Computer Aided Surgery最新文献

Whereas the expansive open-door laminoplasty (EL) has been applied widely and the bone gutter on the hinge side is essential for EL, little is known regarding the mandatory width of the bone gutter. This study addressed the essential parameters of bone gutters for EL. Preoperative axial CT images of 20 patients suffering from cervical myelopathy were downloaded and entered into a computer. EL was then simulated using a computer-assisted technique and the thickness of the laminae at the gutter sites was measured. Accordingly, the width of the bone gutter was linked mathematically with the angle of the lifted lamina and the thickness of the lamina at the lamina-lateral mass junction. Furthermore, the average thickness of the laminae at the gutter site was 6.19 mm, and the appropriate bone gutter for EL was 5.13 to 7.15 mm. The width of the bone gutter can thus be planned precisely preoperatively, which may help improve the safety and accuracy of expansive open-door laminoplasty.

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.

A learning curve for returning to conventional total knee arthroplasty (TKA) after using computer-assisted (CAS) TKA has not yet been established. In this study, the postoperative mechanical axes of the first 30 consecutive CAS TKAs performed by a single surgeon were compared to his subsequent 120 conventionally performed TKAs. A "re-learning curve" of 30 conventional TKAs was necessary to attain an average postoperative mechanical axis statistically indistinguishable from the average CAS mechanical axis (1.99°). This is a trend of which surgeons should be aware when converting from CAS TKA to conventional TKA. As a secondary goal, the authors identify the first clinical parameter, preoperative deviation from neutral mechanical axis, that may potentially serve as a guide for the selective use of CAS in TKA.

This study sought to develop a completely automatic method for image segmentation of the thoracic aorta. We used a total of 4682 images from 10 consecutive patients. The proposed method is based on the use of level set and region growing, automatically initialized using the Hough transform. The results obtained were compared to those of manual segmentation as performed by an external expert radiologist. Concordance between the developed method and manual segmentation ranged from 92.79 to 95.77% in the descending regions of the aorta and from 90.68 to 96.54% in the ascending regions, with a mean value of 93.83% being obtained for total segmentation.

Objective: CT-based spinal navigation systems have widespread clinical applications, and spatial registration is a major source of the application error for these systems. However, the feedback that a surgeon may receive from the system, i.e., the surface registration error (SRE), is misleading, and it is still unclear how to achieve an optimal registration. The objective of this study was to investigate how the number and distribution of the points selected on the posterior surface of the vertebra influence the spatial registration accuracy, and how an optimal distribution can be achieved.

Materials and methods: We simulated the spatial registration in the image space to investigate how the number and distribution of points selected on the vertebra influenced the target registration error (TRE). First, we divided the posterior side of the vertebra into five zones and chose 30 points, evenly distributed in different combinations of zones, to simulate the points selected on the vertebra during real navigation. We registered these points to a point cloud representing the surface of the vertebra and calculated the SRE and TRE in the region of interest to determine which combination of zones was optimal. We then chose different numbers of points in the optimal zone combination to study the influence of the number of points on the registration accuracy.

Results: The combination including the lamina, both sides of the spinous process, and the four articular processes resulted in a smaller TRE than those combinations including only the lamina or the lamina with one other zone. Further enlarging the area by adding the transverse processes made no difference. In addition, the TRE decreased with the increase in the number of points, while the SRE remained almost unchanged.

Conclusion: Surgeons should select approximately 30 points distributed evenly across the lamina, both sides of the spinous process, and the four articular processes for surface matching in CT-based spinal navigation.

Objective: To develop an image visualization system based on graphic processing unit (GPU) hardware acceleration for clinical use in hepatocellular carcinoma (HCC) interventional planning.

Methods: We developed a liver tumor planning tool to assist the physician in providing patient-specific analysis and visualization. We employed a spatial distance computation algorithm to determine the spatial location of tumors and their relation to the main hepatic vessels. GPU hardware acceleration was implemented for rapid calculation of the spatial distance from the tumor surface to the surrounding vascular territories.

