The Study on Fatigue Crack Growth Rate of 4130X Material under Different Hydrogen Corrosion Conditions.

In this paper, the fatigue crack growth rates of typical pressure vessel material 4130X under different corrosion conditions are investigated, and the effects of corrosion modes and loading frequency on the fatigue crack growth rate of 4130X are discussed. The results show that under the same loading conditions, the pre-corroded crack propagation rate is increased by 1.26 times compared with the uncorroded specimens. The plastic deformation mechanism of the crack tip in air is dominated by phase transformation but the hydrogen introduced by pre-corrosion causes a small number of dislocations at the crack tip. The crack growth rate obtained by corrosion fatigue is four times that of the uncorroded specimen, and the fracture surface shows a strong corrosion effect. The molecular dynamics simulation shows that the hydrogen atoms accumulated at the crack tip make the plastic deformation mechanism dominated by dislocation in the crack propagation process, and the coupling interaction between low frequency and the corrosion environment aggravates the hydrogen embrittlement of the crack tip. In the air condition, the loading frequency has no obvious effect on the crack growth rate: when the frequency decreases from 100 Hz to 0.01 Hz and other conditions remain unchanged, the fatigue crack growth rate increases by 1.5 times. The parameter n in the Paris expression is mainly influenced by frequency. The molecular dynamics simulation shows that low frequency promotes crack tip propagation.

Percutaneous versus open pedicle screw instrumentation in treatment of thoracic and lumbar spine fractures: A systematic review and meta-analysis.

BACKGROUND: To assess the safety and efficacy of percutaneous short-segment pedicle instrumentation compared with conventionally open short-segment pedicle instrumentation and provide recommendations for using these procedures to treat thoracolumbar fractures. METHODS: The Medline database, Cochrane database of Systematic Reviews, Cochrane Clinical Trial Register, and Embase were searched for articles published. The randomized controlled trials (RCTs) and non-RCTs that compared percutaneous short-segment pedicle instrumentation to open short-segment pedicle instrumentation and provided data on safety and clinical effects were included. Demographic characteristics, clinical outcomes, radiological outcomes, and adverse events were manually extracted from all of the selected studies. Methodological quality of included studies using Methodological Index for Non-Randomized Studies scale and Cochrane collaboration's tool for assessing the risk of bias by 2 reviewers independently. RESULTS: Nine studies encompassing 433 patients met the inclusion criteria. Subgroup meta-analyses were performed according to the study design. The pooled results showed there were significant differences between the 2 techniques in short- and long-term visual analog scale, intraoperative blood loss, operative time, postoperative draining loss, hospital stay, and incision size, although there were no significant differences in postoperative radiological outcomes, Oswestry Disability Index, hospitalization cost, intraoperative fluoroscopy time, and adverse events. CONCLUSION: Percutaneous short-segment pedicle instrumentation in cases with achieve satisfactory results, could replace in many cases extensive open surgery and not increased related complications. However, further high-quality RCTs are needed to assess the long-term outcome of patients between 2 techniques.

Long noncoding RNA HOXD-AS1 aggravates osteosarcoma carcinogenesis through epigenetically inhibiting p57 via EZH2.

Osteosarcoma is the most common primary malignant bone tumor and long non-coding RNAs (lncRNAs) have been proved to epigenetically regulate the oncogenesis of osteosarcoma. In this research, we investigate the role of lncRNA HOXD-AS1 on the osteosarcoma oncogenesis. Results revealed that HOXD-AS1 expression level was significantly up-regulated in osteosarcoma tissue and cells, moreover, the aberrant overexpression predicted the poor prognosis of osteosarcoma patients. Loss-of-functional experiments indicated that HOXD-AS1 silencing inhibited the osteosarcoma cells proliferation and induced G1/G0 phase arrest in vitro, and repressed tumor cell growth in vivo. Mechanistic investigations showed that HOXD-AS1 epigenetically repressed p57 through recruiting enhancer of zeste homolog 2 (EZH2) to the promoter of p57. Rescue experiments revealed that p57 could recover the oncogenic role of HOXD-AS1 on osteosarcoma. In conclusion, our study confirmed that HOXD-AS1 could interact with EZH2, and then repress p57 expression, to aggravate osteosarcoma oncogenesis. which provide new idea for the osteosarcoma tumorigenesis.

