Sergio Gómez González1, Gerard Cabestany Bastida1, Maria Daniela Vlad1,2, José López López1, Pablo Buenestado Caballero3, Luis Alvarez-Galovich4, Maria Rodríguez-Arguisjuela4, Enrique Fernández Aguado5. 1. Research Group of Interacting Surfaces in Bioengineering and Materials Science (InSup), Technical University of Catalonia (UPC), Avda. Diagonal 647, 08028, Barcelona, Spain. 2. Faculty of Medical Bioengineering, "Grigore T. Popa" University of Medicine and Pharmacy Iasi, Str. Kogalniceanu 9-13, 700454, Iasi, Romania. 3. Department of Mathematics, Technical University of Catalonia (UPC), Avda. Eduard Maristany 16, 08019, Barcelona, Spain. 4. Spine Unit, Hospital Universitario Fundación Jimenez Díaz, Avda. Reyes Católicos 2, 28040, Madrid, Spain. 5. Research Group of Interacting Surfaces in Bioengineering and Materials Science (InSup), Technical University of Catalonia (UPC), Avda. Diagonal 647, 08028, Barcelona, Spain. enrique.fernandez@upc.edu.
Abstract
PURPOSE: 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. METHODS: 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. RESULTS: 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. CONCLUSIONS: 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.
PURPOSE: 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. METHODS: 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. RESULTS: 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. CONCLUSIONS: 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.
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