BACKGROUND:The pelvis has abundant trabecular bone content,but the ability of conventional sacroiliac percutaneous fixation to control trabecular bone is limited,leading to fixation failure.Therefore,the development of devices that can more effectively control trabecular bone tension is of significant importance.OBJECTIVE:The mechanical properties of a novel sacroiliac tension screw were investigated using biomechanical testing and numerical modeling analysis,along with an assessment of the reliability of the pull-out force numerical model.METHODS:A mechanical model was established based on the working principle of the novel sacroiliac tension screw.Numerical methods were employed to analyze its pull-out performance,validated through mechanical testing with polyurethane material to assess the reliability of the pull-out force numerical model.Using pelvic specimens,the mechanical effectiveness of the novel sacroiliac tension screw in repairing sacroiliac joint injuries was analyzed under normal standing posture,along with an evaluation of the load stiffness of different pelvic models in the standing position.RESULTS AND CONCLUSION:(1)The average error between the computed values of the numerical model and the measured values was 13.19％,indicating a certain level of validity for the numerical model.(2)The damage to the polyurethane material after the extraction of the screw was less pronounced in the novel screw group.(3)The average effective holding displacement for the novel screw was approximately(9.24±0.27)mm,significantly greater than the average displacement of(1.71±0.57)mm observed with the lag screws.However,the maximum resistance to pullout for the lag screws was significantly higher than that for the novel screws.(4)The novel screw effectively repaired sacroiliac joint injuries.(5)The stiffness after repair of sacroiliac joint injuries was equivalent when using a single novel screw compared to using two lag screws.(6)These results prove that the theoretical model for the maximum resistance to pullout of the screws established in this study has a certain level of validity and can guide the design of them with improved mechanical performance.The novel sacroiliac spiral blade screw can effectively hold trabecular bone and has practical clinical utility.

BACKGROUND:The pelvis has abundant trabecular bone content,but the ability of conventional sacroiliac percutaneous fixation to control trabecular bone is limited,leading to fixation failure.Therefore,the development of devices that can more effectively control trabecular bone tension is of significant importance.OBJECTIVE:The mechanical properties of a novel sacroiliac tension screw were investigated using biomechanical testing and numerical modeling analysis,along with an assessment of the reliability of the pull-out force numerical model.METHODS:A mechanical model was established based on the working principle of the novel sacroiliac tension screw.Numerical methods were employed to analyze its pull-out performance,validated through mechanical testing with polyurethane material to assess the reliability of the pull-out force numerical model.Using pelvic specimens,the mechanical effectiveness of the novel sacroiliac tension screw in repairing sacroiliac joint injuries was analyzed under normal standing posture,along with an evaluation of the load stiffness of different pelvic models in the standing position.RESULTS AND CONCLUSION:(1)The average error between the computed values of the numerical model and the measured values was 13.19％,indicating a certain level of validity for the numerical model.(2)The damage to the polyurethane material after the extraction of the screw was less pronounced in the novel screw group.(3)The average effective holding displacement for the novel screw was approximately(9.24±0.27)mm,significantly greater than the average displacement of(1.71±0.57)mm observed with the lag screws.However,the maximum resistance to pullout for the lag screws was significantly higher than that for the novel screws.(4)The novel screw effectively repaired sacroiliac joint injuries.(5)The stiffness after repair of sacroiliac joint injuries was equivalent when using a single novel screw compared to using two lag screws.(6)These results prove that the theoretical model for the maximum resistance to pullout of the screws established in this study has a certain level of validity and can guide the design of them with improved mechanical performance.The novel sacroiliac spiral blade screw can effectively hold trabecular bone and has practical clinical utility.

