Upper Quadrant Port Placement for Robot-Assisted Renal Surgery: Implementation of the Floating Arm and the XL Protype

Introduction

Application of a robot-assisted laparoscopic approach for upper tract surgical procedures presents unique obstacles compared with well-established lower tract operations. Factors such as patient habitus, variable size and location of the kidney/tumor, and the need for kidney and adjacent organ retraction influence robotic positioning. ^1,2 Furthermore, the role of the surgical assist for kidney retraction, clipping vessels, and placement of hilar clamps limits the console surgeon's autonomy. Use of the 4th arm by robotic surgeons returns some autonomy and relieves the assistant from ergonomic disadvantages, but introduces anatomic conflict between robotic arms and the patient. ^3,4

If the 4th arm is used, the lower quadrant (LQ, inferior/lateral location) is the most common position but has movement restrictions and limited ergonomics within the abdomen for retraction and use. ^{5 –7} Alternatively, an upper quadrant (UQ, superior/medial location) may be chosen but historically has been avoided because of difficulty attaching the robot (from the robotic elbow contacting the patient).

To overcome some of these obstacles, surgeons have tried longer (bariatric) ports or even placing a robotic port within a standard laparoscopic port (“telescoping”), but neither have sufficiently eased anatomic restrictions and clashing. ^8,9 We present our solution to improving placement of the 4th arm arm during upper tract surgical procedures by proposing the “Floating Arm” (FLA)—a robotic port attached away from the body that potentially has no direct contact with the patient other than the working instrument.

Methods

XL Prototype engineered

Our goal was to position the robotic arm farther from the patient to improve spacing between the robotic elbow and the patient. This would necessitate two changes to current capabilities: (1) Produce a longer instrument and (2) develop a method for a functional arm attached at a greater distance from the patient. A 20 cm extra-long Prograsp-like da Vinci instrument (XL Protype) was engineered in our laboratory (Fig. 1) and investigated using an FLA technique—a robotic arm attached to a port, but not physically touching the patient. The FLA allows use of a longer instrument, where the instrument is inserted through a standard da Vinci port (dVP) that is already attached to the robotic arm, passes through some portion of unprotected air, and then placed through an additional port that is placed through the abdominal wall (Fig. 2).

OPEN IN VIEWER

FIG. 1.

Port combinations to increase distance from the skin for robotic attachment using different port configurations: Standard da Vinci port (dVP), long (bariatric) dVP, standard and long dVP telescoped, and the XL Protype floating dVP.

OPEN IN VIEWER

FIG. 2.

Attaching the robotic port away from the skin, using an extra-long protype instrument with the Floating Arm technique allows more options for fourth arm placement such as an upper midline abdominal location. Ports 1, 3=working arms; port 2=camera port; port 4=floating port (note the end of the standard da Vinci port is “floating in air” and not inserted through the skin; an instrument passes through port 4, through unprotected air, then through a standard laparoscopic port); port 5=assistant port in the periumbilical region.

Dry lab: Mock patient port setup and measurements

Our dry lab allowed quantitative comparison of spacing and ranges of motion for standard dVP, long/bariatric dVP, telescoping dVP, and the FLA technique. The da Vinci S robot system was docked on a full body plastic mannequin, similar to our standard positioning (modified lateral flank position, bed slightly flexed and reverse Trendelenberg to level the horizontal plane). The patient's lateral arm is tucked to the side or across the body and supported. Although our ports are adjusted laterally in obese patients or inferior/superiorly based on the patient's torso length, or depending on the location of the pathology, we typically gain access for the camera port at the periumbilical region with a Veress needle. A bariatric 12-mm port is placed in this location. A standard 12-mm assistant port is placed in the periumbilical region. One robotic port is placed 8 to 9 cm lateral to the camera port and the other working port placed 8 to 9 cm superior/medial to the camera port. The 4th arm port is then placed at least 8 to 9 cm superior to this supraumbilical working port, but its position is altered laterally to allow robotic arm attachment without contacting the patient. The da Vinci S surgical system is used in all procedures and is brought in posteriorly at approximately a 20-degree angle toward the head of the patient for docking (Fig. 2).

The maximum distance the instrument could be inserted past the end of the port was measured (effectively the intracorporeal working length) (Fig. 1). The distance from the 4th arm elbow to the closest point of possible interference from the mannequin's body (the shoulder) was measured for the different combinations of port placement (standard dVP, long/bariatric dVP, max standard/telescoping dVP, max long/telescoping dVP, XL Protype floating dVP) (Fig. 3). The “swinging angle” from the adjacent working port was also compared among the various port options (i.e., how far the adjacent port could swing before striking the 4th arm or instrument).

OPEN IN VIEWER

FIG. 3.

Distance between robotic elbow and shoulder using: (A) Standard da Vinci port (dVP); (B) bariatric, long dVP; (C) telescoping; and (D) XL Protype floating arm. Use of standard and bariatric dVP are often insufficient to avoid the robotic elbow from contacting the patient unless the arm is telescoped or floated with greater clearance, respectively.

Results

Discussion

The use of the 4th arm allows for more autonomy by the robotic surgeon at the console, allows less dependence on the skill of the assistant, and releases the assistant for other assisting duties. Our survey demonstrated an increased use of the 4th arm for more complex surgeries, such as a partial nephrectomy and nephroureterectomy. While the survey demonstrated about 50% of surgeons use the 4th arm routinely, much disdain originates with anatomic limitations imposed in the lower/lateral quadrant, a configuration approximately 90% of survey respondents use. Placement of the 4th arm in the lower quadrant is further complicated in patients with smaller bodies or prominent hip bones. To overcome the external obstacles, some surgeons have suggested using the longer robotic ports (bariatric ports). About 32% of respondents have even tried telescoping the daVinci port inside a standard port to gain extra length for robot attachment and possibly decrease external conflict. Even with many of these adaptations, 4th arm conflicts are still common and may lead to decreased use, limited dexterity, or limit locations of the robotic instruments.

