Medial surface plating of posterior column through the anterior intrapelvic approach in acetabulum fractures with involvement of both columns.

Aims: Posterior column plating through the single anterior approach reduces the morbidity in acetabular fractures that require stabilization of both the columns. The aim of this study is to assess the effectiveness of posterior column plating through the anterior intrapelvic approach (AIP) in the management of acetabular fractures. Methods: We retrospectively reviewed the data from R G Kar Medical College, Kolkata, India, from June 2018 to April 2023. Overall, there were 34 acetabulum fractures involving both columns managed by medial buttress plating of posterior column. The posterior column of the acetabular fracture was fixed through the AIP approach with buttress plate on medial surface of posterior column. Mean follow-up was 25 months (13 to 58). Accuracy of reduction and effectiveness of this technique were measured by assessing the Merle d'Aubigné score and Matta's radiological grading at one year and at latest follow-up. Results: Immediate postoperative radiological Matta's reduction accuracy showed anatomical reduction (0 to 1 mm) in 23 cases (67.6%), satisfactory (2 to 3 mm) in nine (26.4%), and unsatisfactory (> 3 mm) in two (6%). Merle d'Aubigné score at the end of one year was calculated to be excellent in 18 cases (52.9%), good in 11 (32.3%), fair in three (8.8%), and poor in two (5.9%). Matta's radiological grading at the end of one year was calculated to be excellent in 16 cases (47%), good in nine (26.4%), six in fair (17.6%), and three in poor (8.8%). Merle d'Aubigné score at latest follow-up deteriorated by one point in some cases, but the grading remained the same; Matta's radiological grading at latest follow-up also remained unchanged. Conclusion: Stabilization of posterior column through AIP by medial surface plate along the sciatic notch gives good stability to posterior column, and at the same time can avoid morbidity of the additional lateral window.

Tunable narrow band add-drop filter design based on apodized long period waveguide grating assisted co-directional coupler.

Tunable add/drop filter based optical interconnects are an integral part of data centers as well as optical communications. Although add/drop filters based on ring resonators and waveguide Bragg gratings are well developed, long period waveguide grating (LPWG) based add/drop filters have little been investigated so far. In this article, we propose an apodized LPWG assisted co-directional coupler for narrow band add/drop filtering by combining silicon (Si) waveguide with titanium dioxide (TiO2) waveguide geometry. The proposed structure has been analyzed by combining the finite element method (FEM) and transfer matrix method (TMM), showing a good side lobe suppression ratio (SLSR) equal to 25.7 dB and an insertion loss of 0.6 dB. Owing to the high group index difference of Si and TiO2 waveguides, a narrow band response of 1.4 nm has been achieved with 800µm long LPWG. The opposite thermo-optic coefficients of Si and TiO2 ensures a good thermal tunability of the central wavelength. Considering a thin metallic heater of titanium nitride (TiN) the thermal tuning efficiency is found to be 0.07 nm/mW. Further, two LPWGs have been cascaded to realize a tunable dual channel filter with a minimum channel spacing of 185 GHz and a channel crosstalk better than 20 dB, showing its potential application towards dense wavelength division multiplexing.

Highly Sensitive Refractive Index Sensor Based on Polymer Bragg Grating: A Case Study on Extracellular Vesicles Detection.

The measurement of small changes in the refractive index (RI) leads to a comprehensive analysis of different biochemical substances, paving the way to non-invasive and cost-effective medical diagnosis. In recent times, the liquid biopsy for cancer detection via extracellular vesicles (EV) in the bodily fluid is becoming very popular thanks to less invasiveness and stability. In this context, here we propose a highly sensitive RI sensor based on a compact high-index-coated polymer waveguide Bragg grating with a metal under cladding. Owing to the combined effect of a metal under cladding and a high-index coating, a significant enhancement in the RI sensitivity as well as the dynamic range has been observed. The proposed sensor has been analyzed by combining finite element method (FEM) and coupled-mode theory (CMT) approaches, demonstrating a sensitivity of 408-861 nm/RIU over a broad dynamic range of 1.32-1.44, and a strong evanescent field within a 150 nm proximity to the waveguide surface compliant with EV size. The aforementioned performance makes the proposed device suitable for performing real-time and on-chip diagnoses of cancer in the early stage.

Guided-mode resonance-based bandpass filter operating at full conical mounting.

We propose a cost-effective narrow bandpass filter based on a guided-mode resonance (GMR) structure, operating at full conical mounting configuration. Two additional layers above the GMR structure with designed geometry is considered to create a large angle of incidence (AOI) on the GMR structure with an almost normal AOI on the entire structure. In the visible wavelength range, the transmission spectrum contains three peaks: two peaks that are due to the GMR effect and one that is due to thin-film interference. The modal characteristic of the two GMR peaks is identified using a matrix method for the n-layer waveguide structure. The two GMR peaks with bandwidths of ∼1nm and ∼0.5nm correspond to the fundamental TE and TM modes, respectively. The GMR peaks can be pushed away from the thin-film interference peak by modulating the grating depth.