Analysis of bone cement distribution around fenestrated pedicle screws in low bone quality lumbosacral vertebrae
To study the exact distribution of bone cement around augmented fenestrated pedicle screws in both lumbar and sacral vertebrae of patients with low bone quality.
A total of 37 patients with instrumented lumbar fusion were investigated. 3D computed tomography virtual models of the injected cement and screws were obtained. The models were computed for their centroid (i.e. their average mass centre point), and their coordinates (x, y, z) were projected on their respective screw-transversal and screw-longitudinal planes for further analysis.
The results showed better bone cement homogeneous distribution around the screws in lumbar (L4 and L5) than in sacral (S1) vertebrae. In the lumbar region, the centroids were transversally projected near the transversal centre of symmetry of the screws. On the other hand, in the sacral region, the cement flowed preferentially outside the centre of symmetry of the screws, into the sacral ala.
The results confirm the different flow behaviours of bone cement in lumbar versus sacra vertebrae. The computer methodology followed in this study helps to understand the clinical monitoring observations and lays the foundations for better positioning of the screws and specific vertebrae-oriented screw designs.
KeywordsSpine screws Cement augmentation Pedicle screw augmentation Computed tomography—CT Computer assisted design—CAD
The institutional support received through project 2017SGR253 is acknowledged (Agència de Gestiò d’Ajuts Universitaris i de Recerca, Generalitat de Catalunya, Spain).
This work received public funding through project DPI2016-77768-R (Ministerio de Economía y Competitividad, Spain).
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
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