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This study was conducted to evaluate the curing temperature effect on the mechanical properties of high-strength strain-hardening cementitious composite (SHCC) containing waste supplementary cementitious materials (SCMs) and polyethylene (PE) fibers. High-strength SHCC is developed to extend the strain-hardening interval by simultaneously inducing multiple cracks and ensuring the durability and strength of high-strength concrete. The starting point of this study was to enhance the tensile performance and durability of high-strength SHCC by utilizing various SCMs. In addition, the optimal curing conditions were investigated to derive the maximum material potential of each SCM, which aims to advance the performance of high-strength SHCC. The temperatures employed for the curing process were 20, 40, and 90°C. Moreover, ground granulated blast-furnace slag (GGBS), silica fume (SF), and cement kiln dust (CKD), were used as a partial replacement for cement to determine the best mix for achieving optimal tensile performance. Four mix designs were prepared, including a plain test specimen composed entirely of cement as binder; therefore, a total of 12 types of specimens were set considering the three curing temperatures. A compressive strength test was conducted with cube specimens, and a direct tensile test was performed with dog-bone-shaped specimens. Derivative thermogravimetry (DTG) and energy dispersive X-ray spectroscopy (EDS) mapping were conducted to identify the microstructures. The SF-containing SHCC cured at 90°C exhibited the best tensile performance in terms of deformability and energy absorption capacity by achieving the highest strain capacity of 4.37% and g-value of 294.5 kJ/m3. In addition, the performance of each specimen was reconfirmed based on the DTG, EDS mapping, and crack pattern results. Through these results, the optimal SCM mixing amount and curing conditions that led to noticeable performance improvement of high-strength SHCC were identified.

In this study, titanium dioxide (TiO2) and polyethylene (PE) fibers were employed to develop photocatalytic high-performance fiber-reinforced cement composites (HPFRCCs). To achieve high NOx removal capacity, it was necessary to confirm the dispersion of the TiO2 powder. For this purpose, various amounts of viscosity-modifying agent (VMA), ranging from 0% to 1% by weight to cement, were considered along with two types of white Portland cement: Union and Aalborg. Additionally, the PE fiber surface was modified via cold gas plasma and chromic acid treatment to improve the tensile performance of the HPFRCCs. The experimental results indicated that the plastic viscosity of the mortar increases with the addition of VMA. Optimum NOx removal capacities of 5.72 and 8.10 μmol were respectively achieved for the Aalborg and Union cement types in the mortar at a VMA content of 0.5%. The compressive strength of the tested photocatalytic HPFRCC was approximately 72.7–91.8 MPa. In the case of the hybrid argon (Ar) and oxygen (O2) gases being subjected to plasma treatment, optimum tensile performance—in terms of tensile strength, strain capacity, and g-value—was achieved, whereas the samples subjected to chromic acid treatment exhibited poorer tensile performance. Moreover, the single Ar–or O2-gas-based plasma treatment yielded an intermediate tensile performance. The cracking behavior showed trends similar to those of the g-value: the hybrid plasma treatment produced the most microcracks because of its high fiber bridging capacity.

In this study, an attempt was made to investigate the effect of end-hook angle on the rate-dependent bond-slip behavior of novel half-hooked steel fibers embedded in ultra-high-performance concrete (UHPC). For evaluating the effects of the number of plastic hinges and length in the end-hook portion, commercially available hooked steel fiber and short half-hooked steel fiber were additionally used. Three different end-hook angles of 30°, 45°, and 60°, two different fiber inclination angles of 0° and 45° to take into account the random orientation of fibers in the composites, and various loading rates ranging from 0.018 mm/s (static) to 1186 mm/s (impact) were considered. Test results indicated that the most influential factor on the static pullout resistance in terms of the bond strengths and pullout energy was the length in the end-hook portion rather than the number of plastic hinges and end-hook angle if the fibers were pulled out without breakage. Increasing the end-hook angle was effective in enhancing the static and dynamic bond strengths and pullout energies of half-hooked fibers in UHPC given the pullout failure mode, and there was no effect of it if they were ruptured. In addition, the increase in length in the end-hook portion significantly improved the static bond strength and pullout energy in the aligned condition, whereas its effectiveness decreased under the impact loads. The use of half-hooked fiber or shorter length in the end-hook portion was effective in terms of the rate sensitivity to the pullout resistance compared with the commercial hooked fiber or the longer-length one, and the bond strength became more sensitive to the loading rate if the fiber was aligned rather than inclined.

