In this study, the dynamic responses of a riser under the combined excitation of internal waves and background currents are studied. A modified Taylor-Goldstein equation is used to calculate the internal waves vertical structures when background currents exist. By imposing rigid-lid boundary condition, the equation is solved by Thompson-Haskell method. Based on the principle of virtual work, a nonlinear differential equation for riser motions is established combined with the modified Morison formula. Using Newmark-β method, the motion equation is solved in time domain. It is observed that the internal waves without currents exhibit dominated effect on dynamic response of a riser in the first two modes. With the effects of the background currents, the motion displacements of the riser will increase significantly in both cases that wave goes along and against the currents. This phenomenon is most obviously observed at the motions in the first mode
To compare the clinical efficacy between percutaneous vertebroplasty (PVP) and percutaneous kyphoplasty (PKP) in the treatment of Kümmell’s disease in Chinese patients.
The studies using randomized controlled trials to compare clinical efficacy between PVP and PKP in the treatment of Kümmell’s disease in Chinese patients were retrieved from Embase, Pubmed, Central, Cinahl, PQDT, CNKI, CQVIP, Wanfang Data, and CBM (from September 2008 to September 2018). Keywords for both Chinese and English search were: percutaneous vertebroplasty, PVP, percutaneous kyphoplasty, PKP, and Kümmell’s disease. A total of 132 articles were retrieved based on the search strategy through online database searching and manual searching. Finally, one foreign report and seven Chinese reports were included. After extracting the data, statistical software Review Manager 5.3 was used for data analysis.
Through comparison, Cobb angle (95% CI [0.54, 4.42), P = 0.01] and Oswestry Dysfunction Index (ODI) (95% CI [0.21, 2.15], P= 0.02) of PKP group was smaller than that of PVP group. Postoperative anterior vertebral body height of the PKP group was better than PVP group (95% CI [−1.27, −0.66], P < 0.001]. However, the PVP group had shorter operation time than PKP group (95% CI [−13.48, −7.43), P = 0.001]. In the other outcome measures, including Visual Analogue Scale (VAS) score (95% CI [−0.04, 0.27), P = 0.15), cement volume (95% CI [−0.82, 0.32], P = 0.39) and cement leakage (95% CI [0.90, 2.76], P = 0.11), there was no significant differences between the two procedures.
At this stage, there is sufficient evidence to support that PKP is better than PVP in the treatment of Kümmell’s disease in Chinese patients. Although PVP surgery requires much less operation time, PKP has better postoperative radiological results and lower ODI. Moreover, both of them had similar clinical results (e.g., analgesic effects, cement dosage, and leakage rate). Further evidence is dependent on the emergence of randomized controlled trials with higher quality and larger sample sizes in the future.