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 effects of unilateral ureteral obstruction on renal pelvic peristalsis and pacemaker cells in neonatal rats.Methods:An animal experimental study.Thirty-six 2-day-old newborn SD rats were randomly divided into the partial unilateral ureteral obstruction (PUUO) group, complete unilateral ureteral obstruction (CUUO) group, and sham operation group, with 12 rats in each group.One week after surgery, all rats were subjected to renal pelvic pressure (RPP) measurement by puncture.After measurement, the rats were euthanized, and their left renal pelvis and ureter were removed and fixed for histological examination.Parameters such as RPP, peristaltic wave frequency and amplitude at different perfusion speeds were recorded and compared, and the changes in pacemaker cells (atypical smooth muscle cells and Cajal-like interstitial cells) were also compared.The independent samples t-test was used for comparison between 2 groups, and the one-way ANOVA of variance was used for comparison among 3 groups. Results:In the sham operation group, the RPP increased gradually with the increase of perfusion speed; the frequency of peristaltic waves rose rapidly and then dropped after reaching the highest level with the increase of perfusion speed; similarly, the amplitude of peristaltic waves first increased and then decreased as the perfusion speed increased.In the PUUO group, the RPP increased rapidly with the increase of perfusion speed, higher than that in the sham operation group; the frequency of peristaltic waves was higher than that in the sham operation group, and it was relatively constant under the perfusion speed of 40 mL/h, but when the perfusion speed increased again, the frequency began to decline; the amplitude of peristaltic waves increased quickly and then declined at a faster rate than the sham operation group with the increase of perfusion speed.In the CUUO group, the basic RPP was 12 cmH 2O(1 cmH 2O=0.098 kPa); at the perfusion speed of 5 mL/h, the RPP rose gradually, and no plateau appeared; when the RPP reached 73 cmH 2O, the perfusate retrograded from the side of the puncture needle, then the RPP slightly decreased and then balanced, and no regular peristaltic waves were observed in the renal pelvis throughout the whole perfusion process.Immunofluorescence staining analysis showed the pacemaker cells were all located in the smooth muscle of the renal pelvic wall.The sham operation group had the highest positive rate, followed by the PUUO group and then the CUUO group. Conclusions:Ureteral obstruction has a significant impact on the peristalsis of the renal pelvis, and its impact on the peristaltic wave frequency and amplitude and RPP can be predicted.The reduction of pacemaker cells in the renal pelvis may be involved in the changes of renal pelvic peristalsis caused by ureteral obstruction, but further research is needed on how pacemaker cells regulate the peristalsis of the renal pelvis and ureter.

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.