Preoperative Computed Tomography Data Research Articles

Biomechanics and gene expression in abdominal aortic aneurysm

The aim of the study was to detect inter-relations between the mechanical conditions and material properties of abdominal aortic aneurysm (AAA) wall and the underlying local gene expression of destabilizing inflammatory, proteolytic, and structural factors. During open surgery, 51 tissue samples from 31 AAA patients were harvested. Gene expression of collagen types I and III, inflammatory factors CD45 and MSR1, proteolytic enzymes matrix metalloproteinases 2 and 9, and tissue inhibitor of matrix metalloproteinase 1 was analyzed by reverse transcription-polymerase chain reaction. Material properties of corresponding AAA tissue samples were assessed by cyclic sinusoidal and destructive testing. Local mechanical conditions of stress and strain were determined by advanced nonlinear finite element analysis based on patient-specific three-dimensional AAA models derived from preoperative computed tomography data. In the AAA wall, all parameters analyzed were significantly expressed at the messenger RNA level. With respect to mechanical properties of the aneurysmatic wall, expression of collagen III correlated with the stiffness parameter α (r = -0.348; P = .017), and matrix metalloprotease 2 correlated with the stiffness parameter β and wall strength (r = -0.438 and -0.593; P = .005 and P < .001). Furthermore, significant relationships were observed between local AAA diameter and the expression of CD45, MSR1, and tissue inhibitor of matrix metalloproteinase 1 (r = 0.285, 0.551, 0.328; P < .05). However, we found no inter-relation of local calculated wall stresses and strains with gene expression. Our results show for the first time that gene expressions of destabilizing factors within AAA tissue might be correlated to geometric and mechanical properties of the AAA wall. However, we found no influence of local mechanical conditions on gene expression of these factors. Therefore, these preliminary results are still ambiguous.

A simulator for percutaneous hepatic microwave thermal ablation under ultrasound guidance

The purpose of this study was to provide a simulation therapy environment for microwave thermal ablation (MWA) under the guidance of ultrasound, and to present an inexpensive and portable simulator built on real patient-based pre-operative computed tomography (CT) data. We established an experimental simulation system for teaching MWA and present the results of a preliminary evaluation of the simulator’s realism and utility for training. The system comprises physical elements of an electromagnetic tracking device and an abdominal phantom, and software elements providing three-dimensional (3D) image processing tools, real-time navigation functions and objective evaluation function module. Details of the novel aspects of this system are presented, including a portable electromagnetic tracking device, adoption of real patient-based pre-operative CT data of liver, operation simulation of MWA, and recording and playback of the operation simulation. Patients with liver cancer were selected for evaluation of the clinical application value of the experimental simulation system. A total of 50 consultant interventional radiologists and 20 specialist registrars in radiology rated the simulator’s hardware reality and overall ergonomics. Results show that the simulator system we describe can be used as a training tool for MWA. It enables training with real patient cases prior to surgery, and it can provide a realistic simulation of the actual procedure.

The accuracy of computer-assisted primary mandibular reconstruction with vascularized bone flaps: iliac crest bone flap versus osteomyocutaneous fibula flap

BackgroundThe intention of mandibular reconstruction is to restore the complex anatomy with maximum possible functionality and high accuracy. The aim of this study was to evaluate the accuracy of computer-assisted surgery in primary mandibular reconstruction with an iliac crest bone flap compared with an osteomyocutaneous fibula flap.Materials and methodsPreoperative computed tomography data of the mandible and the iliac crest or fibula donor site were imported into a specific surgical planning software program. Surgical guides were manufactured using a rapid prototyping technique for translating the virtual plan, including information on the transplant dimensions and shape, into real-time surgery. Using postoperative computed tomography scans and an automatic surface-comparison algorithm, the actual postoperative situation was compared with the preoperative virtual simulation.ResultsThe actual flap position showed a mean difference from the virtual plan of 2.43 mm (standard deviation [SD] ±1.26) and a surface deviation of 39% <2 mm and 15% <1 mm for the iliac crest bone flap, and a mean difference of 2.18 mm (SD ±1.93) and a surface deviation of 60% <2 mm and 37% <1 mm for the osteomyocutaneous fibula flap. The position of the neomandible reconstructed with an osteomyocutaneous fibula flap indicated a mean difference from the virtual plan of 1.25 mm (SD ±1.31) and a surface deviation of 82% <2 mm and 57% <1 mm, in contrast to a mean difference of 1.68 mm (SD ±1.25) and a surface deviation of 63% <2 mm and 38% <1 mm for the neomandible after reconstruction with an iliac crest bone flap. For shape analysis, a similarly high accuracy could be calculated for both flaps.ConclusionVirtual surgical planning is an effective method for mandibular reconstruction with vascularized bone flaps, and can help to restore the anatomy of the mandible with high accuracy in position and shape. It seems that primary mandibular reconstruction with the osteomyocutaneous fibula flap is more accurate compared with the vascularized iliac crest bone flap.

