The goal of this study was to assess the efficacy of one-stage surgical management for children with spinal tuberculosis by anterior decompression, bone grafting, posterior instrumentation, and fusion. Between January 2002 and December 2006, 15 cases with spinal tuberculosis were treated with one-stage posterior internal fixation and anterior debridement. All cases were followed-up for an average of 30.3 months (range 12-48 months). The average neurological recovery in the patients was 0.93 grades on the scale of Frankel et al. (Paraplegia 7:179-192, 1969). The average preoperative kyphosis was 36 degrees (range 19-59 degrees ), and the average postoperative kyphosis was 23 degrees (range 15-38 degrees ) at final follow-up. At final follow-up, minimal progression of kyphosis was seen, with an average kyphosis of 27 degrees (range 16-40 degrees ). An average loss of correction of 4 degrees was seen at final follow-up. One-stage surgical management for children with spinal tuberculosis by anterior decompression, bone grafting, posterior instrumentation, and fusion was feasible and effective.

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Therapeutic study (systematic review and meta-analysis), Level I.

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OBJECTIVES:No studies have compared monoaxial and polyaxial pedicle screws with regard to the von Mises stress of the instrumentation, intradiscal pressures of the adjacent segment and adjacent segment degeneration.METHODS:Short-segment monoaxial/polyaxial pedicle screw fixation techniques were compared using finite element methods, and the redistributed T11-L1 segment range of motion, largest maximal von Mises stress of the instrumentation, and intradiscal pressures of the adjacent segment under displacement loading were evaluated. Radiographic results of 230 patients with traumatic thoracolumbar fractures treated with these fixations were reviewed, and the sagittal Cobb’s angle, vertebral body angle, anterior vertebral body height of the fractured vertebrae and adjacent segment degeneration were calculated and evaluated.RESULTS:The largest maximal values of the von Mises stress were 376.8 MPa for the pedicle screws in the short-segment monoaxial pedicle screw fixation model and 439.9 MPa for the rods in the intermediate monoaxial pedicle screw fixation model. The maximal intradiscal pressures of the upper adjacent segments were all greater than those of the lower adjacent segments. The maximal intradiscal pressures of the monoaxial pedicle screw fixation model were larger than those in the corresponding segments of the normal model. The radiographic results at the final follow-up evaluation showed that the mean loss of correction of the sagittal Cobb’s angle, vertebral body angle and anterior vertebral body height were smallest in the intermediate monoaxial pedicle screw fixation group. Adjacent segment degeneration was less likely to be observed in the intermediate polyaxial pedicle screw fixation group but more likely to be observed in the intermediate monoaxial pedicle screw fixation group.CONCLUSION:Smaller von Mises stress in the pedicle screws and lower intradiscal pressure in the adjacent segment were observed in the polyaxial screw model than in the monoaxial pedicle screw fixation spine models. Fracture-level fixation could significantly correct kyphosis and reduce correction loss, and adjacent segment degeneration was less likely to be observed in the intermediate polyaxial pedicle screw fixation group.

Commutation failure (CF) at the inverter side is one of the most common failures in the linecommutated converter-based high voltage direct current (LCC-HVDC) system. Effective prediction of CF helps to formulate and implement protection measures timely. Since abnormal commutation voltage and DC current are the main reasons causing CF, these two factors should be fully considered in CF prediction. In this paper, to consider the effect of commutation voltage distortion, the time-domain response of the commutation voltage Fourier coefficient is deduced based on the first-order circuit response. To consider the effect of DC current variation, the time-domain response of the DC current is derived by superimposing its steadystate component and transient component, respectively. Based on these two predictive value, the extinction angle (EA) during the commutation is calculated according to the commutation voltage-time area, and the criterion based on EA is proposed to predict the occurrence of CF. The simulation results of the test system built in the PSCAD/EMTDC demonstrate the effectiveness and validity of this method.

PVB, which resulted in lower cumulative dezocine doses and produced fewer side effects than PCA, can provide effective pain relief for patients undergoing video-assisted thoracic surgery.

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