Ultrasound melted polymer sleeve for improved primary pedicle screw anchorage: A novel augmentation technique. (March 2019)

• Record Type: Journal Article
• Authors: Spicher, Anna; Lindtner, Richard A.; Zimmermann, Simon; Stofferin, Hannes; Schmoelz, Werner
• Is Part Of: Clinical biomechanics. Volume 63(2019)
• Page Start: 16
• Page End: 20
• Publication Date: 2019-03
• Subjects: Ultrasound melted polymer -- Pedicle screw augmentation -- PLDLLA -- ISS technique -- Screw anchorage -- Osteoporosis -- Pedicle screw loosening -- PMMA; Biomechanics -- Periodicals; Osteopathic medicine -- Periodicals; Biomechanics -- Periodicals; Osteopathic Medicine -- Periodicals; 612.76
• DOI: 10.1016/j.clinbiomech.2019.02.007
• Languages: English
• ISSNs: 0268-0033

Abstract

Abstract: Background: C ement augmentation of pedicle screws to prevent screw loosening is associated with significant complications, such as cement leakage or bone necrosis. Therefore, an alternative strategy to improve pedicle screw anchorage has been recently developed: Polymer reinforcement of pedicle screws uses an in situ melted polymer sleeve in order to enhance screw anchorage. This biomechanical study evaluated the effect of polymer-reinforcement by comparing polymer-reinforced pedicle screws to non-augmented as well as cement-augmented screws under cyclic loading. Methods: For each of the two comparisons (polymer-reinforced vs. non-augmented screws and polymer-reinforced vs. cement-augmented screws), polymer-reinforced screws and control screws were placed into the left and right pedicle of seven vertebrae (mean age: 74.0 (SD 9.3) years) to allow for pairwise left–right comparisons. Each screw was subjected to cyclic cranio-caudal loading with an initial load ranging from −50 N to +50 N and with stepwise increasing compressive loads (5 N every 100 cycles) until screw loosening. Findings: Polymer-reinforced pedicle screws resisted a higher number of load cycles until loosening than the contralateral non-augmented control screws (4300 SD 2018 vs. 2457 SD 1116 load cycles, p = 0.015). Screw anchorage of polymer-reinforced pedicle screws was comparable to that of cement augmented control screws (3857 (SD2085) vs. 4300 (SD1257) load cycles until failure, p = 0.64). Interpretation: Our findings indicate that polymer-reinforcement significantly enhances pedicle screw anchorage in low quality bone and that its effect is similar in size than that of cement augmentation. Highlights: Cyclic loading in cranio-caudal direction to investigate pedicle screw anchorage was applied. Reinforcement with a polymer sleeve improved pedicle screws anchorage compared to control. Compared to cement-augmentation reinforcement with a polymer sleeve showed no difference.