Predicting patient-specific mechanical failure of proximal humerus fracture plating with computer simulations (SystemFix II)


The high failure rate of osteoporotic proximal humerus fracture fixations and the expected increase of their incidence indicate the need for improved fixation strategies and careful planning. Validated computer models have high potential to complement or partially replace conventional biomechanical testing, expedite implant optimization and design, refine surgical guidelines, support decision making and allow patient-specific preoperative planning. Ultimately, simulations are expected to help improve patient outcomes of osteoporotic proximal humerus fracture treatment. In the previous (first) project phase, a virtual osteosynthesis test kit was developed to simulate proximal fracture plating and predict mechanical fixation failure. This tool was validated experimentally and utilized in a series of virtual pilot studies to indicate ways of improving plate applications, to compare different implants, and to optimize implant design towards improved stability. However, the models have not yet been demonstrated to predict mechanical fixation failure in real clinical cases.


To extend the osteosynthesis test kit application from virtual to real clinical scenario and validate it clinically by predicting the patient-specific risk of mechanical fixation failure.



Clinical data collection has been successfully started at both study sites Leuven (Belgium) and Innsbruck (Austria). Six out of the planned 40 patients with PHILOS-plated proximal humerus fractures have been recruited so far. The methodology for creation of subject-specific computer simulations from clinical data is under development with implementation of individual post-operative shoulder activities evaluated from sensor data. To strengthen the biomechanical relevance, two experimental sub-studies have been performed to investigate the effect of both screw length and pilot-hole overdrilling on cyclic screw perforation in unstable proximal fractures fixed with locked plates. With the use of this data, the validity of the simulations is extended from the previously investigated cut-through failure to secondary screw perforation. A first validation study has demonstrated that finite element analysis can provide a highly accurate prediction of single screw perforations through the humeral head. Several sub-studies have been published in this project phase, utilizing the virtual osteosynthesis test kit in in-silico trials to investigate selected aspects of locked plating of proximal humerus fractures.

  • Publication

    Dauwe J, Danker C, Herteleer M, Vanhaecht K, Nijs S. Proximal humeral fracture osteosynthesis in Belgium: a retrospective population-based epidemiologic study. Eur J Trauma Emerg Surg. 2020;epub Aug 20

    Fletcher JWA, Windolf M, Richards RG, Gueorguiev B, Buschbaum J, Varga P. The importance of locking plate positioning in proximal humeral fractures as predicted by computer simulations. J Orthop Res. 2019;37(4):957-964

    Fletcher JWA, Windolf M, Grünwald L, Richards RG, Gueorguiev B, Varga P. The influence of screw length on predicted cut-out failures for proximal humeral fracture fixations predicted by finite element simulations. Arch Orthop Trauma Surg. 2019;139:1069-1074

    Fletcher JWA, Windolf M, Richards RG, Gueorguiev B, Varga P. Screw configuration in proximal humerus plating has a significant impact on fixation failure risk predicted by finite element models. J Shoulder Elbow Surg. 2019;28(9):1816-1823

    Ciric D, Mischler D, Qawasmi F, Wenzel L, Richards RG, Gueorguiev B, Windolf M, Varga P. Secondary Perforation Risk in Plate Osteosynthesis of Unstable Proximal Humerus Fractures: A Biomechanical Investigation of the Effect of Screw Length. J Orthop Res. 2019;37(12):2625-2633

    Panagiotopoulou VC, Varga P, Richards RG, Gueorguiev B, Giannoudis PV. Late screw-related complications in locking plating of proximal humerus fractures: A systematic review. Injury. 2019;50(12):2176-2195

    Ciric D. The risk of secondary screw perforation in plate osteosynthesis of unstable proximal humerus fractures: prediction and the effect of screw length. Master Thesis, Flinders University, 2019.

    Burkhard B. Experimental and computational investigation of the risk of overdrilling on the biomechanical competence of proximal humerus plating. Master Thesis, Swiss Federal Institute of Technology Zurich (ETHZ), 2019.

