Vortex-antivortex pair control in quadrupole Gaussian beams.

A multi-vortex system nested in a Gaussian beam forms complex paths when it propagates in a free space. We consider a configuration of vortex quadrupole and present a systematic way to control the creation and annihilation of vortex pairs using only one parameter. It is shown that three classes of quadrupole vortex beams can be identified by the number of vortex pairs created or annihilated. The beam symmetry, asymptotic behavior, and stability are analyzed. The main theoretical results are verified experimentally.

Energy- and time-controlled switching of ultrashort pulses in nonlinear directional plasmonic couplers.

We propose an ultracompact nonlinear plasmonic directional coupler for switching of ultrashort optical pulses. We show that this device can be used to control the routing of ultrashort pulses using either the energy or the duration of each individual pulse as switching parameters. The coupler is composed of two cores of a nonlinear dielectric material embedded into metallic claddings. The intricate nonlinear spatiotemporal dynamics of the system is simulated by the finite-difference time-domain technique.

Vortex Solitons in Twisted Circular Waveguide Arrays.

We address the formation of topological states in twisted circular waveguide arrays and find that twisting leads to important differences of the fundamental properties of new vortex solitons with opposite topological charges that arise in the nonlinear regime. We find that such system features the rare property that clockwise and counterclockwise vortex states are nonequivalent. Focusing on arrays with C_{6v} discrete rotation symmetry, we find that a longitudinal twist stabilizes the vortex solitons with the lowest topological charges m=±1, which are always unstable in untwisted arrays with the same symmetry. Twisting also leads to the appearance of instability domains for otherwise stable solitons with m=±2 and generates vortex modes with topological charges m=±3 that are forbidden in untwisted arrays. By and large, we establish a rigorous relation between the discrete rotation symmetry of the array, its twist direction, and the possible soliton topological charges.

The Cartilage Wear Index: a new evaluation method to improve patient selection in surgical treatment of recurrent posterior glenohumeral instability.

Background: The purpose of this study was to validate glenoid cartilage lesions as a negative prognostic factor and to define a new image-based preoperative evaluation method to identify surgical candidates for arthroscopic labral refixation with suture anchors in posterior shoulder instability. Methods: Twenty-six patients who underwent arthroscopic posterior labral repair for shoulder instability were evaluated. Only patients with structural dynamic posterior instability were included. We evaluated on preoperative magnetic resonance arthrogram: glenoid version, humeral head subluxation, type of capsular insertion, and the cartilage lesions using the new Cartilage Wear Index (CWI). Two subgroups were analyzed with regard to the preoperative CWI and shoulder outcome scores: Single Assessment Numerical Evaluation (SANE) and Western Ontario Shoulder Instability Index (WOSI). Results: The median age at operation was 28 (interquartile range = 21-33) years. Median overall postoperative outcome assessment demonstrated a SANE of 90 and a WOSI of 385. The median CWI was 1.02. Subgroup analysis revealed worse median WOSI and SANE scores in patients with a CWI >1.02 and a strong correlation between a high preoperative CWI and a higher postoperative WOSI score (R = 0.58; P = .038). Conclusion: The CWI can be useful to identify patients who might obtain better outcomes when treated with arthroscopic labral repair in posterior shoulder instability.

Superior capsular reconstruction using a porcine dermal xenograft for irreparable rotator cuff tears: outcomes at minimum two-year follow-up.

PURPOSE: To evaluate midterm outcomes of arthroscopic superior capsular reconstruction (SCR) using a decellularized porcine dermal xenograft in patients with massive, irreparable rotator cuff tears and to determine the influence of concomitant, repairable subscapularis tears. METHODS: This is a retrospective study of 56 patients with a minimum 2-year follow-up. Preoperative and postoperative range of motion, American Shoulder and Elbow Surgeons score, Subjective Shoulder Value, and visual analog score for pain were measured. Postoperative data were collected at 3, 6, 12, 24, and 36 months. RESULTS: Of the 56 patients who underwent arthroscopic SCR, there were 39 men and 17 women. The mean age at operation was 65 ± 9 years, and the mean follow-up was 34 ± 8 months. The mean preoperative American Shoulder and Elbow Surgeons improved from 41 ± 19 to 78 ± 18 at 24 weeks, to 86± 16 at 12 months, and to 90±9 at 24 months, P < .0001. Similarly, the mean preoperative Subjective Shoulder Value improved from 39 ± 17 to 74 ± 18 at 24 weeks, to 80 ± 18 at 12 months, and to 80 ± 11 at 24 months, P < .0001. The mean preoperative visual analog score improved from 6.5 ± 2.1 to 1.4 ± 2.2 at 24 weeks, to 0.7± 1.1 at 12 months, and to 0.2 ± 0.4 at 24 months, P < .0001. There were no differences in outcome scores between patients with intact vs. repaired subscapularis. Similarly, no statistically significant differences were found in forward flexion or external rotation after SCR between patients with an intact vs. repaired subscapularis. Failure of the SCR graft was observed on magnetic resonance imaging in 14 patients, 4 of whom opted for revision to reverse shoulder arthroplasty. Eleven patients were truly pseudoparalytic before surgery; in 5 cases, pseudoparalysis was reversed after SCR. CONCLUSIONS: SCR can alleviate pain and disability from irreparable rotator cuff tears and provide significant improvements in shoulder function; however, the xenograft technique resulted in inconsistent reversal of true pseudoparalysis. No difference was found between patients who required concomitant subscapularis repair vs. those who did not.

