Trackerless ultrasound-integrated bone cement detection using a modular minirobot in revision total hip replacement

Abstract

Medical robots are superior to freehand manipulation if an accurate, precise, and time-efficient implementation of a preplanned intervention is required. In the first part of this contribution a new modular minirobot for automatic ultrasound-based bone cement detection followed by subsequent cement milling in revision total hip replacement is presented. A minirobot integrated ultrasound module eliminates the need for external position tracking (e.g. by an optical system) as well as patient registration since the scanned contours can be directly provided within the robot's coordinate system. Further, the modular minirobot concept allows kinematics, workspace, and mechanical parameters to be easily adapted to the requirements of related or even new surgical applications. In the experimental part, the impact of ultrasound module integration on the implementation of optimized scanning strategies is investigated and evaluated in a laboratory set-up. As wave mode conversion and refraction artefacts due to angular sound incidence influence the detection accuracy, the transducer alignment can be optimized with respect to the number of degrees of freedom (DOFs) provided by the minirobot. A model-based scanning approach using two degrees of freedom (2DOFs), three degrees of freedom (3DOFs), and four degrees of freedom (4DOFs) respectively is presented. For automated scanning path calculation, a 2DOF distal-proximal prescan has been performed to estimate the principal components of the cement cavity's geometry using either a model-based or a statistical approach. In a cadaver study, the model-based approach consistently outperformed the statistical approach. The 3DOFs and 4DOFs scanning strategies yielded a significantly higher scanning accuracy if compared with the 2DOFs approach whereas the 3DOFs approach represents a trade-off between system complexity and detection accuracy.

A Biomechanical Study to Evaluate the Effect of PMMA Augmentation and Restoration of the Strength of Cervical Vertebral Screws Inserted in an Osteoporotic Vertebral Body

“…[32][33][34]41 Thus, use of PMMA is controversial and relatively contraindicated in cases of severe osteopenia. Various studies have proven that BMD has a significant positive correlation with the PPF and torque.…”

Modular design of a miniaturized surgical robot system

“…Structural modularity of the robot is a key element in system design allowing for quick adaption of system properties, such as size and shape of the workspace, to the demands of varying medical applications. Instrument modularity allows for the mounting of different tools, such as high-speed milling devices, needles, endoscopes, or even integrated sensor modules, e.g., robot-assisted data acquisition with ultrasound probes [18].…”

“…An autonomous removal of cement requires information about the geometrical dimensions of the cavity and its position relative to the robot's base coordinate system. To acquire this information, intraoperative, multiplanar fl uoroscopic imaging [10] and intraluminal ultrasound [18] have been proposed. The advantage of using robot-based intraluminal ultrasound in this scenario is the avoidance of optical tracking systems for patient-to-robot registration and the avoidance of ionizing radiation.…”

“…However, the specialization often signifi cantly reduces the system's applicability to other applications or disciplines even if similar requirements could be identifi ed. In consequence, each application comes along with its own robotic system, which reduces clinical usability and increases the cost-to-benefi t ratio of these systems [18]. To overcome these problems, different authors suggested modular robotic systems for well-defi ned families or classes of medical applications [7,33].…”

Evaluation of Motion Compensation Dynamics of the Handheld Robot MINARO HD

“…In order to overcome the problems of a large serial arm, small application-specific kinematics have been developed that are mounted directly on the patient's bone, such as the MINARO (Heger et al, 2010), Arthrobot (Ko et al, 2003), MBARS (Wolf & Jaramaz, 2006) or Mazor Renaissance® (formerly SpineAssist) (Beasley, 2012). Their main advantages are the partially inherent safety due to a limited working space, low inertia and small space requirements (Berkelman et al, 2004).…”