Bony Landmarks of the Anterior Cruciate Ligament Tibial Footprint

Background: Although the importance of tibial tunnel position for achieving stability after anterior cruciate ligament (ACL) reconstruction was recently recognized, there are fewer detailed reports of the anatomy of the tibial topographic footprint compared with the femoral side. Hypothesis: The ACL tibial footprint has a relationship to bony prominences and surrounding bony landmarks. Study Design: Descriptive laboratory study. Methods: This study consisted of 2 anatomic procedures for the identification of bony prominences that correspond to the ACL tibial footprint and 3 surrounding landmarks: the anterior ridge, lateral groove, and intertubercular fossa. In the first procedure, after computed tomography (CT) was performed on 12 paired, embalmed cadaveric knees, 12 knees were visually observed, while their contralateral knees were histologically observed. Comparisons were made between macroscopic and microscopic findings and 3-dimensional (3D) CT images of these bony landmarks. In the second procedure, the shape of the bony prominence and incidence of their bony landmarks were evaluated from the preoperative CT data of 60 knee joints. Results: In the first procedure, we were able to confirm a bony prominence and all 3 surrounding landmarks by CT in all cases. Visual evaluation confirmed a small bony eminence at the anterior boundary of the ACL. The lateral groove was not confirmed macroscopically. The ACL was not attached to the lateral intercondylar tubercle, ACL tibial ridge, and intertubercular space at the posterior boundary. Histological evaluation confirmed that the anterior ridge and lateral groove were positioned at the anterior and lateral boundaries, respectively. There was no ligament tissue on the intercondylar space corresponding to the intercondylar fossa. In the second investigation, the bony prominence showed 2 morphological patterns: an oval type (58.3%) and a triangular type (41.6%). The 3 bony landmarks, including the anterior ridge, lateral groove, and intertubercular fossa, existed in 96.6%, 100.0%, and 96.6% of the cases, respectively. Conclusion: There is a bony prominence corresponding to the ACL footprint and bony landmarks on the anterior, posterior, and lateral boundaries. Clinical Relevance: The study results may help create an accurate and reproducible tunnel, which is essential for successful ACL reconstruction surgery.

Accuracy of implant placement in the posterior maxilla as related to 2 types of surgical guides: A pilot study in the human cadaver

The position of implants may have an effect on obtaining osseointegration without complications and on the outcome of the prostheses. The purpose of this study was to compare the accuracy of implant placement with computer-guided surgery and freehand surgery in the atrophic area of the posterior maxilla. Six human cadavers (Kennedy-Applegate class I) were included in the study. The specimens were randomly classified into 2 categories by using a computer: computer-guided surgery (n=3) and freehand surgery (n=3). Thirty-nine implants were planned with the software. Two types of surgeries were performed. The preoperative computed tomography data were matched with the postoperative computed tomography data by using voxel-based registration software. The position of the planned implants was compared to the actual position of the implants. A multivariate analysis was used for each variable (bone density, length of implant, implant angulation, and surgical technique) to evaluate the effect of these variables on the implant accuracy (α=.05). The statistical tests (Kolmogorov-Smirnov bootstrap) found that guided surgery offered significantly better accuracy for the platform (P=.002), apex (P=.001), and angle (P<.001). However, the accuracy of the 2 methods was similar for the depth parameter (P=.186). The bone density did not influence the implant placement accuracy. Computer-guided surgery was more accurate than a freehand approach for placing implants into bilateral edentulous zones in the posterior maxilla.

