BACKGROUND:Biomechanical studies on elderly subtrochanteric fracture by different fixation ways were more, but study on relatively proximal femoral nail antirotation-II (PFNA) and Asia 2 femur nail (A2FN) fixation for femoral subtrochanteric fractures in the elderly was less. OBJECTIVE:To study the biomechanical analysis of intramedul ary nail PFNA-II and A2FN fixation for elderly femoral subtrochanteric fractures. METHODS:Three-dimensional finite element models of femoral subtrochanteric fractures fixed by PFNA-II and A2FN in the elderly were established. Three-dimensional finite element analysis was used to analyze stress distribution and displacement after femoral subtrochanteric fractures by PFNA-II and A2FN fixation. RESULTS AND CONCLUSION:(1) The overal maximum stress, nail maximum stress and hip screw or spiral blade maximum stress values of PFNA-II intramedul ary fixation system were higher than that of A2FN intramedul ary fixation system. The distal locking maximum stress value and femoral head surface maximum stress values of PFNA-II intramedul ary fixation system were lower than that of A2FN intramedul ary fixation system. (2) The maximum displacement of PFNA-II intramedul ary fixation system was mainly concentrated in the large trochanter and femoral head pole. The maximum displacement of A2FN intramedul ary fixation system was mainly concentrated in the large trochanter. The maximum displacement of PFNA-II intramedul ary fixation system was higher than that of A2FN intramedul ary fixation system. The maximum axial displacement of PFNA-II intramedul ary fixation system was higher than that of A2FN intramedul ary fixation system. The maximum sagittal displacement of PFNA-II intramedul ary fixation system was higher than that of A2FN intramedul ary fixation system. The maximum coronal displacement of PFNA-II intramedul ary fixation system was higher than that of A2FN intramedul ary fixation system. (3) The lateral fissure, front fissure and rear fissure of PFNA-II intramedul ary fixation system were higher than that of A2FN intramedul ary fracture fixation system, but the difference was less pronounced. (4) The maximum stress value on fracture section of PFNA-II intramedul ary fracture fixation system was lower than that of A2FN intramedul ary fixation system. (5) Results showed that A2FN intramedul ary fixation system for intertrochanteric fractures has better biomechanical stability than PFNA-II intramedul ary fixation system for intertrochanteric fractures.

BACKGROUND:Core decompression may provide insufficient support for the subchondral bone in the treatment of early avascular necrosis of the femoral head and increase the risk of fracture and colapse. Quadratus femoris implantation cannot only provide good biological support, but also promote the revascularization at necrotic regions, thus repairing the necrosis of femoral head. OBJECTIVE: To compare the clinical effects of core decompression with bone paste implantation and core decompression with quadratus femoris implantation on early and middle-stage avascular necrosis of the femoral head. METHODS:Eighty-three patients with early avascular necrosis of the femoral head (92 hips) admitted at the Department of Orthopedics, the First Affiliated Hospital of Zhengzhou University, China, from January 2009 to January 2012 were enroled and divided into groups of core decompression with bone paste implantation (46 cases, 49 hips) and core decompression with quadratus femoris implantation (37 cases, 43 hips) that were respectively injected with bone meal and autogenous bone and osteoinductive materials. RESULTS AND CONCLUSION: Al involved patients were folowed up. After 1 year of treatment, Harris scores in the two groups were both increased (P < 0.05). But the Harris score of core decompression with bone paste implantation group was lower than that of core decompression with quadratus femoris implantation group (P < 0.05). After 3 years of treatment, X-ray scores in the core decompression with quadratus femoris implantation group were significantly higher than those in the core decompression with bone paste implantation group (P < 0.05). These findings indicate that compared with core decompression with bone paste implantation, core decompression with quadratus femoris implantation is better to prevent femoral head colapse, improve hip function and delay the process of osteonecrosis of the femoral head.

Objective To investigate the effects of transient plateau factor on acute lung injury induced by phosgene poisoning in rabbits.Methods Forty New Zealand white rabbits of both sexes,aged 2.0-2.5 kg,were randomly divided into 4 groups (n =10 each) using a random number table:control group (group C),plateau factor group (group H),phosgene poisoning group (group P),and phosgene poisoning and plateau factor group (group HP).In group H,the rabbits were exposed to a simulated altitude of 33000 m for 2 h.In group P,the rabbits were exposed to phosgene for 3 min only.In group HP,the rabbits were exposed to phosgene for 33 min and then to a simulated altitude of 3000 m for 2 h.Respiratory rate (RR) was recorded and blood samples were taken before exposure to phosgene (T1),after exposure to phosgene (T2),and at 0,1 and 6 h after onset of exposure to a simulated altitude of 33000 m (T3-5) for determination of PaO2 and oxygenation index (OI) was calculated.The chests were opened at T5 and lungs removed for determination of lung water content (LC) and for microscopic examination.Lung coefficient (LC) was calculated.Results Compared with C group,RR was significantly increased at T3 in group H (P ＜ 0.05),and RR was increased and OI was decreased at T2-5 in P and HP groups (P ＜ 0.05 or 0.01).Compared with P group,RR was increased and OI was decreased at T3-5 in HP group (P ＜ 0.05 or 0.01).LW and LC were significantly higher in P and HP groups than in group C,and in HP group than in group P (P ＜ 0.05 or 0.01).The microscopic examination showed that pathological changes were observed in P and HP groups,however,the changes were severer in HP group.Conclusion Transient plateau factor can obviously aggravate the degree of acute lung injury induced by phosgene poisoning in rabbits.