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Background The proper anchoring zone at the anterior sacral cortex is vital for the stability of S1 bicortical pedicle screw. During implantation, de-orbiting S1 bicortical pedicle screw is encountered occasionally and immediate correction is biomechanically required, especially in osteoporotic condition. Nevertheless, the biomechanical changes of the de-orbiting S1 bicortical pedicle screw after correction in different bone qualities remain unclear. The purpose of this study was thus to evaluate the biomechanical changes of the de-orbiting S1 bicortical pedicle screw after correction. Methods 18 fresh-frozen human sacra were divided into the normal and osteoporotic groups. The control and de-orbiting S1 bicortical pedicle screws were established randomly on either side of the sacrum. Following fatigue loading test, the subsidence displacement and axial pull-out strength were measured and analyzed. Findings In normal group, the subsidence displacement of the de-orbiting screw was increased significantly by comparison with the control one (median 0.37 vs. 0.36 mm) (P = 0.009); but no significant difference of the maximum pull-out strength between the two screws (median 359 vs. 353 N) (P = 0.262) was observed. In osteoporotic group, when compared with the control screw, the subsidence of the de-orbiting screw increased significantly (median 1.14 vs. 0.74 mm) (P = 0.012) and the maximum pull-out strength decreased obviously (median 151 vs. 252 N) (P = 0.012). Interpretation For normal bone quality, comparable stability could be achieved in the de-orbiting S1 bicortical pedicle screw after correction. Nevertheless, in osteoporotic condition, the correction procedure could not effectively prevent the loss of anchoring strength, and hence additional immediate augmentation fixation should be considered.

Based on London theory a general form of wave equation is formulated for both dielectric medium and superconductor. Using the wave equation and applying plane wave expansion, we have numerically calculated the band structures and density of states of a photonic crystal, whose intersection is constructed by a two-dimensional triangular lattice of superconductor padding in dielectric medium. Results indicate a wider band gap in the superconductor-medium photonic crystal than that in conventional photonic crystals. And part of original energy levels are found to be rearranged upon consideration of the superconductivity. The dependence of band gap on penetration length and filling factor is also discussed. Band gap width decreases monotonically with the penetration length, but not with the filling factor. Band gaps can be partially shut down or opened by adjusting filling factor.

This article presents an unusual case of arachnoiditis ossificans after spinal surgery. A case of arachnoiditis ossificans secondary to lumbar fixation and decompression surgery for the treatment of multilevel lumbar fractures is reported and the relevant literature is reviewed. A 29-year-old man who previously underwent posterior pedicle screw fixation and fusion for multiple lumbar spine fractures reported lower back stiffness and discomfort 23 months postoperatively. A laminectomy was performed at L2 and at L3–L4. At L2, bone fragments from the burst fracture had injured the dural sac and some nerve roots. A posterolateral fusion was performed using allogeneic bone. Postoperatively, there were no signs of fever, infection, or systemic inflammatory responses. Arachnoiditis ossificans of the thecal sac from L1–L5 was diagnosed by magnetic resonance imaging and computed tomography at the 2-year follow-up. His postoperative neurological status progressively improved and he regained motor and sensory functions. Because of neurological improvements, fixation hardware was removed without further decompression. The authors report a case of arachnoiditis ossificans secondary to lumbar fixation and decompression surgery, which involved a large region. Arachnoiditis ossificans is a relatively rare disorder with unclear etiologies and limited treatment options. Spinal surgical intervention of arachnoiditis ossificans should be carefully considered because it may lead to poor outcomes and multiple revision surgeries. [ Orthopedics. 2015; 38(5):e437–e442.]

AIM: To study the frameshift mutations of the retinoblastoma protein-interacting zinc finger gene RIZ in gastric cancer with microsatellite instability, and to identify two coding polyadenosine tracts of RIZ. METHODS: Frameshift mutations at (A)8 and (A)9 tracts of RIZ were detected in 70 human gastric cancer (HGC) specimens by DHPLC and DNA sequencing. Microsatellite instability (MSI) status was assessed by two mononucleotide markers, BAT26 and BAT25, by means of denaturing high-performance liquid chromatography (DHPLC). RESULTS: In 70 HGC samples, 8 (11.4%) were found positive for instabilities at BAT26 and BAT25. In 7 of the 8 cases with instabilities at both BAT26 and BAT25 (MSI-H), 1 was unstable at BAT26 but stable at BAT25. Frameshift mutations were identified in 4 (57.1%) of the 7 samples with MSI-H in the (A)9 tract of RIZ without mutations in the (A)8 tract. In contrast, frameshift mutations were found in neither of the polyadenosine tracts in 63 samples of MSI-L or MSI stable tumors. Pro704 LOH detection in 4 cases with frameshift mutations did not find LOH in these cases. CONCLUSION: Frameshift mutations of RIZ may play an important role in gastric cancers with MSI.

Based on the transfer matrix method, the recursion of an electromagnetic wave propagating in an asymmetric Kerr nonlinear medium is analytically formulated, from which the rectification effect is clearly presented. The effects on the rectification region of the linear part and nonlinear coefficient of permittivity are both studied, and the energy densities before and after rectification are discussed. We use a rectifying factor to describe the intensity of the rectification effect. The result shows that every transmission peak is divided into two parts when the symmetry is broken, and nonlinear asymmetry has a more significant effect on the rectification effect than the linear asymmetry. The rectification intensity and area will be enlarged when the asymmetry factor is increased in a certain range.

AIM: To explore the contribution of AXIN1, AXIN2 and beta-catenin, components of Wnt signaling pathway, to the carcinogenesis of gastric cancer (GC), we examined AXIN1, AXIN2 exon7 and CTNNB1 (encoding betacatenin) exon3 mutations in 70 GCs. METHODS: The presence of mutations was identified by polymerase chain reaction (PCR)-based denaturing high-performance liquid chromatography and direct DNA sequencing. Beta-catenin expression was detected by immunohistochemical analysis. RESULTS: Among the 70 GCs, 5 (7.1%) had mutations in one or two of these three components. A frameshift mutation (1 bp deletion) in exon7 of AXIN2 was found in one case. Four cases, including the case with a mutation in AXIN2, had frameshift mutations and missense mutations in AXIN1. Five single nucleotide polymorphisms (SNPs), 334 C>T, 874 C>T, 1396 G>A, 1690 C>T and 1942 T>G, were identified in AXIN1. A frameshift mutation (27 bp deletion) spanning exon3 of CTNNB1 was observed in one case. All four cases with mutations in AXIN1 and AXIN2 showed nuclear betacatenin expression. CONCLUSION: These data indicate that the mutations in AXIN1 and AXIN2 may contribute to gastric carcinogenesis.