Limits of conventional temporal bone computed tomography in the management of cholesteatoma otitis media: Report of 96 cases

Cholesteatoma is a dangerous chronic otitis media, with keratine accumulation causing bone erosion and invasive damages. Computed tomography (CT) is commonly indicated to evaluate the extension and the complications of cholesteatoma. In 96 patients with cholesteatoma otitis, preoperative CT data were compared with surgical findings using the sensitivity, specificity, and the predictive value of a CT-scan for anatomical structures. A CT scan offers an adequate anatomical conformation of the tympanomastoid cavities. The lysis of the tegmen (Se = 61%, Sp = 79%) and the erosion of the scutum (Se = 100%, Sp = 51%) are well visualized on coronal sections. CT is very sensitive to objective ossicular chain lysis (Se = 90%) but with a low specificity (Sp = 71%). The performance of CT in the facial canal erosion (Se = 45%, Sp = 78%) and in the labyrinthine fistulae (Se = 46%, Sp = 98%) was insufficient with the conventional scanning machine used. A CT-scan should be a routine exam before cholesteatoma surgery, but with improved resolution, and therefore sensitivity, to characterize all middle ear structures and complications of the disease.

Accuracy of Computational Soft Tissue Predictions in Orthognathic Surgery From Three-Dimensional Photographs 6 Months After Completion of Surgery: A Preliminary Study of 13 Patients

This study aimed at a preliminary evaluation of the accuracy of computed three-dimensional (3D) predictions in orthognathic surgery by comparing predicted and real postoperative results. Pre- and postoperative 3D photographs and time-matching computed tomography (CT) and cone-beam CT scans of the face of 13 patients with dentofacial deformities were analyzed. Three-dimensional photographs were fused with preoperative CT data using dedicated software (3dMDvultus, version 2.2.0.8). Postoperative CT data were superposed on the preoperative skull. With an activated rendering function, the osteotomies were simulated in the preoperative CT data and the bony segments moved to their real postoperative position, resulting in a textured soft tissue prediction. This computed skin surface was compared with the real postoperative result by dividing the face into a surgically treated lower half and an untreated upper half. A statistical quantitative analysis of the surfaces was performed. The mean differences between surfaces were +0.27mm for the untreated upper half and -0.64mm for the surgically treated lower half (p<0.001). Averaged distributions of absolute errors showed more discrepancies between predicted and real postoperative results in the lower half of the face. Errors exceeding 3mm were encountered in 4% of the upper halves versus 29.8% of the lower halves (p<0.001). The accuracy of a specific software platform for predicting 3D soft tissue changes after surgery was insufficient. This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

Mandibular reconstruction using custom-made titanium mesh tray and particulate cancellous bone and marrow harvested from bilateral posterior ilia

The objective of this study is to evaluate usefulness of mandibular reconstructions using a custom-made titanium mesh (Ti-mesh) tray and particulate cancellous bone and marrow (PCBM). A consecutive nine patients who underwent mandibular reconstruction were enrolled in this study. They were five men and four women (mean age: 53.9 years). Virtual reality simulation was performed using computer software based on the pre-operative computed tomography data. A 3-dimensional (3-D) skull model was constructed using a 3-D printer. A tray was custom-made from a Ti-mesh sheet bent to adapt to the model. After PCBM harvesting from bilateral posterior ilia, the tray was fixed to the host bone. New bone formation and configuration of the reconstructed mandible were assessed radiologically. Complications were recorded in each patient during the follow-up period. Patients, satisfaction with post-operative facial contour was evaluated using a visual analogue scale (VAS score, range = 0–100). In six of nine patients, excellent new bone formation was recognised and expected results were radiologically achieved. Complications occurred in four patients. These complications included Ti-mesh fracture, Ti-mesh exposure in the oral cavity, and delayed infection. Mean VAS score on patient satisfaction was 77.6. Although the data are preliminary, the results suggest that this method is clinically useful.

