Sacroiliac versus transiliac–transsacral screw osteosynthesis in osteoporotic pelvic fractures: a biomechanical comparison

Introduction Pelvic fractures were often associated with high-energy trauma in young patients, but data show a significant increase in osteoporotic pelvic fractures in old age due to the progressive demographic change. There is an ongoing discussion about the best fixation techniques, which are ranging from lumbopelvic fixation to sacral bars or long transiliac–transsacral (TITS) screws. This study analyzes TITS screw osteosynthesis and sacroiliac screw osteosynthesis (SI), according to biomechanical criteria of fracture stability in osteoporotic human pelvic cadavers ex vivo. Methods Ten osteoporotic cadaveric pelvises were randomized into two groups of 5 pelvises each. An FFP-IIc fracture was initially placed unilaterally and subsequently surgically treated with a navigated SI screw or a TITS screw. The fractured side was loaded in a one-leg stance test setup until failure. Interfragmentary movements were assessed by means of optical motion tracking. Results No significant difference in axial stiffness were found between the SI and the TITS screws (21.2 ± 4.9 N and 18.4 ± 4.1 N, p = 0.662). However, there was a significantly higher stability of the fracture treatment in the cohort with TITS-screws for gap angle, flexion, vertical movement and overall stability. The most significant difference in the cycle interval was between 6.000 and 10.000 for the gap angle (1.62 ± 0.25° versus 4.60 ± 0.65°, p = 0.0001), for flexion (4.15 ± 0.39 mm versus 7.60 ± 0.81 mm, p = 0.0016), interval 11.000–15.000 for vertical shear movement (7.34 ± 0.51 mm versus 13.99 ± 0.97 mm, p < 0.0001) and total displacement (8.28 ± 0.66 mm versus 15.53 ± 1.07 mm, p < 0.0001) for the TITS and the SI screws. Conclusions The results of this biomechanical study suggest a clear trend towards greater fracture stability of the TITS screw with significantly reduced interfragmentary movement. The application of a TITS screw for the treatment of the osteoporotic pelvic ring fracture may be prioritized to ensure the best possible patient care.