Purpose: Set up a new technique to reproduce the cavitation effect in the process of brain deceleration impact Methods: A transparent physical brain model with tiny air bubbles was built and loaded on an upright brain deceleration impacting moveable platform. Then, in the high strength lighting circumstance, the moveable platform was made to free fall from a height of 40cm and impacted on a fixed platform, and the whole deceleration impacting process was recorded by a high-speed video camera. Using the serial pictures analysing software, the volume and mean pressure change of the air bubbles were calculated and the cavitation effect of the brain tissue during the impact was studied. Results: The volume of the air bubble in the contrecoup site increased obviously in the impacting process, the volume of the air bubble in the coup site decreased in the impacting process and the volume change of the air bubble in the middle site was not evident enough in the impacting process. Conclusion: The results proved the negative pressure and the cavitation phenomenon in the contrecoup site. The experiments explicitly and directly showed the cavitation effect in the contrecoup site during the decelerating impact It was helpful to better understand the distribution characters of the dynamic stress of the brain tissue in the brain decelerating impact in a certain extent, and it could also provide some methods and experimental foundation to clarify the mechanical mechanism of the brain contrecoup injury which was often taken place in traffic accidental injury. Besides, the methods were of significance to research the biomechanism, diagnosis and prevention of the brain deceleration impacting injury.

Objective to research the mechanical style(compressive or tensile force)of the key site of brain tissue in brain deceleration impact.Method a transparent physical brain model with air bubbles was built and loaded on an upright brain decaler ation impacting expedmentel platform.Then,the moveable platform was made a free fall from a height of 400mm and impacted on the fixed platform,and the whole deceleration impacting process was recorded by a high-speed video camera.Using the serial pictures analyzing Software,the length change of the long ads(vertical to the impacting direction)and the short axis(in the impacting di-rection)of the air bubbles were analyzed and calculated.Result the length change of the long axis of air bub-ble with in site coup was smallerthan the absolute value of that of the short axis;while with the air bubble in the contrecoup site,the length change of the long axis was bigger than the absolute value of the short axis.Conclusions the results showed that the air bubble in the coup site mainly suffered from the tensile force vertical to the impacting direction and the air bubble in the contrecoup site mainly suffered from the compres-sive force in the impacting direction.Since the propeny of tensile resistance of the brain tissue is inferior to the property of compressive resistance of the brain tissue, the injury is often easier to occur in the contrecoup site than in coup site. The results were of significance to the research of biomechanical mechanism, diagnosis and prevention of the brain deceleration impacting injury.

OBJECTIVETo study the biomechanical mechanism of head injuries beaten with sticks, which is common in the battery or assaultive cases.

METHODSIn this study, the Hybrid-III anthropomorphic test device and finite element model (FEM) of the total human model for safety (THUMS) head were used to determine the biomechanical response of head while being beaten with different sticks. Total eight Hybrid-III tests and four finite element simulations were conducted. The contact force, resultant acceleration of head center of gravity, intracranial pressure and von Mises stress were calculated to determine the different biomechanical behavior of head with beaten by different sticks.

RESULTSIn Hybrid-III tests, the stick in each group demonstrated the similar kinematic behavior under the same loading condition. The peak values of the resultant acceleration for thick iron stick group, thin iron stick group, thick wooden stick group and thin wooden stick group were 203.4 g, 221.1 g, 170.5 g and 122.2 g respectively. In finite element simulations, positive intracranial pressure was initially observed in the frontal comparing with negative intracranial pressure in the contra-coup site. Subsequently the intracranial pressure in the coup site was decreasing toward negative value while the contra-coup intracranial pressure increasing toward positive values.

CONCLUSIONSThe results illustrated that the stiffer and larger the stick was, the higher the von Mises stress, contact force and intracranial pressure were. We believed that the results in the Hybrid-III tests and THUMS head simulations for brain injury beaten with sticks could be reliable and useful for better understanding the injury mechanism.

