Automated Needle Targeting (ANT) Device-Assisted Renal Access during Percutaneous Nephrolithotripsy (PCNL) Puncture: A Pilot Study to Assess the Safety and Efficacy of a Novel Technique

doi:10.21203/rs.3.rs-32132/v1

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Automated Needle Targeting (ANT) Device-Assisted Renal Access during Percutaneous Nephrolithotripsy (PCNL) Puncture: A Pilot Study to Assess the Safety and Efficacy of a Novel Technique

https://doi.org/10.21203/rs.3.rs-32132/v1

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Background: To explore the use of an automated needle targeting (ANT) device as an assistive intraoperative navigation modality during PCNL for the treatment of large renal stones, with the aim of reducing surgical durations and radiation exposure.

Methods: This open-label, single-surgeon clinical trial included patients with a diagnosis of renal stones for whom PCNL using the ANT device via the percutaneous access technique was indicated. Ethical approval was obtained from the UMMC ethics review board (Ref. 20118105-6740). The ANT was assembled after an initial motor calibration, and the image calibration was performed using the patient’s fluoroscopic images. Subsequently, the ANT software calculated a bullseye alignment before percutaneous puncture. Accurate renal access was confirmed by the efflux of urine in the Chiba biopsy needle, as well as by imaging with the C-arm intensifier at different angles. The primary endpoints were the time to successful renal access (from ANT set-up to urine efflux) and adverse events.

Results: In all cases, successful renal access was achieved with a single attempt. The mean time to renal access was 6 minutes, 8 seconds. The mean fluoroscopy duration was 101 seconds, with a mean radiation dose of 23.46 mGy. No adverse events were documented.

Conclusion: The ANT device enabled successful, safe and efficient renal access for PCNL in this study. Further research is needed to justify the effectiveness of this device in terms of enabling accurate renal access while reducing the surgical duration and radiation exposure to both surgeons and patients.

Urology & Nephrology

PCNL

renal stone

staghorn calculi

ANT assisted renal access

Percutaneous nephrolithotomy (PCNL) is currently considered the treatment of choice for staghorn calculi or large renal stones. Compared with open nephrolithotomy, PCNL is less invasive and is associated with reduced morbidity, while yielding good stone clearance.¹ However, inexperienced new surgeons may find it difficult to master PCNL, as the achievement of an accurate initial puncture is essential to obtain renal access and achieve a successful outcome. Targeting of the renal calyx using 2d fluoroscopy images for guidance can be difficult particularly in situations where the stones are lodged in the calyx of the kidney.² To overcome this learning curve, researchers have explored improvements in intra-operative imaging and, more recently, the introduction of intra-operative navigation systems. The Johns Hopkins University Group reported on PAKY-RCM, a joystick-driven system that uses a robotic arm to support a puncture needle and direct its insertion.³ In 2011, Cinquin et al. reported a similar system wherein the robotic arm functioned as an adjunct to compliment the surgeon’s movement during renal access.⁴

The automated needle targeting (ANT) device is a software-controlled automated electromechanical robot arm. This device was developed to provide needle guidance and stabilization for surgeons during the establishment of renal access for PCNL. The aim of the device is to reduce the time required to establish accurate renal access and thus minimize the exposure of surgeons, theatre personnel and the patient to radiation.⁵ The ANT device-assisted technique couples intra-operative fluoroscopic imaging with image registration software, which uses a closed-loop feedback system to align the puncture needle to the desired calyx prior to the actual puncture. The ANT robot is mainly composed of medical-grade polyether ether ketone (PEEK), and is constructed from three main components: the robot, motor controller box and the articulated arm (Fig. 1).⁵ In this report, we describe our initial experience with the ANT device and the associated safety and efficacy during the establishment of the initial puncture and renal access for PCNL.

This was a phase one first-in-man, open-label, non-randomized, parallel-design safety and efficacy study of subjects who underwent PCNL with ANT device-assisted renal access. Ethical approval for the study was obtained from the University Malaya Medical Centre (UMMC) ethics review board (Ref No. 20118105-6740). This study was carried out following principles of the Declaration of Helsinki and International Conference on Harmonization Good Clinical Practice guidelines.

This pilot study included five patients at the UMMC in Kuala Lumpur who were diagnosed with renal calculi within a 3-month period and for whom prone PCNL with ANT device-assisted renal access was indicated. The inclusion criteria were age older than 18 years, informed consent to participate, renal calculi larger than 1 cm and no history of treatment for renal calculi. Patients who had previously received extracorporeal shockwave lithotripsy (ESWL) or ureterorenoscopy were excluded. The clinical decision to undergo PCNL instead of another treatment modality (such as retrograde intrarenal surgery, ESWL) depended entirely on the clinical indication according to existing guidelines and the standard of care. In this study, all PCNL procedures were performed by a single consultant urologist.