Real-time in situ three-dimensional integral videography and surgical navigation using augmented reality: a pilot study

To evaluate the feasibility and accuracy of a three-dimensional augmented reality system incorporating integral videography for imaging oral and maxillofacial regions, based on preoperative computed tomography data. Three-dimensional surface models of the jawbones, based on the computed tomography data, were used to create the integral videography images of a subject's maxillofacial area. The three-dimensional augmented reality system (integral videography display, computed tomography, a position tracker and a computer) was used to generate a three-dimensional overlay that was projected on the surgical site via a half-silvered mirror. Thereafter, a feasibility study was performed on a volunteer. The accuracy of this system was verified on a solid model while simulating bone resection. Positional registration was attained by identifying and tracking the patient/surgical instrument's position. Thus, integral videography images of jawbones, teeth and the surgical tool were superimposed in the correct position. Stereoscopic images viewed from various angles were accurately displayed. Change in the viewing angle did not negatively affect the surgeon's ability to simultaneously observe the three-dimensional images and the patient, without special glasses. The difference in three-dimensional position of each measuring point on the solid model and augmented reality navigation was almost negligible (<1 mm); this indicates that the system was highly accurate. This augmented reality system was highly accurate and effective for surgical navigation and for overlaying a three-dimensional computed tomography image on a patient's surgical area, enabling the surgeon to understand the positional relationship between the preoperative image and the actual surgical site, with the naked eye.

Short rigid scope and stereo‐scope designed specifically for open abdominal navigation surgery: clinical application for hepatobiliary and pancreatic surgery

We have reported the utility of an image display system using augmented reality (AR) technology in hepatobiliary surgery under laparotomy. Among several procedures, we herein report a system using a novel short rigid scope and stereo-scope, both designed specifically for open abdominal navigation surgery, and their clinical application for hepatobiliary and pancreatic surgery. The 3D reconstructed images were obtained from preoperative computed tomography data. In our specialized operating room, after paired-point matching registration, the reconstructed images are overlaid onto the operative field images captured by the short rigid scopes. The scopes, which are compact and sterilizable, can be used in the operative field. The stereo-scope provides depth information. Eight patients underwent operations using this system, including hepatectomy in two, distal pancreatectomy in three, and pancreaticoduodenectomy in three patients. The stereo-scope was used in five patients. All eight operations were performed safely using the novel short rigid scopes, and stereo images were acquired in all five patients for whom the stereo-scope was used. The scopes were user friendly, and the intraoperative time requirement for our system was reduced compared with the conventional method. The novel short rigid scope and stereo-scope seem to be suitable for clinical use in open abdominal navigation surgery. In hepatobiliary and pancreatic surgery, our novel system may improve the safety, accuracy and efficiency of operations.

Examining the use of imaging during T-AVI: focus on online 3D DynaCT

Transcatheter aortic valve implantation (T-AVI) is a closed heart procedure with lack of direct vision to the native valve. This makes precise imaging important before and during T-AVI. Aortic annulus diameter, distance between coronary ostia and aortic annulus, as well as conditions of the femoral and coronary arteries has to be preoperatively evaluated by echocardiography, computed tomography and angiography. During T-AVI, echocardiography and fluoroscopy/angiography play important roles for precise implantation of the prosthesis, for functional assessment after implantation and for detecting/excluding any potential complications. Syngo DynaCT (Siemens AG, Forchheim, Germany) is an intraprocedural imaging tool for T-AVI allowing for 3D visualization of the aortic root and for delineating some important landmarks, such as the coronary ostia and the nadirs. DynaCT eases the T-AVI procedure, and together with further integration of echo and preoperative computed tomography data by means of fusion imaging, ...

