ORIGINAL ARTICLE Repeatability and reproducibility of a telemanipulated fracture reduction system Eduardo M. Suero 1 • Ralf Westphal 2 • Musa Citak 1 • Volker Stueber 1 • Ullrich Lueke 1 • Christian Krettek 1 • Timo Stuebig 1 Received: 1 June 2017 / Accepted: 4 September 2017 Ó Springer-Verlag London Ltd. 2017 Abstract We evaluate the inter- and intraobserver vari- ability of a telemanipulated femur fracture reduction sys- tem using a joystick device. Five examiners performed virtual reduction of 3D femur fracture models on two separate occasions. We assessed the inter- and intraob- server variability for the final alignment and reduction. The average difference between testing rounds was only 0.3 mm for overall displacement and 0.5° for overall rotation. There was an average time reduction between rounds of 11.7 s. The mean differences in overall dis- placement between examiners ranged between 0.2 and 0.9 mm; between 0.2° and 3.2° for overall rotation; and between 9 and 82 s for time to reduction. The time required to complete the reduction did not have a significant effect on the overall displacement or rotation of the final model. Telemanipulated fracture reduction is a reliable and reproducible technique, which does not require extensive training. Keywords Distal locking Á Intramedullary nailing Á Robotic fracture reduction Á Telemanipulated fracture reduction Introduction Fractures of the femoral shaft are a highly traumatic event, usually caused by high-energy injury mechanisms such as motor vehicle accidents. Femoral shaft fractures are com- monly treated with intramedullary nailing [1]. The tech- nique has good overall outcomes, with union rates above 90% [2, 3]. However, there are several problems associated with it, such as high radiation exposure and rotational malalignment. Several technological advances aimed at improving outcomes after femoral nailing have been described. Computer navigation has been available for over 10 years and has proven to be a useful tool in the treatment of femoral fractures [4–8]. Preoperative computer segmenta- tion has also been described as a tool used to understand complex fractures and to plan complicated procedures [9]. Robotic procedures have also been designed in an attempt to improve some of the most difficult portions of the intramedullary nailing technique. Lei et al. described a robotic technique for distal locking of intramedullary nails [10]. Oszwald et al. developed a robotic technique for improving the entry-point access of antegrade femoral nailing [11]. To address the great forces that must be applied to overdistract fracture fragments before reduction and nailing, Fuechtmeier et al. designed a robotic proce- dure aimed at improving holding effort and precision [12]. We have previously developed a combined computer- assisted and robotic framework for the treatment of femoral fractures [13–16]. The technique has the overall aim of improving reduction accuracy and of reducing the inci- dence of femoral malrotation [13, 17, 18]. Fracture tele- manipulation is an important part of this project. We have shown that it is feasible to perform virtual fracture reduc- tions using a joystick. However, further validation of this & Eduardo M. Suero EduardoSueroMD@gmail.com 1 Trauma Department, Hannover Medical School, Carl-Neuberg-Str. 1, 30625 Hannover, Germany 2 Institute for Robotics and Process Control, Braunschweig University of Technology, Brunswick, Germany 123 J Robotic Surg DOI 10.1007/s11701-017-0749-2