Laparoscopic surgical instrument as a needle holder

Description

[0001] The invention relates to a needle holder for holding a suture thread for robot-assisted laparoscopic operations performed by means of a surgical robot with at least one robot arm, comprising a mounting head for coupling to the robot arm, a shaft element, a ball joint arranged at the distal end of the shaft element, and a pincer gripper arranged on the ball joint head to be tiltable about at least two axes by means of a first and second drive means, wherein the drive means are cable pulleys guided over deflection pulleys, wherein force detectors (3) are arranged in the needle holder (1) which detect the tension force of the suture thread (S) held by the pincer gripper (14).

[0002] Such a laparoscopic surgical instrument is known from CA 3 073 355 A1 in the form of a surgical robotic system, comprising a surgical robotic instrument having an end effector at a distal end, the end effector comprising two opposing jaws, each actuated by a pair of actuators, and an antagonistic pair of cables that exert forces when tensioned by the pair of actuators; and wherein the system comprises: a controller comprising one or more processors coupled to the surgical robotic instrument, the processors being configured to receive an input from an input module to effect a desired state of the end effector, the input including at least a pitch angle and a yaw angle of the end effector and a jaw angle between the two jaws; measuring the positions of the actuator pairs using sensors on the actuator units;Measuring the clamping forces on the antagonistic cable pairs using sensors; determining a desired end effector position based on the pitch and yaw angles and a desired gripping force between the two jaws based on the jaw angle; generating a first drive command for each actuator of the actuator pairs based on the desired position and the measured positions and clamping forces; estimating a current gripping force between the two opposing jaws based on the measured clamping forces on the antagonistic cable pairs; generating a second drive command for each actuator of the actuator pairs based on a difference between the desired gripping force and the estimated current gripping force;and driving the actuator pairs to achieve the desired position and gripping force, using a compound drive command based on a summation of the first and second drive commands. The method described here for determining the gripping force appears to be very complex and prone to errors.

[0003] Furthermore, US Patent 2020 / 384643 A1 describes a computational method for estimating joint friction in a joint of a robotic wrist of an end effector. This method involves sensor measurements of force or torque in a transmission that mechanically couples a robotic wrist to an actuator. The joint friction in a joint of the robotic wrist driven by the actuator is calculated by applying the sensor measurements of force or torque to a mathematical expression that relates the force or torque variables of the transmission to a joint friction variable. A tracking error of the end effector is also calculated using a closed-form mathematical expression that relates the joint friction variable to the tracking error.This evaluation method also appears computationally intensive and dependent on mathematical approximations, which in turn may contain errors.

[0004] GB 2599101 A further describes a surgical robotic instrument comprising: a shaft; an end effector comprising a first end effector element with a first surface and a second end effector element with a second surface configured to interact with the first surface; and a joint connecting the end effector to the shaft, the joint allowing the first end effector element to rotate about a first axis and the second end effector element about a second axis, the first and second axes being transverse to the longitudinal axis of the shaft; wherein, when the end effector is aligned with the shaft and the first and second surfaces are connected, the orientation of the first surface relative to the first axis is greater than zero degrees. This is intended to specify a surgical instrument that offers the highest level of precision and increases efficiency.

[0005] A minimally invasive instrument is known from DE 10 2012 207 707 A1, which allows surgical material to be inserted into the patient's body more easily and quickly. For this purpose, a manual control element is also provided, with which the functional element, for example forceps, remains operable while the instrument is detached from the surgical robot.

[0006] German patent DE 10 2006 059 952 B3 describes a robotic structure for minimally invasive surgery in which gripping forces are measured directly at the joint using a sensor element. Similarly, US patent 2009 / 0157092 A1 describes a force sensor device comprising a tube section with multiple radial ribs and a strain gauge positioned over each of the radial ribs, a proximal end of the tube section that functionally couples to the shaft of a surgical instrument, which in turn functionally couples to a manipulator arm of a surgical robotic system, and a distal end of the tube section that is proximally connected to a wrist joint, which is coupled to an end effector. A disadvantage of this design is that the sensor element and the necessary deflections must be located at the joint of the gripper, meaning that this technology must be inserted into the patient's body during minimally invasive procedures.Accordingly, this technique puts a strain on the instrument's smallest possible joint head, which affects its stability and / or dimensions, its sterile cleaning capability, and the cost of its replacement.

