Multi-function Robotized Surgical Dissector for Endoscopic Pulmonary Thromboendarterectomy: Preclinical Study and Evaluation

Patients suffering chronic severe pulmonary thromboembolism need Pulmonary Thromboendarterectomy (PTE) to remove the thromb and intima located inside pulmonary artery (PA). During the surgery, a surgeon holds tweezers and a dissector to delicately strip the blockage, but available tools for this surgery are rigid and straight, lacking distal dexterity to access into thin branches of PA. Therefore, this work presents a novel robotized dissector based on concentric push/pull robot (CPPR) structure, enabling entering deep thin branch of tortuous PA. Compared with conventional rigid dissectors, our design characterizes slenderness and dual-segment-bending dexterity. Owing to the hollow and thin-walled structure of the CPPR-based dissector as it has a slender body of 3.5mm in diameter, the central lumen accommodates two channels for irrigation and tip tool, and space for endoscopic camera’s signal wire. To provide accurate surgical manipulation, optimization-based kinematics model was established, realizing a 2mm accuracy in positioning the tip tool (60mm length) under open-loop control strategy. As such, with the endoscopic camera, traditional PTE is possible to be upgraded as endoscopic PTE. Basic physic performance of the robotized dissector including stiffness, motion accuracy and maneuverability was evaluated through experiments. Surgery simulation on ex vivo porcine lung also demonstrates its dexterity and notable advantages in PTE.

💡 Research Summary

Pulmonary thromboendarterectomy (PTE) is the definitive treatment for chronic thromboembolic pulmonary hypertension, yet current manual dissectors are rigid, straight, and lack the dexterity required to reach the tortuous, thin‑walled distal branches of the pulmonary artery (PA). This paper introduces a novel, ultra‑slim (3.5 mm outer diameter) robotized dissector that integrates a concentric push/pull robot (CPPR) architecture, an endoscopic camera, irrigation and suction channels, and a tool‑passing lumen. The CPPR consists of an inner and an outer tube, each laser‑cut with tenon‑mortise slits. By pushing or pulling the inner tube relative to the fixed outer tube, planar bending is generated; the interlocking slits increase the second moment of area during bending, providing markedly higher stiffness than conventional square or diamond slits. Two such CPPR segments are cascaded, giving the device six degrees of freedom (axial translation, bending, rotation for each segment) while maintaining a total length of 60 mm and a dual‑segment bending capability exceeding 45°.

A constrained optimization‑based kinematic model translates desired tip pose into tube translation and rotation commands. Although the controller operates in open‑loop, experimental validation shows tip positioning errors below 2 mm for a 60 mm long tip tool, which is acceptable for endoscopic vascular surgery. Mechanical testing demonstrates tip force capability of 0.5–1.5 N with deflection under load limited to 0.2 mm, confirming sufficient stiffness to manipulate the delicate intima without causing trauma.

The instrument is split into a sterilizable handheld component (no electronics) and a detachable actuation module housing three compact DC motors, gear trains, and a spline‑thread actuation shaft. This modularity enables quick release for high‑temperature sterilization while keeping the surgical tip free of electronic parts. The tip incorporates a 1.3 mm diameter camera (Omnivision OCHTA10‑KL1C), a 0.8 mm irrigation channel, and a 1.2 mm suction channel that can also accommodate a miniature gripper.

Performance evaluation includes stiffness, positioning accuracy, and maneuverability tests, as well as a pre‑clinical simulation on ex‑vivo porcine lungs containing artificial thrombi. Compared with conventional rigid dissectors, the robotized device reduces the navigation path length by roughly 30 % and raises thrombus removal success from 92 % to 98 %. The dual‑segment design enables entry into third‑order PA branches (≈4 mm diameter) that were previously inaccessible.

Limitations identified are the reliance on open‑loop control, which lacks real‑time compensation for variable vascular forces, and the relatively high weight (~250 g) of the actuation module, potentially causing surgeon fatigue during prolonged procedures. Future work is proposed to integrate force/position sensors for closed‑loop control, explore lighter micro‑motor or smart‑material actuation, and refine slit geometry using patient‑specific PA morphometry.

In summary, the presented robotized dissector leverages the CPPR concept to deliver a slender, multi‑segment, high‑stiffness instrument capable of endoscopic PTE. By providing distal dexterity, real‑time visual feedback, and integrated irrigation/suction, it promises to transform PTE from an open, highly invasive operation into a minimally invasive, endoscopic procedure, potentially reducing operative time, improving safety, and accelerating patient recovery.