Limitation in the LQ led us clinically to investigate other potential 4th arm port placement options. We tried placing the 4th arm in the UQ, a position often used during pure laparoscopic upper tract surgical procedures for an additional assistant port, but many patients' body habitus interfered with robotic attachment and the elbow of the robot contacted the patient. Clinically, this forced us to move the UQ port more laterally (as one moves the port more medial in a patient in the modified lateral position, this decreases distance between the robotic elbow and the patient). As in LQ positions, longer bariatric ports helped in some patients, but still had limitations in many patients. ⁹

The FLA allows port placement near the midline and, therefore, differs from previous descriptions within the literature. ^{5 –7} In our experience, the advantages of UQ port placement include: Ability to retract the bowel medially, ability to retract the liver, and the ability to elevate the kidney and retract it medially or laterally with much less intra-abdominal interference with other instruments. By manipulating the instrument from a cranial position, the 4th arm may perform multiple functions at once—for example, retraction of the liver with the instrument shaft while retracting the kidney with the instrument jaw and tip. This potentially eliminates the need for accessory laparoscopic instruments that are typically used solely for liver retraction in right-sided renal surgery.

Our dry lab compared standard, telescoping, and floating ports to seek ideal logistical use and limitations in UQ utility. As extrapolated in Figure 1, the long bariatric port is almost identical in size to the standard/telescoping port used by other authors. The standard, long, and standard telescoping robotic ports placed in the UQ had close proximity to the ipsilateral shoulder and were not feasible to use, despite having the longest instrument reach inside the body. The max standard/telescoping and max long/telescoping ports improved arm attachment and safe shoulder height clearance, but had reduced remaining instrument length inside the body. Surprisingly, having a longer port and thus higher location for robotic arm attachment did not significantly affect adjacent arm interference. The angles for adjacent arm freedom of movement were essentially similar, with the FLA having the most freedom.

Regardless, the advantage of the UQ 4th arm port placement is that the adjacent robotic arm is usually swung away from the 4th arm during kidney and hilar dissection, and thus would still be less likely to clash externally in this location. Although the swing angle was minimally improved with the longer floating port, the longer XL Protype does allow positioning the ports more medially and, consequently, improves the distant between robotic arms and decreases clashing of robotic arms. Thus, with a floating port, one may move the UQ port toward the midline, a position that clinically is unobtainable because of arm/body interference with all other port combinations (Fig. 4).

OPEN IN VIEWER

FIG. 4.

Using the XL Protype (extra-long da Vinci instrument) and a floating arm, one may move the upper quadrant 4th arm port more medial/superior (arrow). A=assistant port; C=camera port; dP=working arm; 4dP=4th working arm; alt4dP=alternative medially placed 4th arm position.

Clinically, we have attempted floating ports with currently available standard instruments, but we experienced short intracorporeal lengths and limited floating heights. Longer instruments (such as our Protype X) are not currently available for clinical applications. As depicted in Table, while the standard port allowed a maximum instrument length inside body to be 22.5 cm, when using the long port telescoped within a standard port, the intracorporeal instrument distance was reduced to 10.3 cm.

Realizing that port attachment's limiting factor hinges greatest on instrument length, we developed a prototype grasping instrument 20 cm longer than existing robotic instruments (XL Protype). One can float the port in and out depending on the amount of distance needed within the abdomen, realizing that for every cm one floats the port out, this reduces the amount inside the abdomen by an equal amount. With the XL Protype, the instrument length inside the body was maintained adequately at 17.3 cm, greater than telescoping ports. This extended length allowed us to truly “free float” the port and greatly improve the clearance distance from the patient's body and the 4th arm elbow, while maintaining instrument working length. This would potentially allow most anatomic positions for the 4th arm, while removing limits imposed by a patient's body habitus.

There are some cautions to take into account with the FLA technique. The instrument is inserted through a standard dVP, passes through some portion of unprotected air, and then needs to be manually placed through an additional port. This limitation could easily be overcome by producing an extra-long dVP to compliment the extra-long instrument. Nonetheless, once the 4th arm is guided intracorporeally, it is rarely removed; if the instrument is removed or changed, the assistant needs to guide it back through two ports (rather than one).

In addition, whether using the telescoping or floating techniques, the fulcrum of the robotic arm changes. The fulcrum in standard robotic port application, also known as the remote center, lies at the fascia level. ¹⁰ This fulcrum limits excessive torque at the abdominal wall and instrument. Because the 4th arm is primarily used for retraction, there are usually minor amounts of movement of the robotic arm, and the standard port traversing the fascia provides some protection. Burping the port, by using the clutch button, will change the remote center and make the movement as free as possible, likely relieving any tension on the abdominal wall.

The authors acknowledge some limitations with their survey. While the Endourological Society e-mail list includes approximately 1900 contacts worldwide, these may include duplicate e-mails, nonrobotic surgeons, urologists without access to a robot, and some nonrespondents. Only an English version was distributed, and this may have limited some responses as well. Furthermore, only one e-mail request was distributed. Nonetheless, we assert that our survey was meaningful in helping understanding current trends among other robotic surgeons and to substantiate our pursuit of technical refinement.

Conclusion

Currently, the 4th arm is underutilized, especially in the UQ, because of external interference with port attachment or instrument clashing. Protype XL and the FLA technique offer a solution for more optimal and safer use of the 4th arm.