Endpoints

The primary endpoints for this study were a successful needle puncture that enabled the surgeon to proceed to dilatation and stone fragmentation and extraction, as well as the assessment of any adverse events arising from the use of the ANT device. The following parameters were assessed: needle insertion time, time to target, total time for puncture, number of needle insertion attempts to obtain access and total radiation dosage (measured from placement of the robot until the efflux of urine). The needle insertion time was measured from the mounting of the ANT device until the efflux of urine during successful renal access. The time to target was defined as the time from the targeting of the needle on the skin to successful needle targeting via software and fluoroscopy image coordination. The total time for puncture was defined as the time from identification of the calyx to the efflux of urine via successful needle puncture.

Preoperative Preparation and Positioning

In accordance with the standard protocol for prone PCNL at our center, all patients were first placed in the lithotomy position. A ureteric catheter was inserted, and its placement was confirmed via fluoroscopy. Subsequently, the patient was turned to the prone position and sterilized and draped according to the standard PCNL procedure. The ANT device was then assembled and mounted to the operating table as shown in Fig. 2. The device was positioned between the C-arm and the patient and aligned with the renal stone in a sterile manner (Fig. 2). The target calyx for renal access was chosen according to the surgeon’s clinical judgement and preference.

ANT-assisted Renal Access

Once positioned, motor calibration of the ANT device was performed by coupling the intraoperative fluoroscopy images with the ANT software (Fig. 3). The puncture needle within the needle sheath was placed in the articulated arm of the device. The ANT software performed an oriented calculation to achieve a bullseye alignment and optimal trajectory. To overcome renal mobility with breathing, respiration was stopped during renal access with the ANT device. The surgeon then performed the PCNL puncture by advancing the needle within the sheath into the renal calyx. With assistance from the anaesthetist, respiration was resumed once needle alignment and puncture was done. Accurate renal access was confirmed by the efflux of urine into the needle sheath, as well as by imaging with the C-arm positioned at variable angles. A guide wire was then passed into the renal collecting system before the ANT device was disassembled and removed from the operating table. Subsequently, the standard PCNL procedure, which comprised access tract dilatation followed by stone fragmentation and complete extraction, was performed.

All the 5 cases in this pilot study required only a single puncture to achieve successful renal access (Table 1). The mean needle insertion time was 6 minutes and 8 seconds, the mean time to target was 3.8 minutes and the mean total time for puncture was 8.18 minutes. The mean duration of radiation exposure during placement of the ANT device was 1.41 minutes, which corresponded to a dose of 23.46 mGy (Table 1). No adverse events were documented.

Table 1

Outcomes of cases of PCNL in which the ANT device was used to achieve renal access
Patient	Needle insertion time (min)	Time to target (min)	Total time for puncture (min)	Number of needle insertion attempts to obtain access	Radiation dosage from placement of robot to efflux of urine (min, mGy)
1	6:26	2:34	6:42	1	0:58, 10.1
2	8:11	2:08	9:48	1	0:22, 11.9
3	4:40	4:14	8:19	1	3:67, 49.4
4	5:29	5:09	7:45	1	1:14, 35.0
5	6:32	5:35	9:36	1	1:42, 10.9
Mean	6.08	3.8	8.18	1	1.41, 23.46

In this pilot study, we are successful in executing the concept of the ANT device and its safety in establishment of the initial puncture and renal access for PCNL.

Learning Curve

PCNL is currently the standard of care for large renal stones (> 2 cm) and can achieve a good stone-free rate. However, this technique remains challenging to master,¹ as evidenced by the increased morbidity associated with the procedure, especially when performed by an inexperienced urological surgeon.⁶ It has been reported that a new urologist could achieve surgical competence in PCNL after performing 40–60 procedures, including the mastery of all key steps such as calyceal puncture, track dilatation, endoscopic manipulation, lithotripsy and nephrostomy insertion.² Based on our findings, we contend that the ANT device could assist new surgeons with this learning curve by improving the calyceal puncture step. The ANT device uses a bullseye technique to achieve renal access, and surgeons can use this tool as a guide to orientate and advance the puncture needle into the renal calyx. In a future study ANT-assisted renal access should be compared with conventional free-hand puncture.

Renal Access

The common major complications (Clavien–Dindo grade > III) of PCNL are associated with percutaneous puncture during renal access, and may include injury to the adjacent organs, violation of the pleural space, bleeding or infection.⁷ In our cohort of patients, renal access was completed successfully with a single needle puncture attempt in all cases. This result suggests that the ANT device may help to reduce the risk of renal access-related complications caused by the number of puncture attempts. In the future, insufficient experience may no longer be a major cause of complications associated with PCNL. Moreover, the reduced number of puncture attempts will help to reduce the total procedural duration.

