Objective To investigate the risk factors related to failure of proximal femoral nail anti-rotation(PFNA)internal fixation for intertrochanteric fracture of femur.Methods A retrospective research was done on 249 cases with intertrochanteric fracture of femur after PFNA internal fixation.The failure ratios related to sex,fat,fracture pattern,osteoporosis,replace condition in operation and tip-apex distance(TAD)were calculated.And the risk factors related to failure of PFNA were statistically analysed.Results Two hundred and forty-three cases were followed up ranged from 10 months to 3 years after operation.Plain AP and lateral radiographs were obtained at each follow-up patient,13 of 243 cases resulted in failing by PFNA internal fixation.The failure ratios in PFNA internal fixation with fat,unstable fracture,TAD≥25 mm and bad replace condition in operation were 8.5％(12/141),7.8％(12/153),18.5 ％(5/27)and 26.1％(6/23),respectively,which were higher than those in PFNA internal fixation with nonobese,stable fracture,TAD ＜ 25 mm and good replace condition in operation[1.0％(1/102),1.1％(1/90),3.7％(8/216)and 3.2％(7/220),respectively](P＜0.05 or ＜0.01).Conclusions Fat,unstable fracture,TAD≥25 mm and bad replace condition in operation are the relatively independent risk factors related to failure of PFNA internal fixation for intertrochanteric fracture of femur.Furthermore,it will prevent and reduce the ratio of complications to avoid these risk factors when PFNA internal fixation is selected for treatment intertrochanteric fracture of femur.

Objective To explore the effect of the proximal femoral nail antirotation(PFNa) for the treatment of femoral intertrochanteric fracture.Methods 272 consecutive patients with femoral intertrochanteric fracture were treated with PFNa.Results The mean operative time was 55min(range 35 ～95)min.The mean blood loss was 85ml (range:20 ～200)ml.The mean follow-up was 15.6months( range:6 ～36)monthsand achieved bone healing with an average time of 14.5weeks.According to the Harris criterion for evaluation.Conclusion PFNa was more comfortable for human's biomechanism and more favorable for the healing of the fracture as well as the recovery of the hip function.It had the advantage of simple manipulation,fewer trauma,strong fixation,anti-rotation,less osclerotin.PFNa was an ideal treatment for intertrochanteric fracture,specially the unstable intertrochanteric fracture and senile osteoporosis.

Objective Ionization chamber detector is commonly used for direct and continuous measurement of tritium concentration in the air. However, the measurement sensitivity is low due to the limitations of weak current measurement technology. It is necessary to develop a proportional counter for measuring tritium in the air. Methods This study involved the design of a proportional counter, considering various factors such as materials and structure. The stability, plateau curve, detection efficiency, and energy spectrum of the counter were tested. Results The coefficient of variation of the proportional counter was 3.14%, which met the standard requirement of being less than 15%. The plateau length was 260 V and the plateau slope was 0.80%/100V, which met the requirement of being less than 1%/100V. The tritium detection efficiency reached 68.02%. The energy spectrum measurement indicated a significant difference between tritium signal generated by the proportional counter and background signal, and the distribution of tritium in the energy spectrum was more concentrated. The background counting rate during tritium gas activity measurement could be reduced through energy spectrum measurement. Conclusion The proportional counter can provide a reference for the direct and continuous measurement of tritium in the air.

Objective To investigate the prevalence and risk factors of injury among both primary and middle school students in Changning District， Shanghai， and to provide evidence for injury prevention. Methods In 2018， data of basic characteristics and injury-related factors were obtained through field questionnaire survey among the selected primary and middle schools （2 of each）. Results The study finally included 1 821 students， with injury incidence rate of 30.1%. Among them， the injury incidence rate for the primary schools was 32.0%， and 28.8% for the middle schools. The top three injury types were falls， sharps injuries， and blunt injuries. Age， gender， myopia， and injury-related knowledge/behaviors were significantly related to injury incidence. Conclusion Falls should still be the priority of injury prevention for primary/middle school students in Changning District. The effect of reducing injuries can be achieved by improving health education about injury-related knowledge/behaviors.