The effects of carbon fiber and its surface treatment through chemical solutions on the mechanical properties and electromagnetic (EM) shielding of ultra-high-performance fiber-reinforced concrete (UHPFRC) were analyzed. Three types of carbon fibers chemically treated with sodium hydroxide, nitric acid, and ammonia solutions were evaluated, along with a plain carbon fiber control sample, at two different concentrations of 0.1% and 0.3% by weight. The surface of carbon fiber was oxidized by chemical solutions. The conductivity of UHPFRC increased with increasing the carbon fiber content, and slightly better conductivity was obtained using the chemically treated carbon fibers than plain fibers at the lower content of 0.1 wt%. Both steel and carbon fibers were effective at improving the shielding effectiveness of ultra-high-performance concrete, and a higher shielding effectiveness was achieved for higher carbon fiber content. Surface treatment using the nitric acid solution was the most effective at enhancing the tensile performance and EM shielding effectiveness, and the best shielding effectiveness (49.0 dB at 1 GHz) was achieved for UHPFRC with 0.1 wt% nitric acid treated carbon fibers. The shielding effectiveness was found to be generally proportional to the electrical conductivity, although its increase was minor relative to that of the conductivity.

The drop-weight impact behavior of the ductility enhanced high-strength strain-hardening cementitious composites (dHS-SHCC) is compared to that of conventional reactive powder concrete (RPC) to validate its super-impact resistance. All materials have an identical fiber volume fraction of 2%. The compressive strengths of RPC and dHS-SHCC are approximately 210 and 115 MPa, respectively. RPC has the highest ultimate tensile strength of 17.9 MPa, while the developed dHS-SHCC has the highest tensile strain capacity and energy absorption capacity up to the peak ( g -value) of 5.9% and 526.0 kJ/m3 , respectively. It also absorbs 3.2 times higher energy up to the peak under flexure (toughness) as compared to that of RPC. The RPC beams completely fail upon impact of a drop hammer with a potential energy of 490 J. However, the dHS-SHCC beams are only partially damaged along with multiple microcrack formations and rebounds. Moreover, it produces at least four times the microcracks and is more sensitive to the strain-rate than those of RPC. Consequently, it can be determined that using developed dHS-SHCC is effective in resisting impact loads as compared to RPC.

The modified Broström procedure (MBP) is widely accepted as the primary operative treatment for chronic lateral ankle instability (CLAI). However, the MBP does not produce good clinical results in all patients, and anatomic reconstruction using a free tendon graft may be considered in those patients. The purpose of this study was to evaluate the efficacy of the MBP using distal fibular periosteal flap augmentation for CLAI in patients who were not candidates for standard repair.Thirty-eight patients (39 ankles) who underwent surgery for CLAI were retrospectively analyzed. The patients were divided into 2 groups: an anatomic lateral ligament reconstruction group (reconstruction group) consisting of 17 ankles and an MBP group using distal fibular periosteal flap augmentation (augmentation group) consisting of 22 ankles. Preoperative and postoperative clinical evaluations were performed using the visual analog scale (VAS), American Orthopaedic FootAnkle Society (AOFAS), and Karlsson-Peterson (Karlsson) scores.The mean VAS, AOFAS, and Karlsson scores significantly improved from 4.0 to 1.8, 54.7 to 92.9, and 46.4 to 92.7, respectively, in the reconstruction group ( P.001, P.001, P.001), and from 4.1 to 1.5, 60.1 to 94.9, and 52.6 to 94.1, respectively, in the augmentation group ( P.001, P.001, P.001). There were no significant differences in the mean postoperative AOFAS and Karlsson scores between the groups ( P = .214, P = .299).The MBP using distal fibular periosteal flap augmentation was also an effective option for CLAI in cases of generalized ligament laxity, severe attenuation of the soft tissue, previous failed surgery, high demand activity, and obesity.Level III, comparative series.

To improve the tensile performance and sustainability of high-strength strain-hardening cementitious composites (SHCC), waste cement kiln dust (CKD) was used, replacing 30% of ordinary Portland cement (PC), and polyethylene (PE) fibers were modified through chromic acid and plasma treatments. The chemical structure and morphology of the PE fiber surface were modified by exposure to chromic acid and plasma treatment with two gas types, argon (Ar) and oxygen (O2), at various power levels and frequencies. The effect of surface treatment method on enhancing the tensile performance of SHCC was investigated. The surface oxidation and increased roughness of the fibers were verified through X-ray photoelectron spectroscopy and atomic force microscopy analyses. The oxygen/carbon atomic ratio and surface roughness of the PE fibers increased by up to 5.3 and 2.4 times, respectively, by the O2 gas plasma treatment. With 30% of PC replaced by CKD, 12% higher energy absorption capacity prior to tension softening could be obtained. The tensile ductility and energy absorption capacity of SHCC were significantly enhanced by using PE fibers treated with chromic acid for 10 min, approximately 145% and 64%, respectively, although its tensile strength decreased. The Ar-gas plasma effectively improved the compressive strength and tensile performance of the SHCC relative to the O2-gas plasma given an identical power level and frequency. The SHCC containing O2-plasma-treated fibers under 300 W and 40 kHz exhibited the best tensile performance and absorbed the highest energy of 310 kJ/m3, approximately two to five times greater than those of ordinary SHCC materials.

