Objective:To explore risk factors for refracture after percutaneous kyphoplasty(PKP)in elderly patients with osteoporotic vertebral compression fractures(OVCF)and provide clinical guidance.Methods:A retrospective analysis was conducted on clinical data from elderly patients with OVCF who underwent PKP surgery at the Department of Orthopedics, Shanxi Bethune Hospital, between January 2017 and December 2022.All patients were followed up for a minimum of one-year post-surgery.The elderly patients were categorized into a refracture group(59 cases)and a non-refracture group(200 cases)based on post-surgery refracture occurrence.Univariate analysis was initially conducted on the collected data, followed by multivariate Logistic regression analysis on statistically significant indicators to identify risk factors for refracture in elderly patients with OVCF following PKP.Results:The results of the univariate analysis indicated that there was no statistically significant difference in gender, history of diabetes mellitus, history of smoking, history of hormone medication, and body mass index(BMI)between the refracture group and the non-refracture group of elderly patients.However, the refracture group was found to be older than the non-refracture group( t=9.085, P=0.003).Additionally, there were no significant differences in preoperative indicators such as preoperative calcium, preoperative phosphorus, and site of first fracture(all P>0.05).The time from first fracture to surgery being greater than 14 days was more common in the refracture group compared to the non-refracture group( χ2=20.409, P=0.001), and the number of vertebrae fractured for the first time was higher in the re-fracture group( t=6.189, P=0.017).Cement injection method, amount of cement injected, and distribution of cement did not show significant differences between the two groups(all P>0.05).However, there were statistically significant variations in the proportion of postoperative anti-osteoporosis treatment( χ2=13.431, P=0.001)and bone mineral density( χ2=13.431, P=0.001)between the refracture and non-refracture groups.Furthermore, multifactorial Logistic regression analysis revealed that increasing age( OR=1.061, 95% CI: 1.021-1.103, P=0.003), time from first fracture to surgery exceeding 14 days( OR=5.026, 95% CI: 1.968-12.835, P=0.001), lack of anti-osteoporosis treatment( OR=3.493, 95% CI: 1.239-9.846, P=0.018), and decreased bone mineral density( OR=10.682, 95% CI: 2.707-42.151, P=0.001)were identified as influential factors in the occurrence of secondary vertebral compression fracture after surgery. Conclusions:The independent risk factors for refracture after PKP in elderly patients with OVCF include increasing age, time from first fracture to surgery greater than 14 days, lack of anti-osteoporosis treatment, and decreased bone mineral density.In clinical practice, targeted interventions can be implemented for prevention and effective management based on these risk factors to enhance the prognosis of elderly patients with OVCF.

BACKGROUND:The angle of screw placement in anterior cervical discectomy and fusion plays a crucial role in determining the stability of the internal fixation system. OBJECTIVE:To predict the impact of different screw placement angles on the stress experienced by the internal fixation system in anterior cervical discectomy and fusion utilizing finite element analysis,with the ultimate goal of identifying the optimal screw placement angle. METHODS:A three-dimensional reconstruction method was employed to establish a mechanical model of the cervical spine,enabling the simulation of three distinct working conditions:scoliosis,uprightness,and forward flexion.In SolidWorks 2017,the anterior cervical plate and screw models were built according to different placement angles of the screws,with a as the inward offset,b as the ideal position,c as the outward offset,d as the downward offset,and e as the upward offset.The stress distribution of internal fixation system at different screw placement angles was observed,and the stress and displacement were recorded. RESULTS AND CONCLUSION:(1)By constructing a finite element model of the entire cervical spine and incorporating an anterior titanium plate,it was found that the biomechanical changes in the spine did not significantly differ based on the various angles of screw insertion on the titanium plate under the same working conditions.(2)However,microscopic analysis revealed that the outward offset(c)screw position exhibited the most effective resistance against side bending,while the downward offset(d)screw demonstrated optimal load-bearing capacity in the upright condition.Additionally,the outward deviation(c)screw displayed superior anti-bending effects in the reverse buckling condition.(3)The fixation effect of the internal fixation device remained relatively stable across different motion conditions.Although there was a 10％variation in the internal fixation effect under the three working conditions when the screw was placed inward,outward,downward,or upward,the displacement changes were minimal.These findings suggest that the requirements of load bearing,bending resistance,and flexion resistance could be simultaneously met without a specific optimal screw location in clinical practice.(4)The placement direction of titanium plate screw in anterior cervical disc-resection and fusion has little effect on the mechanical stability of the cervical spine.The screw angles in different directions have little influence on the stability of the internal fixation device in the lateral,upright,and forward flexion movements of the cervical spine.There is no need to pursue the direction of screw placement in clinical operations.