Numerical Investigation on Air Film Fusion of Pressure-Equalizing Exhaust around Shoulder Ventilation of Submarine-Launched Vehicle

In order to study the influence of pressure-equalizing exhaust at the shoulder of a submarine-launched vehicle on the surface hydrodynamic characteristics, this paper establishes a numerical calculation method based on the VOF multiphase flow model, the standard RNG turbulence model and the overset mesh technology; the method compares the fusion characteristics of the air film at the shoulder of the underwater vehicle, as well as the distribution of surface pressure along the vehicle’s axial direction. The results show that the approximate isobaric zone derived from air film fusion can greatly improve the hydrodynamic characteristics of the vehicle, and the number of venting holes determines the circumferential fusion time of the air film. The greater the number of venting holes, the sooner circumferential fusion starts.

Contralateral radiculopathy after unilateral transforaminal lumbar interbody fusion: causes and prevention

Background Unilateral transforminal lumbar interbody fusion (TLIF) with a single cage can provide circumferential fusion and biomechanical stability. However, the causes and prevention of contralateral radiculopathy following unilateral TLIF remain unclear. Methods In total, 190 patients who underwent unilateral TLIF from January 2017 to January 2019 were retrospectively reviewed. Radiological parameters including lumbar lordosis, segmental angle, anterior disc height, posterior disc height (PDH), foraminal height (FH), foraminal width, and foraminal area (FA) were measured preoperatively and postoperatively. Preoperative and postoperative visual analog scale scores were also recorded. Results The incidence of contralateral radiculopathy after unilateral TLIF was 5.3% (10/190). The most common cause was contralateral foraminal stenosis. Unilateral TLIF could increase the lumbar lordosis, segmental angle, and anterior disc height but decrease the PDH, FA, and FH in patients with symptomatic contralateral radiculopathy. The intervertebral cage should be placed to cover the epiphyseal ring and cortical compact bone of the midline, and the disc height can be increased to enlarge the contralateral foramen. Conclusion The most common cause of contralateral radiculopathy is contralateral foraminal stenosis. Careful preoperative planning is necessary to achieve satisfactory outcomes. Improper unilateral TLIF will decrease the PDH, FA, and FH, resulting in contralateral radiculopathy.

Restoration of sagittal alignment in high-grade isthmic spondylolisthesis using the reverse Bohlman technique with anterior lumbar interbody fusion using a hyperlordotic cage at L4–5: illustrative case

BACKGROUND Circumferential fusion with or without reduction is the preferred treatment for high-grade isthmic spondylolisthesis. Reduction presents significant risk of neurological injury. The authors present one case in which the “reverse Bohlman” technique was used with the addition of a hyperlordotic interbody cage at L4–5 as a means to correct sagittal malalignment while avoiding the reduction of L5 on S1. OBSERVATIONS The patient was a 22-year-old woman with a long-term history of lower back pain and bilateral L5 radiculopathy secondary to high-grade isthmic lumbar spondylolisthesis. She underwent anterior lumbar interbody fusion using the reverse Bohlman technique plus a hyperlordotic interbody cage at L4–5, followed by decompression and posterior spinal instrumentation and fusion from L4 to the pelvis. At 2-year follow-up, she was found to have complete resolution of symptoms with clinical and radiographic evidence of fusion. Her spinopelvic parameters had significantly improved. LESSONS The reverse Bohlman technique with the addition of a hyperlordotic interbody cage at L4–5 is a potential alternative treatment method to correct sagittal malalignment while avoiding possible injury to the L5 nerve roots that can be seen in the reduction of high-grade isthmic spondylolisthesis.

Clinical and Radiological Outcomes in Patients of Isthmic Spondylolisthesis Treated with Transforaminal Lumbar Interbody Fusion - A Retrospective Cohort Study, New Delhi

BACKGROUND Operative treatment and fusion for isthmic spondylolisthesis can be achieved by various fusion techniques such as posterolateral fusion (PLF), anterior lumbar interbody fusion (ALIF), posterior lumbar interbody fusion (PLIF), transforaminal lumbar interbody fusion (TLIF) and circumferential fusion. The purpose of this study is to evaluate the clinical outcome and radiological correction achieved after TLIF and assess the correlation between them if any. METHODS This is a retrospective cohort study analysing 30 cases of adult isthmic spondylolisthesis who failed conservative treatment and were then treated with transforaminal lumbar interbody fusion between 2011 and 2013. The clinical follow-up was done with the modified Oswestry disability index (ODI) and visual pain analogue score (VPAS). For the radiological follow-up radiographs were taken and several radiographic parameters were noted and analysed. RESULTS The mean of the Oswestry disability index scores in all patients decreased from 67.73 to 13.1 at final follow up. Similarly, visual pain analogue score reduced from mean 8.43 to 1.76 at final follow up. The average anterolisthesis was significantly reduced from the preoperative 27.1 ± 14 % to 7.1 ± 5 % at final follow-up radiographs (P < 0.001). Segmental lordosis increased from a mean of 11.5 degrees to 15.7 degrees. The difference in slip angle was significant from preoperative -4.87 ± 4.8 degrees and - 7.23 ± 4.63 degrees on the initial postoperative and - 7.2 ± 4.57 degrees at final follow-up radiographs (P = 0.14 and 0.13 respectively). CONCLUSIONS Thus, adult isthmic spondylolisthesis can be safely and effectively treated by TLIF with significant clinical relief and decrease in disability. TLIF procedure in isthmic spondylolisthesis is capable of reducing the sagittal translation and restoring disc height. Also, sagittal alignment and lordosis can be restored to a large extent. KEYWORDS Spondylolisthesis, Pelvic Incidence, Sagittal Balance, TLIF

Effects and Safety of Lumbar Fusion Techniques in Lumbar Spondylolisthesis: A Network Meta-Analysis of Randomized Controlled Trials

Study Design: Network meta-analysis of randomized controlled trials. Objectives: Lumbar spondylolisthesis is a common indication for spinal fusion. Lumbar interbody fusion (LIF) is popular method to achieve arthrodesis, but previous syntheses usually used head-to-head comparison of 2 surgical methods, and no of them pooled analysis with high-quality. This network meta-analysis of randomized controlled trials was carried out to simultaneously compare fusion techniques in the treatment of lumbar spondylolisthesis. Methods: Three databases were searched for randomized controlled trials (RCTs) on this topic. After critical appraisal, fusion rate, overall adverse events, operative time, Oswestry Disability Index, and pain were extracted for analysis. We conduced network meta-analysis using contrast-based method. Primary outcomes were reported as risk ratio (RR) with 95% confidence interval (CI). Results: Fifteen RCTs (n = 992) met our eligibility criteria. The RCTs treated patients posterolateral fusion (PLF), posterior LIF (PLIF), transforaminal LIF (TLIF), minimally invasive (MIS) TLIF, extreme lateral LIF (XLIF), and circumferential fusion. The pooled estimate showed that circumferential fusion led to significantly higher fusion rate than PLF (RR = 2.15, 95%CI:1.41–3.28), PLIF (RR = 2.11, 95%CI:1.38–3.22), TLIF (RR = 2.13, 95%CI:1.39–3.27), MIS-TLIF (RR = 2.13, 95%CI:1.35–3.35), and XLIF (RR = 2.01, 95%CI: 1.25–3.22). Moreover, circumferential fusion exhibited the best balance in probability between fusion rate and adverse event rate. No evidence showed inconsistency or small-study effect in the results. Conclusions: Collectively, circumferential fusion might be worth to be recommended because it exhibits the best balance between fusion rate and overall adverse event. PLF is still an inferior procedure and requires shorter operative time.