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Biomechanical study on three posterior ring pelvic fixation methods in the elderlyObjective: About 60% of the stability of the pelvis depends on the posterior pelvic structure.There is a significant difference between elderly patients with pelvic fractures and young patients.Currently,biomechanical studies specifically targeted at the elderly are still very lacking.The purpose of this study was to evaluate and compare the biomechanical stability of three common posterior pelvic ring fixation methods in the elderly.Methods: Six cadaver pelves were used to imitate the injuried pattern of symphysis diastasises on anterior pelvic ring and sacral alar fracture on posterior pelvic ring.The anterior ring was fixed with reconstruction plate.The posterior ring was fixed with 3 different methods(Group A: triangular osteosynthesis;Group B: double-sacroiliac screw fixation(S1+S2);Group C: posterior tension band plate fixation).Each pelvic specimen was repeatedly fixed by the 3 methods,and tested for 3 indicators :(1)axial rigidity of pelvis;(2)displacement at the sacral fracture;(3)displacement at the symphysis pubis.Results: In group A,the axial rigidity of the pelvis was 35.44±7.24N/mm,the displacement at the sacral fracture was 1.14±0.40 mm,the displacement at the symphysis pubis was 0.99±0.30 mm.In group B,the axial rigidity of the pelvis was 33.93±12.45 N/mm,the displacement at the sacral fracture was 2.50±1.37 mm,the displacement at the symphysis pubis was 1.39 0.71 mm.In group C,the axial rigidity of the pelvis was 21.76±6.00 N/mm,the displacement at the sacral fracture was 3.42±1.71 mm,the displacement at the symphysis pubis was 2.12±1.00 mm.All the 3 indicators in group A were significant different from these in group C(P < 0.05).Conclusions:(1)Triangular osteosynthesis is suggested for treating FFP ?b type pelvic fractures in the elderly.(2)Percutaneous sacroiliac screw is a very suitable fixation method for posterior ring pelvic fractures in the elderly because of adequate biomechanical stability and minimally invasive advantage.Part ? A novel guide device for pelvic corridor screw insertion: design details and clinical application for iliosacral screw insertionObjective: Iliosacral screw fixation is a popular method for the management of posterior pelvic ring fractures in the elderly because of adequate biomechanical stability and minimally invasive advantage.Our aim in this study was to describe the use of a new patient-specific external template to guide the insertion of iliosacral screws and to evaluate the efficacy and safety of this technique compared with the conventional fluoroscopy-guided technique.Methods: This was a retrospective study of patients with incomplete or complete posterior pelvic ring disruptions who required iliosacral screw fixation.For analysis,patients were divided into two groups: the external template group(38 screws in 22 patients)and the conventional group(30 screws in 18 patients).The operative time per screw,radiation exposure dose and the rate of screw perforation were compared between groups.In the external template group,the difference between the actual and planned iliosacral screw position was also compared.Results: In the conventional group,the average operative time per screw was 39.8 ± 10.6 min,with an average radiation exposure dose of 1904.0 ± 844.5 c Gy/cm2,with 4 cases of screw perforation.In the external template group,the average operative time per screw was 17.9 ± 4.5 min,with an average radiation exposure dose of 742.8 ± 230.6 c Gy/cm2 and 1 case of screw perforation.In the template group,the mean deviation distance between the actual and planned screw position was 2.8 ± 1.1 mm at the tip,1.8 ± 0.7 mm in the nerve root tunnel zone and 1.5 ± 0.5 mm at the entry point,with a mean deviation angle of 1.7 ± 0.8°.Conclusions: The external template provides an accurate and safe navigation tool for percutaneous iliosacral screw insertion that could decrease the operative time and radiation exposure.Considering the high accuracy in iliosacral screw placement that we achieved using an external template,we propose that this technique could potentially be used for other percutaneous insertions of screws in pelvic or acetabular surgery.Part ? A new combinational anatomic plate on quadrilateral area for acetabular fractures: design details and finite element analysisObjective: The intrapelvic approaches were increasingly used these years,which enlarge adequate exposure of the deep quadrilateral area.Complying with this new tendency,our team developed a new combinational anatomic plate on quadrilateral area(screws should be placed in deep quadrilateral area)according to “periacetabular fixation frame” theory.This study would evaluate the biomechanical stability of the new plate by finite element analysis.Methods: CT data of a healthy male adult were obtained to create pelvic model with anterior column and posterior hemitransverse type fracture.Four different fixations were applied on this model,including(A)combinational anatomic plate based on infrapectineal plate(B)combinational anatomic plate based on suprapectineal plate,(C)two plates on anterior column and posterior column,(D)suprapectineal plate + long peri-articular screws parallel to the quadrilateral surface.The displacement on the fracture line and stress distribution on fixator were observed when 700 N loading in standing position.Results: Among the 20 observation points along the fracture line,the displacement on point 1-11 was larger than that on point 12-20.The comparison result of the displacement of 4 fixation methods were: D < A < B < C.The maximal stress was located near the last screw hole of the ilioischial plate when combinational anatomic plating,and was located at the middle part of the posterior column plate when two plate fixed on anterior column and posterior column.Conclusions: the two combinational anatomic plate fixation methods are stiffer than the method of two plates placed on both columns in ACPHT fractures.In the case of osteoporotic patients,it is suggested that 2 screws should be inserted into the last 2 screw holes of the ilioischial plate for a better stress distribution.Part ? Internal fixation of acetabular fractures in the elderly using combinational plate on quadrilateral area: a case seriesObjective: On designing stage of anatomic combinational plate,we used reconstruction plates to imitate combinational plate on quadrilateral area to treat elderly patients with acetabular fractures.This part of study was planned to evaluate the clinical outcome preliminarily.Methods: The clinical data of 10 elderly patients with acetabular fractures who were treated with quadrilateral combinational plate from August 2016 to December 2017 were reviewed.There were 5 males and 5 females,with an average age of 64.5±2.3 years.All patients were treated through supra-ilioinguinal approach using quadrilateral combinational plate based on infrapectineal plate(simulated by reconstruction plates).The operation time,blood loss,fracture reduction,functional outcome,fracture healing and other common indicators were evaluated.Intraoperative and postoperative complications were also analyzed.Results: The operative time was 100-180 min,with an average of 136.0±26.7min.The intraoperative blood loss was 350-1100 ml,with an average of 650.0±249.4ml.According to the Matta standard,anatomic reduction was performed in 6 cases,satisfactory reduction in 2 cases,and unsatisfactory reduction in 2 cases,with an excellent and good rate of 80.0%(8/10).No lose of reduction was seen in the follow-up.According to the Merle d 'aubigne-postel standard,the functional outcome was excellent in 4 cases,good in 3 cases,fair in 2 cases and poor in 1 case.Complications included intraoperative peritoneal rupture in 1 case,postoperative obturator nerve palsy in 1 case,lateral femoral cutaneous nerve palsy in 1 case,and incision fat liquefaction in 1 case.Conclusion: Combinational plate on quadrilateral area performed good results in preliminary clinical application,and no serious complications have been observed.With the assistance of 3D printing technology,reconstruction plates could be shaped preoperatively and used as quadrilateral combinational plate conveniently during operation.This internal fixation method is a good alternative to anatomic products. |
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