Does Cement Augmentation of the Sacroiliac Screw Lead to Superior Biomechanical Results for Fixation of the Posterior Pelvic Ring? A Biomechanical Study

Abstract

Background and Objectives: The stability of the pelvic ring mainly depends on the integrity of its posterior part. Percutaneous sacroiliac (SI) screws are widely implanted as standard of care treatment. The main risk factors for their fixation failure are related to vertical shear or transforaminal sacral fractures. The aim of this study was to compare the biomechanical performance of fixations using one (Group 1) or two (Group 2) standard SI screws versus one SI screw with bone cement augmentation (Group 3). Materials and Methods: Unstable fractures of the pelvic ring (AO/OTA 61-C1.3, FFP IIc) were simulated in 21 artificial pelvises by means of vertical osteotomies in the ipsilateral anterior and posterior pelvic ring. A supra-acetabular external fixator was applied to address the anterior fracture. All specimens were tested under progressively increasing cyclic loading until failure, with monitoring by means of motion tracking. Fracture site displacement and cycles to failure were evaluated. Results: Fracture displacement after 500 cycles was lowest in Group 3 (0.76 cm [0.30] (median [interquartile range, IQR])) followed by Group 1 (1.42 cm, [0.21]) and Group 2 (1.42 cm [1.66]), with significant differences between Groups 1 and 3, p = 0.04. Fracture displacement after 1000 cycles was significantly lower in Group 3 (1.15 cm [0.37]) compared to both Group 1 (2.19 cm [2.39]) and Group 2 (2.23 cm [3.65]), p ≤ 0.04. Cycles to failure (Group 1: 3930 ± 890 (mean ± standard deviation), Group 2: 3676 ± 348, Group 3: 3764 ± 645) did not differ significantly between the groups, p = 0.79. Conclusions: In our biomechanical setup cement augmentation of one SI screw resulted in significantly less displacement compared to the use of one or two SI screws. However, the number of cycles to failure was not significantly different between the groups. Cement augmentation of one SI screw seems to be a useful treatment option for posterior pelvic ring fixation, especially in osteoporotic bone.

Cerclage augmentation of S1–S2 transsacral screw fixation in osteoporotic posterior pelvis ring injuries: A biomechanical feasibility study

“…A similar biomechanical investigation of cement augmentation of SI screws in osteoporotic bone found significantly less displacement, when compared with the use of one or two SI screws; however, regarding the number of cycles to failure, no significant difference between the groups could be found. 24 Other known disadvantages of cement augmentation are the possible leakage of cement into the fracture gap/spinal canal and cement embolism.…”

Comparative outcome of different treatment options for fragility fractures of the sacrum

“…As in our case, Höch et al [ 64 ] found a significant and sustained reduction in pain postoperatively in older, osteoporotic patients. Biomechanically, cement augmentation also reduces screw loosening in osteoporotic bone, supporting this approach [ 66 ]. In 8 out of 59 osteosyntheses, a transsacral screw fixation was performed, which allows an alternative to the cemented iliosacral screw due to a bilateral anchorage of the screw in the ilium [ 67 ], whereby no difference was found in the outcome in our patients.…”

Long-Term Follow-Up after Iliosacral Screw Fixation of Unstable Pelvic Ring Fractures

“…Before the introduction of this minimally invasive technique, posterior stabilization was performed using posterior and extensive surgical approaches, which are associated with a substantial soft tissue damage [13,14]. Advantages of the iliosacral screw are the minimally invasive surgical technique, the excellent biomechanical characteristics and the safe and effective clinical use [10,[15][16][17].…”