Total Wrist Arthroplasty: An International Perspective.

Concerns about implant durability and technical difficulty continue to make total wrist arthroplasties a specialized procedure with a narrow scope of indications. As a result, more routinely performed total or partial wrist arthrodesis continues to maintain popularity over arthroplasty. However, wrist motion preservation is undoubtedly preferable for patients and current literature is trending to more favorable outcomes for total wrist arthroplasties. In the setting of the evolving role of wrist arthroplasties in clinical practice, it is important to focus on providing hand surgeons a practical approach to incorporating total wrist arthroplasty into the treatment toolbox available to them when treating patients with painful wrist arthritis.

Biometric and refractive changes following the monocular application of peripheral myopic defocus using a novel augmented-reality optical system in adults.

The prevalence of myopia is growing at an alarming rate and is associated with axial elongation of the eye. The cause of this undesirable physiological change involves multiple factors. When the magnitude of myopia approaches high levels, this accompanying mechanical effect increases the risk of developing other clinical conditions associated with permanent vision loss. Prior work has investigated how we may halt or reverse this process of axial elongation associated with myopic progression when we expose the eye to a peripheral myopic defocus stimulus. Specifically, the known, short-term response to myopic defocus stimulation is promising and demonstrates the possibility of establishing more permanent effects by regulating the axial length of the eye with specific defocus stimulation. However, how to directly convert these known, short-term effects into more long-term, permanent changes to effectively prevent these unfavourable physiological and refractive changes over time is yet to be understood. Here, we show for the first time that we can produce sustained, long-term reductions in axial length and refractive endpoints with cumulative short-term exposure to specific myopic defocus stimuli using a novel optical design that incorporates an augmented reality optical system. We believe that this technology will have the potential to improve the quality of vision in mankind.

Use of the Antegrade Posterior Interosseous Artery Flap for Coverage of Complex Elbow Wounds.

SUMMARY: One of the most versatile soft-tissue flaps available for elbow coverage that is reliable, quick, and easy to perform, with minimal donor defect and without the sacrifice of a major blood vessel, is the antegrade posterior interosseous artery flap. A large amount of vascularized fascia can be dissected with the flap, and it can be useful in lining the elbow joint or any exposed implant(s). After flap harvest, the donor site is often amenable to primary closure or requires a simple skin graft for closure. This article explains the technique for harvesting an antegrade posterior interosseous artery flap and describes 10 cases in which the flap was used for complex soft-tissue defects of the elbow not amenable to local wound care or skin grafting.

Effect of short-term peripheral myopic defocus on ocular biometrics using Fresnel "press-on" lenses in humans.

This study assessed axial length and choroidal thickness changes following short-term peripheral myopic defocus in normal adult subjects. Twenty subjects underwent defocus sessions by viewing a full-field projected movie 4 m away for 4 h in the morning, while wearing spectacle lenses, corrected for distance vision in both eyes. The right eye, serving as the test eye, was peripherally defocused using a Fresnel lens overlay of + 3.50 D with a central clear aperture of 11.5 mm (correlating to a clear central visual field of approximately 23°), while the left eye served as the control (with no Fresnel lens overlay). A subset of 10 subjects from the same cohort also underwent additional defocus sessions with + 5.00 D of peripheral defocus. Axial length was measured and radial sub-foveal choroidal scans were obtained before and after the defocus sessions. The increase in axial length of the test eyes were significantly less than the control eyes under both peripheral defocus conditions (p < 0.05). The difference in mean change for choroidal thickness between test and control eyes was not significant for either dioptric condition. Our results demonstrated that short-term peripheral myopic defocus significantly inhibited axial elongation in adult humans, without significant changes in choroidal thickness.

Visual Performance as a Function of Clear Central Aperture Diameter with a Defocused Myopic Periphery.

