Miguel Pishnamaz1, Henning Lange2, Christian Herren3, Hong-Sik Na4, Philipp Lichte5, Frank Hildebrand6, Hans-Christoph Pape7, Philipp Kobbe8. 1. University of Aachen Medical Center, Department of Orthopaedic Trauma, Pauwelsstraße 30, 52074 Aachen, Germany. Electronic address: mpishnamaz@ukaachen.de. 2. University of Aachen Medical Center, Department of Orthopaedic Trauma, Pauwelsstraße 30, 52074 Aachen, Germany. 3. University of Aachen Medical Center, Department of Orthopaedic Trauma, Pauwelsstraße 30, 52074 Aachen, Germany. Electronic address: cherren@ukaachen.de. 4. University of Aachen Medical Center, Department of Diagnostic and Interventional Radiology, Pauwelsstraße 30, 52074 Aachen, Germany. Electronic address: hna@ukaachen.de. 5. University of Aachen Medical Center, Department of Orthopaedic Trauma, Pauwelsstraße 30, 52074 Aachen, Germany. Electronic address: plichte@ukaachen.de. 6. University of Aachen Medical Center, Department of Orthopaedic Trauma, Pauwelsstraße 30, 52074 Aachen, Germany. Electronic address: fhildebrand@ukaachen.de. 7. University of Zurich, Department of Trauma, Rämistrasse 100, 8091 Zürich, Switzerland. Electronic address: Hans-Christoph.Pape@usz.ch. 8. University of Aachen Medical Center, Department of Orthopaedic Trauma, Pauwelsstraße 30, 52074 Aachen, Germany. Electronic address: pkobbe@ukaachen.de.
Abstract
BACKGROUND: The aim of this comparative biomechanical human cadaveric study was to investigate the anchorage of augmented screws with two different volumes of bone cement. For this purpose the effect of cranio-caudal loadings on pedicle screws was evaluated and axial pullout tests were performed. METHODS: A total of 50 pedicle screws (25 augmented/25 non-augmented) were instrumented into osteoporotic vertebra of fresh human cadavers. The augmented screws were grounded by two different volumes of bone cement (1.5cm3 vs 4cm3). Biomechanical performance was assessed by performing a cyclic loading protocol (frequency: 3Hz, load range: 20-200N, number of cycles: 100,000), followed by axial pullout (13 augmented/11 non-augmented) or by either directly measuring axial pullout strength (12 augmented/12 non-augmented). FINDINGS: The median T-score of the specimens was -4.25 (range: -6.38 to -2.4). Pullout tests with and without cyclic preloading showed significantly increased pullout strength in augmented screws (Fmax: augmented: 1159N (SD 395N); non-augmented: 532N (SD 297N); p<0.05). No significant difference in the pullout strength was found concerning the quantity of cement (Fmax (direct pullout): 4.0cm3: 1463N (SD 307N); 1.5cm3: 1214N (SD 236N); p>0.05). The pullout strength significantly decreased in high-volume augmented screws after cyclic loading (Fmax (4.0cm3): direct pullout 1463N (SD 307N); cyclic preload: 902N (SD 435N); p<0.05). INTERPRETATION: Biomechanical advantages of augmented pedicle screws can also be found after cyclic preload. However, our results indicate that the anchoring stability of high-volume augmented pedicle screws after cyclic loading is disadvantageous compared to moderate augmented screws; thus high-volume augmentation should be avoided.
BACKGROUND: The aim of this comparative biomechanical human cadaveric study was to investigate the anchorage of augmented screws with two different volumes of bone cement. For this purpose the effect of cranio-caudal loadings on pedicle screws was evaluated and axial pullout tests were performed. METHODS: A total of 50 pedicle screws (25 augmented/25 non-augmented) were instrumented into osteoporotic vertebra of fresh human cadavers. The augmented screws were grounded by two different volumes of bone cement (1.5cm3 vs 4cm3). Biomechanical performance was assessed by performing a cyclic loading protocol (frequency: 3Hz, load range: 20-200N, number of cycles: 100,000), followed by axial pullout (13 augmented/11 non-augmented) or by either directly measuring axial pullout strength (12 augmented/12 non-augmented). FINDINGS: The median T-score of the specimens was -4.25 (range: -6.38 to -2.4). Pullout tests with and without cyclic preloading showed significantly increased pullout strength in augmented screws (Fmax: augmented: 1159N (SD 395N); non-augmented: 532N (SD 297N); p<0.05). No significant difference in the pullout strength was found concerning the quantity of cement (Fmax (direct pullout): 4.0cm3: 1463N (SD 307N); 1.5cm3: 1214N (SD 236N); p>0.05). The pullout strength significantly decreased in high-volume augmented screws after cyclic loading (Fmax (4.0cm3): direct pullout 1463N (SD 307N); cyclic preload: 902N (SD 435N); p<0.05). INTERPRETATION: Biomechanical advantages of augmented pedicle screws can also be found after cyclic preload. However, our results indicate that the anchoring stability of high-volume augmented pedicle screws after cyclic loading is disadvantageous compared to moderate augmented screws; thus high-volume augmentation should be avoided.
Authors: Martin Schulze; Oliver Riesenbeck; Thomas Vordemvenne; Michael J Raschke; Julia Evers; René Hartensuer; Dominic Gehweiler Journal: BMC Musculoskelet Disord Date: 2020-03-06 Impact factor: 2.362