A biomechanical comparison of different fixation techniques for fractures of the acetabular posterior wall

This study aimed to evaluate the biomechanical stability of different fixation techniques for fractures of the acetabular posterior wall. The hypothesis was that a reconstruction plate, combined with compression screw fixation and a plate placed lateral to the screws, would achieve a higher peak load to failure and stiffness and reduced gapping during cycle loading than other fixation techniques.

A total of 24 Sawbone pelvis models were created with simulated fractures at the posterior wall of the acetabulum. Anatomic reduction and internal fixation were performed randomly using one of four techniques: (A) reconstruction plate and compression screw fixation was placed with a plate medial to the screws; (B) plate and screw fixation with the plate located lateral to the screws; (C) plate fixation alone, and (D) screw fixation alone. Six models were tested in each group under cyclic and sustaining loading tests. Peak load to failure and stiffness were calculated from load displacement curves.

Peak load to failure and stiffness in group B (3698.71 N and 2900.48 N/mm, respectively), featuring reconstruction plate and compression screw fixation with the plate placed lateral to the screws, were significantly higher than groups C (2508.74 N, 1602.75 N/mm) and D (2332.06 N, 1454.26 N/mm). No statistical differences were observed when group A (2941.60 N, 2136.50 N/mm) was compared with the other groups. There were no significant differences in gapping between groups.

Fixation using a reconstruction plate and compression screws placed lateral to the screws may address acetabular posterior wall fractures in a more appropriate manner than techniques using only plates or screws. However, this study does not provide evidence to support the fact that placing the plate lateral to the screws is advantageous in comparison with other techniques.