Showing papers by "Tao Ji published in 2010"

Surgical treatment of pelvic chondrosarcoma involving periacetabulum

Abstract: Background and Objectives Surgical treatment of pelvic chondrosarcoma involving acetabulum is challenging. Primary goals of surgical treatment include local control and prevention of distant metastases. A secondary goal is maintenance of quality of life by avoiding major amputative surgery. The purpose of the study was to review the oncological outcome, functional outcome, and the surgical complications of patients with periacetabular chondrosarcomas in the context of resection and reconstruction treated at one tumor center in the past decade. Methods Forty-five cases between June 1998 and June 2007 were retrospectively reviewed. There were 26 men and 19 women with an average age of 41.2 (18–63) years. Patients were followed up for a median time of 37 months (18–119 months). There were 32 patients with conventional chondrosarcomas, 9 with dedifferentiated chondrosarcomas, and 4 with mesenchymal chondrosarcomas. According to Enneking's classification there were: Type II-1, Type I + II-8, Type II + III-23, Type I + II + IV-8, and Type I + II + III-5. Six patients had an external hemipelvectomy, whereas 39 patients underwent a limb-salvage procedure. In 27 patients the defect was reconstructed by a modular hemipelvic endoprosthesis and in 4 patients reconstruction by saddle endoprosthesis. Five patients received reconstruction with devitalized tumor bone and three underwent iliofemoral arthrodesis. Results The 5-year estimated survival was 62.6%. Local recurrence occurred in 10 (22.2%) patients at an average of 18 months after operations. Ten (22.2%) patients had distant metastasis. The average MSTS 93 score was 68.3% (33.3–100). Eighteen complications occurred in 13 patients (28.9%). Wound complication occurred in six (13.3%) patients. Deep infection rate was 11.1%. Conclusions Favorable oncological and functional outcome can be achieved in selected patients with periacetabular chondrosarcomas. The complication rates were still high; however, facing the goal of limb salvage, a certain number of complications is acceptable. J. Surg. Oncol. 2010;101:160–165. © 2009 Wiley-Liss, Inc.

Reconstruction of type II+III pelvic resection with a modular hemipelvic endoprosthesis: a finite element analysis study.

Abstract: Objective: To conduct a biomechanical study of the whole reconstructed pelvic ring using a modular hemipelvic endoprosthesis. Methods: A subject-specific finite-element (FE) model of the whole pelvic ring, including the pelvis, sacrum and main ligaments, was constructed. Type II+III pelvic resection was simulated on the FE model. Then a three-dimensional model of a reconstructed pelvic ring with a modular hemipelvic endoprosthesis was developed, and FE analysis performed to compare the stresses along the bilateral arcuate lines of the reconstructed and normal pelvis in the bipedal standing position. Comparison between bilateral stress distributions along the sciatic notch was also performed. The characteristics of load transmission within the endoprosthesis were also studied. Results: No significant difference in the stresses along the bilateral arcuate lines was observed between the reconstructed and normal pelvis. The stress distribution on the prosthesis along the sciatic notch paths was significantly greater than that on the unaffected side in the same position. The peak stress of the implant on the S1 vertebral body was 182.9 MPa under a load of 600N. Study of load transfer on the implant showed that the posterior side of the column between the point of iliac fixation and the acetabulum was subject to the greatest stress. Conclusion: This FE study showed that a modular hemipelvic endoprosthesis can restore load transfer between the sacrum and acetabulum on simple standing. Future implant design should aim to decrease the stress concentration and make the biomechanical performance more balanced.

Arsenic trioxide inhibits the growth of adriamycin resistant osteosarcoma cells through inducing apoptosis.