Software simulations of changing offsets and thus soft tissue tension when revising anatomic to reverse total shoulder arthroplasty in convertible platform systems.

BACKGROUND: Revision shoulder arthroplasty may involve the need to remove a well-fixed humeral stem. To avoid this, convertible platform systems have been introduced. The biomechanics of reverse total shoulder arthroplasty (rTSA) differs from anatomic shoulder arthroplasty (aTSA). The different humeral osteotomy and soft tissue tension may jeopardize the optimal results of the converted rTSA. The aim was to evaluate the radiographic parameters of soft tissue distraction when converting an aTSA to rTSA in a platform system and assess the capability of conversion without "over-stuffing" the shoulder in the "best-case scenario". METHODS: Radiographic analysis of soft tissue distraction parameters: difference in acromio-humeral distance, difference in lateral humeral offset and difference in latero-inferior displacement were evaluated in aTSA and in the converted rTSA in six different implants. Image analysing software was used on 10 non-deformed osteoarthritic shoulder X-rays to simulate conversion. RESULTS: The greatest increase in arm length was found for Tornier Ascend Flex (26.8 ± 3.6 mm) while the smallest increase was observed with Lima SMR (19.3 ± 4 mm). The humerus remained most lateralized with the Zimmer Anatomical/Inverse ( - 1.4 ± 2.9 mm) while Lima SMR ( - 15.8 ± 2.7 mm) was more medialized. The greatest increase in latero-inferior distance was found in the onlay systems. A group analysis of onlay rTSA showed an increase of 46% in arm length (p < 0.0001), 83% larger humeral offset (p < 0.0001) and 144% increase in latero-inferior distraction (p < 0.0001) when compared to inlay rTSA. CONCLUSION: The conversion of aTSA to rTSA using a convertible platform system may lead to significant increase in radiographic parameters corresponding to soft tissue tension. This may alter the biomechanics, restrict the convertibility or jeopardize the optimal clinical outcome of rTSA even in the best-case scenario.

Topological edge states of nonequilibrium polaritons in hollow honeycomb arrays.

We address topological currents in polariton condensates excited by uniform resonant pumps in finite honeycomb arrays of microcavity pillars with a hole in the center. Such currents arise under combined action of the spin-orbit coupling and Zeeman splitting, which breaks the time-reversal symmetry and opens a topological gap in the spectrum of the structure. The most representative feature of this structure is the presence of two interfaces, inner and outer ones, where the directions of topological currents are opposite. Due to the finite size of the structure, polariton-polariton interactions lead to coupling of the edge states at the inner and outer interfaces, which depends on the size of the hollow region. Moreover, switching between currents can be realized by tuning the pump frequency. We illustrate that currents in this finite structure can be stable and study bistability effects arising due to the resonant character of the pump.

Talipes Equinovarus Treatment in Infants Treated by the Ponseti Method Compared With Posterior-Only Release: A Mid-Childhood Comparison of Results.

The aim of this study is to evaluate children in middle childhood with clubfoot treated with Ponseti method vs posterior-only release and to compare their results to a control group with 4 modules (physical examination, gait study, radiographic measurements, and questionnaires). From 01/01/2004 until 01/01/2009, 31 children (45 feet) were treated with the posterior-only release protocol and 22 patients (34 feet) were treated with the Ponseti method. In 2016, patients were evaluated and compared with 25 children without neuromuscular disorders. Parents completed 3 outcome questionnaires. Radiographs evaluated residual deformity and osteoarthritis. A physical examination and a 3-dimensional gait analysis were performed to evaluate range of motion, kinematic, and kinetic data. Recurrence rate was similar between treatment groups; however, type of surgery to treat residual deformity was more aggressive in the posterior-only release (91% required major surgery), p = .024. Radiographic examination showed similar residual deformity with greater hindfoot varus in posterior-only release (68%), p = .02. Reduced cadence, increased stance dorsiflexion, calcaneus gait and forced eversion prior to swing were the main characteristics of gait in posterior-only release. Four (11%) feet treated with posterior-only release vs 11 (33%) feet treated with Ponseti method had a normal gait, p = .016. Our study showed that biomechanical function and long-term outcomes of children in middle childhood treated with the Ponseti method more closely compare with healthy individuals than those treated using posterior-only surgical technique.

