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Unilateral biportal endoscopic (UBE) spine surgery for spinal diseases has been increasing in popularity because of its favorable outcomes. The goal of this systemic review is to analyze the status of outcomes and complications in lumbar disc herniation during UBE discectomy.A comprehensive search of the PubMed, Embase, Web of Science, and OVID databases published until June 30, 2021, was performed. The outcomes of interest were indications, operative time, blood loss, hospital stay, complications, visual analog scale score, and Oswestry Disability Index.Seven studies were included in our research. UBE surgery for lumbar stenosis was excluded. A total of 230 patients with lumbar disc herniation were enrolled in the 7 selected studies. The mean operative time was 74.4 minutes, and the mean length of hospital stay was 4.5 days. Mean incidence of complications reported in the 7 articles was 6.2%. UBE showed shorter hospital stays than did microdiscectomy, no significant differences of Oswestry Disability Index or visual analog scale scores, and good recovery rate among other discectomy techniques (microdiscectomy, full endoscopic transforaminal endoscopic lumbar discectomy, and interlaminar endoscopic lumbar discectomy) at 1 month follow-up.Even with the small number of studies and reports analyzed, biases were the main limitation of this analysis; overall, the clinical outcomes and complication rates associated with UBE discectomy were relatively good. It is clear that UBE discectomy is a good treatment choice for lumbar disc herniation, but to prevent unique UBE surgery complications, a clear understanding of the surgical procedures and careful efforts to overcome the learning curve are necessary.

Objective: This study aimed to evaluate the radiologic and clinical outcomes of minimally invasive transforaminal lumbar interbody fusion (MIS-TLIF) and conventional posterior lumbar interbody fusion (PLIF) at the L5–S1.Methods: We retrospectively reviewed patients who underwent posterior lumbar fusion (MIS-TLIF and PLIF) at only the L5–S1 and were followed up for more than 12 months. Age, sex, body mass index (BMI), bone mineral density (BMD), diagnosis, comorbid conditions, fusion rate, perioperative results, and pre- and postoperative radiographic parameters at the L5–S1 level, pelvic parameters and degree of spondylolisthesis, and clinical results were analyzed.Results: A total of 102 patients (46 male, 56 female) with a mean age of 57.1 years were evaluated. Fifty and fifty-two patients underwent MIS-TLIF and PLIF surgeries, respectively. Radiologic parameters increased from their preoperative measures at the last follow-up study; similarly, there were no intergroup differences. The fusion rates in the MIS-TLIF and PLIF groups were 86% and 82.7%, respectively. The subsidence rates in the MIS-TLIF and PLIF groups were 6% and 3.8%, respectively. There was no intergroup difference in terms of fusion rate and subsidence. Clinical outcomes also gradually improved after surgery in both groups without intergroup differences.Conclusion: In L5–S1 posterior spinal surgery, there was no significant difference between MIS-TLIF and conventional PLIF. Considering the operation time and estimated blood loss, MIS-TLIF is more effective than PLIF surgery in terms of postoperative health care and economics.

OBJECTIVE Mechanical complications should be considered following the correction of multilevel posterior cervical instrumented fusion. This study aimed to investigate clinical data on the patients’ pre- and postoperative cervical alignment in terms of the incidence of mechanical complications after multilevel posterior cervical instrumented fusion. METHODS Between January 2008 and December 2018, 156 consecutive patients who underwent posterior cervical laminectomy and instrumented fusion surgery of 4 or more levels and were followed up for more than 2 years were included in this study. Age, sex, bone mineral density (BMD), BMI, mechanical complications, and pre- and postoperative radiographic factors were analyzed using multivariate logistic regression analysis to investigate the factors related to mechanical complications. RESULTS Of the 156 patients, 114 were men and 42 were women; the mean age was 60.38 years (range 25–83 years), and the mean follow-up duration of follow-up was 37.56 months (range 24–128 months). Thirty-seven patients (23.7%) experienced mechanical complications, and 6 of them underwent revision surgery. The significant risk factors for mechanical complications were low BMD T-score (−1.36 vs −0.58, p = 0.001), a large number of fused vertebrae (5.08 vs 4.54, p = 0.003), a large preoperative C2–7 sagittal vertical axis (SVA; 32.28 vs 23.24 mm, p = 0.002), and low preoperative C2–7 lordosis (1.85° vs 8.83°, p = 0.001). The clinical outcomes demonstrated overall improvement in both groups; however, the neck visual analog scale, Neck Disability Index, and Japanese Orthopaedic Association scores after surgery were significantly worse in the mechanical complication group compared with the group without mechanical complications. CONCLUSIONS Low BMD, a large number of fused vertebrae, a large preoperative C2–7 SVA, and low C2–7 lordosis were significant risk factors for mechanical complications after posterior cervical fusion surgery. The results of this study could be valuable for preoperative counseling, medical treatment, or surgical planning when multilevel posterior cervical instrumented fusion surgery is performed.

