Is the transverse screw really necessary? Biomechanical comparison of fixation strategies in periasetabular osteotomy

Abstract This study aims to compare the biomechanical stability of different screw and plate configurations used in the fixation of acetabular fragments after periacetabular osteotomy (PAO). A total of 42 synthetic hemipelvis models were categorized into six fixation groups: three iliac screws (3 V), four iliac screws (4 V), three screws + lateral compression (LC) screw (3 V + LC), locking three-screw plate (3P), plate + LC screw (3P + LC), and eight-screw plate (4P). All samples were evaluated for stiffness under a constant load of 700 N and for stiffness under maximum load. The greatest failure load was observed in the 3 V group (1249.4 N), whereas the 3P group demonstrated the lowest (658.5 N). In terms of maximum force, both the 3 V and 4 V groups were significantly superior to the 3P (P = .003 and P = .018, respectively) and 3P + LC (P = .006 and P = .021, respectively) groups. Although the 4P configuration showed the highest fracture stiffness (155.1 N/mm), this did not differ significantly among groups. Stiffness at a constant load of 700 N, the 3 V and 3 V + LC groups demonstrated higher stiffness than the 3P and 3P + LC groups, with comparisons to the 3P group approaching statistical significance (P = .064 and P = .063, respectively). Traditional iliac screw structures (especially 3 V and 4 V) provide effective fixation in terms of load-bearing and stiffness, while plate-based systems require a high number of screws and optimal placement to provide adequate stability. Although the LC screw increases stiffness, it provides only a limited contribution to breaking strength.