Biomechanical comparison of three minimally invasive fixations for unilateral pubic rami fractures

BACKGROUND: To compare the mechanical characteristics of a percutaneous superior pubic intramedullary screw, percutaneous bridging plate and percutaneous screw-rod system of the anterior ring for the treatment of unilateral vertical pubic fractures to provide a reference for clinical application. METHODS: A finite element model of pelvic anterior ring injury (unilateral vertical pubic fracture) was produced. The fractures were fixed with a percutaneous superior pubic intramedullary screw, percutaneous bridging plate and percutaneous screw-rod system of the anterior ring and their combinations in 5 types of models. The fracture stabilities under vertical, bilateral and anterior-posterior load were quantified and compared based on the displacement of the hip joints’ midpoint as quantificational index of fracture stability. RESULTS: In the condition of bilateral and anterior-posterior load, the vertical, bilateral and anterior-posterior displacements of the hip joints’ midpoint of different models were significantly different respectively. In general, the displacements of the 5 pelvic anterior ring fixations were ranked from maximum to minimum as follows: bridging plate, pelvic anterior screw-rod system, combination of bridging plate and pelvic anterior screw-rod system, superior pubic intramedullary screw and combination of superior pubic intramedullary screw and pelvic anterior screw-rod system. CONCLUSION: For the fixation in unilateral pubic fractures of pelvic ring injury, the percutaneous superior pubic intramedullary screw is optimal, the percutaneous pelvic anterior screw-rod system is the second choice, and percutaneous bridging plate ranks the third. The percutaneous pelvic anterior screw-rod system can significantly increase fixation stability of the percutaneous superior pubic intramedullary screw and the percutaneous bridging plate.