PLAFOKON: a new concept for a patient-individual and intervention-specific flexible surgical platform.

BACKGROUND: Research in the field of surgery is mainly driven by aiming for trauma reduction as well as for personalized treatment concepts. Beyond laparoscopy, other proposed approaches for further reduction of the therapeutic trauma have failed to achieve clinical translation, with few notable exceptions. We believe that this is mainly due to a lack of flexibility and high associated costs. We aimed at addressing these issues by developing a novel minimally invasive operating platform and a preoperative design workflow for patient-individual adaptation and cost-effective rapid manufacturing of surgical manipulators. In this article, we report on the first in-vitro cholecystectomy performed with our operating platform. METHODS: The single-port overtube (SPOT) is a snake-like surgical manipulator for minimally invasive interventions. The system layout is highly flexible and can be adapted in design and dimensions for different kinds of surgery, based on patient- and disease-specific parameters. For collecting and analyzing this data, we developed a graphical user interface, which assists clinicians during the preoperative planning phase. Other major components of our operating platform include an instrument management system and a non-sterile user interface. For the trial surgery, we used a validated phantom which was further equipped with a porcine liver including the gallbladder. RESULTS: Following our envisioned preoperative design workflow, a suitable geometry of the surgical manipulator was determined for our trial surgery and rapidly manufactured by means of 3D printing. With this setup, we successfully performed a first in-vitro cholecystectomy, which was completed in 78 min. CONCLUSIONS: By conducting the trial surgery, we demonstrated the effectiveness of our PLAFOKON operating platform. While some aspects - especially regarding usability and ergonomics - can be further optimized, the overall performance of the system is highly promising, with sufficient flexibility and strength for conducting the necessary tissue manipulations.

A new 3D-printed overtube system for endoscopic submucosal dissection: first results of a randomized study in a porcine model.

BACKGROUND AND STUDY AIM: Endoscopic therapy of early malignant alterations can be difficult and cumbersome. Our research study group took advantage of new methods for rapid prototyping (i. e. 3D printing) to design and test an overtube system with two manipulator arms at the tip. Both arms can be steered independently from each other by a dedicated user platform. METHODS: This animal study involved a randomized evaluation of the new overtube device for endoscopic submucosal dissection (ESD) compared with a conventionally performed ESD. In total, 12 ESDs in six pigs were performed. Six ESDs were performed in the stomach and six in the colon. Size (in cm(2)) of resected specimens, the time needed to perform endoscopic resection, and adverse events were assessed. RESULTS: The overtube-assisted ESD was faster and therefore more effective than the conventional ESD technique (0.45 ±â€Š0.24 cm(2)/min vs. 0.22 ±â€Š0.11 cm(2)/min; P = 0.029). Only one adverse effect was recorded in the conventional group.  CONCLUSIONS: The overtube-assisted ESD was feasible in an animal model. ESD can be performed more quickly and potentially more effectively with the newly designed overtube device compared with the conventional ESD technique.

A new instrument for endoscopic submucosal dissection (with videos).

BACKGROUND: Although it is effective for treatment of early neoplasms, endoscopic submucosal dissection (ESD) can be technically demanding and time consuming. Furthermore, use of multiple instruments is often mandatory for performing various steps associated with the procedure. OBJECTIVE: To design, create, and evaluate a new instrument for ESD. DESIGN: Feasibility study by using an acute porcine model. SETTING: Center for preclinical research, university hospital. SUBJECTS: This study involved 6 female pigs. INTERVENTION: Gastric ESDs including circumferential incision and coagulation of bleeding vessels were performed by using a single device. Incision was done with the prototype instrument in a closed position by using cutting current. Submucosal dissection was performed by using an approach with 4 steps: (1) open forceps, (2) grasp submucosal fibers, (3) elevate and retract tip to avoid contact with muscle layer, (4) dissect fibers by using cutting current. Bleeding was terminated with the same instrument by grasping vessels and applying coagulation current. MAIN OUTCOME MEASUREMENTS: Overall feasibility and performance, time needed to achieve complete resection. RESULTS: The new instrument was useful for performing all single steps needed. Mean (± standard deviation [SD]) time needed for the whole procedure was 48.5 ± 9.9 minutes. Mean (± SD) time needed for incision and dissection was 37.8 ± 8.8 minutes. LIMITATIONS: Animal study, limited number. CONCLUSION: The new instrument has potential advantages in comparison with standard instruments used for ESD. Incision, dissection, and coagulation of vessels can be performed with a single instrument, and the technique of lifting submucosal fibers during dissection potentially decreases the risk of perforation. Comparison studies with larger gastric lesions treated with standard ESD techniques are needed.