SIGNIFICANCE: Visual performance is affected least by a 15° radial aperture surrounded by peripheral myopic defocus. This finding has important applications for spectacle and contact lens designs and myopia control optimization. PURPOSE: The purpose of this study was to assess the effect of clear central apertures of different diameters with a defocused retinal periphery, using a range of visual performance tasks. METHODS: Thirty visually normal subjects (mean age, 24.4 ± 3.3 years; 20 females; mean spherical equivalent of -1.28 D) were enrolled. Subjects wore five different spectacles during testing, all corrected for distance refraction, in random order: three single-vision spectacles with clear central apertures of 10, 12.5, and 15° radii with the periphery defocused using Fresnel "press-on" lenses (+3.5 D sphere), progressive addition lens (PAL) spectacles with a +3.5 D addition, and single-vision lens (SVL) spectacles with no peripheral defocus. Static and kinetic visual field sensitivities, reading rate and comprehension, head movements, global saccadic tracking, and saccadic visual search were evaluated. RESULTS: Reading rate and comprehension did not differ across the five test conditions; however, increased head movement was found with the smallest aperture compared with the PAL condition with adjusted P < .05. Static visual field sensitivity was reduced for all three apertures in eccentric regions when compared with the SVL and PAL conditions with adjusted P < .05, whereas kinetic sensitivity did not differ for any lens condition. The 15° aperture was superior to the 10 and 12.5° apertures based on its similarity to the SVL and PAL spectacle conditions in head movement during reading, the Michigan Tracking Test, and the vertical results of the Developmental Eye Movement Test. CONCLUSIONS: Visual performance is least affected adversely by a 15° aperture surrounded by a peripheral myopic defocus. This finding has important applications for spectacle and contact lens designs to optimize myopia treatment with minimal impact on visual performance.

Stability and Performance Analysis of Networked Control Systems: A Lifted Sample-Time Approach with L2 Induced Norm.

The lifted sample-time approach has been extensively applied to analyze the behavior of a Networked Control System (NCS) under instances of packet-drop and/or variable communication latency (jitter) of varying durations. This paper combines the simplicity of the lifted sample-time approach in modeling an NCS under arbitrary but bounded instances of packet-drop and/or jitter with the proven L2induced norm based approach of controller design to realize an NCS which is capable of preserving the designed value of the norm under assumed conditions of packet-drop and/or jitter and hence a satisfactory time response under these conditions. The design methodology presented in this paper assumes a state feedback controller and uses a simple criterion based on a Linear Matrix Inequality (LMI). The methodology is validated using credible offline and real-time simulations.

Assessment of Distal Radioulnar Joint Stability After Reconstruction With the Brachioradialis Wrap.

BACKGROUND: The brachioradialis (BR) wrap technique is an option to restore the stability of the distal radioulnar joint (DRUJ). The technique capitalizes on the BR's advantageous insertion point on the radial styloid and the ability of the BR to be harvested with minimal to no deficit. The tendon can then be wrapped around the radius and ulna, tunneling under the pronator quadratus and extensor compartments and secured back into its insertion to provide stability. In this cadaveric study, we used micro-computed tomography (CT) to assess the stability restored by this procedure. METHODS: Axial CT scans were taken of cadaveric specimens (n = 10) in 3 different positions (neutral, 60° pronation, and 60° supination) to establish the baseline measurements of each DRUJ. Surgical disruption of the dorsal and volar ligaments of each DRUJ then simulated a destabilizing injury and the specimens were scanned again. The specimens then underwent the BR wrap procedure and were scanned once more. Degree of ulnar subluxation with respect to the Sigmoid notch was determined using the modified radioulnar line method. RESULTS: The mean percentages of subluxation in the neutral position for the normal, injured, and reconstructed DRUJ were 22.4±4.9%, 56.2±12.9%, and 29.0±6.5%, respectively. In 60° pronation, these values were 15.4±4.7%, 53.5±15.0%, and 36.5±11.8%, respectively. In 60° supination, these values were 18.6±2.5%, 69.7±20.5%, and 31.9±8.7%, respectively. CONCLUSIONS: Values differed significantly between normal and injured conditions in all positions. No significant difference was noted between normal and reconstructed conditions, suggesting reconstruction improves DRUJ biomechanics and more closely approximates normal stability.

