Navigated laparoscopic microwave ablation of tumour mimics in pig livers: a randomized ex-vivo experimental trial.

BACKGROUND: In order to efficiently perform laparoscopic microwave ablation of liver tumours precise positioning of the ablation probe is mandatory. This study evaluates the precision and ablation accuracy using the innovative laparoscopic stereotactic navigation system CAS-One-SPOT in comparison to 2d ultrasound guided laparoscopic ablation procedures. METHODS: In a pig liver ablation model four surgeons, experienced (n = 2) and inexperienced (n = 2) in laparoscopic ablation procedures, were randomized for 2d ultrasound guided laparoscopic or stereotactic navigated laparoscopic ablation procedures. Each surgeon performed a total of 20 ablations. Total attempts of needle placements, time from tumor localization till beginning of ablation and ablation accuracy were analyzed. RESULTS: The use of the laparoscopic stereotactic navigation system led to a significant reduction in total attempts of needle placement. The experienced group of surgeons reduced the mean number of attempts from 2.75 ± 2.291 in the 2d ultrasound guided ablation group to 1.45 ± 1.191 (p = 0.0302) attempts in the stereotactic navigation group. Comparable results could be observed in the inexperienced group with a reduction of 2.5 ± 1.50 to 1.15 ± 0.489 (p = 0.0005). This was accompanied by a significant time saving from 101.3 ± 112.1 s to 48.75 ± 27.76 s (p = 0.0491) in the experienced and 165.5 ± 98.9 s to 66.75 ± 21.96 s (p < 0.0001) in the inexperienced surgeon group. The accuracy of the ablation process was hereby not impaired as postinterventional sectioning of the ablation zone revealed. CONCLUSION: The use of a stereotactic navigation system for laparoscopic microwave ablation procedures of liver tumors significantly reduces the attempts and time of predicted correct needle placement for novices and experienced surgeons without impairing the accuracy of the ablation procedure.

[Navigated liver surgery : Current state and importance in the future]. / Navigierte Leberchirurgie : Aktueller Stand und Bedeutung in der Zukunft.

The preoperative computer-assisted resection planning is the basis for every navigation. Thanks to modern algorithms, the prerequisites have been created to carry out a virtual resection planning and a risk analysis. Thus, individual segment resections can be precisely planned in any conceivable combination. The transfer of planning information and resection suggestions to the operating theater is still problematic. The so-called stereotactic liver navigation supports the exact intraoperative implementation of the planned resection strategy and provides the surgeon with real-time three-dimensional information on resection margins and critical structures during the resection. This is made possible by a surgical navigation system that measures the position of surgical instruments and then presents them together with the preoperative surgical planning data. Although surgical navigation systems have been indispensable in neurosurgery and spinal surgery for many years, these procedures have not yet become established as standard in liver surgery. This is mainly due to the technical challenge of navigating a moving organ. As the liver is constantly moving and deforming during surgery due to respiration and surgical manipulation, the surgical navigation system must be able to measure these alterations in order to adapt the preoperative navigation data to the current situation. Despite these advances, further developments are required until navigated liver resection enters clinical routine; however, it is already clear that laparoscopic liver surgery and robotic surgery will benefit most from navigation technology.

[Computer-assisted 3D-navigated laparoscopic resection of a vanished colorectal liver metastasis after chemotherapy]. / Die verschwundene Lebermetastase - Neues Einsatzgebiet für die computerassistierte 3D-navigierte laparoskopische Leberesektion?

BACKGROUND: Modern chemotherapy regimen for colorectal cancer results in complete radiologic remission in a substantial number of cases. However, these "vanished liver metastases" (VLM) often contain vital tumor cells, which mandates the resection of such lesions. In these cases, intraoperative identification of VLM can be challenging, in particular in laparoscopic approaches. We describe the first laparoscopic computer-assisted 3D-navigated resection of a VLM. CASE REPORT: A 60-year-old patient with a synchronous liver metastasis (segment IVb) of sigmoid colon cancer (T4 N1 M1) was referred to our center for elective liver resection after laparoscopic sigmoid resection and systemic chemotherapy (FOLFIRI/Panitumumab). The metastasis was not visible anymore on preoperative CT or sonography. Thus, a 3 D reconstruction of the liver was performed. The size of the initial metastasis (before chemotherapy) was transferred into the current CT. A computer-assisted 3D-navigated laparoscopic resection of the metastasis was performed on these fused images. The metastasis was also not clearly visible upon intraoperative ultrasound. Histology of the resected specimen revealed a 0.5 cm metastasis with predominantly vital tumor cells (regression degree 4 of Rubbia-Brandt) and a sufficient resection margin of at least 7 mm. The postoperative course was uneventful. CONCLUSION: Computer-assisted 3D-navigation enabled a safe oncologic resection of a vanished liver metastasis after chemotherapy. This technique was particularly helpful due to the limited haptic feedback of laparoscopic surgery. Further studies are necessary to verify the clinical benefit of computer assisted 3D-navigated liver surgery.

