Biomechanical Comparison of Different Fixation Techniques for Typical Acetabular Fractures in the Elderly: The Role of Special Quadrilateral Surface Buttress Plates

BACKGROUND: Anterior column-posterior hemitransverse fractures are prevalent in the elderly and are often associated with quadrilateral surface (QLS) comminution. Several special QLS buttress plates have been introduced, but evidence of their comparability with traditional fixation devices is lacking. This biomechanical study aimed to compare special QLS buttress plates with traditional fixation devices. METHODS: Anterior column-posterior hemitransverse fractures with an isolated QLS fragment were created on 24 composite hemipelves and were allocated to 4 fixation groups: (1) infrapectineal QLS buttress plate, (2) suprapectineal QLS buttress plate, (3) suprapectineal reconstruction plate with 3 periarticular long screws, and (4) infrapectineal reconstruction plate with 3 periarticular long screws. Specimens were loaded to simulate partial weight-bearing (35 to 350 N) or full weight-bearing (75 to 750 N). A testing machine was synchronized with a 3-dimensional video tracking system to optically track displacement at the points of interest and to calculate construct stiffness. The fixation systems were compared using the Kruskal-Wallis and Mann-Whitney U tests. RESULTS: The experimental results of the partial and full weight-bearing simulations were surprisingly similar. During 40 loading cycles, the maximum displacement on the 6 predetermined points did not exceed 1.1 mm. Multiple-group comparisons of relative displacements of each predetermined measurement point did not differ significantly (p > 0.05). The suprapectineal reconstruction plate with 3 periarticular long screws demonstrated the greatest construct stiffness and significantly greater stiffness than the infrapectineal plate with long screws (p < 0.017). However, no significant difference (p > 0.017) in stiffness was identified between the infrapectineal QLS buttress plate and the suprapectineal reconstruction plate with long screws. CONCLUSIONS: The suprapectineal pelvic brim plate with 3 periarticular long screws remains the gold standard to treat anterior column-posterior hemitransverse fractures. The special infrapectineal QLS buttress plate provides stiffness and stability comparable with those of standard fixation. However, moving the pelvic brim plate from the suprapectineal border to the infrapectineal border is not recommended for anterior column-posterior hemitransverse fractures because it significantly decreases fixation stiffness. CLINICAL RELEVANCE: Special QLS buttress plates may be an alternative fixation method for anterior column-posterior hemitransverse acetabular fractures in the elderly, especially when a less invasive anterior intrapelvic approach is selected.