Soft tissue coverage of the elbow.

Our discussion considers pedicled flaps about the elbow and free flaps. Local pedicle flaps are indicated in situations in which anatomic structures or implants are exposed and are absent native tissue or blood supply, or are at risk of infection.

Nonunion of the scaphoid distal pole.

This study was undertaken to determine the incidence of and assess factors affecting nonunion of scaphoid distal pole fractures. A total of 193 established scaphoid nonunions were treated in our clinics between the years 1999 and 2004; of which, eight cases involved the distal pole of the scaphoid. These were further analyzed to determine factors that may have contributed to the development of nonunion. This study reveals that distal pole nonunions account for 4.1% of all scaphoid nonunions. We found inadequate initial treatment to be the cause for nonunion in 63% of patients. Type IIC fracture pattern according to Posser's classification was seen in 100% of patients and a persistent Dorsal Intercalated Segmental Instability (DISI) pattern in 100% patients. In addition, 100% of fractures occurred at the watershed zone between the two vascular networks of the scaphoid. We believe the key features leading to the likelihood of nonunion at the distal pole include a Type IIC fracture pattern associated with a continued deforming force that eventually leads to a DISI deformity. The watershed area between the proximal vascular network supplying the waist and the distal one supplying the distal pole is especially vulnerable to poor healing.

Improved model reduction and tuning of fractional-order PI(λ)D(µ) controllers for analytical rule extraction with genetic programming.

Genetic algorithm (GA) has been used in this study for a new approach of suboptimal model reduction in the Nyquist plane and optimal time domain tuning of proportional-integral-derivative (PID) and fractional-order (FO) PI(λ)D(µ) controllers. Simulation studies show that the new Nyquist-based model reduction technique outperforms the conventional H(2)-norm-based reduced parameter modeling technique. With the tuned controller parameters and reduced-order model parameter dataset, optimum tuning rules have been developed with a test-bench of higher-order processes via genetic programming (GP). The GP performs a symbolic regression on the reduced process parameters to evolve a tuning rule which provides the best analytical expression to map the data. The tuning rules are developed for a minimum time domain integral performance index described by a weighted sum of error index and controller effort. From the reported Pareto optimal front of the GP-based optimal rule extraction technique, a trade-off can be made between the complexity of the tuning formulae and the control performance. The efficacy of the single-gene and multi-gene GP-based tuning rules has been compared with the original GA-based control performance for the PID and PI(λ)D(µ) controllers, handling four different classes of representative higher-order processes. These rules are very useful for process control engineers, as they inherit the power of the GA-based tuning methodology, but can be easily calculated without the requirement for running the computationally intensive GA every time. Three-dimensional plots of the required variation in PID/fractional-order PID (FOPID) controller parameters with reduced process parameters have been shown as a guideline for the operator. Parametric robustness of the reported GP-based tuning rules has also been shown with credible simulation examples.

Handling packet dropouts and random delays for unstable delayed processes in NCS by optimal tuning of PIλDµ controllers with evolutionary algorithms.

The issues of stochastically varying network delays and packet dropouts in Networked Control System (NCS) applications have been simultaneously addressed by time domain optimal tuning of fractional order (FO) PID controllers. Different variants of evolutionary algorithms are used for the tuning process and their performances are compared. Also the effectiveness of the fractional order PI(λ)D(µ) controllers over their integer order counterparts is looked into. Two standard test bench plants with time delay and unstable poles which are encountered in process control applications are tuned with the proposed method to establish the validity of the tuning methodology. The proposed tuning methodology is independent of the specific choice of plant and is also applicable for less complicated systems. Thus it is useful in a wide variety of scenarios. The paper also shows the superiority of FOPID controllers over their conventional PID counterparts for NCS applications.

On the selection of tuning methodology of FOPID controllers for the control of higher order processes.