Hydrogen can provide pure and clean energy; however, to use it as an energy source, facilities such as hydrogen carriers and recharging stations need to be constructed. Structural steels are affected by hydrogen embrittlement (HE), and their susceptibility to this needs to be investigated prior to their use in construction. Most structural steels are normally fabricated using thermomechanical controlled processing, which produces a large dislocation density to increase strength. This study investigated the prestrain effect on HE susceptibility of EH 36 steels using thermal desorption spectroscopy (TDS) and in situ slow-strain-rate testing. Hydrogen was electrochemically charged into specimens, and the reversible hydrogen content and that relating to trap sites were measured using TDS. With an increase in prestrain, there was increase in the diffusible hydrogen content; furthermore, with hydrogen charging, there was a drastic reduction in total elongation with an increase in prestrain. In addition, there was an increase in HE susceptibility with an increase in prestrain compared to when an air condition was employed. Specifically, there was an abrupt increase in HE sensitivity at a prestrain value between 10 and 15%; strain hardening was more dominant below a prestrain value of 10%; and HE was more dominant above a prestrain value of 15% for EH 36 steels.

This study investigates the effect of stainless steel (STS) 308 L and high-entropy alloy (HEA) filler metals on gas tungsten arc (GTA) welding. The weldability of the cast CoCrFeMnNi HEAs was determined based on the microstructural and mechanical properties of the welds. The cast HEA exhibited larger dendrite packets than the weld metals (WMs). The hardness in the WM was superior compared with that in the base metal (BM). The WM using STS 308 L exhibited a fully face-centred cubic (FCC) structure with no indication of δ-ferrite and lower hardness than that using HEA filler. The GTA welds using both fillers showed tensile properties comparable to the cast BM at 298 K, and the tensile fracture of the transverse welds occurred near the cast BM. The cryogenic tensile properties in the GTA welds were superior compared with the room-temperature property due to the significant formation of deformation twins and high dislocation density at 77 K. This was probably due to the decrease in the stacking fault energy at the cryogenic temperature compared with that at the room temperature. Therefore, it is possible to apply commercial STS 308 L filler metal for the CoCrFeMnNi HEA in cryogenic applications.

The material behaviors of two types of bearing steels at hot working conditions are investigated. Stress-strain curves at various temperatures (900–1300°C) and strain rates (1–50/s) are obtained by compression tests with a computer controlled servo-hydraulic Gleeble 3800 testing machine. Elongation and reduction of the area are also obtained by tensile tests with the Gleeble 1500 testing machine. Flow stresses are calculated from the experiments and are used to predict the temperature distribution and the metal flow of a workpiece during a multistage hot forging process of a bearing race. A rigid-thermoviscoplastic finite element method is applied. The experimental and numerical results are summarized to reveal the reasons for internal crack formation.

In this paper, the stress-strain curves of bearing steels at hot working conditions are obtained by hot compression test with a computer controlled servo-hydraulic Gleeble 3800 testing machine and elongations and reductions of area of the bearing steels are also obtained by hot tensile test with a Gleeble 1500 testing machine. Experiments are conducted under the various strain-rates and temperatures and their results are used to obtain the flow stress information. A rigid thermo-viscoplastic finite element method is applied to the multi-stage hot forging process in order to predict temperature distribution of workpiece. The experimental results and the analysis results are used to obtain an optimal hot forging condition.