Biomechanical Comparison of Axial Load Between Cannulated Locking Screws and Noncannulated Cortical Locking Screws

Full article available online at Healio.com/Orthopedics. Search: 20130920-26 Biomechanical Comparison of Axial Load Between Cannulated Locking Screws and Noncannulated Cortical Locking Screws Shan-Wei Yang, MD, PhD; ShYh Ming Kuo, PhD; ShWu Jen Chang, PhD; Tian-Shiang Su, MS; hSiang-ho Chen, PhD; Jenn-huei Renn, MD, PhD; Ting-Sheng Lin, PhD The goal of this study was to compare the biomechanical stability of cannulated locking screws and noncannulated cortical locking screws in a periarticular locking plate. Twelve fresh-frozen porcine tibias with a 1-cm gap created distal to the tibial plateau were used to simulate an unstable proximal tibial fracture. All specimens were fixed with a periarticular proximal lateral tibial locking plate and divided into 2 groups based on whether the proximal metaphyseal screw holes of the plate were inserted with either cannulated locking screws or noncannulated cortical locking screws. An axial compressive load was applied to cause failure in each specimen using a materials testing instrument. The axial stiffness and maximum failure strength in axial loading were recorded. Axial stiffness of the constructs using noncannulated cortical locking screw was significantly higher than that of the constructs using cannulated locking screws (P5.006). Axial failure strength of the constructs using noncannulated cortical locking screw was significantly higher than that of the constructs using cannulated locking screws (P5.002). The failure mode observed in all specimens was a permanent screw-bending deformity over the head-shaft junction of proximal metaphyseal screws, irrespective of whether they were cannulated or noncannulated cortical locking screws. Fixation with noncannulated cortical locking screws offered more stability than cannulated locking screws with regard to axial stiffness and failure strength in a porcine model with unstable proximal tibial fractures. The authors are from the Department of Orthopedics (S-WY, J-HR), Kaohsiung Veterans General Hospital; the Department of Biomedical Engineering (SMK, SJC, T-SS, T-SL), I-Shou University, Kaohsiung; and the Department of Physiology (H-HC), Taipei Medical University, Taipei, Taiwan. The authors thank Drs M.H. Lee and C.H. Chen and Mss B.F. Lin and C.Y. Liao, Department of Orthopedics, Kaohsiung Veterans General Hospital, for their assistance during model setting. The authors have no relevant financial relationships to disclose. Correspondence should be addressed to: Ting-Sheng Lin, PhD, Department of Biomedical Engineering, I-Shou University, No. 8, Yida Rd, Yanchao District, Kaohsiung 82445, Taiwan (tslin@ isu.edu.tw). doi: 10.3928/01477447-20130920-26 Figure: Photograph of an unstable proximal tibial fracture in a porcine model showing a 1-cm gap created over the proximal metaphysis approximately 1 cm distal to the articular surface.