In this paper, a comparative study is done on the time and frequency domain tuning strategies for fractional order (FO) PID controllers to handle higher order processes. A new fractional order template for reduced parameter modelling of stable minimum/non-minimum phase higher order processes is introduced and its advantage in frequency domain tuning of FOPID controllers is also presented. The time domain optimal tuning of FOPID controllers have also been carried out to handle these higher order processes by performing optimization with various integral performance indices. The paper highlights on the practical control system implementation issues like flexibility of online autotuning, reduced control signal and actuator size, capability of measurement noise filtration, load disturbance suppression, robustness against parameter uncertainties etc. in light of the above tuning methodologies.

Tuning of an optimal fuzzy PID controller with stochastic algorithms for networked control systems with random time delay.

An optimal PID and an optimal fuzzy PID have been tuned by minimizing the Integral of Time multiplied Absolute Error (ITAE) and squared controller output for a networked control system (NCS). The tuning is attempted for a higher order and a time delay system using two stochastic algorithms viz. the Genetic Algorithm (GA) and two variants of Particle Swarm Optimization (PSO) and the closed loop performances are compared. The paper shows that random variation in network delay can be handled efficiently with fuzzy logic based PID controllers over conventional PID controllers.

Fractional order phase shaper design with Bode's integral for iso-damped control system.

The phase curve of an open loop system is flat in nature if the derivative of its phase with respect to frequency is zero. With a flat-phase curve, the corresponding closed loop system exhibits an iso-damped property i.e. maintains constant overshoot with the change of gain. This implies enhanced parametric robustness e.g. to variation in system gain. In the recent past, fractional order (FO) phase shapers have been proposed by contemporary researchers to achieve enhanced parametric robustness. In this paper, a simple methodology is proposed to design an appropriate FO phase shaper to achieve phase flattening in a control loop, comprising a plant controlled by a classical Proportional Integral Derivative (PID) controller. The methodology is demonstrated with MATLAB simulation of representative plants and accompanying PID controllers.

High spectral purity microwave oscillator: design using conventional air-dielectric cavity.

We report exceptionally low PM noise levels from a microwave oscillator that uses a conventional air-dielectric cavity resonator as a frequency discriminator. Our approach is to increase the discriminator's intrinsic signal-to-noise ratio by use of a high-power carrier signal to interrogate an optimally coupled cavity, while the high-level of the carrier is suppressed before the phase detector. We developed and tested an accurate model of the expected PM noise that indicates, among other things, that a conventional air-dielectric resonator of moderate Q will exhibit less discriminator noise in this approach than do more esoteric and expensive dielectric resonators tuned to a high-order, high-Q mode and driven at the dielectric's optimum

Conjugate regenerative dividers.

We discuss a novel design of a self-starting regenerative divider that permits division by 3, 4, 5, 6 ... instead of the usual 2. This is accomplished by having the loop oscillate simultaneously at two harmonically related conjugate frequencies, e.g., at nu/4 and 3nu/4. A prototype of the divide-by-four circuit has been constructed for an input frequency of 400 MHz. This divider exhibits very low phase noise, Fourier frequency (1 kHz) = -162 dBc/Hz and Fourier frequency (100 kHz) = -170 dBc/Hz, which is approximately 9 dB lower than that of its constituent parts. Simple modifications of the feedback loop of this circuit enabled it to divide by 3, 5, and 8. Operation at higher division ratios appears feasible under certain conditions.

A distributed simulation technique for multiple input multiple output systems.

Distributed computing concepts have been attempted in the realm of real-time process control for a long time. This started with the systolic arrays of processors and an enormous amount of research has been done in this field. This paper proposes a methodology by which a multiple input multiple output system representing a plant and defined in terms of connected blocks of transfer functions can be decomposed into a set of parallel simulation processes in a message passing environment viz. a network of work stations. The paper also analyzes the scope of optimization of the processing time associated with each task. The methodology includes online reconfiguration of the system.