SciCombinator

Discover the most talked about and latest scientific content & concepts.

Journal: Computer aided surgery : official journal of the International Society for Computer Aided Surgery

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Abstract Introduction: Individual planning of complex maxillofacial corrections may require 3D models which can be manufactured based on DICOM datasets. The gold standard for image acquisition is still high-resolution multi-slice computed tomography (MSCT). However, appropriate datasets for model fabrication can be acquired by modern Cone-Beam CT (CBCT) devices that have been developed specifically for maxillofacial imaging. The clinical utility of individual models fabricated on the basis of CBCT datasets was assessed. Methods: In five patients affected by different deficiencies of the maxillofacial skeleton, preoperative imaging was performed with ILUMA CBCT. Segmentation of hard tissues was performed manually by thresholding. Corresponding STL datasets were created and exported to an industrial service provider (Alphaform, Munich, Germany) specializing in rapid prototyping, and 3D models were fabricated by the selective laser sintering (SLS) technique. For variance analysis, landmark measurements were performed on both virtual and 3D models. Subsequently, maxillofacial surgery was performed according to the model-based planning. Results: All CBCT-based DICOM datasets could be used for individual model fabrication. Detailed reproduction of individual anatomy was achieved and a topographic survey showed no relevant aberrance between the virtual and real models. The CBCT-based 3D models were therefore used for planning and transfer of different maxillofacial procedures. Conclusions: CBCT-based datasets can be used for the fabrication of surgical 3D models if the correct threshold is set. Preoperative workflow and patient comfort is improved in terms of the fast-track concept by using this “in-house” imaging technique.

Concepts: Surgery, Reconstructive surgery, Dentistry, Oral and maxillofacial surgery, Microsurgery, Rapid prototyping, Selective laser sintering, Craniofacial surgery

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Objective: Transfixation of the acromioclavicular (AC) joint is a well-established technique for treating Rockwood IV to VI lesions. However, several complications, including pin breakage or pin migration due to incorrect placement, have been reported in the literature. A cadaveric study was performed to investigate whether the use of 3D navigation might improve the accuracy of AC joint transfixation. Methods: Seventeen transfixations of the AC joint (8 non-navigated, 9 navigated) were performed minimally invasively in cadaveric shoulders. For the navigated procedures, a 3D C-arm (Ziehm Vision FD Vario 3D) and a navigation system (BrainLab VectorVision) were used. Reference markers were attached to the spina scapulae, then a 3D scan was performed and the data transferred to the navigation system. Two Kirschner wires (K-wires) were placed either freehand under fluoroscopic control (in the non-navigated group) or with the use of a navigated drill guide. Radiological analysis was performed with OsiriX software, measuring the distance of the K-wires from the center of the AC joint. For statistical analysis, Student’s t-test was performed, with the significance level being set to p < 0.05. Results: The maximum distance of the K-wires from the center of the AC joint was 5.4 ± 1.1 mm for the freehand non-navigated group and 3.1 ± 1.6 mm for the navigated group (p = 0.0054). The minimum distance of the K-wires from the AC joint center was 3.0 ± 0.6 mm for the freehand group and 1.6 ± 0.6 mm for the navigated group (p = 0.0002). The radiation time was significant lower for the freehand group (41.25 ± 20.4 seconds versus 79.5 ± 13.3 seconds for the navigated group, p = 0.004). There was no statistical difference between the groups with respect to the time required for surgery (11.25 ± 3.6 min for the freehand group and 12.6 ± 4.6 min for the navigated group; p = 0.475). In the freehand group, the AC joint was penetrated by both K-wires in 87.5% of the procedures, compared to 100% in the navigated group. Both K-wires were placed completely intraosseously in the clavicula in 50% of the procedures in the freehand group, compared to 88% in the navigated group. Conclusion: Three-dimensional navigation may improve the accuracy of AC joint transfixation techniques. However, the radiation time is increased when using the navigated procedure, while the overall operation time remains comparable. Nevertheless, a 3D C-arm with a variable isocentric design is recommended for the acquisition of the shoulder scans.

Concepts: Statistics, Statistical significance, Student's t-test, Statistical hypothesis testing, Synovial joint, Clavicle, Scapula, Acromioclavicular joint

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Primary and metastatic liver tumors constitute a significant challenge for contemporary medicine. Several improvements are currently being developed and implemented to advance image navigation systems for percutaneous liver focal lesion ablation in clinical applications at the diagnosis, planning and intervention stages. First, the automatic generation of an anatomically accurate parametric model of the preoperative patient liver was proposed in addition to a method to visually evaluate and make manual corrections. Second, a marker was designed to facilitate rigid registration between the model of the preoperative patient liver and the patient during treatment. A specific approach was implemented and tested for rigid mapping by continuously tracking a set of uniquely identified markers and by accounting for breathing motion, facilitating the determination of the optimal breathing phase for needle insertion into the liver tissue. Third, to overcome the challenge of tracking the absolute position of the planned target point, an intra-operative ultrasound (US) system was integrated based on the Public Software Library for UltraSound and OpenIGTLink protocol, which tracks breathing motion in a 2D time sequence of US images. Additionally, to improve the visibility of liver focal lesions, an approach to determine spatio-temporal correspondence between the US sequence and the 4D computed tomography (CT) examination was developed, implemented and tested. This proposed method of processing anatomical model, rigid registration approach and the implemented US tracking and fusion method were tested in 20 anonymized CT and in 10 clinical cases, respectively. The presented methodology can be applied and used with any older 2D US systems, which are currently commonly used in clinical practice.