Objective To investigate the biomechanical properties of a novel sacroiliac lag screw with a spiral blade.Methods Percutaneous sacroiliac lag screws were used as the controls.Polyurethane material was used to simulate the trabecular bone,and the pullout resistance performance was tested on an Instron mechanical testing machine.Subsequently,pelvic specimens were utilized to analyze the static stiffness and dynamic stability of the novel sacroiliac lag screw in repairing sacroiliac joint injuries under normal standing conditions,with normal pelvis,single-sided sacroiliac joint injury pelvis,percutaneous sacroiliac lag screw-single screw repair,and percutaneous sacroiliac lag screw-double screw repair as controls.Results The damage to the polyurethane material after screw extraction was smaller in the novel sacroiliac lag screw group.The average effective holding displacement of the novel sacroiliac lag screw was significantly greater than that of the percutaneous sacroiliac lag screw(P＜0.05).However,the maximum resistance to the pullout force for the percutaneous sacroiliac lag screw was significantly higher than that for the novel sacroiliac lag screw(P＜0.05).The stiffness after repair of sacroiliac joint injuries was significantly higher when using a single sacroiliac lag screw than when using two percutaneous sacroiliac lag screws(P＜0.05).The displacement amplitude was the highest in the sacroiliac joint injury group,followed by that in the normal group.The displacement amplitudes in the other groups were similar;however,the differences were statistically significant(P＜0.05).The dynamic stability of the sacroiliac lag screw repair group was the best,slightly better than that of the percutaneous sacroiliac lag screw-double screw repair group,and the dynamic stability of the sacroiliac joint injury group was the worst.The novel sacroiliac lag screw effectively repaired the sacroiliac joint injuries.Conclusions The novel sacroiliac lag screw can effectively hold the trabecular bone and has practical clinical utility.

BACKGROUND:The stability of the pelvis is mainly determined by the posterior pelvic ring and the sacroiliac joint.The posterior pelvic ring injury and the dislocation of the sacroiliac joint caused by high energy impacts such as car accidents increase year by year.Surgical treatment is the best method,and there are many kinds of endophytorepair methods in clinical practice,but which treatment method has the best biomechanical properties is still controversial. OBJECTIVE:To compare the biomechanical properties of three kinds of internal implants:anterior double plates,posterior bridging plate and tension nail in the repair of unilateral unstable pelvic posterior ring injury,to provide a reference for the clinical treatment and development of a new pelvic tension screw. METHODS:(1)Finite element simulation:Mimics,Wrap and SolidWorks were used to establish normal pelvic model,unilateral injured pelvis model,and three kinds of internal implant repaired models(anterior double plates,posterior bridging plate and tension nail).Ansys was used to analyze the stress and deformation of the models.(2)Biomechanical test:A total of 15 intact pelvic specimens were randomly grouped into five groups,normal pelvic model,unilateral injured pelvis model,anterior double plates,posterior bridging plate and tension nail groups.The mechanical test was performed using an Instron E10000 testing machine. RESULTS AND CONCLUSION:(1)Simulation:In the normal pelvic model,the average displacement of the sacrum was 0.174 mm,and the maximum stress of the sacral iliac bone was 10.51 MPa,and the stress distribution was uniform.The mean sacral displacement of the unilateral injured pelvis model was 0.267 mm,and the stress concentration of the model was obvious.The mean displacement of the sacrum in the three repaired models was close to that in the normal pelvic model,and the stress distribution of the sacral iliac bone in the tension nail repaired model was uniform.(2)Mechanical test:The stiffness of the normal pelvic model was(226.38±4.18)N/mm,and that of the unilateral unstable pelvic model was the smallest(130.02±2.19)N/mm.The deviation of the normal pelvic model stiffness and the three repaired models'stiffness were all within(±10%),and the repair effect was obvious.(3)The simulation results were in agreement with the experimental results.(4)The biomechanics of the tension nail repaired model was the most similar to that of the normal pelvis,and this method was the best.The repairing stiffness of the anterior double plate was too large,and the stress shielding effect was more significant.The posterior bridging plate repair could not solve the compensatory effect of the normal side soft tissue and had defects.This study provides an optimal basis for clinical surgery.(5)The new type of pelvic tension nail should be improved from the point of view of the tension nail to retain the good biomechanical properties of the tension nail,while adding other advantages,such as being used for the osteoporotic pelvis.

