VOx Matrix Confinement Approach to Generate Sub-3 nm L10-Pt-Based Intermetallic Catalysts for Fuel Cell Cathode.

Pt-based intermetallic compounds (IMCs) are considered as a class of promising fuel cell electrocatalysts, owing to their outstanding intrinsic activity and durability. However, the synthesis of uniformly dispersed IMCs with small sizes presents a formidable challenge during the essential high-temperature annealing process. Herein, a facile and generally applicable VOx matrix confinement strategy is demonstrated for the controllable synthesis of ordered L10-PtM (M = Fe, Co, and Mn) nanoparticles, which not only enhances the dispersion of intermetallic nanocrystals, even at high loading (40 wt%), but also simplifies the oxide removal and acid-washing procedures. Taking intermetallic PtCo as an example, the as-prepared catalyst displays a high-performance oxygen reduction activity (mass activity of 1.52 A mgPt -1) and excellent stability in the membrane electrode assemblies (MEAs) (the ECSA has just 7% decay after durability test). This strategy provides an economical and scalable route for the controlled synthesis of Pt-based intermetallic catalysts, which can pave a way for the commercialization of fuel cell technologies.

Amorphous TiOx Stabilized Intermetallic Pt3Ti Nanocatalyst for Methanol Oxidation Reaction.

Intermetallic compounds, featuring atomically ordered structures, have emerged as a class of promising electrocatalysts for fuel cells. However, it remains a formidable challenge to controllably synthesize Pt-based intermetallics during the essential high-temperature annealing process as well as stabilize the nanoparticles (NPs) during the electrocatalytic process. Herein, we demonstrated a Ketjen black supported intermetallic Pt3Ti nanocatalyst coupled with amorphous TiOx species (Pt3Ti-TiOx/KB). The TiOx can not only confine Pt3Ti NPs during the synthesis and electrocatalytic process by a strong metal-oxide interaction but also promote the water dissociation for generating more OH species, thus facilitating the conversion of COad. The Pt3Ti-TiOx/KB showed a significantly enhanced mass activity (2.15 A mgPt-1) for the methanol oxidation reaction, compared with Pt3Ti/KB and Pt/C, and presented an impressively high mass activity retention (∼71%) after the durability test. This work provides an effective strategy of coupling Pt-based intermetallics with functional oxides for developing highly performed electrocatalysts.

3D-MRI combined with signal-to-noise ratio measurement can improve the diagnostic accuracy and sensitivity in evaluating meniscal healing status after meniscal repair.

PURPOSE: This study compared the diagnostic accuracy of second-look arthroscopy, clinical assessment, and magnetic resonance imaging (MRI) in evaluating meniscal healing following repair. To explore the application of 3D-MRI sequences with signal-to-noise ratio (SNR) measurements and the analysis of sensitivity and accuracy in evaluating meniscal healing status after meniscal repair. METHODS: This study included 75 patients (75 menisci; mean age, 25.4 ± 6.6 years) who underwent arthroscopic meniscal repair (medial menisci, 45; and lateral menisci, 29). Follow-up evaluation included clinical assessment, magnetic resonance imaging (MRI), and second-look arthroscopy (mean follow-up, 10.2 ± 3.4 months). The criteria defined for unhealed menisci were: on arthroscopy, presence of cleft; on clinical assessment, presence of joint-line tenderness, swelling, locking, or positive McMurray test; on MRI, grade III signal intensity at the site of repair. Finally, the SNR on 3D-MRI of the healed and the unhealed groups were compared. RESULTS: On second-look arthroscopy, 68 (90.7%) menisci were found to be completely healed. With the arthroscopic healing rate as the standard, the clinical healing rate was 69.3% (63 menisci) [sensitivity, 85.7%; specificity, 75.0%; accuracy, 76.0%; positive predictive value (PPV), 26.1%; negative predictive value (NPV), 98.1%]. Similarly, the sensitivity, specificity, accuracy, PPV and NPV, respectively, for MRI in four sequences were as follows: 2D-T2W-Sag: 71.4, 79.4, 78.7, 26.3, and 96.4%; 2D-T2W-Cor: 71.4, 82.4, 81.3, 29.4, and 96.6%; 3D-PDW-Sag: 100.0, 50.0, 54.7, 17.1, and 100.0%; 3D-PDW-Cor: 100.0, 58.8, 62.7, 20.0, and 100.0%. The mean SNRs of the healed group (3D-PDW-Sag, 66.7 ± 11.9; 3D-PDW-Cor, 63.9 ± 12.4) were significantly lesser than that of the unhealed group (3D-PDW-Sag, 89.2 ± 9.6; 3D-PDW-Cor, 82.2 ± 18.5) (P < 0.05). Identifying grade 3 meniscal damage on 3D-PDW images prior to applying the different SNR cut-off points revealed SNR values 80 in the sagittal plane and 70 in the coronal plane as having better diagnostic accuracy and sensitivity. The clinical relevance of the study was that 3D-MRI combined with SNR measurement may be a noninvasive and accurate method of assessment clinically, and a reliable alternative to second-look arthroscopy. LEVEL OF EVIDENCE: III.