Abstract: Given that arsenic trioxide (As(2)O(3)) has been successfully used as a chemotherapeutic agent for refractory malignant tumors, this study is aimed at investigating the effect of As(2)O(3) on human Adriamycin resistant osteosarcoma cell line Saos-2. The mechanism underlying multi drug resistance (MDR) in osteosarcoma cells and the anti-tumor effect of As(2)O(3) on Adriamycin resistant osteosarcoma cells were analyzed. In our experiment, we first selected Adriamycin resistant osteosarcoma cell line by growing the classic osteosarcoma cell line Saos-2 in the medium with increasing drug concentrations. Then, we compared the IC50s of the osteosarcoma cells treated with different anticancer drugs by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. Subsequently, we assessed the expression of classic MDR related molecules, Pgp, multidrug resistance-associated protein (MRP) and glutathione (GSH) activity in the wild type and Adriamycin resistant Saos-2 cells. Furthermore, the apoptosis was assessed by concerning DNA fragment and flow cytometry with Annexin-V staining. To elucidate the underlying mechanism of the apoptosis, related proteins Bcl-2, Bcl-xL, Bax, Bak, cleaved Caspase-3 and cleaved Caspase-9 were analyzed by western blotting. The data showed that the resistance to Adriamycin affected the sensitivity of osteosarcoma cell to other chemotherapeutic agents. The IC50s of Saos-2/ADM cells for methotrexate (1.74-fold), Cisplatin (1.43-fold) and As(2)O(3) (1.21-fold) were increased compared with Saos-2 control cells. The expression of Pgp was upregulated comparing with the control cells. No significant difference was detected about the MRP and the glutathione-S-transferase activity and intracellular GSH concentration among different treated osteosarcoma cells. Apoptosis was observed and proved. The western blotting showed that the expression of Bcl-2 and Bcl-xL was downregulated. Meanwhile, the level of Bax, Bak, cleaved Caspase-3 and cleaved Caspase-9 was upregulated after treated with As(2)O(3). The study suggests that Adriamycin resistant osteosarcoma cells have good response to As(2)O(3)-based chemotherapy in vitro, probably via the pathway of inducing apoptosis. And As(2)O(3) might serve as an excellent alternative candidate for adjuvant chemotherapeutic agent on this incurable pediatric sarcoma.

Evaluation of surgical treatment of pelvic osteosarcoma

Abstract: Objectives To investigate the clinical outcome of consecutive pelvic osteosarcoma treated with surgery and chemotherapy in a single institution, and to discuss the surgical strategy, resection and reconstruction. Methods Twenty-one consecutive cases with pelvic osteosarcoma underwent surgical procedures between June 2000 and June 2009. There were 12 male and 9 female with a mean age of 32 years. According to Enneking and Dunham pelvic classification system, type I was 3 cases, type I + IV 3 cases,type I + Ⅱ 4 cases,type Ⅱ + Ⅲ 4 cases,type I + Ⅱ + Ⅲ 1 case,type Ⅲ 1 case,and type I + Ⅱ + Ⅳ 5 cases. Among the 21 cases, 19 were diagnosed as classical osteosarcoma and 2 were diagnosed as low-grade pathologically. All the tumors were stage Ⅱ B. All the patients received en-bloc resection with 13 wide resection and 8 marginal resection. Thirteen patients underwent modular hemipelvic endoprosthesis reconstruction, and 5 patients underwent rod-screw system reconstruction combined with autograft. Two patients received hemipelvectomy and one type Ⅲ patients had resection without reconstruction. The mean follow-up period was 30. 3 months (range,6. 0-87. 0). Results Thirteen patients out of 21 survived after treatment The overall survival rate was 61. 9% , and 23. 8% patients were alive without disease. The estimated 5-year survival rate was 44. 2% based on Kaplan-Meier curve. The local recurrence rate was 28.6% , among which 4 cases were type Ⅱ resection, 1 was type I resection, 1 was type I + Ⅳ resection. No local relapse was found on the hemipelvectomy and type Ⅲ resection cases. The local recurrence rate after wide resection was 23. 1% ,and 37. 5% for marginal resection. Nine patients had lung metastases and one patient was found bone and lymph node metastases. The MSTS 93 function score was 20. 6±5. 4 for 13 patients,and 22. 5±2. 1 for rod-screw reconstruction cases. The function score was 17. 7±5. 5 for hemipelvic prosthetic reconstruction. Conclusion Limb salvage procedures could be performed on most pelvic osteosarcoma cases, and satisfying function outcome could be achieved with proper reconstruction,however,the overall survival is still lower compared with those in extremities. Key words: Osteosarcoma; Pelvis; Surgical treatment

[Ewing's sarcoma of bone:treatment results and prognostic factors].

Abstract: Objective To determine the prognostic factors from the view of clinic and pathology.Methods A retrospective analysis was performed on a data set of 78 patients with Ewing's sarcoma treated at Peking University People's Hospital Musculoskeletal tumor center between July 1998 and July 2007. Fiveyear overall survival(OS), reccurence rate and prognostic factors were analyzed in this study. Univariate and multivariate analysis were performed to determine the prognostic factors for OS. Results Fifty-three cases were followed up, follow-up time ranged from 8.0 to 101.0 months (median 37.6 months). The 5-year overall survival rate and local reccurence rate were 33.7% and 20.8% respectively. Univariate showed age ＜20 years, metastases free at diagnosis, tumor located at extremities, tumor size ＜10 cmm, adequate surgical margin had better survival rate( all P ＜0.05). Multivariate analysis demonstrated that metastases at diagnosis, primary site and tumor size were independent prognostic factors for OS. Conclusion The independent prognostic factors Ewing's sarcoma are metastases at diagnosis, primary site,tumor size. Key words: Sarcoma,Ewing's; Prognosis; Survival rate

Behavioral Prediction of Reactive Powder Concrete Based on Artificial Neural Network

Abstract: Based on orthogonal array testing strategy (OATS), the effects of sand-binder ratio (S/B), water-binder ratio (W/B), and the ratio of steel fiber volume to reactive powder concrete (RPC) volume (STF/R) on the compressive strength and chloride diffusion coefficient of RPC were investigated using an artificial neural network method. Research results reveal that the compressive strength of RPC approaches summit when STF/R is 2% or W/B is 0.18-0.2%, and decreases with the increasing of S/B. Furthermore, the chloride diffusion coefficient increases with W/B or STF/R and decreases with S/B.