A patient-specific 3D model of the knee to compare the femoral rollback before and after total knee arthroplasty (TKA).

PURPOSE: Total knee arthroplasty (TKA) is nowadays performed as a standard procedure on a large number of patients suffering from arthrosis. Replacing the knee joint causes changes in the geometry and kinematics of the knee, which are unique to each individual. This research focuses on the method to detect these changes after TKA and on the impact on the knee movement. This approach could reduce complications in patients with post-operative pain and reduce the number of revisions. METHODS: A 3D model of a patient's knee was made by measuring the movement with a medically certified infrared stereo camera. This measurement was combined with the 3D model of the patient's bones, previously segmented from the CT scan. This model is printed in 3D, one part being the mechanism that follows the movement of the patient, and the other part being the 3D copy of the femur and tibia bones. The knee replacement operation is performed directly on the model and the resulting rollback is being measured before and after TKA. RESULTS: We observe a difference in the rollback before and after TKA on the 3D printed model. The variation in size and shape of the femoral implant compared to the natural femur condyles is one of the reasons for the changes in the rollback effect. The rollback is half as large after the prosthesis insertion, which confirms the fact that the femoral prosthesis geometry influences the knee kinematics. CONCLUSIONS: In this study, a first 3D model combining the patient-specific kinematic and the geometry of his bones has been constructed. This model allows the surgeon to validate the plan of the operation, but also to understand the problems and consequences generated by the prosthesis insertion. The rollback is one of the most important motion of the knee joint and this behavior could be quantified, providing comparative analysis of the knee joint before and after the operation. As a future study, the model could be used to analyse more parameters of the TKA such as the impact of different implantation methods.

[A new X-ray-free measurement method for postoperative 3D-position analysis of navigated inserted implants]. / Ein neues Verfahren zur bildfreien Kontrolle der postoperativen Genauigkeit navigiert gesetzter Implantate.

In this article a new X-ray-free measurement method for postoperative 3D-position analysis of dental implants is proposed. The advantage of this new method is the possibility of precise 3D comparison to preoperative planning data without the use of X-rays. Standard methods for postoperative implant analysis are performed manually on the basis of orthopantomography or computer tomography scans. The proposed method uses a navigation system and a specially designed measurement device. Analysis of the measurement data shows a mean position error of 0.2 mm +/-0.1 mm and a mean depth error of 0.4 mm +/- 0.3 mm. Thus, this method is suitable for postoperative analysis of the horizontal implant position and for comparison to preoperative planning

Evaluation of a navigation system for ENT with surgical efficiency criteria.

