A novel adjustable locking plate (ALP) for segmental bone fracture treatment Omer Subasi, Atacan Oral, Ismail Lazoglu* Manufacturing and Automation Research Center, Koc University, Istanbul 34450, Turkey A R T I C L E I N F O Article history: Received 8 March 2019 Accepted 19 August 2019 Keywords: Bone fracture Bone plate Adjustable dynamic plate Locking compression plate Finite element analysis Bending strength Fatigue life A B S T R A C T A novel Ti6Al4V adjustable locking plate (ALP) is designed to provide enhanced bone stability for segmental bone fractures and to allow precise positioning of disconnected segments. The design incorporates an adjustable rack and pinion mechanism to perform compression, distraction and segment transfer during plate fixation surgery. The aim of this study is to introduce the advantages of the added feature and computationally characterize the biomechanical performance of the proposed design. Structural strength of the novel plate is analyzed using numerical methods for 4-point bending and fatigue properties, following ASTM standards. An additional mechanical failure finite element test is also conducted on the rack and pinion to reveal how much torque can be safely applied to the mechanism by the surgeon. Simulation results predict that the new design is sufficiently strong to not fail under regular anatomical loading scenarios with close bending strength and fatigue life properties to clinically used locking compression plates. The novel ALP design is expected to be a good candidate for addressing problems regarding fixation of multi-fragmentary bone fractures. © 2019 Elsevier Ltd. All rights reserved. Introduction Stabilization of fractures with compression plates are among the most widely used surgical treatments in orthopedics. While, in the past, dynamic compression plates (DCP) have been extensively used to provide absolute stability to the fracture site and promote fast primary healing, nowadays, the locking compression plates (LCP) have mostly replaced them [1,2]. By bridging the two ends of the fracture, LCPs provide relative stability to the site which promotes a slower but stronger secondary healing [2,3]. Relative stability also allows micromotions between the two ends of the fracture that helps callus formation at the early stages of healing [4]. Most commonly, LCPs are successfully utilized for treatment of upper extremity fractures [5–8]. The design behind the surgical fixation plates are straightfor- ward, yet, rudimentary from an engineering point of view. Although LCPs have a gamut of advantages over its predecessor plate types, they are still static in nature and fail to properly address more complex complications such as multi-fragmented or comminuted fractures. Moreover, during the surgical operation, they allow no flexibility in terms of adjusting the geometry of the fracture; after the placement of the screws and locking of the plate, the fracture area is firmly stabilized. If there is a complication in the initial implementation of the plate that might lead to nonunion or malunion due to non-adequate support, there are no quick methods to modify to fracture line besides completely reposition- ing the plate [9]. Extra procedures during operations that lead to increased surgery duration, inevitably exacerbate the risk of infection and side effects of prolonged use of anesthesia on the patient [10]. In order to tackle the problems that arise from the inherent immobile design of straight plates, various adjustable plate designs have been proposed. This innovative research area in orthopedics also attempts to push the boundary of fracture fixation design to investigate potential benefits of having moving elements and added features to the simpler benchmark designs that could facilitate both the surgical procedures and enhance healing. However, adjustable plate studies are very limited in number and relatively recent in literature. Most notably, in 2016 Karakasli et al. proposed an adjustable design with an embedded spring mechanism that can generate compression forces up to 300 N [11]. Conducting in-vitro torsion and bending tests on 4th generation composite femurs, they have demonstrated that while the biomechanical performance was not compromised in comparison to a benchmark plate, the increased compressive forces at the fracture ends could facilitate bone healing [11]. Our research group proposed a novel, Ti6Al4V ALP design with an embedded rack and pinion mechanism, under WIPO, US and EU * Corresponding author. E-mail address: ilazoglu@ku.edu.tr (I. Lazoglu). https://doi.org/10.1016/j.injury.2019.08.034 0020-1383/© 2019 Elsevier Ltd. All rights reserved. Injury, Int. J. Care Injured xxx (2019) xxx–xxx G Model JINJ 8296 No. of Pages 8 Please cite this article in press as: O. Subasi, et al., A novel adjustable locking plate (ALP) for segmental bone fracture treatment, Injury (2019), https://doi.org/10.1016/j.injury.2019.08.034 Contents lists available at ScienceDirect Injury journal homepa ge: www.elsev ier.com/locate /injury