Biomechanical Analysis And Clinical Study Of Ilioischial Plate Combined With Posterior Column Lag Screw For Acetabulum Posterior Column Fractures

Objective:1.To investigate the fixation strength of acetabulum posterior column fracture model with different combinations of plate and lag screw in sitting position.2.To investigate the feasibility and clinical efficacy of the combination of ilioischial plate and posterior column lag screw fixation methods in actual clinical practice.Methods:1.To investigate the mechanical strength of different combinations of plate and posterior column lag screw fixation in the sitting position of the acetabulum posterior column fracture model.A moistened human hip bone model（hip bone was disconnected from the sacroiliac joint and pubic symphysis）was taken,and soft tissues such as muscles were removed,leaving the articular pelvis intact.Physical observation and X-ray plain radiographs were used to exclude bony abnormalities.The model was built according to the protocol reported by Knight^[1].The different fixation protocols were combined with each other into 4 groups.（1）ilioischial plate group.（2）posterior column plate group.（3）2 paralleling posterior column lag screws group.（4）ilioischial plate combined with one paralleling posterior column lag screw group.The fixed fracture model was placed on the testing machine,and both ends were fixed with type II denture base resin,and the mechanics machine was pressed on the sciatic tuberosity and iliac crest to simulate sitting position.The displacement of the fracture ends was measured using the Digital Image Correlation Method（DICM）.The axial load that the internal fixation model could withstand was recorded and the shear stiffness of each group of models was compared at each moment to analyze the strength of the internal fixation effect.2.To explore the feasibility and clinical efficacy of the combination of ilioischial plate and posterior column lag screw fixation methods in actual clinical application.Retrospective analysis of the clinical data of 15 patients with a total of 20 lateral acetabulum posterior column fractures treated with ilioischial plate combined with posterior column lag screw from December 2019 to June 2021 in our hospital.There were 10 male cases and 5 female cases,and the mean age of the patients was 48.5 years.The operative time,operative blood loss,fracture healing time,short-term as well as long-term complications were recorded precisely and in detail for each patient.Reconstruction as well as postoperative recovery outcome of the patients was assessed by Matta score,modified Merle D’Aubigne&Postel score and Majeed score.Result:1.In the specimen experiment,all four groups of internal fixation models showed no irreversible damage after internal fixation and during loading,and the internal fixation devices did not loosen,pull out or break.Among them,the simple ilioischial plate and simple posterior column plate fixation groups shifted up to 3 mm when loaded to a mean of735 N and 413 N,respectively（the difference was not statistically significant）.In contrast,the 2 paralleling posterior column lag screws and the ilioischial plate combined with 1paralleling screw group reached a displacement of 3 mm at a mean loading to 747N and1194N（the difference was statistically significant）.The four groups of internal fixation models provided strength in the order of ilioischial plate combined with one paralleling posterior column lag screw group>2 paralleling posterior column lag screws group>plate fixation group alone,and the differences were statistically significant.The model of the ilioischial plate combined with 1 paralleling posterior column lag screw group showed different fracture displacement directions under the same loading method.2.In the clinical retrospective analysis,the surgery was successfully completed in all 15patients with a mean operative time of 188（125-270）min.The mean intraoperative blood loss was 583.3（200-2000）ml.The bedside radiographs were reviewed on the next day of surgery,and the effect of the repositioning was assessed by Matta score,with an excellent rate of 86.7%.The patients were followed up satisfactorily for a mean of 13.7 months,with a mean fracture healing time of（3.2±0.6）months and satisfactory hip mobility in the long term.The patient’s Merle d’Aubigne and Postel hip function scores at the 12 month were（15.3±1.8）;Majeed pelvic function score was（78.6±8.5）.Conclusion:By using both the ilioischial plate and the posterior column lag screw,it was possible to visualize the fixation of the acetabulum posterior column through a single incision.This provides higher internal fixation stiffness without additional exposure and may allow earlier weight-bearing activities than previously.The quality of repositioning and the long-term follow-up of patients with this solution were found to be satisfactory during actual follow-up,and it has clinical value.