Restoration of the sagittal profile according to the Roussouly classification reduces mechanical complications and revision surgery in older patients undergoing surgery for adult spinal deformity (ASD).

PURPOSE: The mechanical complications related to ASD remain a concern due to their morbidity and associated revision surgery. Restoration of each patient's Roussouly profile may reduce these. Our aim was to examine if the restoration of the Roussouly profile reduced these complications and revision rates in older patients operated for degenerative ASD. METHODS: Retrospective analysis of a single-centre, 2-year minimum follow-up patient database. All patients undergoing corrective surgery (≥ 4 levels) for ASD were included with analysis of demographic data, operative records, restoration of Roussouly sagittal profile, mechanical complications and revision rates. Univariate and multivariate analysis was conducted. RESULTS: Fifty-two patients were included (mean age was 72.3 years, average follow-up 56.3 months). Twenty-six patients had a "restored" profile (50%) and 26 an "unrestored" profile (50%). The incidence of mechanical complications was 7 (27%) and 23 (88%) for the restored and unrestored groups, respectively (p < 0.001). Revision rates were 4 (15.4%) and 18 (69.2%), respectively (p < 0.000), in the restored and unrestored profiles. Univariate analysis determined that profile restoration and BMI were associated with mechanical complications and revision surgery, whilst only the profile restoration status maintained its statistical power in multivariate analysis (p = 0.002 and p = 0.002, respectively). Age was not a significant factor in univariate analysis. The relative risk for mechanical failure and revision surgery was 5.6 times (CI 1.929-16.39) and 3.08 times (CI 1.642-5.734) greater if the profile was not restored. CONCLUSIONS: Achieving each patient's ideal Roussouly profile is associated with a reduced incidence of mechanical complications and revision rates in the older population after surgery for degenerative ASD.

Mortality following surgery for geriatric hip fractures: is it the timing or the co-morbidities?

BACKGROUND: Hip fractures are prevalent in the elderly population and present serious health, social and economic problems, with an impact on morbidity and mortality. Today, it is common practice to surgically repair these fractures as early as possible, preferably within 48 hours of hospital admission. However, there is conflicting evidence in the literature about the effect of the timing of surgery on postoperative mortality. OBJECTIVES: To assess the association between surgery delay and other demographic and clinical variables with an increased mortality rate after surgical treatment of hip fractures in the elderly. METHODS: A retrospective study was conducted on patients aged ⩾65 years with a primary diagnosis of hip fracture. All patients underwent surgery in our Medical Center from 2015 to 2017. A multivariate model of logistic regression, Cox regression model and Kaplan-Meier survival analysis were used to evaluate the relationship between various variables and mortality rates at 3- and 12-month follow-ups. RESULTS: A total of 877 patients were included, 30% were men and 70% women; the mean age was 83.3 years. Multivariate analysis showed that mortality was significantly higher among patients who underwent late surgery, after adjusting for gender, age, co-morbidity, age of surgeon, duration of surgery and duration of hospitalisation (p = 0.030). Surgical delay was significantly associated with higher mortality rates both at 3 month (p = 0.041) and at 12 months after surgery (p = 0.013). The presence of ischemic heart disease, congestive heart failure, paroxysmal atrial fibrillation and chronic renal failure, as well as male gender and older age, were also significantly associated with higher early and late mortality. CONCLUSIONS: In elderly patients, hip fracture surgery should be performed within 48 hours of admission. Male and older patients, as well as patients with the aforementioned co-morbidities, are at higher risk of mortality at 3 and 12 months after surgery.

Who might benefit from early aspirin after coronary artery surgery?

A best evidence topic in cardiac surgery was written according to a structured protocol. The question addressed was whether early administration of aspirin might optimize vein graft patency. More than 250 papers were found using the reported search, of which 4 new papers in addition to the previous 7 represented the best evidence to answer the clinical question. The authors, journal, date and country of publication, patient group studied, study type, relevant outcomes and results of these papers are tabulated. Early postoperative aspirin administered within 6 h following coronary artery bypass grafting (CABG) has been shown to be optimal for prevention of vein graft occlusion. Early aspirin has significant benefit in reducing vein graft occlusion, mortality, myocardial infarction, stroke, renal failure and bowel infarction. The efficacy of early postoperative aspirin on vein graft patency diminishes the later it is administered. It has optimal benefit at 6 h, some benefit at 24 h and no benefit after 48 h post CABG. ACC/AHA, EACTS and ACCP have issued guidelines recommending administration of early aspirin or an alternative (clopidogrel, ticlopidine and indobufen) at 6 h or soon after bleeding has settled as the standard of care for optimization of vein graft patency. The ACCP guideline has also suggested that optimal prevention of cardiovascular complication should have higher value than prevention of postoperative bleeding. Several randomized, controlled studies, including a meta-analysis, have shown that early administration of aspirin following CABG is not associated with increased blood loss or transfusion requirement. Postoperative bleeding has been identified as a significant reason for non administration of early aspirin in a prospective study. It is essential to define/quantify the postoperative blood loss that precludes administration of early aspirin. This will enhance prompt administration in some cases and guide judgement, especially in patients with high-risk factors for vein graft thrombosis. Administration at 6 h is the optimal time to give aspirin as long as bleeding has settled.

