Novel Robotic System with Semi-Automatic Planning and Collision Detection for Long Bone Fracture Reduction

Clinical usability and efficacy of a robotic bone fracture reduction system: A pilot animal study

To overcome possible drawbacks of bone fracture reduction such as risks of malrotation, radiation exposure, as well as laborious traction, image-guided robotic surgery systems have been proposed. However, the use of optical tracking systems (OTS) creates inherent line-of-sight problems that cause frequent interruptions during surgery. We propose an OTS-free image-guided bone fracture reduction system utilizing a Stewart robot platform to solve the problem of conventional OTS-based robotic systems. The system applies inverse kinematics to compute the relative positions between the broken bone fragments. Each fragment is pre-operatively registered in the robotic system with a semi-automatic image-based registration method using an attachable jig designed for the proposed platform. This approach is particularly effective when the image features are not clearly detected in the fluoroscopic images. The accuracy of the proposed system was evaluated via pre- and post-operative computed tomography (CT) scans of femoral phantoms. Ex-vivo experiments were also performed on caprine legs to assess the clinical feasibility. In the phantom and ex-vivo experiments, the mean rotational errors of the reduction were 1.79° and 1.76°, respectively. The mean time for the reduction was approximately 3 min. This letter proposes a new method to compute the relative positions between the bone fragments using inverse kinematics and semi-automatic robot-patient registration without requiring a C-arm and an OTS. The OTS-free robotic surgery system has the potential advantages to enhance the accuracy of fracture reduction and reduce the surgery time and radiation exposure.

Objective: Long bone fracture reduction during intramedullary nailing can result in a small but significant rate of angular and rotational malalignment, which can in turn lead to long-term morbidity. Current techniques for intraoperative reduction rely heavily on fluoroscopy, and their reproducibility can be limited. We suggest that fluoroscopy-based navigation may improve the precision of long bone fracture reduction and reduce radiation exposure.Methods: A cadaveric tibia was stripped of soft tissues and fractured at its midline. The ends were then cemented to two mobile brackets within a fracture/deformity simulator. Optical trackers were drilled into each fragment. Radiographs were obtained including AP and lateral views of the proximal and distal ends of the bone as well as the fracture site. These radiographs were stored in the computer navigation system. Fracture reduction was performed using a fluoroscopy-based navigation system with virtual intraoperative planning software. The system used 4 sets of lines drawn by the surgeon on the fluoroscopic AP and lateral images. While navigating the reduction of the fracture these lines aligned together, providing graphic and numerical descriptions of the reduction. The lines included the anatomic axis of the bone, the matching of the fracture lines, the short segment anatomic axis (near the fracture site), and the AP mid-sagittal joint line (MSJL) of both the plateau and the plafond. Anatomic reduction was then performed and the computer assessment of the angulation and translation of the fragments was recorded. Each stage was repeated 25 times for each set of lines. For the control group the surface of the bone was tracked using an optical probe.Results: The accuracy of the system varied according to the planning method. The most accurate technique was matching of the fracture lines, which yielded 2.68 ± 1.18 mm of translation and 2.5 ± 1.27° of angulation. The next most accurate method was using the short segment anatomic axis, followed by using the anatomic axis method. The control group was the most accurate (1.78 ± 0.67 mm translation, 1.58 ± 0.97° angulation). The AP MSJL yielded errors greater than 10°.Conclusions: Fluoroscopy-based navigation is sufficiently accurate for long bone fracture reduction, potentially increasing angular and translational accuracy while reducing the amount of intraoperative fluoroscopy. Navigation may improve the outcome of treatment of a long bone fracture by better restoring the normal mechanical axis of the limb in a less-invasive closed manner.

Accurate alignment of long bone fractures under minimally invasive procedures is a prerequisite for excellent treatment outcomes. However, the existing technologies suffer from the drawbacks of complex operations and excessive dependence on the surgeon's expertise. To solve these problems, we have developed a novel computer-assisted system to achieve rapid and effective reduction of fractures. The automatic registration of the bone-fixator is accomplished based on the principal component analysis and the markers recognition. Then, the fracture reduction target is acquired by utilizing the Iterative Closest Point algorithm on the mirrored contralateral bone model. Next, the optimal reduction trajectory is automatically generated by considering collision detection, muscle pull force analysis, and trajectory optimization. Finally, the strut adjustment plan of the fixator is provided to the surgeon, combined with the results of bone-fixator registration. Modeling experiments verified the high accuracy of the system registration and the superiority of the reduction planning method, and clinical trials demonstrated the effectiveness and feasibility of the proposed system for fracture treatment. The proposed system facilitates accurate and efficient planning of fracture reduction for surgeons through simple manipulation. Our system enables a one-stop automatic acquisition of prescriptions for external fixation treatment of fractures.