Radiation Exposure

In a previous report, Bohdan et al. reported an average fluoroscopy time during PCNL of approximately 175 seconds.⁸ Moreover, Allen et al. reported that the fluoroscopy time and radiation dose only reached plateaus after 115 cases.⁹ In our cohort, the mean fluoroscopy time was 101 seconds. A reduced fluoroscopy time and consequently decreased radiation exposure would benefit not only the patient but also the surgeon, particularly as the cumulative radiation dose would increase with an increasing number of cases. Furthermore, the ANT device removes the need for the surgeon’s hand to be in close proximity of radiation area during bullseye alignment and therefore reduces risk of radiation exposure. One might argue that the use of ultrasound-guided renal access during the PCNL procedure could also significantly minimize the radiation exposure. However, ultrasound imaging is operator-dependent, and successful renal access under the guidance of this modality would require the mastery of a completely different learning curve. Furthermore, intra-operative ultrasound devices are not readily available at all centers.

Robotic-assisted PCNL devices

Since the first introduction of “robotic”-assisted PCNL in 2009,¹ the common limitations faced by users have included difficulty with the initial set-up, the absence of tactile feedback from the robot and difficulty with sterilization of the robot. The ANT device was developed to address these disadvantages. Similar to a self-retaining retractor, the ANT device can be easily mounted to the operative field using a clip and screw-on hinge placed on the operating table. The flexible working arm can be adjusted easily and focused on the operating field. Once renal assess is successfully achieved, the ANT device can be unscrewed and removed swiftly. Moreover, the ANT device assists the surgeon in achieving an accurate bullseye allocation and placement of the puncture needle, and functions as a sheath to ensure constant and steady needle angulation during the renal access puncture. This design thus preserves tactile feedback during the performance of a renal access puncture, which may be especially useful as it allows the surgeon to feel the “give” during renal access and thus avoid the risk of injury to the surrounding structures. Finally, the ANT device is autoclavable, which facilitates device sterilization and thus effectively prevents the transmission of device-related infectious diseases.

Limitations

This was a pilot study to assess the safety and efficacy of the ANT device. Therefore, we did not attempt to achieve renal access in complex scenarios, such as patients with full staghorn calculi, a non-hydronephrotic kidney or a complex renal anatomy. A future study involving a larger cohort and a control group will better enable us to assess the role of the ANT device in such difficult cases. Moreover, we did not test the ANT device during the performance of renal access in the supine position. This may also be a subject of future research. It came to our attention that ceasing respiration is important to assist in accurate renal access using the ANT device. Moving forward, future research and developments can look into negating this by syncing the ANT device with movements caused by respiration. As this is a phase one study with the ANT device, a variance in the targeting time could also be due to the surgeon familiarizing with the device.

Our pilot study demonstrates the promising capability of the ANT device to enable successful, safe and efficient renal access for PCNL. Further studies are needed to justify the efficacy and accuracy of this device for the achievement of renal access while reducing surgical duration and radiation exposure to both surgeons and patients.

PCNL: Percutaneous nephrolithotomy

ANT: Automated Needle Targeting

PEEK: Polyether Ether Ketone

UMMC: University Malaya Medical Centre

ESWL: Extracorporeal Shockwave Lithotripsy

Ethics approval and consent to participate

Ethical approval for the study was obtained from the University Malaya Medical Centre (UMMC) ethics review board (Ref No. 20118105-6740). This study was carried out following principles of the Declaration of Helsinki and International Conference on Harmonization Good Clinical Practice guidelines. Informed written consent was obtained from all participants involved in this study.

Consent for publication

Not applicable

Availability of data and materials

The datasets used and/or analysed during the current study are available from the corresponding author on reasonable request.

Competing interests

The authors declare that they have no competing interest.

Funding

This study is Funded by NDR Pvt Ltd company and National Research Foundation, Singapore under its AI Singapore Programme (AISG Award No: AISG-100E-2018-011).

NDR Pvt Ltd company provided the usage of the ANT device for the research.

Financial support for the research was provided by NDR PVT Ltd Company, through research Grant from National Research foundation, Singapore under its AI Singapore programme (AISG Award No: AISG-100E-2018-011).

Authors’ contributions

CAC assisted in the surgery for the study, interpreted the patient data, wrote the manuscript for study and submission of the manuscript as well as read and approved the final manuscript.

WSY assisted in the surgeries for the study, interpreted the patient data and edited, read and approved the final manuscript.

TAO, ANF, SK, KPA, JL read, edited and approved the final manuscript.

AHAR was the only surgeon performing surgeries in this study, read and approved the final manuscript.