The aim of this study is the evaluation of a navigation system (NaviBase) for ENT surgery. For this purpose, a new methodology for the evaluation of surgical and ergonomic system properties has been developed. The practicability of the evaluation instruments will be examined using the example of the overall assessment of the system in comparison with the current surgical standard and with other systems using clinical efficiency criteria. The evaluation is based on 102 ENT surgical applications; of these, 89 were functional endoscopic sinus surgeries (FESS). The evaluation of surgical and ergonomic performance factors was performed by seven ENT surgeons. To evaluate surgical system properties, the Level of Quality (LOQ) in 89 cases of the FESS was determined. It compares the existing information of the surgeon with that of the navigation system on a scale of 0 to 100 and with a mean value of 50 and places it in a relationship to the clinical impact. The intraoperative change of the planned surgical strategy (Change of Surgical Strategy) was documented. The ergonomic factors of the system with the categories of Overall Confidence (Trust), awareness of the situation (Situation Awareness), influence on the operating team, requirements for specific skills (Skill Set Requirement), and cognitive load (Workload Shift) were recorded for all surgical procedures as Level of Reliance (LOR). In the evaluation of the surgical system properties, an average evaluation of the quality of the information, as an LOQ of 63.59, resulted. Every second application of the navigation system (47.9%), on average, led to a change in the surgical strategy. An extension/enhancement of the indication of the endonasal approach through the use of the navigation system was shown in 7 of 102 (6.8%) cases. The completion of the resection in the FESS was rated by 74% of group I and 11% of group II as better in comparison with the standard approach. Total confidence shows a positive evaluation of 3.35 in the LOR. To supplement the evaluation of the navigation system, the technical parameters were included. The maximum deviation, Amax, of the displayed position of the reference value amounted to 1.93 mm. The average deviation was at 1.29 mm with an SD above all values, sd, of 0.29. The subsequent economic evaluation resulted in an effective average extra expenditure of time of 1.35 minutes per case. The overall evaluation of the system imparts application-relevant information beyond the technical details and permits comparability between different assistance systems.

Physiological shift of facial skin and its influence on the change in precision of computer-assisted surgery.

Methods of recording landmarks on the facial skin without the use of markers have become increasingly accepted in image-guided surgery. However, position or muscular activity may change the skin's geometry and generate a lack of agreement between the facial contours recorded before and those recorded during the operation. In the present study, we measured this physiological shift of facial skin and evaluated its influence on the accuracy of stereotactic recording. We made laser-scans of the skin of 20 conscious patients while they were sitting and lying, both at rest and when smiling. The laser-scans were referenced to the corresponding computed tomographic dataset, and the accuracy of the recording was calculated. Gravitational or muscular shifts of the skin reduced the mean (S.D.) accuracy of recording to 1.7 (0.3)mm. The loss of accuracy was significantly correlated with the dynamic and gravitational wrinkling of the facial skin and with the body mass index of each patient.

Developments in flexible endoscopic surgery: a review.

Flexible endoscopy is increasingly developing into a therapeutic instead of a purely diagnostic discipline. Improved visualization makes early lesions easily detectable and allows us to decide ad hoc on the required treatment. Deep enteroscopy allows the exploration of even the small bowel - for long a "white spot" for gastrointestinal endoscopy - and to perform direct treatment. Endoscopic submucosal dissection is a considerable step forward in oncologically correct endoscopic treatment of (early) malignant lesions. Though still technically challenging, it is increasingly facilitated by new manipulation techniques and tools that are being steadily optimized. Closure of wall defects and hemostasis could be improved significantly. Even the anatomy beyond the gastrointestinal wall is being explored by the therapeutic use of endoluminal ultrasound. Endosonographic-guided surgery is not only a suitable fallback solution if conventional endoscopic retrograde cholangiopancreatography fails, but even makes necrosectomy procedures, abscess drainage, and neurolysis feasible for the endoscopist. Newly developed endoscopic approaches aim at formerly distinctive surgical domains like gastroesophageal reflux disease, appendicitis, and cholecystitis. Combined endoscopic/laparoscopic interventional techniques could become the harbingers of natural orifice transluminal endoscopic surgery, whereas pure natural orifice transluminal endoscopic surgery is currently still in its beginnings.

Laser-scan-based navigation in cranio-maxillofacial surgery.

BACKGROUND: In computer-assisted surgery, a correlation between a volume data set and the surgical site is required in order to localize the patient's head on the operating table. Registration markers are commonly used for this procedure. However, the marker registration is associated with high logistics, since the markers have to be placed prior to data set acquisition and have to be kept in their position until the patient enters the operating room. This study deals with a new markerless registration method in cranio-maxillofacial surgery that is based on a high-resolution laser-scan of the patient's (relaxed) skin surface. PATIENTS: 20 patients with tumours, bone malformations or foreign bodies, scheduled for computer-assisted surgery, were involved in the study. STUDY DESIGN: The clinically applied accuracy of the laser-scan-based registration was measured through additionally placed registration markers. The inherent precision of the laser-scan registration system was controlled in phantom studies. RESULTS: The clinically applied accuracy of the new laser-scan-based registration technique ranged between 0.2 and 1.8 mm with a mean deviation of 1.1mm and a standard deviation of 0.3 mm. CONCLUSION: The facial skin surface can serve as a sufficiently stable and invariable reference base in order to register patients for computer-assisted cranio-maxillofacial surgery.