This study aims to develop a novel type of ultra-high-performance fiber-reinforced concrete (UHPFRC) with excellent mechanical properties and nitrogen oxide (NOx) removal capability. To achieve this, an inert filler, silica flour, was replaced with titanium dioxide (TiO2), which is known as a photocatalyst. The test results indicated that the average bond strength of a straight steel fiber embedded in ultra-high-performance concrete (UHPC) increased by replacing the silica flour with TiO2 powder up to 75% in general. Approximately 53% and 63% higher bond strengths and pullout energies, respectively, were thus achieved at 50% replacement rate. The tensile properties of UHPFRC were improved by TiO2, and its tensile strength slightly increased, while the strain capacity and g-value substantially increased. The energy absorbing capacity increased by as much as 78% due to the addition of TiO2 powder. Furthermore, the plain sample exhibited almost zero NOx removal efficiency, but increased with the replacement ratio of TiO2 powder up to 75%. The best NOx removal capability in the UHPC sample containing 75% TiO2 powder was thus 7.7 times higher than that of the plain sample.

Single fiber pullout behavior has been investigated extensively at various embedment lengths, and to generalize the test results of the existing studies, the implication of embedment length on the pullout behavior needs to be analyzed. To this end, experiments were conducted with two types of steel fibers in ultra-high-performance concrete (UHPC) at three embedment lengths and two inclination angles. The effect of embedment length on the pullout behavior was more significant in the half-hooked fiber than the straight one. Its pullout performance was also better than that of the straight fiber up to an embedment length of 10 mm; however, the effectiveness decreased with an increase in the embedment length. At the longest embedment length of 15 mm, the pullout energy and equivalent bond strength obtained for the half-hooked fiber samples were poorer than those obtained for the straight fibers. Therefore, its maximum length is suggested to be below 30 mm at a diameter of 0.375 mm to prevent premature rupture in UHPC.

Gradual wear and tear can cause a local inflammatory response in tendons. The trauma and inflammatory reaction eventually impair the biomechanical properties of the tendon. In this study, we prepared lactoferrin-immobilized, heparin-anchored, poly(lactic-co-glycolic acid) nanoparticles (LF/Hep-PLGA NPs) and evaluated their in vitro anti-inflammatory effects on interleukin-1β (IL-1β)-treated tenocytes and in vivo tendon healing effects in a rat model of Achilles tendinitis. Long-term LF-deliverable NPs (LF/Hep-PLGA NPs) remarkably decreased mRNA levels of pro-inflammatory factors [cyclooxygenase-2 (COX-2), IL-1β, matrix metalloproteinase-3 (MMP-3), MMP-13, IL-6, and tumor necrosis factor-α (TNF-α)] and increased mRNA levels of anti-inflammatory cytokines (IL-4 and IL-10) in both IL-1β-treated tenocytes and the Achilles tendons of a collagenase-induced Achilles tendinitis rat model. Interestingly, anti-inflammatory LF/Hep-PLGA NPs greatly enhanced collagen content, mRNA levels of tenogenic markers [collagen type I (COL1A1), decorin (DCN), tenascin-C (TNC)], and biomechanical properties such as tendon stiffness and tensile strength. These results suggest that anti-inflammatory LF/Hep-PLGA NPs are effective at restoring tendons in Achilles tendinitis.

This study aims to examine the mechanical, shrinkage and chemical properties of photocatalytic cementitious materials containing synthetic fibers and a shrinkage-reducing admixture (SRA). Two types of titanium dioxide (TiO2) powders and white Portland cement were considered along with ordinary Portland cement (OPC) as a control. Two types of synthetic fibers, i.e., glass and polyethylene (PE), and an SRA with contents varying from 0% to 3% were also considered. Using the TiO2 powders and the white Portland cement was effective in reducing the nitrogen oxides (NOx) concentration in cement composites. The use of PE fibers was more effective than glass fibers in terms of the mechanical properties, i.e., the compressive strength and tensile performance. With the addition of TiO2 powders and SRA or the replacement of OPC with white cement, the mechanical properties of the cement mortar generally deteriorated. The total shrinkage of the mortar could be reduced by incorporating the fibers at volume fractions greater than 1%, and the glass fiber was more effective than the PE fiber in this regard. The TiO2 powders had no significant impact on the shrinkage reduction of the cement mortar, whereas the SRA and the white Portland cement effectively reduced shrinkage. The addition of 3% SRA decreased the total shrinkage by 43%, while the replacement of the OPC with white cement resulted in a 20% reduction in the shrinkage.

