BACKGROUND Percutaneous vertebroplasty(PVP)has been widely used in osteoporotic vertebral compression fracture(OVCF).Following surgery,the bone cement would be positioned permanently.However,in some cases of lumbar de...BACKGROUND Percutaneous vertebroplasty(PVP)has been widely used in osteoporotic vertebral compression fracture(OVCF).Following surgery,the bone cement would be positioned permanently.However,in some cases of lumbar degenerative disease,the cemented vertebrae needs to be fixed after decompression and fusion procedure.It is difficult to implant traditional pedicle screws into the cemented vertebrae because of the bone cement filling.At present,the main treatment strategy is to skip the cemented vertebra and conduct a long segment fixation.This article presents a cortical bone trajectory(CBT)fixation technique for cemented vertebrae.CASE SUMMARY PVP involving the L3 and L4 was performed in an 82-year-old man due to OVCF.During the surgery,bone cement leakage occurred,resulting in compression of the root of the right L3 nerve.We performed a partial facetectomy to retrieve the leaked bone cement and to relieve the patient’s neurological symptoms.After 3 mo,the patient developed lumbar disc herniation in L3/4,potentially due to instability caused by the previous surgery.Therefore,it was necessary to perform intervertebral fusion and fixation.It was difficult to implant traditional trajectory pedicle screws in L3 and L4 because of the bone cement filling.Hence,we implanted CBT screws in the L3 and L4 vertebrae.As a result,the patient’s symptoms resolved and he reported satisfaction with the surgery at follow-up after 8 mo.CONCLUSION It is feasible to utilize CBT in cemented vertebrae for the treatment of lumbar degenerative disease.展开更多
The flow field in the tip region of an axial ventilation fan is investigated with a particle image velocimeter （PIV） system at the design condition. Flow fields with three different tip clearances are surveyed on th...The flow field in the tip region of an axial ventilation fan is investigated with a particle image velocimeter （PIV） system at the design condition. Flow fields with three different tip clearances are surveyed on three different circumferential planes, respectively. The phase-locked average method is used to investigate the generation and the development of a tip leakage vortex. The result from PIV system is compared with that from a particle dynamics anemometer（PDA） system. Both data are in good agreement and the structure of the tip leakage vortex for the rotor is illustrated. The characteristic of a leakage vortex is described in both velocity vectors and vortical contours. The unsteadiness of the leakage vortex and the position of the vortex are surveyed in detail, which interprets the discrepancy between the numerical simulation and PDA experimental results to a certain extent. The center loci of tip leakage vortex at different times and the mean center loci of the leakage vortex are displayed particularly. Finally, the trajectories of the tip leakage vortex by the experimental measurement are compared with predictions from the existing models for high speed and high-pressure compressors and turbines when appropriately interpreted. A good agreement is obtained.展开更多
文摘BACKGROUND Percutaneous vertebroplasty(PVP)has been widely used in osteoporotic vertebral compression fracture(OVCF).Following surgery,the bone cement would be positioned permanently.However,in some cases of lumbar degenerative disease,the cemented vertebrae needs to be fixed after decompression and fusion procedure.It is difficult to implant traditional pedicle screws into the cemented vertebrae because of the bone cement filling.At present,the main treatment strategy is to skip the cemented vertebra and conduct a long segment fixation.This article presents a cortical bone trajectory(CBT)fixation technique for cemented vertebrae.CASE SUMMARY PVP involving the L3 and L4 was performed in an 82-year-old man due to OVCF.During the surgery,bone cement leakage occurred,resulting in compression of the root of the right L3 nerve.We performed a partial facetectomy to retrieve the leaked bone cement and to relieve the patient’s neurological symptoms.After 3 mo,the patient developed lumbar disc herniation in L3/4,potentially due to instability caused by the previous surgery.Therefore,it was necessary to perform intervertebral fusion and fixation.It was difficult to implant traditional trajectory pedicle screws in L3 and L4 because of the bone cement filling.Hence,we implanted CBT screws in the L3 and L4 vertebrae.As a result,the patient’s symptoms resolved and he reported satisfaction with the surgery at follow-up after 8 mo.CONCLUSION It is feasible to utilize CBT in cemented vertebrae for the treatment of lumbar degenerative disease.
基金This project is supported by National Natural Science Foundation of China (No.50406017).
文摘The flow field in the tip region of an axial ventilation fan is investigated with a particle image velocimeter （PIV） system at the design condition. Flow fields with three different tip clearances are surveyed on three different circumferential planes, respectively. The phase-locked average method is used to investigate the generation and the development of a tip leakage vortex. The result from PIV system is compared with that from a particle dynamics anemometer（PDA） system. Both data are in good agreement and the structure of the tip leakage vortex for the rotor is illustrated. The characteristic of a leakage vortex is described in both velocity vectors and vortical contours. The unsteadiness of the leakage vortex and the position of the vortex are surveyed in detail, which interprets the discrepancy between the numerical simulation and PDA experimental results to a certain extent. The center loci of tip leakage vortex at different times and the mean center loci of the leakage vortex are displayed particularly. Finally, the trajectories of the tip leakage vortex by the experimental measurement are compared with predictions from the existing models for high speed and high-pressure compressors and turbines when appropriately interpreted. A good agreement is obtained.