[0007] Robot-assisted laparoscopic surgery has become a preferred method for many surgical procedures in recent developments. Needle holders are well-known as robot-guided tools for suturing tissue in general surgery. These robot-guided tools utilize a forceps gripper that can tilt around two axes. The gripper and joints are actuated via cables connected to pulleys. The laparoscopic surgical tool is an interchangeable component of the robotic system. The motorized drive for the tool's cable pull is a component of the robot arm. The laparoscopic surgical tool is a component that can be replaced via the mounting head on the robot arm of the surgical robot. The mounting head is the mechanically actuating, detachable connection to the robot arm.The robot arm incorporates actuators, such as electric motors, which transmit the drive force to the assembly head via gears. There, the gears drive associated pulleys, which in turn power the drive mechanism for the laparoscopic surgical instrument, in this case, a needle holder. Thus, the motorized drive for the pulleys within the surgical instrument (needle holder) is a component of the robot arm. The laparoscopic surgical instrument, which can be exchanged via the assembly head and is designed here as a needle holder, is the part that, with its forceps and shaft element, is inserted into the human body to perform the minimally invasive procedure. Since, despite elaborate cleaning methods, minute residual contamination on the laparoscopic surgical instrument cannot be completely ruled out, these instruments are currently disposed of after 10 uses.

[0008] The technical advancements and clinical advantages of laparoscopic surgery in the 1990s have thus far had only a minor impact on vascular surgery. In contrast to laparoscopy, robotic instruments, thanks to Endo-Wrist technology, are inherently more flexible, easier to use, and manipulable in all degrees of freedom. This makes it possible to perform topographically complex surgical procedures, which are difficult to access using classic laparoscopic techniques, with robotic assistance and precision. In vascular surgery, this applies particularly to the paravisceral segment with regard to renal and mesenteric bypasses. Due to the difficult and traumatic exposure—especially in obese patients—these procedures are currently primarily the domain of endovascular repair, often at the cost of a low patency rate for endovascular vascular repair.

[0009] The primary reason for the limited use of laparoscopy in vascular surgery is the difficulty of suturing vascular anastomoses, resulting in prolonged vessel clamping times. Currently, robot-assisted aneurysm repair and aortofemoral bypass grafting represent the standard procedures in vascular surgery. However, thanks to excellent single-center experience, the advantages of robot-assisted vascular surgery can now be demonstrated, as described in P. Stádler, L. Dvorácek, P. Vitásek, P. Matous, - Robot assisted Aortic and Non-aortic Vascular Operations, Eur J Vasc Endovasc Surg (2016) 52, 22-28. This is due not only to years of expertise with the robotic system but also to the establishment of specialized techniques for anastomosis and the use of specific materials (e.g., shortened, tear-resistant PTFE sutures, connectable vascular clamps, etc.).

[0010] Due to the minimally invasive nature of the procedure, patients primarily benefit from shorter hospital stays, earlier rehabilitation, and a return to their usual activities and work life. The procedure is particularly well-suited for obese patients; technically demanding operations requiring a clear surgical field can now be performed without complex retraction systems, positioning modalities, or post-laparotomy wound healing problems.

[0011] Technological advancements in computers increase the safety and precision of instrument guidance within the patient's body (master and slave principle). Furthermore, it is possible, using data networking, to couple a virtual mapping of preoperative cross-sectional image data with the surgical site and to provide the surgeon with virtual on-demand information during the procedure.

[0012] The Department of Vascular Surgery was integrated into the Kurt Semm Robotics Center at the University Hospital Schleswig-Holstein (UKSH Kiel) as early as 2016. Initial vascular surgical experience was gained through experimental interdisciplinary training courses using cadaveric donors. Clinically, a study (n=18) of robot-assisted patch anastomoses in the iliacofemoral region was initiated, focusing on surgical access, anastomosis duration, and clinical outcomes.

