Biomechanical analysis of anterior ring fixation of the ramus in type C pelvis fractures
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This biomechanical study compared the stability of four different ramus fracture fixation methods for Type C pelvic ring injuries in the absence of posterior fixation.
A 5-mm vertical osteotomy of the mid-superior and inferior pubic ramus was created in 12 synthetic pelvic models. Four surgical constructs were compared: (1) two-pin AIIS external fixation, (2) 3.5-mm reconstruction plating, (3) bicortical, fully threaded 3.5-mm, and (4) 6.5-mm pubic ramus screws. Specimens were tested in a simulated one-legged stance on a hemiarthroplasty implant in three stages: (1) no applied load, (2) application of the loading fixture preload to the sacrum (6N), and (3) following six cycles of a 250N load. Stability was assessed based on resultant displacement of the fracture sites at the superior ramus and the anterior sacroiliac joint.
The bicortical, fully threaded 6.5-mm pubic ramus screw provided the most stable ramus fracture fixation (0.5 ± 0.4 mm) displacement under load and was the only construct to finish testing without gross posterior pelvic disruption. Plate constructs finished the final loading stage with only a small increase (3.1 ± 2.3 mm) in ramus fracture gap size, but had significant displacement at the SI joint (>20 mm). 3.5-mm screw constructs had 1.6 ± 0.7 mm of ramus displacement in the preload stage, but had complete posterior pelvic disruption (>20 mm) that prevented further testing. External fixation was unstable at the ramus and sacroiliac sites in the initial setup.
The bicortical, fully threaded 6.5-mm pubic ramus screw was the only anterior fixation construct tested that controlled motion at both the anterior and posterior pelvic rings in the absence of posterior fixation.
KeywordsPelvic fracture Anterior ring fixation Biomechanical stability
Compliance with ethical standards
Conflict of interest
Dr. Kreder is currently receiving grant funding from AO Trauma and Biomet. For the remaining authors none were declared.
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