Comparison of four kinds of internal fixation for acetabular fracture of the lower anterior column: a finite element analysis

Objective To compare the biomechanical stability of 4 internal fixations in treatment of acetabular fracture of the lower anterior column through finite element analysis. Methods One normal adult male pelvis was subjected to 0. 7mm thin-section CT scanning and 379 CT pictures were obtained. Finite element modeling software was used to establish internal fixation models for acetabular fracture of the lower anterior column, including lag screws(A), anterior column reconstruction plate(B), subcutaneous plate not crossing the pubic symphysis(C)and subcutaneous plate crossing the pubic symphysis(D). Finite element analysis was carried out to compare the biomechanical differences among the 4 internal fixation models which were subjected to the same loading conditions at both standing and sitting positions. Results At standing and sitting positions, the maximum displacement and the mean node displacement of fracture lines were the greatest in group A(0. 558 mm and 0. 462 ± 0. 092 mm at standing; 0. 634 mm and 0. 473 ±0. 108 mm at sitting), the smallest in group D(0. 512 mm and 0. 425 ±0. 083 mm at standing; 0. 031 mm and 0. 025土0. 004 mm at sitting), and in between in group B(0. 513 mm and 0. 432 ± 0. 085 mm at standing; 0. 630 mm and 0. 466 ± 0. 109 mm at sitting)and in group C(0. 514 mm and 0. 433 ± 0. 085 mm at standing; 0. 627 mm and 0. 464 ±0. 107 mm at sitting). At both standing and sitting positions, the maximum stress at the fracture line was the greatest in group D(10. 519 MPa and 24. 879 MPa), the smallest in group A(3. 254 MPa and 8. 954 MPa), and in between in group B(4. 873 MPa and 9. 431 MPa)and in group C(4. 384 MPa and 10. 128 MPa). Conclusions In treatment of acetabular fracture of the lower anterior column, subcutaneous plate crossing the pubic symphysis may result in the greatest biomechanical stability, lag screws the smallest biomechanical stability, and anterior column reconstruction plate and subcutaneous plate not crossing the pubic symphysis the moderate biomechanical stability. Key words: Acetabulum; Fractures, bone; Fracture fixation, internal; Finite element