A Modified Arthroscopic Technique of Gracilis Tendon Graft with Double Fixation System for Treatment of Type V Acromioclavicular Injuries: A Case Report.

CASE: A 48-year-old male patient with a type V acromioclavicular injury with a 3-tendon acute cuff tear, anterior glenohumeral dislocation, and an axillary posttraumatic neuropathy is presented. The rotator cuff tear was sutured and an all-arthroscopic-modified coracoclavicular ligaments (CCLs) reconstruction technique was performed with a gracilis tendon graft and a double knotless suture fixation system. CONCLUSIONS: An arthroscopic approach allows the surgeon to identify and treat associated glenohumeral lesions in type V acromioclavicular dislocations. In addition, the modified CCL reconstruction technique addresses effectively the AC instability.

Optical Amplification in Hollow-Core Negative-Curvature Fibers Doped with Perovskite CsPbBr3 Nanocrystals.

We report a hollow-core negative-curvature fiber (HC-NCF) optical signal amplifier fabricated by the filling of the air microchannels of the fiber with all-inorganic CsPbBr3 perovskite nanocrystals (PNCs). The optimum fabrication conditions were found to enhance the optical gain, up to +3 dB in the best device. Experimental results were approximately reproduced by a gain assisted mechanism based on the nonlinear optical properties of the PNCs, indicating that signal regeneration can be achieved under low pump powers, much below the threshold of stimulated emission. The results can pave the road of new functionalities of the HC-NCF with PNCs, such as optical amplification, nonlinear frequency conversion and gas sensors.

Toward Metal Halide Perovskite Nonlinear Photonics.

The possibility of controlling light using the nonlinear optical properties of photonic devices opens new points of view in information and communications technology applications. In this Perspective, we review and analyze the potential role of metal halide perovskites in a framework different from their usual one in photovoltaic and light-emitting devices, namely, the one where they can play as nonlinear photonic materials. We contextualize this new role by comparing the few extant results on their nonlinear optical properties to those of other known nonlinear materials. As a result of this analysis, we provide a vision of future developments in photonics that can be expected from this new perspective on metal halide perovskites.

Treatment of Cavitary Bone Defects in Chronic Osteomyelitis: Biogactive glass S53P4 vs. Calcium Sulphate Antibiotic Beads.

Aim: To evaluate the efficacy of bioglass (BAG-S53P4) in the treatment of patients with chronic osteomyelitis and compare the results with calcium sulphate antibiotic beads in one medical centre. Methods: Retrospective analysis of 25 cases. INCLUSION CRITERIA: patients diagnosed clinically and radiographically of osteomyelitis and treated surgically (Group 1: cavitary bone defects treated with bioglass and Group 2: cavitary bone defects treated with calcium sulphate antibiotic beads) during the period of 2014 and 2015 in one medical centre. Results: Patients in group 1 (bioglass treatment): total of 12 patients (11 males and 1 female) with mean age: 50 years (30-86). Average length of hospital stay was 22 days and mean follow-up time: 23 months (16-33). Mean erythrocyte sedimentation rate (ESR) and mean c-reactive protein (CRP) before sugery: 55mm/hr and 54 mg/L, respectively. Mean ESR and mean CRP in last blood exam: 18 mm/hr and 8 mg/L, respectively. There were 2 postoperative complications: seroma formation and delayed wound healing. Only 1 patient had recurrence of infection. Patients in group 2 (calcium sulphate antibiotic beads treatment): total of 13 patients (9 males and 4 females) with mean age: 48 years (17-67). Average length of hospital stay was 21 days and mean follow-up time 22 months (16-29). Mean ESR and mean CRP before surgery: 51mm/hr and 41 mg/L, respectively. Mean ESR and mean CRP in last blood test: 15 mm/hr and 11 mg/L. 2 postoperative complications were registered: chronic expanding hematoma of the muscle flap donor site and seroma formation. 1 patient had recurrence of infection. Overall, there were no differences in recurrence of infection, p=0.740 and in complication rate, p=0.672. 11 (91,7%) patients in group 1 and 12 (92,3%) patients in group 2 showed no signs of recurrence of infection both clinically and radiologically at final follow-up. The most frequent cause of osteomyelitis in group 1 was post traumatic while a postsurgical aetiology was more frequent in group 2. The distal tibia was the most common location. The most frequent pathogen isolated in both groups was methicillin sensible staphylococcus aureus. Conclusions: An advance in treatment of patients with cavitary bone defects in chronic osteomyelitis is the use of synthetic bone substitutes although current evidence is low. In this study, we demonstrate how bioglass without local antibiotics and calcium sulphate antibiotic beads are both equally effective treatment options. Overall, there were no differences between groups in mean hospital stay, complication rates and recurrence of infection.

