Quantitative analysis with load-displacement ratio measured via digital arthrometer in the diagnostic evaluation of chronic ankle instability: a cross-sectional study.

BACKGROUND: Arthrometry has been introduced to evaluate the laxity of ankle joint in recent years. However, its role in the diagnosis of chronic ankle instability is still debatable. Therefore, we assessed the diagnostic accuracy of a digital arthrometer in terms of sensitivity and specificity. METHODS: According to the inclusion and exclusion criteria proposed by the International Ankle Consortium, we recruited 160 uninjured ankles (control group) and 153 ankles with chronic ankle instability (CAI group). Ankle laxity was quantitively measured by a validated digital arthrometer. Data of loading force and joint displacement were recorded in a continuous manner. Differences between the control and CAI groups were compared using 2-tailed independent t test. A receiver operating characteristic curve analysis was used to calculate area under a curve, sensitivity and specificity. RESULTS: Load-displacement curves of the two groups were depicted. Differences of joint displacement between the control and CAI groups were compared at 30, 45, 60, 75, 90, 105 and 120 N, which were all of statistical significance (all p < 0.001) with the largest effect size at 90 N. Statistical significance was found in the differences between the two groups in load-displacement ratio at 10-120 N, 10-40 N, 40-80 N and 80-120 N (all p < 0.001), with the largest effect size at 10-40 N. Load-displacement ratio at the interval of 10-40 N had the highest area under a curve (0.9226), with sensitivity and specificity of 0.804 and 0.863, respectively, when the cutoff point was 0.1582 mm/N. CONCLUSION: The digital arthrometer measurement could quantitively analyze the ankle laxity with high diagnostic accuracy. The load-displacement ratio would be a reliable and promising approach for chronic ankle instability diagnosis. Level of evidence level II.

Angstrom-Scale Active Width Control of Nano Slits for Variable Plasmonic Cavity.

Nanogap slits can operate as a plasmonic Fabry-Perot cavity in the visible and infrared ranges due to the gap plasmon with an increased wavenumber. Although the properties of gap plasmon are highly dependent on the gap width, active width tuning of the plasmonic cavity over the wafer length scale was barely realized. Recently, the fabrication of nanogap slits on a flexible substrate was demonstrated to show that the width can be adjusted by bending the flexible substrate. In this work, by conducting finite element method (FEM) simulation, we investigated the structural deformation of nanogap slit arrays on an outer bent polydimethylsiloxane (PDMS) substrate and the change of the optical properties. We found that the tensile deformation is concentrated in the vicinity of the gap bottom to widen the gap width proportionally to the substrate curvature. The width widening leads to resonance blueshift and field enhancement decrease. Displacement ratio ((width change)/(supporting stage translation)), which was identified to be proportional to the substrate thickness and slit period, is on the order of 10-5 enabling angstrom-scale width control. This low displacement ratio comparable to a mechanically controllable break junction highlights the great potential of nanogap slit structures on a flexible substrate, particularly in quantum plasmonics.

Comparison of Locking and Frag-Loc Screws for Fixation of Die-Punch Fragments.

Background The Frag-Loc (FL) compression screw system was designed to stabilize dorsally displaced intra-articular dorsoulnar (die-punch) fragments in distal radius fractures. Purpose Comparison of the biomechanical properties of fixation of the die-punch fragment (stiffness, ultimate strength, and displacement ratio of the fragment), using the FL and traditional locking screw (LS), and using simulated distal radial fractures in cadaveric specimens under axial compressive loading. Both screws were used with a volar locking plate (VLP). Materials and Methods Eight matched pairs of formalin-fixed cadaveric specimens of the radius were used to simulate distal radius fractures with die-punch fragments. The die-punch fragment was fixed using VLP with either FL group or LS group. Biomechanical properties for the two fixation systems were evaluated under axial compression loading, applied at a constant rate of 0.5 mm/min until failure. Load data were recorded and the ultimate strength and change in the gap between the die-punch and proximal fragments measured, with the displacement ratio calculated by dividing the value of the gap before loading by the gap after loading. Failure was defined as 10 mm or more of fragment displacement, or screw failure. Results There were no differences in ultimate strength ( p = 0.47) or stiffness ( p = 0.061) between the two fragment fixation systems. However, the displacement ratio was lower for the FL than for the LS system ( p = 0.049). Conclusion Compared with LS, the FL system lowers the displacement of die-punch fragments under compressive loading. Clinical Relevance The FL system is effective for the treatment of distal radius fractures with die-punch fragments.