The results obtained by the extensive experiments with the telemanipulator system clearly revealed the potential of robotic systems supporting fracture reduction of the femur. Not only is it possible to achieve very high accuracies in the reductions, but also the exposure of the operation team to X-ray radiation can be reduced, utilizing a robotic system in the presented way. The direct and well controlled motions of the robotically moved fracture segments might support a gentle reduction, when compared with manually performed reductions, which generally suffer from repetitive motions under high forces, implying high stress to the soft tissue surrounding the fracture. However, whether or not this really has an impact on the healthy soft tissue, will have to be proven in the future. One further point is remarkable here. The operation time could not be reduced utilizing a robot as telemanipulator when compared to the manual control groups. Keeping in mind the experience from clinical practice this is a surprising result, because from the possibility of a direct and well defined motion control utilizing the robot in combination with high resolution and detailed 3D imaging data we would have expected to shorten the operation time significantly. So far we haven't been able to determine the reasons for this, but the surgeon who performed the manual control groups observed, that the rigid soft tissue situation in the formalin conserved specimens eases the reduction considerably. How this circumstance influences the telemanipulated reductions and the results obtained by it too, can only be hypothesized at this time. Future experiments on fresh cadavers with soft tissue properties very close to the real life surgical situation will have to be done in order to clarify this point. The implemented way of visualizing the fracture and interacting with the robotic system by means of a simple input device with two main and one supplementary DoF has proven to be very efficient and intuitive for the surgeons, who performed the experiments. However, this input device has its limitations, as torques can not be fed back intuitively via its force feedback interface. Future work will have to be done in order to evaluate whether input devices with six DoFs for input as well as force/torque feedback might have the potential of further improving this telemanipulated robotic approach. In this context the evaluation of how much of the benefit of the present method is due to the 3D fracture visualization and how much is due to the robotized fracture reduction would be of interest, too. Comparing the robotized reductions with reductions manually performed but supported by a navigation system with 3D visualization capabilities like (Hazan & Joskowicz, 2003; Joskowicz et al., 1998a) can answer this question.

BackgroundThe hexapod external fixator (HEF), such as the Taylor spatial frame (TSF), offering the ability of multidirectional deformities correction without changing the structure, whereas there are so many parameters for surgeons to measure and subjective errors will occur inevitably. The purpose of this study was to evaluate the effectiveness of a new method based on computer-assisted three-dimensional (3D) reconstruction and hexapod external fixator for long bone fracture reduction and deformity correction without calculating the parameters needed by the traditional usage.MethodsThis retrospective study consists of 25 patients with high-energy tibial diaphyseal fractures treated by the HEF at our institution from January 2016 to June 2018, including 22 males and 3 females with a mean age of 42 years (range 14–63 years). Hexapod external fixator treatments were conducted to manage the multiplanar posttraumatic deformities with/without poor soft-tissue that were not suitable for internal fixation. Computer-assisted 3D reconstruction and trajectory planning of the reduction by Mimics were applied to perform virtual fracture reduction and deformity correction. The electronic prescription derived from the length changes of the six struts were calculated by SolidWorks. Fracture reduction was conducted by adjusting the lengths of the six struts according to the electronic prescription. Effectiveness was evaluated by the standard anteroposterior (AP) and lateral X-rays after reduction.ResultsAll patients acquired excellent functional reduction and achieved bone union in our study. After correction, the mean translation (1.0 ± 1.1 mm) and angulation (0.8 ± 1.2°) on the coronal plane, mean translation (0.8 ± 1.0 mm) and angulation (0.3 ± 0.8°) on the sagittal plane were all less than those (6.1 ± 4.9 mm, 5.2 ± 3.2°, 4.2 ± 3.5 mm, 4.0 ± 2.5°) before correction (P < 0.05).ConclusionsThe computer-assisted three-dimensional reconstruction and hexapod external fixator-based method allows surgeons to conduct long bone fracture reduction and deformity correction without calculating the parameters needed by the traditional usage. This method is suggested to apply in those unusually complex cases with extensive soft tissue damage and where internal fixation is impossible or inadvisable.

While performing musculoskeletal long bone fracture reduction surgery, assistant surgeons can often suffer from physical fatigue as they provide resistance against the tension from surrounding muscles pulling on the patient's broken bones. These days, robotic systems are being actively developed to mitigate this physical workload by realigning and holding these fractured bones for surgeons. This has led to one consortium proposing the development of a robot-assisted fracture reduction system consisting of a 6-DOF positioning robot along with a 1-DOF traction device. With the introduction of the 1-DOF traction device, the positioning robot does not have to fight these contraction forces so can be compact improving its maneuverability and overall convenience; however, considering surgeon-robot interactions, this approach adds the requirement of controlling two different types of robots simultaneously. As such, an advanced cooperative control methodology is required to control the proposed bone fracture reduction robot system. In this paper, a human-robot-robot cooperative control (HRRCC) scheme is proposed for collaboration between the surgeon, the positioning robot, and the traction device. First, the mathematical background of this HRRCC scheme is provided. Next, we describe a series of experiments that show how the proposed scheme facilitates a reduction in the load placed on the positioning robot from strong muscular contraction forces making it possible to conduct fracture reduction procedures more safely despite the muscular forces.