[0013] The challenge in laparoscopic or robot-assisted vascular surgery lies in the handling of the vascular suture. The unique aspect of vascular suturing is its manual and technical differences compared to other specialties, such as general / visceral surgery or urology. In these fields, the suture serves as tissue adaptation and requires only minimal tension during the anastomosis. In contrast, vascular reconstruction, particularly aortic surgery, requires significantly greater force to guide the suture. This demands experience in handling the suture material as well as an understanding of the vulnerability of the vessels. If the suture is guided too tightly and held under excessive tension, the result will either be tearing in or out of the vessel, or the suture itself will break under this stress. If the suture is guided too loosely, complications will arise after blood flow is restored (e.g., after the anastomosis is performed).From the aorta to the anastomosed aortic prosthesis, bleeding from the anastomosis site can occur because the seal between the vessel and the prosthesis is not guaranteed – the suture is too loose. In open surgery, this is remedied by having the assistant constantly maintain tension on the thread end, which, depending on the tissue consistency, ranges from approximately 5 to 30 N. This tension is maintained until the next stitch is placed, at which point the loose end of the suture is pulled through, and the taut thread is released accordingly. The result is a vascular suture performed under tension, which optimally approximates the vessel and the aortic prosthesis and – provided the appropriate suture channel spacing is maintained – ensures a tight seal.

[0014] The problem here is that the tension on the suture is very difficult to control during laparoscopic or robot-assisted surgical procedures. While laparoscopic surgical techniques provide haptic feedback on the tension of the suture through direct manual control at the needle holder, this is not possible in modern robotic systems due to their remotely controlled force application.

[0015] As a result of excessive tensile force, the suture breaks and the anastomosis must be redone. This is very common with monofilament suture material (e.g., Prolene). Therefore, PTFE sutures (synonym: Teflon sutures) are generally used for vascular sutures, as they offer increased strength and a degree of elasticity. However, this type of suture also suffers from the same problem: the tensile force acting on the suture is not controllable, and the suture does not continuously approximate the vascular anastomosis under consistent tension, consequently preventing a primarily leak-proof vascular anastomosis. This surgical suture material, for example, GORE-TEX SUTURE SIZE CV-8 to CV-0, has tensile strengths of 0.3 to 5.3 kg when knotted. This corresponds to tensile forces of 3 to 53 N.

[0016] The task of the invention is therefore to specify a needle holder for holding a suture thread for robot-assisted laparoscopic operations, with which the respective tensile strength of the suture thread can be controlled.

[0017] This problem is solved with a needle holder according to claim 1. The force detectors in the needle holder can detect the tension of the suture thread held by the forceps gripper, so that the surgeon receives feedback on the current suture tension force at their control console during the robot-assisted laparoscopic operation. Tension force sensors are arranged on each cable pull as force detectors, measuring the tensile force acting on the cable pull. The feedback can be displayed via the actuators on the surgeon's console of the surgical robot by electrically applied "counterforces" or by displaying the current suture tension as an absolute value or as a visually represented target value between a lower and an upper limit.This allows the surgeon to precisely apply the correct tension to the suture thread from their control console, ensuring neither overloading the tissue being sutured and / or the suture itself, nor making the thread too loose, thus preventing bleeding from the anastomosis area. For example, the suture tension can be maintained at a value of 5 to 30 N.

[0018] The tension of the suture should always be measured as close as possible to the point of application. However, measuring directly at the forceps or the ball joint is hardly feasible, as the surgical instrument intended for minimally invasive surgery in the human body is very small, mechanically sensitive, and, for hygienic reasons, should have as few moving parts and / or additional sensors, cables, etc., as possible. Therefore, measuring the cable tension on the cables within the surgical instrument—that is, indirectly measuring the forces by determining the tension in the cables that actuate the ball joint for the forceps—is necessary. This allows for an indirect measurement of the tensile force acting on the suture as it is held in the forceps of the needle holder.