Objective:To summarize the technical points of laparoscopic pancreaticoduodenectomy (LPD) carried out in a single center.Methods:The clinical data of 102 patients who underwent laparoscopic pancreaticoduodenectomy in 2018 at the Department of Hepatobiliary Surgery of the Second Hospital of Hebei Medical University were retrospectively analyzed, and the general conditions, operation time, intraoperative blood loss, and surgical operation were analyzed. Post-operative complications, hospital stay and other indicators were studied.Results:Of the 102 patients who were included, there were 57 males and 45 females, aged 15.0 to 79.0 (59.9±11.8) years old, with a body mass index (23.6±3.6) kg/m 2. For the 102 patients who underwent LPD, 6 were total pancreatic resection. Three were combined with vascular resection in the form of portal vein-superior mesentery vein segmental resection. The operation time was (376.6±87.2) min, the intraoperative blood loss was 350 (100, 800) ml, and the postoperative hospital stay was (17.0±5.9) days. Postoperative complications occurred in 26 of the 102 patients (25.5%), and more than two complications occurred in 17 patients. B/C grade pancreatic fistula occurred in 9 patients (9.4%), abdominal bleeding in 8 patients (7.8%), gastrointestinal bleeding in 2 patients (2.0%), biliary fistula in 4 patients (3.9%), and gastric emptying disorder in 5 patients (4.9%), 8 patients had pulmonary infection (7.8%). Five patients (4.9%) died during the perioperative period. Conclusion:The main technical points of LPD included en bloc resection, pancreaticojejunostomy, and vascular reconstruction. The basis of LPD is en bloc resection. Combined resection and reconstruction of vascular segments is a sign of maturity of LPD technology and a prerequisite for further development as a routine procedure.

Objective To evaluate the use of endoscopic papillary balloon dilation in treatment of choledocholithiasis associated with peripapillary duodenal diverticulum.Methods From January 2017 to July 2018,a retrospective study was conducted on 124 patients with choledocholithiasis associated with peripapillary duodenal diverticula at the Department of Hepatobiliary Surgery,Second Hospital of Hebei Medical University.These patients were divided into the small endoscopic sphincterotomy combined with balloon dilation group (sEST+EPBD,n =60) and the simple papillary balloon dilation group (EPBD n =64).The operation time,one-time success rate of stone removal,complication and hospitalization stay were compared between the two groups of patients.Results The hospitalization expenses of the EPBD group was significantly less than the sEST+EPBD group (P＜0.05).The operation time of the EPBD group was significantly shorten than the sEST+EPBD group (P＜0.05).There were no significant differences in the one-time success rate of stone removal,complication rates and hospitalization stay between the two groups (P＞0.05).Conclusions Compared with sEST+EPBD,treatment of choledocholithiasis in patients with peripapillary duodenal diverticula using simple balloon dilation shortened the operation time,did not increase the complication rates and hospitalization stay.The procedure was safe and effective,and resulted in almost the same one-time success rate of stone removal.

Objective To explore the value of endoscopic retrograde cholangiopancreatography (ERCP) in patients with choledocholithiasis after Billroth Ⅱ gastrointestinal anastomosis.Methods A retrospective cohort study was conducted to retrospective review the data of 189 patients with choledocholithiasis treated by ERCP from December 2015 to November 2017 in Department of Hepatobiliary Surgery,Second Hospital of Hebei Medical University.According to the history of Billroth Ⅱ gastrointestinal anastomosis,the patients who have not undergone digestive surgery were divided into the normal group(n =167) and patients who have undergone digestive surgery were divided into reconstruction group (n =22).The operation time,the success rate of stone extraction,complications,the hospitalization time,total hospitalization expenses were compared between the two groups.Measurement data with normal distribution were represented as (Mean ± SD) and comparison between groups was analyzed using the t test.Measurement data with skewed distribution were described as M (range).Comparisons of count data were analyzed using the x2 test or Fisher exact probability.Results The operation time of the normal group was (40.18 ± 11.80) min,and the success rate of ERCP was 97.60％ (163/167),the operation time of reconstruction group was(61.81 ± 13.21) min,and the success rate of ERCP was 81.82％ (18/22),There were significant differences between the two groups (t =0.105,x2 =10.400,P ＜ 0.05).The complications,the hospitalization time and the total hospitalization expense of the normal group were 16.17％ (27/167),(3.47 ± 1.55) d,(20 620.69 ± 3 117.88) yuan,the reconstruction group were 18.18％ (4/22),(4.18 ± 2.08) d,(22 426.41 ±5 916.30) yuan,with no statistically significant difference (x2 =0.000,t =4.204),t =10.828,P ＞ 0.05).Conclusions ERCP is safe and feasible for patients with choledocholithiasis after Billroth Ⅱ gastrointestinal anastomosis.It also has a high success rate of stone removal and small trauma,which is worthy of promotion.