Percutaneous Nephrolithotomy Access: Robotic

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Percutaneous Nephrolithotomy Access: Robotic

Michelle Jo Semins,¹ Dan Stoianovici,² & Brian R. Matlaga²

¹ Department of Urology, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA

² James Buchanan Brady Urological Institute, Johns Hopkins University School of Medicine, Baltimore, MD, USA

Introduction

Since the latter part of the twentieth century, robotic technology has been applied to a number of industrial and manufacturing processes. Due in great part to potential advantages of motion finesse associated with robotic manipulation, recent years have witnessed an increased interest in the introduction of robotics to the healthcare system. Robots were first introduced to the surgical field in the 1980s, and at that time were focused primarily on neurosurgical and orthopedic applications [1]. As interest in robotics expanded into other medical specialties, urologic applications were soon identified. Since that time, robotics has rapidly assumed an integral role in the urologic armamentarium.

The first reported urologic application of robotic technology was described by Davies et al. in 1989, who designed a robot (PROBOT) to perform transurethral resection of the prostate [2–4]. Since that time, a number of targeted research projects have been undertaken to identify and develop applications for robotics within the urologic specialty. In many cases, robot‐assisted surgical approaches have become commonly accepted; robot‐assisted laparoscopic radical prostatectomy and partial nephrectomy may be the best examples of this.

The suitability of robotics for urologic surgical applications derives from the properties inherent to robotic technology, namely that these devices are versatile, mechanically capable, and programmable. Tasks that are particularly suited to robotic technology are those that require accuracy, reproducibility, fine motor movements, as well as motion that is difficult to perform by hand due to constrained access, such as for laparoscopy, and ergonomic limitations, such as for magnetic resonance imaging (MRI)‐guided interventions. To that end, robotic technology can improve on conventional techniques in, for example, securing percutaneous access to the renal collecting system. In this chapter we review the genesis and present applications of robotic systems designed to facilitate percutaneous renal access.

Goals of robotic percutaneous renal access

Urology has been one of the surgical disciplines at the forefront of the application of robotic technology, and the kidney is rapidly becoming a target organ for this technology. Robot‐assisted laparoscopic renal surgery, although only recently described, is becoming a standard surgical approach for renal malignancy and reconstruction. Image‐guided percutaneous surgery is likely to be the next generation of renal surgery to benefit from robotic technology [5]. Percutaneous renal surgery encompasses a wide diversity of procedures: nephrostomy tube placement, percutaneous nephrolithotomy (PCNL), percutaneous treatment of transitional cell carcinoma, renal biopsy, renal cyst or abscess drainage, radiofrequency ablation of renal tumors, and percutaneous renal tumor cryoablation. These many procedures are all potential clinical applications for a robot designed to gain renal access percutaneously.

There are a number of practical advantages to robotic assistance for percutaneous renal therapies. For the urologist, one of the most significant challenges of a percutaneous procedure is applying the three‐dimensional (3D) renal anatomy to a two‐dimensional image representation. In many cases, this anatomic transposition may be confusing. Reliably and safely attaining an optimal point of renal access can require extensive training and experience. Certain clinical situations, such as entry into a nondilated renal collecting system or anatomical variation (e.g. duplex system, malrotation, horseshoe kidney), can be challenging, even for the experienced clinician. There is associated risk of injury to adjacent structures with percutaneous renal access and complex cases may increase this risk. An additional complexity for the urologist, which is not encountered in the orthopedic and neurosurgical fields, is the mobility of the kidney within the retroperitoneum, including its continuous movement with respirations. At many institutions, urologists lack the requisite experience in placing percutaneous access, and such procedures are performed by the interventional radiologist. A lack of participation by the urologist in obtaining percutaneous access for PCNL, for example, may result in the patient undergoing more than one procedure if the access and nephrolithotomy portions of the procedure are performed at times and locations remote from one another. The urologist may also have insights into the manner in which stone removal should be performed, and a lack of such input may result in suboptimal access location. This may translate to longer operative and fluoroscopic times, and subsequently greater risk for complications and higher radiation exposure. Additionally, there are certain complex clinical scenarios where multiple access sites may be necessary, thus requiring further procedures.

Unlike humans, robots are digital devices that are controlled in 3D space. With proper image registration and navigation algorithms, these can be used to address many of the challenges associated with renal access: improved spatial accuracy, programmable, mechanical, and flexible capabilities, and once designed they can be reproducibly used by a surgical novice. With novel technology that allows constant impedance measurements and rotating needle drivers, many of the above‐mentioned challenges, such as renal mobility, could possibly be overcome.

The ultimate goals in applying robotic technology to percutaneous access are to increase the ease and decrease the technical challenges of this task, while improving accuracy, efficiency, and reproducibility. Robotic technology holds the potential to provide greater precision than the human hand can, with improved puncture accuracy. Robotic assistance for percutaneous access may ultimately improve surgical performance and decrease complication rates, radiation exposure to patient and providers, and operative times [6].

Development and evolution of robotic percutaneous renal access systems

Robotic percutaneous renal access systems were first proposed by Potamianos et al., who performed pioneering work in the creation of a passive robot to facilitate needle placement for percutaneous surgery [7–9]. The system was mounted on an operating room table, required fluoroscopic imaging to guide placement, and had five degrees of freedom (DOF). System performance experiments reported at that time described a 1.5 mm targeting accuracy.

In 1996 our urology engineering program, URobotics, was initiated at Johns Hopkins Medicine [10]. This program is dedicated to the development of new technology and gathers both clinical and technical personnel working in close communication to achieve the goal of robotic image‐guided surgery. Many of the robotic systems that have been developed over the last 15 years were developed through this program; these systems are discussed below.

Modified LARS

A prototype system using a modified Laparoscopic Assistant Robotic System (LARS) was introduced in 1997 by Cadeddu et al. [9]. LARS was a modified laparoscopic assistant active robotic system which maintained seven DOF. Each robotic joint was moved by an electric motor, so the access procedure was totally automated. Biplanar fluoroscopic imaging was used to guide the access procedure. The authors described that in vitro accuracy was 0.43 mm, and ex vivo success with the first attempt was 83%. The authors noted that problems arose with tissue and needle deflection. No comparison to nonrobotic human placement was done with this device, but rather this was a proof‐of‐concept experiment. This study, despite its limitations, demonstrated that robotic percutaneous access was feasible, although the need for multiple improvements and modifications, such as advanced software, increased DOF, and improved needle design and feedback mechanisms, were identified.