Finite element analysis for modular hemipelvic endoprosthesis during loaded gait cycle

Abstract: OBJECTIVE To analyze the biomechanical characteristics of modular hemipelvic endoprosthesis in gait cycle using finite element analysis method, and the effect of pubic connection plate on stress distribution. METHODS Three dimensional finite element model of periacetabular defect reconstructed with modular hemipelvic endoprosthesis was established. The hip contact forces, which were published from Free University of Berlin, under gait cycle were applied in the load of Abaqus 6.7. Then the simulation was conducted and four characteristic time points were identified, 17%, 36%, 43% and 86% of gait cycle. The von Mises stress distribution of the prosthesis was calculated. Stress concentration was ascertained and the difference of stress distribution between reconstruction with and without pubic connection plate was analyzed. The displacement and stress peak value of iliac fixation part under the four points of gait cycle were recorded; Comparison of stress on the four transverse iliac fixation screws was studied and the effect of pubic connection plate ascertained. RESULTS During the gait cycle, both the stress peak and maximum displacement occurred in the single-leg stance phase, according to 17%-36% of gait cycle. More rational stress distribution could be achieved under the reconstruction with pubic connection plate at 17% and 86% of gait cycle, representing ipsilateral and contralateral single-leg stance respectively, resulting in more even distribution. The maximum stresses of the iliac fixation part were 148.5 MPa and 270.1 MPa under the reconstruction with and without pubic connection plate, with significant difference (P=0.04); The mean displacements of the iliac fixation part were 9.3 mm and 11.7 mm with and without pubic connection plate reconstruction (P=0.03). The average stress level of iliac fixation part could be decreased to 50% and 24% for the iliac fixation screws. However, no micromotions were decreased under the reconstruction with pubic connection plate. Also no significant difference was observed for the relative shift of the iliac fixation part with and without pubic connection plate (P=0.41). CONCLUSION The stability of the implant could satisfy the normal walk activity. The pubic connection plate played an important role in the stability of the endoprosthesis, decreasing the stress peak and elongation of the durability.

Numerical Analysis of Causes and Cures of Longitudinal Reflection Cracking on Side-by-Side PC Box-Girder Bridge Deck

Abstract: Finite element analysis, based on various construction and service stages, of a genetic bridge was carried out to find the potential reasons causing longitudinal reflection cracking on top of bridge deck as well as the cures for solving this problem. Meanwhile, the effect of applied transverse posttensioning magnitude and tendon location as well as bearing pads’ supporting restraint was modeled in the FEA to investigate their effect on the distribution of transverse posttensioning force along the joints between adjacent box-girders. Results show that (1) transverse posttensioning and diaphragms reduce efficiently the tensile stress on top of deck; but this efficiency slows down significantly in bridge corner area, where exists still relatively higher tensile stress than other locations; (2) In some cases of loading combination, most locations on top of deck along the joints exist transverse tensile stresses, but the magnitude is less than 0.7Mpa, which could not cause the cracking if the decking concrete cover and keyway grout are properly selected and cast to the designated specifications; (3)Two patterns of transverse posttensioning output almost same result in the clamping stress along the joints for this proposed particular bridge model; (4)The vertical spacing between two tendon locations (upper and low level) should be farther spaced than the currently specified 1/3 girder depth so that less tensile stress or compressive stress is expected on top of deck; (5) The restrain from bearing pads modeled in this FEA has little effect on the stress distribution along joints between box girders.

Effects of Packing Degree and Calcium-Silicon Ratio of Cementitious Material on Strength of Reactive Powder Concrete

Abstract: Aim & Goff model was used to predict the packing degree of cementitious materials including cement and silica fume. The mix proportions of reactive powder concrete (RPC) with different packing degree and calcium-silicon ratio of cementitious materials were designed and a strength test was carried out. The study results reveal that the flexural strength and compressive strength of RPC are related to the packing degree and calcium-silicon ratio of cementitious materials. For the mix proportion of RPC with the calcium- silicon molar ratio of 1.353 that is slightly less than the theoretical value of 1.42, where calcium hydroxide can react with silicon dioxide more fully, its strength of RPC approaches summit although its packing degree of cementitious material is not the largest one.