[0019] It must be considered that the point of application of the thread tension is at the end of the gripper. If, for example, this is angled at 90° to the longitudinal axis of the surgical tool, a corresponding torque is exerted. This torque then tensions the cable, which is used to actuate the gripper around this pivot axis. If, for example, a GORE-TEX CV-6 suture thread with a tensile strength of F1 = 6.5 N is used, the required torque for the gripper angle described above would be M = F1 * L = tensile strength in the thread * length of the gripper (e.g., 15 mm) = 100 N * mm. With a radius of r = 3 mm for the pulley attached to this pivot axis for the relevant cable, the equilibrium of the torques acting on the cable results in a five times greater tension with F2 = M / r, i.e., F2 = 33 N. This force, or rather...The rope tension must be detected by the force sensor in the mounting head of the tool (needle holder) as a limit force that must not be exceeded under any circumstances.

[0020] The force sensor preferably has three rotatable rollers arranged in series, over which the cable is alternately guided. Two outer rollers are fixed in the needle holder, and a middle roller is resiliently movable in its radial plane perpendicular to the cable. The force acting on the cable causes a deflection of the middle roller, resulting in a measurable force that is proportional to the force acting on the cable. This force sensor is located in the mounting head because sufficient space is available there, and the proximal end of the surgical instrument, with its mounting head, remains as far away as possible from the surgical site. Consequently, it is not, or only minimally, contaminated with bodily fluids, thus minimizing or eliminating hygienic contamination.

[0021] By incorporating a shallow bend of 1° to 15° in the cable around the central pulley, the force acting against the spring force at the central pulley, which is to be measured, is significantly reduced compared to the force acting in the direction of the cable pull. This allows for relatively small measurement ranges, such as 0 to 5 N. Such force ranges can be measured using miniature bending beam tensile / compressive force sensors, such as the type 8510 from Burster Präzisionsmesstechnik GmbH & Co. KG, Talstraße 1-5, 76593 Gernsbach, Germany. The forces to be measured on the cable, for example, vary in the range of 20 to 24 N.

[0022] The subject matter of the application is described in detail below with reference to the attached drawings.

[0023] It shows: Fig. 1 shows an embodiment of a laparoscopic surgical instrument as a needle holder, and Fig. 2 shows a partially cutaway detail view of the needle holder according to... Fig. 1 with a tensile force sensor for force detection on a cable pull.

[0024] In Fig. 1 A surgical robot R with a robot arm A is shown schematically in dashed lines. A laparoscopic surgical instrument in the form of a needle holder 1 is attached to the free end of the robot arm A via a mounting head 11. The needle holder 1 also has an elongated shaft element 12 that extends from the mounting head 11 to a ball joint 13. A gripper 14 is attached to the ball joint 13. The ball joint 13 allows pivoting about two mutually perpendicular axes, which are essentially perpendicular to the longitudinal axis of the shaft element 12. Furthermore, the shaft element 12 is rotatably mounted in the mounting head 11 about its longitudinal axis. Accordingly, the gripper 14 can perform a variety of movements.

[0025] In Fig. 2 The needle holder 1 is shown in detail, namely the mounting head 11 and the adjoining shaft element 12. Three drive elements in the form of cables are indicated in the hollow interior of the shaft element 12. A first cable 21 causes a pivoting motion about a first pivot axis Y (dashed line in the figure) via a deflection pulley (not shown) on the ball joint 13. Fig. 1 Furthermore, a second drive element, in the form of a second cable pulley 22, is provided inside the shaft element 12. This cable pulley, not shown, is directed to the second pivot axis Z (dotted in inset). Fig. 1 ) acts. A third drive element, a third cable pull 23 in the shaft element 12, leads to the gripper 14, with which the gripper can be opened and closed.

[0026] In the mounting head 11, a tensile force sensor 3 is shown in detail for the first cable pull 21 ( Fig. 2The tensile force sensor 3 consists of a first outer roller 31 and a second outer roller 32, both of which are fixedly arranged in the mounting head 11. A middle roller 33 is arranged between the first outer roller 31 and the second outer roller 32, and is spring-loaded and movable in its radial plane perpendicular to the cable pull. A tensile force measuring device 34 is attached to this middle roller, which can measure the cable tension of the first cable pull 21 based on the slight kink in the cable pull between the first outer roller 31, middle roller 33, and second outer roller 32. The measurement signals determined by the tensile force measuring device 34 are transmitted via the operating line 35 in the mounting head 11 to the surgical robot R via the robot arm A.