Concepts: Cancer, Oncology, Medical imaging, Liver, Physician, Anatomy, Java, Automotive navigation system

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To introduce easy and useful methods using 3D navigation system with skin-fixed dynamic reference frame (DRF) in anterior cervical surgery and to validate its accuracy.

Concepts: Java, Frame of reference

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We developed a novel method of producing accurate range images of the velopharynx using a three-dimensional (3D) endoscope to obtain detailed measurements of velopharyngeal movements. The purpose of the present study was to determine the relationship between the distance from the endoscope to an object, elucidate the measurement accuracy along the temporal axes, and determine the degree of blurring when using a jig to fix the endoscope.

Concepts: Present, Scientific method, Sample size, Measurement, Psychometrics, Reliability, Accuracy and precision, Quantity

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In total hip arthroplasty, it is important to assess postoperative implant orientation. The computed tomography-based (CT-based) three-dimensional (3D) templating method using 3D preoperative planning software is generally recommended. In this method, postoperative implant orientation within a bony coordinate system can be measured by overlaying a 3D computerized model of the implant on a real postoperative CT image of the implant. The bony coordinate system consists of several reference points (RPs) marked on a CT image of the bone surface. Therefore, preoperative and postoperative coordinate systems do not always match. We investigated how the difference between coordinate systems constructed from RPs chosen by manual methods (M1 and M2) and those constructed by the computer matching method influences the results of measurement validation.

Concepts: Geometry, Hip replacement, Orthopedic surgery, Coordinate system, Analytic geometry, Frame of reference

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Resection of a pelvic tumor is challenging because of its complex three-dimensional (3D) anatomy and deep-seated location with nearby vital structures. The resection is technically demanding if a custom implant is used for reconstruction of the bone defect as the surgeon needs to ensure the resection margin is sufficiently wide and the orientation of intended resection planes must match that of the custom implant. We describe a novel workflow of performing a partial acetabular resection in a patient with pelvic chondrosarcoma and reconstruction with a custom pelvic implant in a one-step operation. A multi-planar bone resection was virtually planned. A computer-aided design implant that both matched the bone defect and biomechanically evaluated was prefabricated with 3D printing technology. The 3D-printed patient-specific instruments (PSIs) were used to reproduce the same planned resection. The histology of the tumor specimen showed a clear resection margin. The errors of the achieved resection and implant position were deviating (1-4 mm) from the planned. The patient could walk unaided with a good hip function. No tumor recurrence and implant loosening were noted at 11 months after surgery. The use of this novel CT-based method for surgical planning, the engineering software for implant design and validation, together with 3D printing technology for implant and PSI fabrication makes it possible to generate a personalized, biomechanically evaluated implant for accurate reconstruction after a pelvic tumor resection in a one-step operation. Further study in a larger population is needed to assess the clinical efficacy of the workflow in complex bone tumor surgery.

Concepts: Oncology, Surgery, Physician, Pelvis, Anatomy, Computer-aided design

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Optimal component alignment in total knee arthroplasty has been associated with better functional outcome as well as improved implant longevity. The ability to align components optimally during minimally invasive (MIS) total knee replacement (TKR) has been a cause of concern. Computer navigation is a useful aid in achieving the desired alignment although it is limited by the error during the manual registration of landmarks. Our study aims to compare the registration process error between a standard and a MIS surgical approach. We hypothesized that performing the registration error via an MIS approach would increase the registration process error. Five fresh frozen lower limbs were routinely prepared and draped. The registration process was performed through an MIS approach. This was then extended to the standard approach and the registration was performed again. Two surgeons performed the registration process five times with each approach. Performing the registration process through the MIS approach was not associated with higher error compared to the standard approach in the alignment parameters of interest. This rejects our hypothesis. Image-free navigated MIS TKR does not appear to carry higher risk of component malalignment due to the registration process error. Navigation can be used during MIS TKR to improve alignment without reduced accuracy due to the approach.

Concepts: Better, Surgery, Orthopedic surgery, Knee replacement, Autologous chondrocyte implantation

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Recently, two topical issues in total hip arthroplasty (THA) have been robot-assisted surgery and use of a short stem. The purpose of this study was to evaluate the effects of robotic milling on the accuracy of short femoral stem positioning and on the short-term clinical outcome in THA using a prospective, randomized design.

Concepts: Hip replacement

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The individualized Starfix® miniframe belongs to a new generation of stereotactic systems enabling high-precision electrode placement with considerably better time-efficiency in deep brain stimulation (DBS). We evaluated the usability and reliability of this novel technique in patients with idiopathic Parkinson’s disease (IPD) and compared surgical and clinical results with those obtained in a historical group in which a conventional stereotactic frame was employed.

Concepts: Medicine, Neurology, Parkinson's disease, Deep brain stimulation, Neurosurgery, Stereotactic surgery, Cyberknife, Robin Finck