Coherent perfect absorption and reflection in slow-light waveguides.

We identify a family of unusual slow-light modes occurring in lossy multimode grating waveguides, for which either the forward or backward mode components, or both, are degenerate. In the fully degenerate case, the response can be modulated between coherent perfect absorption (zero reflection) and perfect reflection by varying the wave amplitudes in a uniform input waveguide. The perfectly absorbed wave has anomalously short absorption length, scaling as the inverse one-third power of the absorptivity.

Degenerate band edge resonances in coupled periodic silicon optical waveguides.

Using full three-dimensional analysis we show that coupled periodic optical waveguides can exhibit a giant slow light resonance associated with a degenerate photonic band edge. We consider the silicon-on-insulator material system for implementation in silicon photonics at optical telecommunications wavelengths. The coupling of the resonance mode with the input light can be controlled continuously by varying the input power ratio and the phase difference between the two input arms. Near unity transmission efficiency through the degenerate band edge structure can be achieved, enabling exploitation of the advantages of the giant slow wave resonance.

Bistability suppression and low threshold switching using frozen light at a degenerate band edge waveguide.

We predict that nonlinear waveguides which support frozen light associated with a degenerate photonic band edge, where the dispersion relation is locally quartic, exhibit a tunable, all-optical switching response. The thresholds for switching are orders-of-magnitude lower than at regular band edges. By adjusting the input condition, bistability can be eliminated, preventing switching hysteresis.

Frozen and broadband slow light in coupled periodic nanowire waveguides.

We develop novel designs enabling slow-light propagation with vanishing group-velocity dispersion ("frozen light") and slow-light with large delay-bandwidth product, in periodic nanowires. Our design is based on symmetry-breaking of periodic nanowire waveguides and we demonstrate its vailidy through two- and three-dimensional simulations. The slow-light is associated with a stationary inflection point which appears through coupling between forward and backward waveguide modes. The mode coupling also leads to evanescent modes, which enable efficient light coupling to the slow mode.

Degenerate band edges in optical fiber with multiple grating: efficient coupling to slow light.

Degenerate band edges (DBEs) of a photonic bandgap have the form (ω-ω(D)) ∝k(2m) for integers m>1, with ω(D) the frequency at the band edge. We show theoretically that DBEs lead to efficient coupling into slow-light modes without a transition region, and that the field strength in the slow mode can far exceed that in the incoming medium. A method is proposed to create a DBE of arbitrary order m by coupling m optical modes with multiple superimposed gratings. The enhanced coupling near a DBE occurs because of the presence of one or more evanescent modes, which are absent at conventional quadratic band edges. We furthermore show that the coupling can be increased or suppressed by varying the number of excited evanescent waves.

Tunability of the optical band edge in thin PbS films chemically deposited on GaAs(100).

The optical properties of chemical-solution-deposited thin films of lead sulfide (PbS) were investigated using infrared transmission and photoluminescence spectroscopies. The synthesized films are characterized by a wide range of microstructures, from 15 nm nanocrystals up to monocrystals. Energy bandgap values for bulk and nanostructured layers varied from 0.41 eV up to 0.48 eV, respectively. Blueshifts in both absorbance and emission peaks of the nanostructured layers were obtained due to quantum size effects. The optical properties of the films are shown to be size-dependent, with the band edge increasing with temperature.

Silicon photonic crystals doped with colloidally synthesized lead salt semiconductors nanocrystals.

The fabrication of two-dimensional and three-dimensional silicon photonic crystals doped with lead salt nanocrystals is reported. The silicon based photonic crystals of macro-porous silicon are fabricated by electro-chemical etching via masked silicon wafers with the periodicity along the third dimension is achieved by modulating the anodization current and voltage. The chemical solution deposition technique has been utilized to deposit thin layers of lead salts (PbS and PbSe) nanocrystals into the pores. Infrared transmission measurements revealed a considerable red-shift of the photonic band gap in a good agreement with numerical calculations.