[0027] A similar setup is also provided for the other drive elements, namely the second cable pull 22 and optionally the third cable pull 23 with corresponding force sensors 3, which are not shown individually here. After coupling the assembly head 11 to the robot arm A of the surgical robot R, drive forces from actuators, in particular electric motors within the robot arm A, are transmitted via gears and corresponding coupling mechanisms to associated gears 20 in the assembly head 11, which are operatively connected to the respective drive element, here the first cable pull 21. The drive force is then transmitted to the needle holder 1 in a known manner. However, the integrated force sensors 3 and their feedback to the surgical robot R now detect the force in the associated cable pull, here the first cable pull 21.By determining the tension in the respective cable pull, the forces acting on the forceps gripper 14 can be indirectly detected. Accordingly, the tensile force acting on a suture thread held in the forceps gripper 14 can be measured, and a maximum load that must not be exceeded can be monitored. The surgical robot R can then provide the surgeon with an acoustic and / or visual warning signal indicating that the recommended tensile force for, for example, a vascular suture can be reached.

[0028] Thus, a tension sensor 3 is integrated as an electronic device in the needle holder 1, which is used in robot-assisted laparoscopic surgery. The suture tension or force at the gripper is detected via the tension in the tool's cables. Two of the tool's three cables actuate the two joints. A device for detecting the cable tension is therefore proposed that does not affect the integrity of the cable and thus the reliability of the system. Reference symbol list

[0029] 1 Laparoscopic surgical instrument, needle holder 11 Mounting head 12 Shaft element 13 Joint head 14 Forceps gripper 2 Drive means 20 Gear 21 First drive means, first cable pull 22 Second drive means, second cable pull 23 Third drive means, third cable pull 3 Tensile force sensor, force detector 31 First outer roller 32 Second outer roller 33 Middle roller 34 Tensile force measuring device 35 Working line ARobot arm ROperational robot SNutrade XLongitudinal axis Yerste swivel axis Zzweiste swivel axis

Claims

1. Needle holder (1) for holding a suture thread (S) for robot-assisted laparoscopic surgery performed by means of a surgical robot (R) with at least one robot arm (A), comprising a mounting head (11) for coupling to the robot arm (A), a shaft element (12), a joint head (13) arranged at the distal end of the shaft element (12) and a pair of forceps grippers (14) arranged on the joint head (13) so as to be tiltable about at least two pivot axes (Y, Z) by means of a first and second drive means (21, 22), wherein the drive means are cable pulls (21, 22) guided over deflection rollers, force detectors (3) being arranged in the needle holder (1) which detect the tension force of the suture thread (S) held by the pair of forceps grippers (14), characterised in that tensile force sensors (3) are arranged as force detectors on each cable pull (21, 22), which measure the tensile force acting on the cable pull (21, 22), wherein each tensile force sensor (3) has three rotatable rollers (31, 32, 33) arranged one behind the other, over which the cable pull (21, 22) is guided alternately, wherein two outer rollers (31, 32) are mounted fixedly in the needle holder and a middle roller (33) is resiliently movable in its radial plane perpendicular to the cable pull (21, 22), wherein the tensile force acting on the cable pull causes a deflection of the middle roller (33) with a resulting force to be measured which is proportional to the tensile force acting on the cable pull (21, 22), and the tension force sensor(s) (3) are arranged in the mounting head (11).

2. Needle holder according to claim 1, characterised in that a flat bend of 1° to 15° of the cable pull (21, 22) around the middle roller (33) is provided.

3. Needle holder according to claim 1 or 2, characterised in that the pair of forceps grippers (14) is designed to be driven by a third drive means (23), wherein the third drive means is a third cable pull (23) also guided via deflection rollers.