BACKGROUND:Pauwels Ⅲ femoral neck fracture is a typical unstable fracture characterized by high vertical shear force and high incidence of postoperative complications.At present,there are many fixation methods for Pauwels Ⅲ fracture,and there is no clear conclusion as to which internal fixation is the best fixation method for Pauwels Ⅲ femoral neck fracture in young adults. OBJECTIVE:To compare the clinical effect of three inverted triangle cannulated screws assisted transverse lag screws and femoral neck system in fixing Pauwels Ⅲ femoral neck fractures of young adults. METHODS:From May 2021 to December 2022,21 young and middle-aged patients with Pauwels Ⅲ femoral neck fracture were treated with three inverted triangle cannulated screws assisted by transverse lag screws and femoral neck system in Affiliated Hospital of Southwest Medical University.Of them,9 patients were treated with three inverted triangle cannulated screws and one transverse lag screws perpendicular to the fracture line as the 3+1 cannulated screw group and 12 patients were treated with femoral neck system as the femoral neck system group.The two fixation methods were compared in terms of operation time,intraoperative blood loss,total incision length,intraoperative fluoroscopy times,fracture healing time,and limb function. RESULTS AND CONCLUSION:(1)All patients were followed up.Patients in the 3+1 cannulated screw group were followed up for 10-25 months,with a mean of(17.44±4.30)months.The patients in the femoral neck system group were followed up for 8-24 months,with a mean of(15.58±4.68)months.(2)The intraoperative fluoroscopy times and Harris score at 3 months postoperatively in the femoral neck system group were better than those in the 3+1 cannulated screw group,and the difference was statistically significant(P<0.05).The intraoperative blood loss,total incision length,and femoral neck shortening distance in the 3+1 cannulated screw group were better than those in the femoral neck system group,and the differences were statistically significant(P<0.05).There was no significant difference in operation time,fracture healing time,and Harris score at the last follow-up between the two groups(P>0.05).(3)It is indicated that three inverted triangle cannulated screws assisted transverse lag screw and femoral neck system can achieve good clinical effects in the treatment of young and middle-aged Pauwels Ⅲ femoral neck fracture.The femoral neck system has fewer intraoperative fluoroscopy times and better early overall stability,while the 3+1 cannulated screw is more minimally invasive,easier to operate.Both fixation methods are worthy of clinical application and promotion,and can be selected according to the actual clinical situation.

Objective To investigate the clinical effect of coracoclavicular ligament reconstruction by getting tendon palmaris longus for treating acromioclavicular joint dislocation under arthroscopically assisted Endobutton steel plate fixation.Methods Eighteen patients with acute closed acromioclavicular joint dislocation treated in this hospital from January 2013 to March 2015 were selected and treated by coracoclavicular ligament reconstruction by getting tendon palmaris longus and double Endobutton steel plate fixation under arthroscopy.The visual analogue scale(VAS) was adopted before and after operation.The Karlsson treatment effect score was adopted at the end of follow up period.The patients satisfaction was investigated.Results The wounds in 18 cases were stage Ⅰ first grade healing and the reduction of acromioclavicular joint dislocation was good.The postoperative VAS score was(0.56±0.62) points,which was significantly decreased compared with(2.44± 1.20) points before operation(t=5.945,P＜0.01).During the follow-up visit,1 case appeared dislocation recurrence and treated by adopting clavicle hook plate fixation;average follow up time was 17.72 months,the Karlsson score at the end stage was excellent in 12 cases,good in 5 cases and poor in 1 case,the excellent and good rate was 94.44 ％,the patient satisfaction degree was 88.89 ％.Conclusion Arthroscopically assisted Endobutton steel plate fixation combined with ligament reconstruction by tendon palmaris longus for treating acromioclavicular joint dislocation has small trauma and reliable fixation,and promotes the joint function recovery.