Results: The algorithm for spatial distance provided an accurate minimum value for the distance from the tumor surface to the surrounding duct system as well as the region of interest (ROI). Analyzing the data (mean CPU time = 43.14 ± 29.34; mean GPU time = 0.41 ± 0.38) using an independent samples t-test, the result showed a remarkable difference (p < 0.001). Thus, GPU hardware acceleration performed the distance arithmetic at higher rates than conventional CPUs.

Conclusions: The visual assistance tool performs as an intuitive and objective module in clinical cases, and is expected to help physicians achieve a more reliable treatment in liver tumor patients. As such, we believe it represents an improvement in image guided preoperative planning.

Purpose: Anatomic double-bundle ACL reconstruction presents a unique technical challenge for surgeons, requiring precise placement of multiple tunnels in a relatively small area. As the necessity of anatomic reconstruction has been stressed throughout the literature, developing a method to consistently improve the accuracy and precision of tunnel placement is essential. We aimed to investigate whether computer-assisted navigation allows novice surgeons to place double-bundle ACL tunnels with a similar degree of accuracy to experienced surgeons operating without computer assistance.

Methods: A novice surgeon group comprising three medical students performed double-bundle ACL reconstruction using passive computer-assisted navigation in 11 cadaver knees. Their individual results were compared to those of three experienced orthopaedic surgeons, each performing the identical procedure without the use of computer-assisted navigation in 9 cadaver knees.

Results and conclusion: There were no significant differences in placement of either the AM or PL tunnels on the tibial plateau between the novice surgeons using computer-assisted navigation and the experienced surgeons. However, on the lateral femoral condyle, the novice surgeons placed the AM and PL tunnels significantly more anterior along Blumensaat's line, on average, compared to the experienced surgeons.

Objective: The objectives of this study were to evaluate the accuracy of computed tomography (CT)-based navigation and to investigate whether the level of surgeon experience affects the accuracy of cup positioning under navigation.

Methods: This study investigated 117 hips in 103 patients who underwent primary total hip arthroplasty (THA) by 7 surgeons using a CT-based navigation system. Pre- and postoperative CT images were matched using a volume registration technique. Postoperative cup angles and positions were then measured using the same pelvic coordinates, and results were compared for experienced and inexperienced surgeons.

Results: The mean absolute error of the cup angle was 1.8 ± 1.6° for inclination and 1.2 ± 1.1° for anteversion. The mean absolute errors of cup position were 1.9 ± 1.5 mm, 1.4 ± 1.2 mm, and 1.9 ± 1.3 mm on the x-, y- and z-axes, respectively. No significant differences in accuracy were identified between experienced and inexperienced surgeons.

Conclusions: The absolute spatial error of cup position was ≤ 2 mm for each axis, and the angle error was ≤ 2° for the angles of inclination and anteversion. This navigation system could therefore help surgeons perform accurate cup placement irrespective of the surgeon's level of experience.

The purpose of this computational study was to examine the hemodynamic parameters of the velocity fields, shear stress, pressure and drag force field in the complex aorta system, based on a case of type B aortic dissection. The extra-anatomic reconstruction of the complete aorta and bipolar exclusion of the aneurysm was investigated by computational fluid dynamics. Three different cases of the same patient were analyzed: the existing preoperative condition and two alternative surgical treatment options, cases A and B, involving different distal aorto-aortic anastomosis sites. The three-dimensional Navier-Stokes equations and the continuity equation were solved with an unsteady stabilized finite element method. The aorta and large tube graft geometries were reconstructed based on CT angiography images to generate a patient-specific 3D finite element mesh. The computed results showed velocity profiles with smaller intensity in the aorta than in the graft tube in the postoperative case. The shear stress distribution showed low zones around 0.5 Pa in the aneurysm part of the aorta for all three cases. Pressure distribution and, particularly, drag force had much higher values in the preoperative aneurysm zones (7.37 N) than postoperatively (2.45 N), which provides strong evidence of the hemodynamic and biomechanical benefits of this type of intervention in this specific patient. After assessing the outcome obtained with each of the two alternatives A and B, for which we found no significant difference, it was decided to use option A to treat the patient. In summary, computational studies could complement surgical preoperative risk assessment and provide significant insight into the benefits of different treatment alternatives.