Comparison of three different screw trajectories in osteoporotic vertebrae: a biomechanical investigation

Abstract Background Pedicle screw insertion in osteoporotic patients is challenging. Achieving more screw-cortical bone purchase and invasiveness minimization, the cortical trajectory midline techniques represent alternatives to traditional pedicle screws. This study compares fatigue behavior fixation strength of cement-augmented (TT), (CBT), (MC). Methods Ten human cadaveric spine specimens (L1 - L5) were examined. The average age was 86.3 ± 7.2 years. CT scans provided for preoperative planning. CBT MC implanted by using patient-specific 3D-printed placement guide (MySpine®, Medacta International), TT freehand. All ten randomized group A (CBT vs. MC) or B (MC TT). Each loaded 10,000 cycles. failure criterion doubling initial displacement resulting from compressive force (60 N) at first cycle, stop a displacement. After dynamic testing, screws pulled out axially 5 mm/min determine their remaining strength. Results mean pull-out forces did not differ significantly. Concerning performance, only one failed prematurely due loosening after 1500 cycles (L3). Five already loosened during 500 always lower MC. In B, all showed no signs loosening. Three 26 cycles, 1510 2144 subsequent tests, (449.6 298.9 slightly higher compared (401.2 261.4 N). However, (714.5 488.0 inferior (990.2 451.9 Conclusion current demonstrated that have best characteristics lumbar vertebrae, followed CBT. promising alternative if cement augmentation should be avoided. Using contributes improvement screws’ biomechanical properties.