gms | German Medical Science

Objectives: The surgical stabilization of a symphyseal diastasis in partially or fully unstable pelvic ring injuries is an important element when stabilizing the anterior pelvic ring. Currently, open reduction and internal fixation (ORIF) by means of plating presents the gold standard treatment. With general advances in percutaneous fixation techniques, showing improvements in blood loss, surgery time, and scar length, this approach should also be adopted for the treatment of symphyseal injuries. Especially since failure-rates, following ORIF at the symphysis, remain unacceptably high. The aim of this biomechanical study was to assess a semi-rigid fixation technique for such anterior pelvic ring injuries compared to single and double plate osteosynthesis.

Methods: An anterior pelvic ring injury type III APC according to the Young and Burgess classification was simulated in eighteen anatomical composite pelvises, which were stratified into three groups (N = 6) for instrumentation with either a single plate, two orthogonally positioned plates, or the semi-rigid technique using a endobutton-suture implant. Biomechanical testing of each construct was performed in simulated upright standing position at a rate of 2 Hz with a valley load of 20 N and a peak load starting at 200 N that was increased at a rate of 0.05 N/cycle until failure or until 150,000 cycles. Relative displacements of the bone fragments were measured by means of motion tracking.

Results: Initial quasi-static and dynamic stiffness, as well as for dynamic stiffness after 100,000 cycles showed no significant differences between the groups (p = 0.054).

The outcome measures for total displacement, analyzed over the five time points after 20,000, 40,000, 60,000, 80,000, and 100,000 cycles were associated with significantly higher values for group STR versus group SDP (p = 0.025), without further significant. The numbers of cycles to failure and the corresponding load at failure were the highest in group SDP (150000 ± 0/100 ± 0 N), followed by group SSP (132,282 ± 20,465/91.1 ± 10.2 N), and group STR (116,088 ± 12,169/83.0 ± 6.1 N), with significantly lower values in group STR compared to group SDP (p = 0.002).

Conclusion: From a biomechanical perspective, the semi-rigid technique for fixation of pubic symphysis injuries demonstrated promising results with mainly comparable and partially superior outcomes. This knowledge could lay the foundation for the development of stronger and more robust implants, especially designed for the symphysis, which could provide significant results to establish minimally invasive/endoscopic surgical therapies for the fixation of the anterior pelvic ring in the future.