Is cement-augmented sacroiliac screw fixation with partially threaded screws superior to that with fully threaded screws concerning compression and pull-out force in fragility fractures of the sacrum? \u2013 a biomechanical analysis

Juliana Hack,Julia Lenz,Ludwig Oberkircher,Maiwand Safi,Christopher Bliemel,Steffen Ruchholtz,Martin Bäumlein

doi:10.1186/s12891-021-04933-y

Juliana Hack, Julia Lenz + Show 5 more

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https://doi.org/10.1186/s12891-021-04933-y

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Abstract

BackgroundProviding a stable osteosynthesis in fragility fractures of the pelvis can be challenging. Cement augmentation increases screw fixation in osteoporotic bone. Generating interfragmentary compression by using a lag screw also improves the stability. However, it is not known if interfragmentary compression can be achieved in osteoporotic sacral bone by cement augmentation of lag screws.The purpose of this study was to compare cement-augmented sacroiliac screw osteosynthesis using partially versus fully threaded screws in osteoporotic hemipelvises concerning compression of fracture gap and pull-out force.MethodsNine fresh-frozen human cadaveric pelvises with osteoporosis were used. In all specimens, one side was treated with an augmented fully threaded screw (group A), and the other side with an augmented partially threaded screw (group B) after generating a vertical osteotomy on both sides of each sacrum. Afterwards, first a compression test with fracture gap measurement after tightening of the screws was performed, followed by an axial pull-out test measuring the maximum pull-out force of the screws.ResultsThe fracture gap was significantly wider in group A (mean: 1.90 mm; SD: 1.64) than in group B (mean: 0.91 mm; SD: 1.03; p = 0.028).Pull-out force was higher in group A (mean: 1696 N; SD: 1452) than in group B (mean: 1616 N; SD: 824), but this difference was not statistically significant (p = 0.767).ConclusionsCement augmentation of partially threaded screws in sacroiliac screw fixation allows narrowing of the fracture gap even in osteoporotic bone, while resistance against pull-out force is not significantly lower in partially threaded screws compared to fully threaded screws.

Highlights

Providing a stable osteosynthesis in fragility fractures of the pelvis can be challenging
The fracture gap was significantly wider in group A than in group B
Only one study concerning this topic can be found: that of Wähnert et al, who performed a biomechanical study with cement-augmented lag screws in osteoporotic surrogate bones and demonstrated that cement augmentation can significantly improve interfragmentary compression [9]

Summary

Introduction

Providing a stable osteosynthesis in fragility fractures of the pelvis can be challenging. Generating interfragmentary compression by using a lag screw improves the stability. It is not known if interfragmentary compression can be achieved in osteoporotic sacral bone by cement augmentation of lag screws. Because of the weak screw anchorage in osteoporotic bone, lag screws cannot be used to generate interfragmentary compression. Hardly anything is known regarding the question of whether interfragmentary compression can be achieved by cement augmentation of lag screws in osteoporotic bone. Only one study concerning this topic can be found: that of Wähnert et al, who performed a biomechanical study with cement-augmented lag screws in osteoporotic surrogate bones and demonstrated that cement augmentation can significantly improve interfragmentary compression [9]

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