Background: To assess the clinical outcomes of short-term oral corticosteroid therapy for impingement syndrome of the shoulder and determine whether it can be substituted as an alternative to the intra-articular injection. Methods: The clinical outcomes of the 173 patients, the oral steroid group (n=88) and the injection group (n=85), were measured at 3 weeks, 2, 4, and 6 months postoperatively. The clinical outcomes were assessed by measuring the the University of California at Los Angeles (UCLA) score, visual analog scale (VAS) and range of motion (ROM) at every follow-up. Any complications and recurrence rate were noted. A relationship between the treatment outcomes and factors such as demographic factors, clinical symptoms and radiographic findings were determined. Results: No difference was observed in VAS and UCLA scores between the two groups, but forward flexion and internal rotation of ROM were significantly improved in the injection group at the 2nd and 4th postoperative month (p < 0.05). At 6th postoperative month, recurrence rate of symptoms was 26% in the oral steroid group and 22% in the injection group. No major adverse effects were observed. When the clinical outcomes of the oral steroid group were compared to either demographic, clinical symptoms, or radiographic findings, UCLA score was found to be significantly low (p < 0.05) in patients with joint stiffness and UCLA score, whereas VAS score was significantly improved in patients with night pain (p < 0.05). Conclusions: Short-term low-dose oral corticosteroid therapy of impingement syndrome showed comparable clinical outcomes to intraarticular injection without any remarkable adverse effects. Low-dose oral steroids can be regarded as a partial alternative to intra-articular injection for the initial therapy of impingement syndrome of the shoulder. (Clin Shoulder Elb 2014;17(2):50-56)

We performed a single-center, randomized, double-blind study to compare muscle strength in patients who had undergone primary total knee arthroplasty (TKA), performed using either a minimally invasive or a conventional surgical technique. We evaluated 30 knees in healthy age-matched subjects, 22 knees after conventional TKA (conventional group), and 23 knees after minimally invasive surgery TKA (MIS group). The Hospital for Special Surgery (HSS) score, Oxford knee score (OKS), and isokinetic (60º/s) muscle strength were evaluated the day before surgery and 3, 6, and 12 months after surgery. HSS and OKS improved significantly over time during follow-up (p0.001), but there was no significant difference between the groups (p0.05). The extensor peak torque (EPT) and flexor peak torque (FPT) improved significantly over time (p0.001) and EPT was greater in the MIS group than in the conventional group during the follow-up period (p0.05). There was no difference in FPT and the hamstring-to-quadriceps ratio between the groups. Although MIS patients had a significant deficit in extensor strength following TKA, compared with healthy controls, this approach offers a significant improvement in extensor muscle strength over conventional surgery. These results suggest that the MIS approach results in better outcomes with regard to maintaining extensor strength than the conventional surgical approach.

Background The results of operative treatments for symptomatic accessory navicular are debatable. In some cases, recurrent pain may develop after the Kidner procedure. The purpose of this study is to review the reasons for recurrent pain after the Kidner procedure and to suggest possible options for revision surgery. Methods We reviewed the clinical and radiological outcomes in 9 patients who underwent revision surgery for recurrent pain after the Kidner procedure. During the revision surgery, the tibialis posterior tendon was reattached to the navicular either by advancing the tendon in 4 patients or by lengthening the tendon in another 4 patients. In the other 1 patient, the flexor digitorum longus tendon was transferred. Surgeries for the accompanying deformities were performed simultaneously in all patients. The results were evaluated using the American Orthopaedic Foot and Ankle Society ankle-hindfoot score and a visual analog scale. The mean follow-up was 2.3 years (range, 1 to 5 years). Results The mean American Orthopedic Foot and Ankle Society ankle-hindfoot score improved from 71.25 to 81.50 in the advancement group, and 71.75 to 90.00 in the lengthening group. The mean visual analog scale improved from 7.75 to 4.25 in the advancement group and from 7.50 to 1.75 in the lengthening group. Conclusions Recurrent pain after the Kidner procedure was associated with pes planovalgus or hindfoot valgus deformity. In revision surgery, correction of the associated deformities and reattachment of the tibialis posterior tendon after lengthening may need to be considered.