BACKGROUND:At present,wrist protection products designed in and outside China have not solved the contradiction between protecting the wrist joint from injury and maintaining the flexible movement of the wrist joint. OBJECTIVE:To investigate the biomechanical mechanism of dorsiflexion injury of the wrist joint in elderly people after falls,and to provide a biomechanical basis for the prevention and treatment of wrist injury in elderly people after falls. METHODS:A 65-year-old man was selected to obtain the original data by uninterrupted CT scan of the middle and lower 2/3 of his left forearm up to the end of the finger.A finite element model of wrist dorsiflexion was established using ANSYS 12.0 finite element software.The palm surface of the model was constrained,and the model at a velocity load of 2 m/s in the direction of vertical downward was given to simulate the injury state of the palm when the elderly fall.The stress distribution of the soft tissues and bones of the wrist joint and the change of the stress with time were observed after the load was applied. RESULTS AND CONCLUSION:(1)A realistic and effective finite element model of the dorsal extension position of the wrist joint of the elderly was established.The soft tissue stresses were mainly concentrated in the small fissure of the palm and the dorsal side of the wrist after loading.The skeletal stresses were mainly concentrated in the lower end of the ulnar radius dorsally.The stresses in the lower end of the radius were the greatest.The palmar stresses were mainly concentrated in the middle and lower 1/3 of the radius and the hook bone.The stress distribution of the ulnar radius was asymmetric,and the stresses in the radius were more concentrated.(2)The results of the study are consistent with the clinical situation of a fallen wrist injury in elderly people,and can be used to explain the mechanism of wrist dorsiflexion injury,which can provide the biomechanical basis for the design of wrist protection devices that can be used to prevent wrist injury induced by falling and the treatment of wrist injury in elderly people.

Objective To investigate the effect of sub-anesthesia dose of isoflurane in 60％ oxygen on acute lung injury in aged rats with sepsis.Methods Ninety male Sprague-Dawley rats,aged 12-14 months,weighing 500-800 g,were divided into 3 groups (n=30 each) using a random number table:sham operation group (Sham group),sepsis group (S group),and sepsis plus isoflurane plus oxygen treatment group (S+I+O group).Sepsis was induced by cecal ligation and puncture in S and S+I+O groups.In group S+I+O,0.7％ isoflurane in 60％ oxygen was inhaled for 1 h starting from 1 and 6 h after operation.Eighteen rats were selected in each group and observed for 7 days after operation,and the survival rate was recorded.Six rats were selected in each group at 24 h after operation,and bronchoalveolar lavage fluid (BALF) was collected to determine the protein concentrations (by BCA protein assay),blood samples were collected from the femoral artery for blood gas analysis,PaO2 was recorded,and the oxygenation index was calculated.Six rats in each group were sacrificed at 24 h after operation,the left lung specimens were obtained and stained with hematoxylin and eosin for examination of pathological changes,the right lung specimens were obtained for determination of wet to dry weight ratio (W/D ratio),and blood samples were collected from the right atrium for measurement of the concentrations of interleukin-1β (IL-1β),IL-6,tumor necrosis factor-α (TNF-α),high-mobility group box 1 protein (HMGB1) and IL-10 in serum (by enzyme-linked immunosorbent assay).Results Compared with group Sham,the survival rate was significantly decreased,and the concentrations of IL-1β,IL-6,TNF-α,HMGB1 and IL-10 in serum were increased in S and S+I+O groups,and W/D ratio and protein concentrations in BALF were significantly increased,and the oxygenation index was decreased in group S (P＜0.05).Compared with group S,the survival rate was significantly increased,W/D ratio and protein concentrations in BALF were decreased,the oxygenation index was increased,the concentrations of IL-1β,IL-6,TNF-α and HMGB1 in serum were decreased,and the concentration of serum IL-10 was increased (P＜0.05),and the pathological changes were significantly attenuated in group S+I+O.Conclusion Sub-anesthesia dose of isoflurane in 60％ oxygen can reduce acute lung injury in aged rats with sepsis,and the mechanism may be ralated to inhibiting systemic inflammatory responses.