Objective To compare the clinical curative effect of bridge combined internal fixation system (BCFS) and digital customized steel plate(DCSP) for treating complex extremity fracture.Methods Fortyseven cases of complex extremity fracture in this hospital from October 2012 to October 2015 were treated by BCFS and DCSP,among them,26 cases adopted BCFS(BCFS group) and 21 cases were treated by DCSP(DCSP group).Then the operation time,intraoperative blood loss volume,hospitalization time,healing time of fracture,postoperative complications and function evaluation of limbs were compared between the two groups.Results The two group were followed up for 6-15 months with an average of(13.57±1.37)months.The DCSP group was better than the BCFS group in the aspects of operation time and intraoperative blood loss volume,the difference was statistically significant(P＜0.05).The fracture healing time in the BCFS group was significantly shorter than that in the DCSP group,the difference was statistically significant(P＜0.05).The hospitalization time,postoperative complications and function evaluation of limbs had no statistical differences between the two groups(P＞0.05).Conclusion Both BCFS and DCSP can acquire good clinical curative effect in the treatment of complex extremity fracture,however BCFS has a shorter healing time of fracture.

BACKGROUND: Tibia open fracture is a common disease, and intramedullary fixation has become the first choice, but the high risk of postoperative infection limits its clinical application.OBJECTIVE: To investigate the early prevention effect of vancomycin-hydroxyapatite (VCM-HA) coated titanium intramedullary nail in a rabbit model of open femoral fracture combined with wound infection.METHODS: Titanium intramedullary nails coated with three different concentrations of VCM-HA were prepared using biomimetic deposition, and subsequently in vitro bacteriostasis experiment was performed. Forty healthy male New Zealand white rabbits were selected and the model of mid-femur open fracture with wound infection was prepared. The rabbit models were then divided into ordinary intramedullary nail, low-, middle- and high-concentration VCM-HA coated intramedullary nail groups (n=10 per group). The wound appearance of the animals was dynamically observed. The body mass, anal temperature, white blood cells and C-reactive protein contents in the venous blood were monitored. The pathological examination of the soft tissue around the fracture and injured limb X-ray were conducted regularly.RESULTS AND CONCLUSION: The prepared VCM-HA coated titanium intramedullary nail exerted obvious antibacterial effects in vitro. The anal temperature in the ordinary nail group was significantly higher than that in the other three groups at 3 days after modeling (P < 0.05). The white blood cells and C-reactive protein contents in the venous blood in the VCM-HA groups were significantly lower than those in the ordinary nail group at 3, 7, 14 and 28 days after modeling (P < 0.05). The hematoxylin-eosin staining of the peripheral tissues displayed the inflammatory response in the VCM-HA groups was milder than that in the ordinary nail group at each time point after modeling. The injured limb X-ray displayed that the callus grew slowly accompanied with sequestration in the ordinary nail group, while the callus growth in the VCM-HA groups was significantly better than that in the ordinary nail group. To conclude, the VCM-HA coated intramedullary nail can effectively reduce postoperative infection in an animal model of open femoral fracture combined with wound infection.

