Endovascular resection of the native aortic valve before transcatheter aortic valve implantation: state of the art and review.

Transcatheter aortic valve implantation was introduced into clinical practice in 2002 as a rescue approach in patients presenting with symptomatic severe aortic stenosis but not eligible for conventional aortic valve replacement. This technique allows implantation of a balloon expandable bioprosthesis without resection of the native aortic valve. Several complications are described as a consequence of the residual highly calcified valve being squeezed against the aortic wall by the stent of the implant. This can result in deformation of the metal stent and paravalvular leakage, risk of occlusion of the coronary ostia, or central and peripheral embolization of valvular debris. To avoid these complications, many authors suggest the possibility to resect and remove the native aortic valve before transcatheter aortic valve implantation. In this field, different authors have described possible techniques and different sources of energy to resect the calcified valve. In this article, we review the development of these experimental techniques and discuss future prospects in this field.

A novel device for endovascular native aortic valve resection for transapical transcatheter aortic valve implantation.

We developed a novel resection device to use during transapical transcatheter aortic valve implantation (TAVI) using a circular blade. We assessed the device in 15 human cadavers by transapical approach. After the resection, the aortic annulus was measured using standard probes. A careful examination of the aortic wall, left ventricular outflow tract, coronary ostia and mitral valve was performed using an endpoint checklist, developed specifically for the new device. The resection was successfully completed in 14 out of 15 (93%) cases. All the resected leaflets and debris have been successfully evaluated in 15 out of 15 (100%) cases. One case of a bicuspid valve had a prominent calcification of the median raphe. The resection tool could only perform a partial resection. The mean duration of the resection was 45 ± 30 s. The surrounding tissue examination did not reveal any injury to the anatomical structures. Endovascular resection of the native valve using transapical approach is feasible and effective. Further developments are necessary before the definitive clinical use during percutaneous aortic valve implantation.

Computer-assisted and robot-assisted technologies to improve bone-cutting accuracy when integrated with a freehand process using an oscillating saw.

BACKGROUND: In orthopaedic surgery, many interventions involve freehand bone cutting with an oscillating saw. Such freehand procedures can produce large cutting errors due to the complex hand-controlled positioning of the surgical tool. This study was performed to investigate the potential improvements in cutting accuracy when computer-assisted and robot-assisted technologies are applied to a freehand bone-cutting process when no jigs are available. METHODS: We designed an experiment based on a geometrical model of the cutting process with use of a simulated bone of rectangular geometry. The target planes were defined by three variables: a cut height (t) and two orientation angles (beta and gamma). A series of 156 cuts were performed by six operators employing three technologically different procedures: freehand, navigated freehand, and robot-assisted cutting. After cutting, we measured the error in the height t, the absolute error in the angles beta and gamma, the flatness, and the location of the cut plane with respect to the target plane. RESULTS: The location of the cut plane averaged 2.8 mm after use of the navigated freehand process compared with 5.2 mm after use of the freehand process (p < 0.0001). Further improvements were obtained with use of the robot-assisted process, which provided an average location of 1.7 mm (p < 0.0001). CONCLUSIONS: Significant improvements in cutting accuracy can be achieved when a navigation system or an industrial robot is integrated into a freehand bone-cutting process when no jigs are available. The procedure for navigated hand-controlled positioning of the oscillating saw appears to be easy to learn and use.

Development and first in vivo trial of EvoLap, an active laparoscope positioner.

To determine essential specifications for an active endoscope holder, a survey of laparoscopic procedures was conducted. A review of the literature highlighted the advantages and limitations of existing scope-holding systems. From this analysis, basic requirements were listed for such devices. Pursuant to this, an ergonomic and user-friendly laparoscope manipulator was designed to assist the surgeon. A first in vivo procedure demonstrated feasibility of the device and its value in clinical practice, enabling surgeons to work more comfortably.

Design and preliminary in vivo validation of a robotic laparoscope holder for minimally invasive surgery.

BACKGROUND: Manual manipulation of the camera is a major source of difficulties encountered by surgeons while performing minimally invasive laparoscopic surgery. METHODS: A survey of laparoscopic procedures and a review of existing active and passive holders were conducted. Based on these analyses, essential requirements were highlighted for such devices. Pursuant to this, a novel active laparoscope manipulator was designed, paying particular attention to ergonomics and ease of use. Several trials on the pelvitrainer and a first in vivo procedure were performed to validate the original design of our device. RESULTS: Phantom experiments demonstrated ease of use of the robot and advantages of the intuitive joystick with omnidirectional displacements and speed control. The compactness of the device and image stability were appreciated during the surgical trial. CONCLUSIONS: A novel robotic laparoscope holder has been developed and produced. An in vivo trial proved its value in clinical practice, enabling surgeons to work more comfortably.

Accuracy in planar cutting of bones: an ISO-based evaluation.

BACKGROUND: Computer- and robot-assisted technologies are capable of improving the accuracy of planar cutting in orthopaedic surgery. This study is a first step toward formulating and validating a new evaluation methodology for planar bone cutting, based on the standards from the International Organization for Standardization. METHODS: Our experimental test bed consisted of a purely geometrical model of the cutting process around a simulated bone. Cuts were performed at three levels of surgical assistance: unassisted, computer-assisted and robot-assisted. We measured three parameters of the standard ISO1101:2004: flatness, parallelism and location of the cut plane. RESULTS: The location was the most relevant parameter for assessing cutting errors. The three levels of assistance were easily distinguished using the location parameter. CONCLUSIONS: Our ISO methodology employs the location to obtain all information about translational and rotational cutting errors. Location may be used on any osseous structure to compare the performance of existing assistance technologies.

Surgical inaccuracy of tumor resection and reconstruction within the pelvis: an experimental study.

BACKGROUND AND PURPOSE: Osseous pelvic tumors can be resected and reconstructed using massive bone allografts. Geometric accuracy of the conventional surgical procedure has not yet been documented. The aim of this experimental study was mainly to assess accuracy of tumoral resection with a 10-mm surgical margin, and also to evaluate the geometry of the host-graft reconstruction. METHODS: An experimental model on plastic pelvises was designed to simulate tumor resection and reconstruction. 4 experienced surgeons were asked to resect 3 different tumors and to reconstruct pelvises. 24 resections and host-graft junctions were available for evaluation. Resection margins were measured. Several methods were created to evaluate geometric properties of the host-graft junction. RESULTS: The probability of a surgeon obtaining a 10-mm surgical margin with a 5-mm tolerance above or below, was 52% (95% CI: 37-67). Maximal gap, gap volume, and mean gap between host and graft was 3.3 (SD 1.9) mm, 2.7 (SD 2.1) cm3 and 3.2 (SD 2.1) mm, respectively. Correlation between these 3 reconstruction measures and the degree of contact at the host-graft junction was poor. INTERPRETATION: 4 experienced surgeons did not manage to consistently respect a fixed surgical margin under ideal working conditions. The complex 3-dimensional architecture of the pelvis would mainly explain this inaccuracy. Solutions to this might be to increase the surgical margin or to use computer- and robotic-assisted technologies in pelvic tumor resection. Furthermore, our attempt to evaluate geometry of the pelvic reconstruction using simple parameters was not satisfactory. We believe that there is a need to define new standards of evaluation.