Magnetic resonance imaging currently is the imaging procedure of choice for the radiologic diagnosis of VO. Mortality is attributable in part to co-morbidities. However, infections with S. aureus are frequent in this patient population and are associated with a higher rate of complications and a trend towards higher mortality.

The preferred treatment of femoral (thigh bone) shaft fractures nowadays is the minimally invasive technique of intramedullary nailing.However, in addition to its advantages, this technique also has a number of disadvantages, such as the frequent occurrence of malaligned fracture reductions and high X-ray exposure, especially to the operating team. The aim of our research is to overcome these shortcomings by utilizing modern techniques such as three-dimensional (3D) imaging, navigation, and robotics. In this paper we present the current state of our interdisciplinary research project. We first introduce a telemanipulated fracture reduction procedure, which is based on 3D imaging data. This set-up is improved one step further towards an automated fracture reduction procedure. Finally, two drilling tasks, namely the opening of the medullar cavity and the distal locking of the intramedullary nail, are presented, which are supported by automated X-ray-based image analysis and robot-assisted drill guidance. We show that high reduction accuracies can be achieved with our robotic system. Furthermore, the robot-assisted drill guidance achieves superior results with respect to increased precision and decreased Xray exposure compared with the conventional procedure. We conclude that this surgical procedure benefits conspicuously from the support of robotic assistance systems and that further research and development in this field is worthwhile.

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Introduction: Intramedullary nailing has become the gold standard in the treatment of femoral shaft fractures. This procedure involves the placement of distal interlocking bolts using the freehand technique. Accurate placement of distal interlocks can be a challenging task, especially in inexperienced hands. Misplacement of distal interlocking bolts can lead to iatrogenic fracture, instability of the bone-implant construct, or even malalignment of the extremity. Repeated drilling attempts increase radiation exposure and can cause additional bony and soft tissue trauma. We hypothesize that robot-guided placement of distal interlocks is more accurate, precise, and efficient than the freehand technique.Methods: A custom-designed drill guide was mounted onto the arm of an industrial robot. We developed a special device to secure a generic block (Synbone, Malans, Switzerland) into which an intramedullary nail could be inserted in a standardized way. A metric scale allowed later measurements of the drillings. Digital images were taken from each side of the block for analysis of the drilling trajectories. The fluoroscope was adjusted to obtain perfect circles of the distal interlocking holes. The number of images necessary to achieve this was recorded. The axis was recognized automatically by using the differences in contrast between the matrix of the generic bone and the implant (intramedullary nail). The drill trajectories were then computed. The robot with the mounted drill-guide automatically moved onto the calculated trajectory. The surgeon then executed the drilling. We performed 40 robot assisted drillings in generic blocks. Freehand drilling served as our control group.Results: Analysis of the digital images revealed a mean deviation of 0.94 mm and 2.7 • off the ideal trajectory using robotic assistance. In 100% of the cases (n = 40), the distal locking hole was hit. A mean of 8.8 images was acquired. After manual drilling, 92.5% of the distal interlocks were hit. A mean deviation of 3.66 mm and 10.36 • was measured. A mean of 23.4 fluoroscopic images were needed. The differences between the two methods were statistically significant.Conclusion: Robot-guided drilling increases the accuracy and precision of distal interlocking while reducing irradiation. Considering economical and logistical aspects, this application should be integrated with robot-guided fracture reduction.

The first step in treatment of displaced femoral shaft fractures is adequate reduction of the fracture fragments. Manually performed, reduction can be challenging, and is frequently associated with soft tissue damage, especially when repeated reduction attempts are made. The magnitude of local and systemic inflammatory responses caused by prolonged and repeated reduction maneuvers has not been fully established. We devised an operative technique utilizing a robotic reduction device for use in a rat. A femoral fracture was simulated by means of an osteotomy. The robot enabled reproduction of both manual and guided precision reductions, performed in a single path movement. An external fixator was designed specifically to manipulate the rat femur and also for fixation of the osteotomy region. First, reduction accuracy was assessed in eight femurs, then the quality of fixator placement and reduction accuracy was analyzed in 22 femurs. In the first case, 100% of the femurs were accurately reduced. In the second case, 91% had successful stable fixation and an accurate reduction was achieved in 86% of the specimens. We demonstrated the feasibility of a model of robot-assisted fracture reduction that could be used to analyze the effects of reduction on the surrounding soft tissue via biochemical and histopathological means. A future aspect will be to evaluate whether the robot confers an advantage in fracture reduction versus the conventional technique, which would have significant implications for the use of robotic devices in orthopaedic surgery. ß