Virtual simulation of an osseointegrated trans-humeral prosthesis: A falling scenario A.I. Mirulla a, *, L. Bragonzoni a , S. Zaffagnini a,c , M. Bontempi a,b , V. Nigrelli d , T. Ingrassia d a University of Bologna, Italy b Laboratory of Biomechanics and Technology Innovation, Rizzoli Orthopaedic Institute, Italy c II Clinic Rizzoli Orthopaedic Institute, Bologna, Italy d University of Palermo, Italy A R T I C L E I N F O Keywords: Osseointegration Prosthesis Amputees Upper limb Finite element method A B S T R A C T Introduction: Traditional prosthetic solutions expose the amputee to numerous problems that limit his ability to safely perform the normal activities of daily life. In order to eliminate the problems related to the use of the traditional prosthesis with socket, a new technique was developed for fixing the prosthesis to the amputees based on the principle of osseointegration. The aim of this paper is to study and analyze the stress distribution on the interface between a trans-humeral osseointegrated prosthetic implant and the residual bone, identifying the most stressed areas and thus foreseeing possible failure phenomena of the entire prosthetic system and, after, to compare the stress distribution on three different prosthetic designs that differ from each other for some geometric characteristics. Materials and methods: A healthy individual mimics two fall scenarios of which the trans-humeral amputees can most likely be victims: Static fall and Dynamic fall. A force platform (P-6000, BTS Bioengineering) is required for load data acquisition. The CAD model of the trans-humeral osseointegrated implant was created following the guidelines of the OPRA implant. The bone model was created starting from the CAT scan of a left humerus. The FEM simulation was conducted throught a linear analysis. Results: Both during static fall and dynamic fall, similar trends have been observed for the reaction force Fz, the torque moment Tz, the bending moments Mx and My. From the analysis of the von Mises stress distribution it was found that the stress distribution is more homogeneous in the case where the thread of the fixture is made by a triangular profile with height of the thread equal to 0.5 mm. However, it can be seen that, when passing from a thread with height of 0.5 mm to a 1 mm, there is a slight decrease in the stress on the whole contact zone between the fixture and the humerus. The same improvement can also be seen in the case of trapezoidal threading. Conclusion: By modifying the height and/or by varying the thread profile, are obtained slightly better results with respect to the case with a 0.5 mm height triangular thread. © 2018 Elsevier Ltd. All rights reserved. Introduction Amputation of anatomical extremities may occur due to physical trauma or surgery. In the latter case, the choice of amputation stems from the need to stop the process of a disease, such as in cases of cancer and gangrene. Very often, moreover, undergoing an amputation involves several problems on those who suffer it, related to the functional, motor, aesthetic and psychological aspects. These problems that are greatly accentuated if the amputation is performed at the trans femoral, trans humeral and trans radial levels. The purpose of the prosthesis is to reduce these problems as much as possible and restore the patient to a next-to-normal life. Nowadays, prosthetic solutions for amputees can be divided into traditional solutions (external prosthesis) and innovative solutions (internal and external prostheses). In particular, the innovative ones are based on the concept of osseointegration, defined by Per-Ingvar Branemark as a state in which “there is no relative progressive movement between the implant and the bone with it is directly attached” [1]. Traditional prosthetic solutions, despite being the least invasive do not require surgery by protocol, expose the amputee to * Corresponding author at: Department of Biomedical and Neuromotor Sciences, University of Bologna, Via Ugo Foscolo, 7, 40136, Bologna, Italy. E-mail address: agostino.mirulla@unibo.it (A.I. Mirulla). https://doi.org/10.1016/j.injury.2018.03.004 0020-1383/© 2018 Elsevier Ltd. All rights reserved. Injury, Int. J. Care Injured 49 (2018) 784–791 Contents lists available at ScienceDirect Injury journa l home page : www.e lsevier.com/loca te/injury