Computer assisted preoperative planning of bone fracture reduction: Simulation techniques and new trends

Long bone fractures belong to the most common injuries encountered in clinical routine trauma surgery. Preoperative assessment and decision making is usually based on standard 2D radiographs of the injured limb. Taking into account that a 3D - imaging modality such as computed tomography (CT) is not used for diagnosis in clinical routine, we have designed LORENZ, a fracture reduction planning tool based on such standard radiographs. Taking into account the considerable success of so-called image free navigation systems for total knee replacement in orthopaedic surgery, we assume that a similar tool for long bone fracture reposition should have considerable impact on computer-aided trauma surgery in a standard clinical routine setup. The case for long bone fracture reduction is, however, somewhat more complicated since not only scale independent angles indicating biomechanical measures such as varus and valgus are involved. Reduction path planning requires that the individual anatomy and the classification of the fracture is taken into account. In this paper, we present the basic ideas of this planning tool, it's current state, and the methodology chosen. LORENZ takes one or more conventional radiographs of the broken limb as input data. In addition, one or more x-rays of the opposite healthy bone are taken and mirrored if necessary. A most adequate CT model is being selected from a database; currently, this is achieved by using a scale space approach on the digitized x-ray images and comparing standard perspective renderings to these x-rays. After finding a CT-volume with a similar bone, a triangulated surface model is generated, and the surgeon can break the bone and arrange the fragments in 3D according to the x-ray images of the broken bone. Common osteosynthesis plates and implants can be loaded from CAD-datasets and are visualized as well. In addition, LORENZ renders virtual x-ray views of the fracture reduction process. The hybrid surface/voxel rendering engine of LORENZ also features full collision detection of fragments and implants by using the RAPID collision detection library. The reduction path is saved, and a TCP/IP interface to a robot for executing the reduction was added. LORENZ is platform independent and was programmed using Qt, AVW and OpenGL. We present a prototype for computer-aided fracture reduction planning based on standard radiographs. First test on clinical CT-Xray image pairs showed good performance; a current effort focuses on improving the speed of model retrieval by using orthonormal image moment decomposition, and on clinical evaluation for both training and surgical planning purposes. Furthermore, user-interface aspects are currently under evaluation and will be discussed.

External fixation devices for long bone fracture reduction are extensively used. Most of them are implemented by a trial and error process which alternates radiographs and fixation device adjustments in order to achieve a final correct positioning of the two bone segments. Fixation devices with less than six degrees of freedom are frequently used which can provide only an approximated segment positioning. This paper presents two new fixation device architectures having six degrees of freedom. They can be automatically actuated during the fracture reduction process under the surgeon's control. They perform a straight, not iterative, final correct positioning based only on a few radiographs. Finally, some suggestions on the actual workspace determination of the fixation devices have been reported together with some design considerations.

Identification of fracture zones and its application in automatic bone fracture reduction

Bone fracture reduction is an essential step in the treatment of orthopedic fractures. It consists of determining the position and orientation of the fractured bone fragments for their fixation with implants. This paper presents a new method for the automatic reduction of fractured bone models derived from CT scans. The method identifies the bones fracture contact surface pairs based on the fragments surfaces maximum principal curvature and their intensity profiles in the CT scan. It then aligns the two fracture surfaces by rigid registration, thereby obtaining a virtual bone fracture reduction. An experimental evaluation of 192 simulated femoral fractures derived from four clinical CT scans yielded a mean target registration error of 1.8mm (std=1.1mm).

Automated detection and segmentation of cylindrical fragments from calibrated C-arm images for long bone fracture reduction

6-DOF force feedback control of robot-assisted bone fracture reduction system using double F/T sensors and adjustable admittances to protect bones against damage

Automated identification, pose and size estimation, and contour extraction of diaphyseal bone fragments can greatly improve the usability of a computer-assisted fluoroscopy-based navigation system for long bone fracture reduction. In this paper, a two step solution is proposed. The pose and size of a diaphyseal fragment are estimated through 3D morphable object fitting using a parametric cylinder model. The result of fragment identification is then fed to a region information based active contour model to extract the fragment contour. Experimental results show a promising accuracy and robustness of the proposed approach.