Objective To observe the effects of mesenteric lymph drainage on acute lung injury and expression of p38 mitogen activated protein kinase (p38MAPK) signal pathway in rats with bowel repletion pattern. Methods Thirty male Wistar rats were randomly divided into three groups according to random number table method, namely sham operation group (sham group), bowel repletion model group (model group) and mesenteric lymph drainage group (drainage group), 10 rats in each group. The rat model of bowel repletion was established by ischemia/reperfusion (I/R) method, firstly 1 hour occlusion of superior mesenteric artery (SMA) to induce ischemia followed by reperfusion for 2 hours. In the rats of drainage group, the drainage of mesenteric lymph duct began at the end of model establishment and persisted for 3 hours. In the rats of sham group, the SMA and mesenteric lymph ducts were exposed with blunt dissection, and then they were immediately placed back into the abdominal cavity. After 3 hours of mesenteric lymph drainage, the lung and ileum tissues of rats in each group were harvested for evaluation of pathohistological changes and for the determination and comparison of myeloperoxidase (MPO) activity changes; the levels of tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) in bronchoalveolar lavage fluid (BALF) were detected by enzyme linked immunosorbent assay (ELISA), and the expressions of Toll-like receptor 4 (TLR4) mRNA and p38MAPK mRNA in the lung tissues were measured by fluorescence quantitative polymerase chain reaction (PCR).Results Under the light microscope, the pulmonary capillaries markedly dilated and congested, the interstitium width of lung increased with a large amount of inflammatory cells infiltration, the intestinal mucosal layer becoming thinner with detachment of intestinal villi and a large amount of inflammatory cells infiltration were detected in rats of model group. Compared with those in sham group, the levels of TNF-α and IL-6 in BALF, the MPO activity of lung and ileum tissues, and the expressions of TLR4 mRNA and p38MAPK mRNA in the lung tissues were significantly increased in model group.Compared with those in model group, the pathohistological damages in lung and ileum tissues were ameliorated, the levels of TNF-α and IL-6 in BALF, the MPO activity of lung and intestinal tissues and the expressions of TLR4 mRNA and p38MAPK mRNA in the lung tissues were lower in the rats of drainage group [TNF-α in BALF (ng/L): 858.55±27.16 vs. 1 680.58±105.62; IL-6 in BALF (ng/L): 0 vs. 484.71±5.43; MPO activity of lung (U/g): 0.95±0.13 vs. 1.36±0.11; MPO activity of ileum tissues (U/g): 0.75±0.13 vs. 1.30±0.16; TLR4 mRNA: 0.21±0.11 vs. 0.69±0.13, p38MAPK mRNA: 0.21±0.13 vs. 0.47±0.09; allP < 0.05].Conclusion Mesenteric lymph drainage can alleviate acute lung injury in rats with bowel repletion, and its mechanism may be related to the reduction of the expressions of TLR4 mRNA and p38MAPK mRNA and the release of TNF-α and IL-6 in lung tissues.

Objective To evaluate the mid-term effect of total hip arthroplasty (THA) after failed internal fixation of intertrochanteric fracture.Methods Twenty-one patients treated with THA due to failed internal fixation of intertrochanteric fracture from January 2007 to December 2010 were studied retrospectively.There were 10 males and 11 females,at mean age of 71.7 years (range,66-79 years).Sixteen patients were treated with dynamic hip screws/dynamic condyle screws (DHS/DCS),3 proximal femoral nails,2 hollow screws.Mean interval from internal fixation to THA was 29 months (range,10-79 months).Causes for the failed internal fixation were loosening,cutting,and breakage of screws which generated fracture displacement or nonunion in 19 patients and femoral head necrosis in 2 patients.All patients received THA with uncemented acetabulum cups and proximally long-stemmed,porous-coated titanium femoral components including AML stems for 5 patients and Solution stems for 16 patients.Moreover,greater trochanteric fracture was fixed by Luke wire.Harris hip score were measured before operation and at final follow-up.Radiographs were performed before operation,at 3,6 and 12 months after operation,and at final follow-up to assess the fracture restoration,healing,prosthesis initial fixation,and mid-term survival condition.Results One patient was died due to pulmonary infection 1.5 years after operation.Two patients were lost to follow-up and 18 patients were followed up for 3-5 years (mean,3.9 years).At final follow-up,13 patients regained the ability to walk independently,4 needed support of a cane,1 needed assistance of a walker.There were no signs of loosening,subsidence or rupture of the prosthesis.Mean Harris hip score increased from 25.3 points preoperatively to 80.6 points at final follow-up; the score was excellent in 11 patients,good in 6,good in 1,with the excellent and good rate of 94％.Conclusion THA can improve hip function,patients' quality of life and midterm outcome in salvage of failed internal fixation of intertrochanteric fractures.