Evaluation of a portable image overlay projector for the visualisation of surgical navigation data: phantom studies.

INTRODUCTION: Presenting visual feedback for image-guided surgery on a monitor requires the surgeon to perform time-consuming comparisons and diversion of sight and attention away from the patient. Deficiencies in previously developed augmented reality systems for image-guided surgery have, however, prevented the general acceptance of any one technique as a viable alternative to monitor displays. This work presents an evaluation of the feasibility and versatility of a novel augmented reality approach for the visualisation of surgical planning and navigation data. The approach, which utilises a portable image overlay device, was evaluated during integration into existing surgical navigation systems and during application within simulated navigated surgery scenarios. METHODS: A range of anatomical models, surgical planning data and guidance information taken from liver surgery, cranio-maxillofacial surgery, orthopaedic surgery and biopsy were displayed on patient-specific phantoms, directly on to the patient's skin and on to cadaver tissue. The feasibility of employing the proposed augmented reality visualisation approach in each of the four tested clinical applications was qualitatively assessed for usability, visibility, workspace, line of sight and obtrusiveness. RESULTS: The visualisation approach was found to assist in spatial understanding and reduced the need for sight diversion throughout the simulated surgical procedures. The approach enabled structures to be identified and targeted quickly and intuitively. All validated augmented reality scenes were easily visible and were implemented with minimal overhead. The device showed sufficient workspace for each of the presented applications, and the approach was minimally intrusiveness to the surgical scene. CONCLUSION: The presented visualisation approach proved to be versatile and applicable to a range of image-guided surgery applications, overcoming many of the deficiencies of previously described AR approaches. The approach presents an initial step towards a widely accepted alternative to monitor displays for the visualisation of surgical navigation data.

A navigation system for open liver surgery: design, workflow and first clinical applications.

BACKGROUND: The surgical treatment of liver tumours relies on precise localization of the lesions and detailed knowledge of the patient-specific vascular and biliary anatomy. Detailed three-dimensional (3D) anatomical information facilitates complete tumour removal while preserving a sufficient amount of functional liver tissue. METHODS: We present an easy to use, clinically applicable navigation system for efficient visualization and tool guidance during liver surgery. Accurate instrument guidance within 3D planning models was achieved with a fast registration procedure, assuming a locally rigid and temporarily static scenario. After deformations occurring during the procedure, efficient means for registration updates are provided. Special focus was given to workflow integration and the minimization of overhead time. The navigation system was validated with nine clinical cases. RESULTS: Navigated surgical interventions were performed with a median time overhead of 16.5 min. The navigation technology had a median accuracy of 6.3 mm, improving anatomical orientation and the detection of structures at risk. CONCLUSIONS: Successful application of the navigation technology to open liver surgery was achieved by minimizing the procedural complexity and optimizing integration within the existing surgical environment. The assumption of locally rigid patient registration was validated, and clinical evaluation shows clear benefits for the surgeon.

Using rapid prototyping molds to create patient specific polymethylmethacrylate implants in cranioplasty.

Cranioplasty is a commonly performed procedure. Outcomes can be improved by the use of patient specific implants, however, high costs limit their accessibility. This paper presents a low cost alternative technique to create patient specific polymethylmethacrylate (PMMA) implants using rapid prototyped mold template. We used available patient's CT-scans, one dataset without craniotomy and one with craniotomy, for computer-assisted design of a 3D mold template, which itself can be brought into the operating room and be used for fast and easy building of a PMMA implant. We applied our solution to three patients with positive outcomes and no complications.

[Follow-up results of osteosynthesis of medial femoral neck fractures with the dynamic hip screw]. / Spätresultate nach Osteosynthese medialer Schenkelhalsfrakturen mit der dynamischen Hüftschraube.

The operative treatment of subcapital femoral neck fractures of stages Garden III and IV in the young patient is still a problem. The current methods of osteosynthesis show a high rate of avascular necrosis of the femoral head. We controlled 24 patients with subcapital femoral neck fracture, who were treated with a dynamic hip screw (DHS). The average age of these patients is 55 years. They were examined after 30-89 months from the operation. All patients were assessed regarding clinical and radiological parameters. All of the six patients with femoral neck fractures of stages Garden I and II had no pain, their clinical results were good. In one of these patients we found a partial avascular necrosis of the femoral head. Four out of the 18 patients with femoral neck fractures of stages Garden III and IV had painful complications, 3 of them needed a reoperation. Fourteen patients of the group with femoral neck fractures of stages Garden III and IV had no pain and wer satisfied with the result. But in this group we found 7 patients with partial avascular necrosis of the femoral head. These results are discussed and compared with data published elsewhere.