ABSTRACT
BACKGROUND:Deep vein thrombosis after hip replacement has a high incidence rate. Moreover, deep vein thrombosis can induce pulmonary embolism that can endanger patients’ life and dysfunction of distant deep vein. The appearance of deep vein thrombosis is a great obstacle for the gradual y increased hip replacement. OBJECTIVE:To observe the occurrence of deep vein thrombosis of lower limb after total hip replacement in elderly patients, and to screen the risk factors for the occurrence of deep vein thrombosis of lower limbs. METHODS:Clinical data of 128 elderly patients with hip replacement were analyzed retrospectively. Al patients were examined with color Doppler ultrasound in double lower limbs at 1 day before replacement and 7 days after replacement. Multifactor unconditional logistic analysis was conducted on clinical related factors and the formation of lower limb deep vein thrombosis. RESULTS AND CONCLUSION:At 7 days after the operation, 16 patients affected deep vein thrombosis of lower limb. The factors for deep vein thrombosis contained female, general anesthesia, bilateral hip replacement and the application of bone cement (P<0.05). The risk for deep vein thrombosis after total hip replacement significantly increased in elderly patients aged over 70 years. Multifactor unconditional logistic analysis exhibited that the multiple risks of sex, obesity and the use of bone cement in elderly patients with deep vein thrombosis increased to 11.398, 3.109 and 8.925. The patients with a blood type O at the age of over 70 years experienced a decreased risk for deep vein thrombosis after total hip replacement. The occurrence of deep vein thrombosis decreased to 0.186 times after replacement. Blood type O could be considered as a protective factor for the occurrence of deep vein thrombosis.
ABSTRACT
BACKGROUND:The materials for internal fixation of bone allografts have been used in the clinic.However,they are only used in the regions bearing little stress because of low strength.The focus of current studies is how to enhance the fixation strength of the materials to expand application range.OBJECTIVE:To compare the strength difference of cortical bone allografts among different fixation modes and to investigate the possible mechanisms of action.DESIGN,TIME AND SETTING:An in vitro biomechanical experiment was performed at the Laboratory of Biomechanics,Nanhua University between October 2005 and March 2006.MATERIALS:Twenty-seven pieces of cadaveric femurs were included in this study.A total of 45 cortical bone allografts with a size of 110 mm×10 mm×3 mm and 90 bone screws were also used.METHODS:Twenty-seven femurs were made into simulated fracture models and randomized to 3 groups,with 9 models per group:A,B,and C.In the group A,the models were fixed with two cortical bone all6grafts; the models from the groups B and C were fixed with two bone allografts plus 5 bone screws and one bone allograft plus 5 bone screws accordingly.MAIN OUTCOME MEASURES:Biomechanical tests were performed in the above-mentioned 3 groups to measure compressive,bending and torsional stiffness as well as the maximum loads.RESULTS:Different fixation models displayed different mechanical characteristics.The group A exhibited similar compressive stiffness compared to the group B,but the level was significantly higher compared to the group C (P ＜ 0.05).The other two stiffness parameters including bending and torsion were significantly greater in the group A than in the groups B and C (P ＜ 0.05).The maximum loads of compression,bending,and torsion were significantly greater in the group A compared to the group B (P ＜ 0.05) and group C (P ＜ 0.01).CONCLUSION:The strength of bone allograft is highly related to fixation mode. The two bone allografts showed greater strength and stiffness than struts fixed with bone screws,which meet the clinical requirements.