Spinal Navigation

A retrospective clinical and radiological study. To compare the safety and accuracy of pedicle screw insertion using two different computed tomography (CT) data set acquisitions (preoperative and intraoperative) for computer-guidance systems in a series of 100 consecutive patients. Misplacement and pedicle cortical violation occurs in over 20% of screw placements and can result in potential neurovascular complications. Many technological innovations have been described to help reduce this range of error, such as image-guided surgery using fluoroscopy or CT-based image guidance. However, these techniques are not without their drawbacks. The next technological evolution is the use of an intraoperative CT scan, which would allow us to solve some of the critical phases of spinal navigation, such as position-dependent changes, thus granting a higher accuracy of the navigation system. The authors have compared and discussed the results of a preoperative and intraoperative CT data set acquisition mode for spinal navigation. One hundred consecutive patients with a diagnosis of lumbar degenerative spondylolisthesis who underwent a surgical approach of lumbar pedicle screw fixation using a CT-based computer-guidance system were evaluated. The population was divided into two groups: in group I, a preoperative CT scan was used for the navigation system; whereas in group II, an intraoperative CT scan acquired during surgery was used. Epidemiological and surgical data of the patients in the two groups were then analyzed and compared. The Pearson χ test was used for comparisons between groups (significance level 0.05). The evaluation and classification of the screw positioning was performed on the basis of a control CT scan according to the classification proposed by Laine. Out of 504 screws, 471 were correctly inserted into the pedicles (93.5%): the accuracy of group I was of 91.8%, whereas in group II it was 95.2% (no statistical significance). The overall rate of perforation was 6.5% (33 screws): 21 in group I and 12 in group II. Twenty-eight screws had a perforation of the pedicle less than 2 mm (Grade I), three comprised from 2 to 4 (Grade II), and only two more than 4 mm and less than 6 mm (Grade III). Out of 33 misplaced screws only one was replaced (graded as III in group II). Surgical time was shorter for group II, with a statistically significant difference. This result is mainly because of the automatic recognition and merging of the intraoperative images with the surgical anatomy that avoided the phase of registration with a paired-point technique. The results of this study suggest that the CT-based computer-assisted surgical navigation systems are precise, granting an elevated accuracy in pedicle screw positioning.

Interactive surgery simulation for the nose augmentation using CT data

Surgery to reshape the nose with an implant has been a regular procedure for enhancing a patient’s appearance and self-confidence. The purpose of this study was to establish a computed tomography (CT) based three-dimensional assistant plastic surgery systems, which can provide the patients with realistic prediction of their own postoperative appearance in computer and specifically produce a nose implant for an individual patient. Preoperative CT data and 3D reconstruction techniques were employed to generate 3D model of the patient’s skull. 3D collision detection and finite elements model deformation were then applied to simulate nose augmentation surgery and predict postoperative appearance. According to the patient’s expectation, digital models of the nose implants were constantly modified. When the patient is satisfied with the simulated results, custom made silicone implants were produced by a computer controlled device. Accurately regeneration of 3D images and realistic operative simulations could be achieved with this system. The implants produced exactly conformed to the results of simulation. No curving and reshaping were needed during operating. The clinical results extremely matched with the simulations. The system enhances surgeon patient communication and facilitates preoperative planning. It is especially desirable for implant surgery with less guesswork of size, contour, and orientation of the implant. The best chance of optimal results could be achieved.

Imaging-Assisted Endoscopic Surgery: Cleveland Clinic Experience

Our initial experience in using computer-aided image assistance in minimally invasive urology was reported. The system consisted of a computer and a localizer allowing spatial localization of the position of the various surgical instruments, using a magnetic sensor as well as an optical sensor. Available imaging modality included real-time ultrasound as well as preoperative computed tomography (CT) or magnetic resonance imaging (MRI). We first clinically applied the fusion system of real-time US with preoperative CT or MRI for percutanous radiofrequency/cryoablation for renal tumor. We also clinically applied an augmented reality visualization system that helps the laparoscopic surgeon to understand three-dimensional (3D) anatomies beyond the surgical view. Augmented reality was feasible and useful to facilitate the surgeon's direct interpretation of 3D anatomies of cancer or vital anatomies beyond the surgical view, using preoperative CT data during laparoscopic partial nephrectomy and intraoperative transrectal US during laparoscopic radical prostatectomy. To our knowledge, we report the first clinical use of augmented reality technology in urology. Imaging assistance beyond the endoscopic surgical view could increase the precision for and confidence of the surgeon, providing preoperative oncological data and understanding of the surrounding vital anatomies. Novel computer-based emerging techniques with 3D imaging technologies potentially indicate the ideal dissection plane to achieve better oncological outcomes as well as to maximize functional preservation.