Soft tissue scanning for patient registration in image-guided surgery.

Prior to an image-guided surgical intervention, a correlation between the patient's data set and the surgical site is required. This study introduces a markerless registration method for cranio-maxillofacial surgery that is based on a high-resolution laser scan of the patient's skin surface. The Surgical Segment Navigator SSN++ rejects contaminated surface measurements in a way similar to the bluescreen technique. Acquisition of the spatial position and the corresponding surface color of each laser-scanned point facilitates this bluescreen method, removing points with a defined surface color, e.g., blue or green points. The accuracy of the laser-scan-based registration was measured via additional intraoral titanium-markers. These markers served only to check the accuracy of the markerless registration process. In twelve patients, the stability and accuracy of the data set alignment was evaluated for high-(300,000 surface points), medium-, and low-resolution (down to 3,750 surface points) laser scanning. The accuracy of the registration technique was best for high-resolution laser scanning (mean deviation 1.1 mm; maximum deviation 1.8 mm). Low-resolution laser scans revealed inaccuracies up to 6 mm.

Advanced surface-recording techniques for computer-assisted oral and maxillofacial surgery.

Markerless recording of patients based on natural anatomical surfaces makes planning of computer-assisted surgery much easier, as it is not necessary to place and measure markers. Recording of the surgical site with a laser scan takes the place of conventional marker-based recording. We have used auricles as well as the maxilla and mandible as reproducible surfaces. The geometric congruence of the laser scanned surface with the corresponding surface in the computed tomographs data-set and the applied intraoperative accuracy after recording with a laser scanner have been evaluated, and the system was successful in the maxilla (mean precision: 0.8mm, standard deviation: 0.3mm). In the mandible, the tongue and mobile floor of the mouth led to geometric incongruence and inadequate laser scanning. An exact recording using auricles was possible only as long as the auricles had not been temporarily deformed by the head support during CT imaging.

A novel wearable laser device to regulate stride length in Parkinson's disease.

Decreased stride length is a highly relevant characteristic of the gait in patients with Parkinson's disease (PD). In this paper, a novel wearable laser device for stride length regulation is presented. The device is mounted to one foot and can project a red laser light strip to the floor as a visual cue for the other foot. In the experiment twelve healthy volunteers walked a 20 m straight walkway wearing the system on both feet. As an objective result, the stride length regulation reached an accuracy of 96.1 ± 2.5 (94.0 ± 3.5) % for a pre-defined stride length λdef= 55 (65) cm. The subjective evaluation by the participants using a questionnaire revealed that the visual cue projected from the laser device was considered a stable signal that did not shake during walking. 6 of 12 participants felt that this device was not interfering with their gait, 3 of 12 judged this aspect neutrally, and 3 of 12 considered it somehow bothersome.

A technique with manipulator-assisted endoscope guidance for functional endoscopic sinus surgery: proof of concept.

OBJECTIVE: The goal of this study was to examine the theoretical feasibility of a new manipulator system for endoscope guidance in functional endoscopic sinus surgery. STUDY DESIGN: The accuracy of endoscope positioning and time of endoscope movement with an endoscope manipulator system were determined with an artificial sinus model. SETTING: A laboratory trial was performed. The time for 60 repetitions of manual compared to manipulator-assisted endoscope movements directed at 3 different target positions was evaluated. In addition, the alignment of the position vector for each endoscope movement was examined. SUBJECTS AND METHODS: A zero-degree Hopkins II telescope with a camera was used to head for the target positions. First, the endoscope movements were done manually, and afterward the endoscope manipulator system was used for endoscope guidance. The alignment of the position vector of the endoscope was measured with a portable measuring arm. RESULTS: There was no statistical difference between the time for manual and manipulator-assisted endoscope movements for all target positions. The alignment of the position vector of the endoscope was statistically different at 2 target positions: anterior ethmoid left side and ostium of maxillary sinus left side. There was no statistical difference at all other positions. CONCLUSION: The endoscope manipulator system has the potential to be integrated into the operating workflow without extending the time for endoscope guidance. The surgeon will be able to use both hands for the manipulation of the instruments. Less frequent endoscope movements and instrument changes may be expected after technical modification.

