with the donor bed and the morphological features of the implanted sample restructuring, a case-control study was performed using a rabbit model. Samples of hybrid polyoligomer were implanted into the bone defect formed in the left iliac crest in 10 rabbits. In the control group, the prepared allograft samples were transplanted into similar defects in 10 animals. The rabbits were sacrificed 4 and 8 weeks after the operation. The standard morphological methods with hematoxylin and eosin staining and immunohistochemical Ki-67 proliferation marker evaluation were used to assess the state of tissues in the defect area. Results. The results demonstrate that the hybrid polyoligomer is not cytotoxic (cytotoxicity score 0–1), cells adhere well to its surface, retain their viability and typical morphology throughout the entire observation period. No negative impact of material implantation on the health state and behavior of animals was detected. Morphological examination showed the absence of inflammatory changes, formation of thin-walled capillary vessels, and considerable proliferative activity of mesenchymal cells in the defect area, even though it was more intense than in the control group. Conclusion. No inflammation signs were detected by 8 th week of the experiment. It was defined that new bone was beginning to form. The results of analysis support the conclusion that the developed hybrid materials are prospective for further research as potential bone substitute.

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The aim of the study was to develop a new method of vertebral augmentation based on autologous and allogeneic bone chips to be used in pedicle screw fixation and to compare this method with the technique based on polymethyl methacrylate (PMMA). Materials and Methods This prospective non-randomized study included 164 patients with degenerative pathologies or traumatic injuries of the lumbar spine and transitional thoracolumbar segments; 153 of the operated patients were followed up for 18 months. In these patients, radiodensity of the cancellous bone tissue was below 110 HU by the Hounsfield scale. Patients with degenerative spinal disorders underwent pedicle screw fixation using transforaminal interbody fusion; patients with traumatic spinal injuries underwent intermediate pedicle screw fixation, and those with a loss of vertebral body height by >50% underwent anterior fusion. The patients were divided into three groups: in group 1 (n=39), bone tissue augmentation was performed using PMMA; in group 2 (n=21), augmentation was done with bone chips; in group 3 (n=93), no augmentation was performed (control group). The follow-up period was 12 months; cases with fixator breakage or loosening were recorded. Results After augmentation with PMMA, 11 cases (28.2%) of fixator destabilization were detected. With bone chips, fixator instability developed in 2 patients (9.5%) only, whereas in patients operated without augmentation, the instability was observed in 43 cases (46.2%). With PMMA augmentation, the incidence rate of fixator destabilization did not significantly differ from that in the control group (p=0.0801), while the use of bone chips resulted in a statistically significant decrease of this index compared to the control group (p=0.0023). A logistic regression analysis confirmed the superiority of the developed method over the PMMA-based vertebral augmentation. Conclusion The use of bone chips for vertebral augmentation provides a statistically significant decrease in the incidence of pedicle screw fixator destabilization in the post-operative period. By reducing the risk of proximal loosening and eliminating the risk of bone cement drainage into the spinal canal and vascular bed, the proposed method may become especially effective in patients with impaired bone density.

Background. Minimally invasive technology of fusion broadly introduced in clinical practice represent one of modern trends in spinal surgery on the other hand those technical solutions lack to provide posterior fusion. As a consequence, patients treated with minimally invasive techniques are vulnerable in terms of pseudarthrosis and implant instability therefore measures focused on those complications’ prevention are still actual.The study objective is to evaluate efficacy and safety of suggested percutaneous facet joints arthrodesis technique as an auxiliary option to interbody fusion.Materials and methods. This is a prospective non-randomized study of 80 patients with degenerative diseases of the lumbar spine who were treated applying minimally invasive transforaminal lumbar interbody fusion, lateral lumbar interbody fusion and anterior lumbar interbody fusion. In 20 cases out of those enrolled interbody fusion was supplemented with percutaneous posterior facet joints arthrodesis. Computed tomography was administered at the period of 6 and 12 months after surgery to assess anterior and posterior fusion. The minimal follow-up period accounted for 12 months.Results. The suggested percutaneous facet joints arthrodesis fifty-fold increased the probability of posterior fusion formation compared to the rate of spontaneous spinal fusion (p <0.0001, logistic regression was applied). In three cases posterior fusion formed prior to interbody fusion providing stability of segment operated on. No adverse events and no complications associated with percutaneous arthrodesis were detected.Conclusion. The suggested percutaneous facet joints arthrodesis is safe and effective minimally invasive technique that facilitates additional posterior spinal fusion formation in a short-term period herewith decreasing symptomatic pseudarthrosis development in patients operated on using minimally invasive spinal fixation and fusion.