Computer‐assisted tibia preparation for total ankle arthroplasty: a cadaveric study

Most surgeons performing total ankle arthroplasty (TAA) suggest that accurate tibial preparation perpendicular to the tibial shaft axis improves outcomes. Recent studies demonstrate that computerized surgical navigation significantly improves the accuracy of tibial preparation in total knee arthroplasty (TKA). We performed the tibial preparation for TAA in seven matched pairs of cadaver lower extremities. One set of matched pairs was prepared using the conventional external tibial alignment guide/cutting block from the Scandanavian Total Ankle Replacement system (STAR, Waldemar Link GmbH & Co., Hamburg, Germany) under fluoroscopic guidance. The second set of matched pairs was prepared using the VectorVision((R)) navigation system (BrainLAB, Munich, Germany), with currently available computed tomography (CT)-based TKA software. Pre-operative CT data were used to assess the tibial mechanical axis. In both groups, accuracy of the tibial plafond preparation relative to the tibial shaft axis in both the coronal and sagittal planes was determined by fluoroscopic, radiographic and CT analysis. Mean values of the tibial cut for the set of matched-pair tibiae prepared by the conventional surgical method ranged across the three imaging assessment techniques in the ranges 89.3-89.6 degrees (coronal plane, anteroposterior) and 90.3-90.4 degrees (sagittal plane, lateral). For the computer-navigated set, the values were 89.7-89.9 degrees (coronal) and 89.1-89.4 degrees (sagittal). Comparison between the conventional and computer-navigated tibial measurements were not different at the 95% confidence interval (CI) for CT, fluoroscopy or radiographic assessments. Our results demonstrate that accuracy of TAA tibial preparation using computer-navigation equals that of the conventional technique performed by a foot and ankle surgeon experienced in TAA. We anticipate that this investigation will encourage the development of computer-navigation applications specific to TAA, with the potential of improving accuracy over conventional methods.

Early experience with computer-assisted shoulder hemiarthroplasty for fractures of the proximal humerus: Development of a novel technique and an in vitro comparison with traditional methods

A computer-assisted technique was developed for treatment of 4-part proximal humeral fractures via a hemiarthroplasty and tuberosity fixation. This was compared with a standard traditional method in 7 pairs of cadaveric shoulders. The computer-assisted technique used preoperative computed tomography data and computer simulations of anatomic characteristics of the contralateral humerus. This allowed accurate anatomic reconstruction by use of an electromagnetic tracking system and real-time intraoperative feedback. Various anatomic measurements were used to quantify the accuracy of the reconstruction. The differences between the intact and reconstructed values were improved with the computer-assisted technique for 5 of 7 characteristics. However, this was statistically significant only for humeral head offset (P < .05). With further investigation and refinement, this technique should allow for a more anatomic reconstruction of the proximal humerus, potentially resulting in improved patient outcomes. The technique may also prove to be a valuable resource for the laboratory training of inexperienced surgical trainees.

Computer-Assisted Surgical Treatment of Orbitozygomatic Fractures

Orbitozygomatic fractures pertain to the most common injuries in craniofacial trauma patients. Accurate fracture reduction is of high importance for a successful outcome. This pilot study was performed to assess the potential benefit of surgical navigation to aid in orbitozygomatic fracture reduction. A non-comparative series of five consecutive patients with severely displaced orbitozygomatic fractures was treated using the guidance of computed tomography (CT)-based surgical navigation. Using a previously developed software platform, the fracture was reduced virtually by a three-dimensional shifting of the orbitozygomatic complex within the patient's preoperative multimodal CT data set. This treatment plan was transferred to a navigation system. Fracture reduction was performed according to the treatment plan using surgical navigation. Intraoperative control of fracture reduction by comparing the real with the virtual bone position using surgical navigation showed up as a helpful tool. Accurate treatment planning and immediate evaluation of craniofacial surgery outcome are the benefits of the new approach demonstrated. A major drawback of the presented approach is a high consumption of human and financial resources. A larger clinical series with long-term follow-up will be needed to determine reproducibility and cost-effectiveness. In addition to bone repositioning, a future application may include simulation of craniofacial osteotomies.

