Objective To compared different fixation methods for acetabular fractures involving the quadrilateral plate using a finite element model of the acetabulum.Methods A model of acetabular fractures with quadrilateral plate involved was developed in the finite element software and processed in Hypermesh V10.0 to generate internal fixation with dual-column titanium plate (Group A),anterior special titanium moulding plate plus quadrilateral screws (Group B),and anterior special titanium moulding plate plus quadrilateral screws combined with posterior column screws (Group C).Pelvic stress in sitting and standing positions were simulated in sequence with constraint of tuber nodes and inferior femur.Maximum stress and displacement of the acetabulum and displacement of nodes on fracture lines were measured after a force of 600 N was applied to S1 verterbrae in line with the direction of gravity in sitting and standing positions.Results In sitting position,the maximum stress and displacement of the acetabulum exhibited a sequence of Group C (9.47,1.08) ＜ Group B (19.84,1.11) ＜ Group A (29.73,1.14).Moreover,the same result was found in standing position with Group C (9.62,1.09) ＜ Group B (12.18,1.10) ＜ Group A (13.28,1.13).Mean displacement of nodes on fracture lines ranked in order of Group C ＜ Group B ＜ Group A (P ＞ 0.05).Conclusions The finite element model can reflect the distribution of pelvic stress effectively.Anterior special titanium moulding plate plus quadrilateral screws combined with posterior column screws provide favorable biomechanical stability in treatment of acetabular fractures involving the quadrilateral area.

Objective To evaluate the recent clinical outcomes of fixing posterior acetabular wall fractures combining the AO mini plate with reconstruction plate.Methods From Jan 2009 to Jul 2013,28 patients with posterior acetabular wall fracture were fixed by the AO mini-steel plate combined with reconstruction plate,including 17males and 11 females with the mean age of 45.8 years (range,18-65).After admission,reduce the dislocation of hip joint immediately,and take femoral condyle or tibial tubercle traction.Preoperative and postoperative anteroposterior and Judet oblique radiographs,acetabular CT scan and three-dimensional reconstruction imaging were routine taken.Using Kocher-Langenbeck approach,intraoperative,try to protect the soft tissue attached on the small fragments,and reduct the fracture.Cutting the mini plate into proper length with reconstruction plate fix to its surface crossover.The functional outcomes were evaluated by the modified Merle d'Aubigné and Postel clinical grading system.The radiographs were graded according to the Matta/Judet criteria.Results Twenty-three patients are followed up 13 months(82.2％),and 5 cases lost in 12 weeks (17.8％).By the Matta/Judet criteria,22 cases achieved excellent reduction,4 good reduction and two fair reduction,with a good and excellent rate of 92.8％.By the modified Merle d'Aubigné and Postel criteria,functional recovery of the affected hip six month post-operation was rated as excellent in 15 cases,good in 5 cases,fair in 2 cases and poor in one case.with a good and excellent rate of 87.9％.One case occurred femoral head necrosis.In 2 patients 2 years after surgery developed traumatic arthritis.Two patients had heterotopic ossification after six month operation.One patient with injury to the sciatic nerve recovered 3 months post-operation.Conclusion Using the AO mini plate combined with reconstruction plate can fix the acetabular posterior wall fractures stably.The technique meet the requirements of patients with early functional exercise,which provides an effective method of internal fixation.