Comparison of Knee Stability and Synovial Fluid Alterations in Anterior Cruciate Ligament Reconstruction With a Hamstring Autograft or an Allograft.

This study compared knee stability and alterations in the composition of synovial fluid among patients who underwent arthroscopic anterior cruciate ligament (ACL) reconstruction with either a hamstring autograft or a hamstring allograft. This prospective cohort study enrolled 175 patients. Of these patients, 90 underwent hamstring tendon autograft ACL reconstruction. The remaining patients (n=85) underwent hamstring tendon allograft ACL reconstruction. All of the patients had a minimum of 1 year of follow-up (mean, 2.5 years). Side-to-side differences and the proportion of mononuclear cells in knee joint synovial fluid were measured at 5 time points (preoperatively and at postoperative weeks 1, 3, 6, and 12). During the early postoperative phase, side-to-side knee laxity was greater among the allograft group compared with the autograft group (P<.001). Additionally, among the allograft group, the proportion of mononuclear cells remained high at weeks 6 and 12 (mean, 90.0% and 88.9%, respectively) compared with a normal level in the autograft group (mean, 45.1% and 65.7%, separately). However, no significant difference was found between the 2 groups at final follow-up for range of motion, results of the Lachman test, results of the anterior drawer test, results of the pivot shift test, Lysholm score, bone tunnel enlargement, and graft failure rate (P>.05). These findings showed that, in the early postoperative phase, ACL reconstruction with a hamstring allograft resulted in greater knee laxity and immunologic response compared with the hamstring autograft group. However, at relatively long-term follow-up, both grafts achieved similar objective and subjective outcomes. [Orthopedics. 2017; 40(5):e892-e897.].

Combined Anterior and Dual Posterolateral Approaches for Ankle Arthroscopy for Posterior and Anterior Ankle Impingement Syndrome.

BACKGROUND: We introduce a novel method of combining the standard anteromedial and anterolateral approaches and dual posterolateral approaches in the arthroscopic treatment of posterior and anterior ankle impingement syndrome and compare the postoperative outcomes with conventional anteromedial/anterolateral and posteromedial/posterolateral approaches. METHODS: From January 2013 to January 2015, we treated 28 patients with posterior and anterior ankle impingement syndrome by arthroscopy. The patients were divided into the conventional group (n = 13) and the modified group (n = 15) according to the surgical approaches used in the operation. Preoperative and postoperative American Orthopaedic Foot & Ankle Society (AOFAS) score, visual analog scale (VAS) score, range of ankle motion, and operation time were recorded. The average follow-up was 16 months (range 6-24 months). RESULTS: Posterior and anterior ankle impingement syndrome was confirmed arthroscopically in all patients. After the operation, the range of ankle motion in all patients was restored. There was no significant difference in postoperative AOFAS score, VAS score, dorsiflexion, and plantarflexion between the conventional group and the modified group. Moreover, the operation time was significantly reduced in the modified group compared with the conventional group. There was no recurrence of osteophyte and no complications such as infection, neurovascular injury, or delayed healing of surgical incision in the modified group. CONCLUSIONS: Dual posterolateral approaches combined with standard anteromedial and anterolateral approaches was a novel method for arthroscopic treatment of posterior and anterior ankle impingement syndrome. It proved to be safe and effective, and significantly reduced the operation time. Reposition, repeated prep and drape, and limb distraction were avoided. LEVEL OF EVIDENCE: Level IV, retrospective case series.

The FasT-Fix Repair Technique for Ramp Lesion of the Medial Meniscus.

INTRODUCTION: This technical note describes a new arthroscopic technique to repair the peripheral attachment lesion of the posterior horn of the medial meniscus. The operation was performed under arthroscopy using a standard anterior portal. SURGICAL TECHNIQUE: A FasT-Fix needle was inserted obliquely close to the tibial plateau and the first implant was inserted into the joint capsule depending on its bending angle underneath the meniscus. The second implant was inserted through 1/3 periphery of the meniscus into the meniscocapsular area. The pre-tied self-sliding knot was tensioned to achieve secure fixation of the posterior meniscal peripheral attachment at the original attachment point. MATERIALS AND METHODS: From August 2011 to February 2014, 23 knees were diagnosed as ramp lesion, underwent meniscal repair using FasT-Fix technique. RESULTS: All patients were followed up for average 14 months. The Lysholm score improved from preoperative 64.4±4.52 to postoperative 91.2±4.60. CONCLUSIONS: We believe that the FasT-Fix technique via the standard anterior portal can be a more convenient and less traumatic alternative for repair of the peripheral attachment lesion of the posterior horn of the medial meniscus in the anterior cruciate ligament deficient knee.