Image-guided navigation for treatment of complex midfacial fractures

Orbitozygomatic fractures pertain to the most common injuries in craniofacial trauma surgery. Accurate fracture reduction is of high importance for a successful outcome. This pilot study was performed to assess the potential benefit of surgical navigation to aid in orbitozygomatic fracture reduction. Methods A non-comparative series of 10 consecutive patients with moderately displaced orbitozygomatic fractures was treated using the guidance of computed tomography (CT) based surgical navigation. A newly developed software platform was used for the creation of a preoperative treatment plan. On a computer workstation, the fracture was reduced virtually by three-dimensional shifting of the zygomaticomaxillary complex within the preoperative multimodal CT data set. This treatment plan was transferred to a navigation system. Fracture reduction was performed using surgical navigation according to the treatment plan. Results Virtual segmentation and positioning of the zygomaticomaxillary complex was easily performed. Intraoperative control of fracture reduction by comparing the real with the virtual preplanned bone position using surgical navigation showed up as a helpful tool. Conclusion Accurate treatment planning and immediate evaluation of craniofacial surgery outcome are the benefits of the new approach demonstrated. In addition to bone repositioning, a future application may include simulation of craniomaxillofacial osteotomiesness.

Clinical accuracy evaluation of femoral canal preparation using the ROBODOC system

AbstractThe purpose of this study was to evaluate the clinical accuracy of femoral canal preparation using postoperative reconstructed computed tomography (CT) images of 75 consecutive total hip arthroplasties performed with a two-pinbased ROBODOC system. Intraoperatively, the robot milled the femoral canal according to the preoperative planning performed with preoperative CT data and the ROBODOC workstation. Postoperative CT data was obtained 1 month postoperatively. Anteroposterior and lateral synthetic radiographs and axial images were reconstructed from CT data on the workstation. The mean difference between the preoperative planning and the postoperative CT images was less than 5% in canal fill, less than 1 mm in gap, and less than 1° in the mediolateral and anteroposterior alignment. Clinical femoral canal preparation using the ROBODOC system results in a high degree of accuracy.

Extracranial Application of the Frameless Stereotactic Operating Microscope

THE FRAMELESS STEREOTACTIC operating microscope has expanded the potential application of modern stereotaxis to procedures outside of the intracranial compartment by removing the constraint of a rigid frame. We studied seven patients all of whom had a history, examination, and imaging studies consistent with lumbosacral spinal pathology for which they subsequently underwent surgery with the operating microscope. The ability of the frameless stereotactic system with preoperative computed tomography data to locate the level of the lesion as well as define the boundary of the spinal pathology intraoperatively was assessed. In parallel with this application of the frameless system, we analyzed the relationship between the lumbar intervertebral disc spaces (L3-L4, L4-L5, L5-S1) and skin surface fiducials using lateral radiographs. In seven patients with extracranial cases (six herniated lumbar discs and one lumbar spondylolysis with Grade I spondylolisthesis) who underwent operations by this system, the accuracy of the digitization component of the system with respect to localization of an independent test fiducial was 3.28 mm (SD, 0.61). The accuracy of the entire system in locating the independent fiducial within the viewing plane was 6.05 mm (SD, 4.04). Disc space localization had a far greater error of 28.81 mm (SD, 7.49). There was no consistent pattern to the magnitude or direction of the displacement of the lumbar intervertebral discs with respect to the fiducial markers in the sagittal plane. Although accuracy at the level of the fiducial plane was similar to that of intracranial applications, paraspinal tissue and vertebral column deformations rendered poorer accuracy with deeper structures.