Late neurological complications due to laminar hook compression in idiopathic scoliosis surgery.

INTRODUCTION: To provide a review of unusual neurological complications occurring years after spinal instrumentation surgery. CASE PRESENTATION: The authors analyzed the cases of three patients with adolescent idiopathic scoliosis who presented with delayed neurological symptoms (later than 12 months postoperatively) following spinal deformity surgery using Texas Scottish Rite Hospital (TSRH) hook-rod instrumentation. One case presented with conus medullaris syndrome while the last two were rare cases of posterior cord syndrome due to a dislodged laminar hook at the thoracolumbar transition. DISCUSSION: In all three cases, the neurological symptoms were due to direct laminar hook compression. Metallosis was observed extra-spinally around the hook-rod construct but not at the sublaminar site. The dislodged laminar hook responsible for the symptoms was situated at the concavity of the curve with the blade-tip pointing downwards. Symptomatic improvement was observed in all patients following complete hardware removal. Conscientious long-term follow-up of patients undergoing posterior spinal fusion (PSF) for adolescent idiopathic scoliosis (AIS) is important in order to recognize late neurological deficits directly related to instrumentation. Anamnesis and physical examination are key for initial assessment and diagnosis, while myelography and computed tomography (CT) images are of great help to confirm the site of spinal compression. Removal of the dislodged laminar hooks after PSF with TSRH instrumentation in AIS cases can potentially improve neurological symptoms.

Nonlinear phase shift from photon-photon scattering in vacuum.

We show that QED nonlinear effects imply a phase correction to the linear evolution of electromagnetic waves in vacuum. We provide explicit solutions of the modified Maxwell equations for the propagation of a superposition of two plane waves and calculate analytically and numerically the corresponding phase shift. This provides a new framework for the search of all-optical signatures of photon-photon scattering in vacuum. In particular, we propose an experiment for measuring the phase shift in projected high-power laser facilities.

Dipole soliton-vortices.

On universal symmetry grounds, we analyze the existence of a new type of discrete-symmetry vortex solitons that can be considered as coherent states of dipole solitons carrying a nonzero topological charge. Remarkably, they can be also interpreted as excited angular Bloch states. The stability of new soliton states is elucidated numerically.

Discrete-symmetry vortices as angular Bloch modes.

The most general form for symmetric modes of nonlinear discrete-symmetry systems with nonlinearity depending on the modulus of the field is presented. Vortex solutions are demonstrated to behave as Bloch modes characterized by an angular Bloch momentum associated to a periodic variable, periodicity being fixed by the order of discrete point-symmetry of the system. The concept of angular Bloch momentum is thus introduced to generalize the usual definition of angular momentum to cases where O2 symmetry no longer holds. The conservation of angular Bloch momentum during propagation is demonstrated.

Vortex transmutation.

Using group theory arguments and numerical simulations, we demonstrate the possibility of changing the vorticity or topological charge of an individual vortex by means of the action of a system possessing a discrete rotational symmetry of finite order. We establish on theoretical grounds a "transmutation pass" determining the conditions for this phenomenon to occur and numerically analyze it in the context of two-dimensional optical lattices. An analogous approach is applicable to the problems of Bose-Einstein condensates in periodic potentials.

Soliton topology versus discrete symmetry in optical lattices.

We address the existence of vortex solitons supported by azimuthally modulated lattices and reveal how the global lattice discrete symmetry has fundamental implications on the possible topological charges of solitons. We set a general "charge rule" using group-theory techniques, which holds for all lattices belonging to a given symmetry group. Focusing on the case of Bessel lattices allows us to derive also an overall stability rule for the allowed vortex solitons.

Vorticity cutoff in nonlinear photonic crystals.

Using group-theory arguments, we demonstrate that, unlike in homogeneous media, no symmetric vortices of arbitrary order can be generated in two-dimensional (2D) nonlinear systems possessing a discrete-point symmetry. The only condition needed is that the nonlinearity term exclusively depends on the modulus of the field. In the particular case of 2D periodic systems, such as nonlinear photonic crystals or Bose-Einstein condensates in periodic potentials, it is shown that the realization of discrete symmetry forbids the existence of symmetric vortex solutions with vorticity higher than two.