Contributions of Pubic Rami Fracture Morphology and Fixation to Pelvic Ring Stability in Type 1 Lateral Compression Injuries: A Biomechanical Cadaveric Study.

Abstract

Treatment of lateral compression type 1 (LC-1) injuries has historically been nonoperative with immediate weight-bearing. However, management of these injuries remains controversial, with reports of displacement at follow-up for nonoperatively managed LC-1 fractures. The goal of our study was to determine the effect of superior pubic ramus fracture morphology and fixation construct on pelvic stability. Ten fresh-frozen cadaveric were transected into hemi-pelvises. Incomplete Denis type 1 sacral fractures were made. Hemi-pelvises were randomized to receive a transverse-type or oblique-type superior pubic ramus fracture with the contralateral hemi-pelvis receiving the opposing morphology. A lateral load to 135N was applied with an Instron materials testing machine and lateral displacement of the hemi-pelvis was recorded. Deflection and stiffness were calculated. Statistical analysis was conducted using a t test assuming unequal variances with an alpha = 0.05. Oblique-type superior pubic ramus fractures allowed more deflection compared with transverse-type fractures in the absence of fixation (P = 0.018). The posterior-only and combined anterior and posterior fixation configurations on average reduced deflection more than no fixation or anterior fixation only. In all fixation configuration cases, the average deflection for transverse-type fractures was less than that of the oblique-type fractures. Our findings suggest that displacement of LC-1 pelvic injuries may be related to pubic rami fracture morphology. When looking at initial injury imaging, oblique-type pubic rami fractures may suggest an increased potential for displacement over time. In such cases, we recommend an examination under anesthesia to evaluate for underlying instability and consideration for fixation. Therapeutic Level V.