A new ultrasound imaging concept for laparoscopy in urology.

Intraoperative imaging performed by a video laparoscope is the gold standard during laparoscopic resections of tumors in urology. In contrast to ultrasound, laparoscopes cannot provide the surgeon with crucial information that could improve surgical outcome. Therefore, we developed a new concept for ultrasound imaging through the back of a supine patient during laparoscopic interventions. In this article we present a mock-up system to answer initial questions that were raised by the concept. The results of the performed experiments show that the concept is feasible.

The influence of various registration procedures upon surgical accuracy during navigated controlled petrous bone surgery.

OBJECTIVE: The goal of this study was to investigate the dependence of surgical accuracy with a navigated controlled (NC) drill on selected registration procedures. STUDY DESIGN: The target registration error of the instrument and the maximum proximity to a typical high-risk structure (facial nerve) were determined within an artificial petrous bone. SETTING: The studies took place in two groups: group 1, navigation bow with six integrated markers and attachment at the upper jaw, and group 2, landmark registration with four titanium microscrews. Measurement of the target registration error took place at three targets (3 titanium screws) with 20 repeated registration procedures via evaluation of the deviation between a target and the indicated position in the navigation data. SUBJECTS AND METHODS: For measurement of the conversion accuracy of the planned cavity, 20 petrous bone models were milled by inexperienced test subjects. The evaluation of 20 cavities was conducted via a microscope by five jurors. RESULTS: Registration accuracy showed a maximum deviation between the actual position achieved and the computed position in the navigation system of 1.73 mm in group 1 and 0.93 mm in group 2. In group 1, the nerve in five of 20 cases was damaged, and a maximum penetration into the nerve of 1.5 mm (0.25 mm SD; milled beyond) was measured. In group 2, the facial nerve was not damaged at all, and a maximum deviation of 0.5 mm (0.63 mm SD; stopped before) was measured. CONCLUSION: The results for registration and conversion accuracy are significantly better for the landmark-based registration than with the registration of the patient model with registration bow on the upper jaw.

Markerless laser registration in image-guided oral and maxillofacial surgery.

PURPOSE: The use of registration markers in computer-assisted surgery is combined with high logistic costs and efforts. Markerless patient registration using laser scan surface registration techniques is a new challenging method. The present study was performed to evaluate the clinical accuracy in finding defined target points within the surgical site after markerless patient registration in image-guided oral and maxillofacial surgery. PATIENTS AND METHODS: Twenty consecutive patients with different cranial diseases were scheduled for computer-assisted surgery. Data set alignment between the surgical site and the computed tomography (CT) data set was performed by markerless laser scan surface registration of the patient's face. Intraoral rigidly attached registration markers were used as target points, which had to be detected by an infrared pointer. The Surgical Segment Navigator SSN++ has been used for all procedures. SSN++ is an investigative product based on the SSN system that had previously been developed by the presenting authors with the support of Carl Zeiss (Oberkochen, Germany). SSN++ is connected to a Polaris infrared camera (Northern Digital, Waterloo, Ontario, Canada) and to a Minolta VI 900 3D digitizer (Tokyo, Japan) for high-resolution laser scanning. RESULTS: Minimal differences in shape between the laser scan surface and the surface generated from the CT data set could be detected. Nevertheless, high-resolution laser scan of the skin surface allows for a precise patient registration (mean deviation 1.1 mm, maximum deviation 1.8 mm). CONCLUSIONS: Radiation load, logistic costs, and efforts arising from the planning of computer-assisted surgery of the head can be reduced because native (markerless) CT data sets can be used for laser scan-based surface registration.