    Burkhard B, Schopper C, Ciric D, Mischler D, Gueorguiev B, Varga P. Overdrilling increases the risk of screw perforation in locked plating of complex proximal humeral fractures – a biomechanical cadaveric study. J Biomech. 2021;117:110268.

    Panagiotopoulou VC, Ovesy M, Gueorguiev B, Richards RG, Zysset P, Varga P. Experimental and numerical investigation of secondary screw perforation in the human proximal humerus. J Mech Behav Biomed Mater. 2021;116:104344.

    Remppis M. Postoperative shoulder activity tracking of patients with proximal humerus fractures treated with locking plates. 2021 University of Stuttgart (P. Varga, O.Röhrle, B. Gueorguiev) - MSc thesis

    Tenisch L. Prediction of mechanical failure in proximal humerus fracture fixations using patient-specific FE analyses. 2021 ETH Zürich (P. Varga, S.J. Ferguson) – MSc ETH BME thesis

    Herteleer M, Runer A, Remppis M, Brouwers J, Schneider F, Panagiotopoulou VC, Grimm B, Hengg C, Arora R, Nijs S, Varga P. Continuous shoulder activity tracking after open reduction and internal fixation of proximal humerus fractures. Bioengineering. 2023;10(2):128. 

    Kessler F. Biomechanical stability of bone screws in the proximal humerus. 2022 Universität Bern (P. Zysset, P. Varga) – MSc Thesis




  • Presentation

    Fletcher J, Windolf M, Gueorguiev B, Richards RG, Varga P. SystemFix – Using computer simulations to optimise proximal humeral fracture fixation. 2019 ICORS (oral)

    Fletcher J, Windolf M, Richards RG, Gueorguiev B, Varga P. Optimising proximal humerus fracture plating – discoveries from computer simulations. 2019 LSM (poster presentation prize)

    Mischler D, Windolf M, Varga P. Computational optimization of the locking screw angles of a proximal humerus plate. 2019 ESBioMech (oral)

    Wenzel L, Ciric D, Mischler D, Qawasmi F, Gueorguiev B, Richards RG, Windolf M, Varga P. Biomechanical investigation of the effect of screw length on screw perforation in unstable 3-part osteoporotic proximal humerus fractures. 2019 DKOU (oral)

    Mischler D, Schader J, Windolf M, Varga P. Improving fixation techniques of proximal humerus fractures by means of finite element analysis. 2019 EORS (oral)

    Ciric D, Mischler D, Qawasmi F, Wenzel L, Windolf M, Gueorguiev B, Varga P. Longer screws do not increase perforation risk in plating of complex proximal humerus fractures in vitro. 2019 ESBioMech (oral)

    Ciric D, Mischler D, Qawasmi F, Windolf M, Gueorguiev B, Varga P. Predicting cyclic screw perforation in complex proximal humerus fracture plating. 2019 ESBioMech (oral)

    Panagiotopoulou V, Ovesy M, Gueorguiev B, Richards RG, Zysset P, Varga P. Micro finite element simulations accurately predict perforation of single screws in the proximal humerus. Bone Joint J. 2020;102-B(Supp. 11 / Orthop Proc):65 (EORS virtual, oral)

    Burkhard B, Schopper C, Ciric D, Mischler D, Gueorguiev B, Varga P. Cyclic perforation risk is increased by overdrilling in locked plating of complex proximal humerus fractures. Bone Joint J. 2020;102-B(Suppl. 11 / Orthop Proc): 75 (EORS virtual, oral)

    Panagiotopoulou V, Ovesy M, Gueorguiev B, Richards RG, Zysset P, Varga P. Prediction of screw perforation in the proximal humerus using micro finite element analyses. 2021 ES Biomech online (oral)


    Burkhard B, Schopper C, Ciric D, Mischler D, Gueorguiev B, Varga P. Pilot hole overdrilling increases screw perforation risk in locked plating of complex proximal humerus fractures. 2021 ES Biomech online (poster)

  • Partner

    Nijs S (Prof), University Hospital Leuven, Belgium

    Hengg C (MD), Medical University Innsbruck, Austria