Imaging-Assisted Diagnosis and Characteristics of Suspected Spinal Brucellosis: A Retrospective Study of 72 Cases.

BACKGROUND We clarified the imaging features of Brucella spondylitis to enhance our understanding of the disease and to minimize misdiagnosis. MATERIAL AND METHODS Imaging data (X-ray, computed tomography [CT], and magnetic resonance imaging [MRI] data) of 72 Brucella spondylitis patients treated from 2010 to 2017 were retrospectively analyzed; diagnoses was made by evaluating laboratory and pathological data. RESULTS X-ray films revealed changes in intervertebral space heights, the number of lateral osteophytes, and bone destruction, which were more severe in the following order: lumbosacral vertebrae (56 cases, 77.8%), cervical spine (6 cases, 8.3%), thoracic spine (5 cases, 6.9%), and multi-segmental mixed vertebrae (5 cases, 6.9%). CT revealed osteolytic destruction attributable to early-stage Brucella spondylitis (endplate and vertebral lamellar osteolysis), usually associated with multiple vertebral involvement, with the middle and late disease stages being characterized by osteophytes in the vertebral margins and bony bridges, endplate sclerosis, and vertebral osteosynthesis. We encountered 54 cases (75%) with endplate lamellar osteolysis, 37 (51.4%) with vertebral lamellar osteolysis, 59 (81.9%) with marginal osteophytes, 10 (13.9%) with bony bridges, 25 (34.7%) with vertebral laminar sclerosis, and 17 (23.6%) with vertebral osteosynthesis. MRI revealed early, low-intensity, differential T1WI vertebral and intervertebral signals, with occasional iso-signals, T2WI iso-signals or high-intensity signals; and T2WI-FS vertebral and intervertebral high-intensity signals, commonly from vertebral soft tissues and rarely from paravertebral abscesses. CONCLUSIONS A better understanding of the X-ray, CT, and MRI features of Brucella spondylitis could aid in diagnosis when combined with epidemiological and laboratory data, thus minimizing misdiagnosis.

Incidence and risk factors for infection in spine surgery: A prospective multicenter study of 1764 instrumented spinal procedures.

BACKGROUND: Surgical site infection (SSI) is a common complication in spinal surgery, imposing a high burden on patients and society. However, information about its characteristics and related risk factors is limited. We designed this prospective, multicenter study to address this issue. METHODS: From January 2015 through February 2016, a total of 1764 patients who had spinal trauma or degenerative spinal diseases were treated with instrumented surgeries and followed up for 1 year with complete data. Data on all patients were abstracted from electronic medical records, and SSIs were prospectively inspected and diagnosed by surgeons in our department. Any disagreement among them was settled by the leader of this study. SPSS 19.0 was used to perform the analyses. RESULTS: A total of 58 patients (3.3%, 58 of 1764) developed SSI; 1.1% had deep SSI, and 2.2% had superficial SSI. Of these, 60.6% (21 of 33) had a polymicrobial cause. Most of them (51 of 58) occurred during hospitalization. The median occurrence time was 3 days after operation (range: 1-123 days). SSI significantly prolonged hospital stays, by 9.3 days on average. The univariate analysis revealed reason for surgery as the only significant risk factor. The multivariate analysis, however, revealed 8 significant risk factors, including higher BMI, surgical site (cervical), surgical approach (posterior), surgery performed in summer, reasons for surgery (degenerative disease), autograft for fusion and fixation, and higher preoperative platelet level. CONCLUSION: Identification of these risk factors aids in stratifying preoperative risk to reduce SSI incidence. In addition, the results could be used in counseling patients and their families during the consent process.