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Surgical Planning Literature Roundup
Posted on 12 May 2025 by Kerim Genc
We continue to see exciting improvements in surgical planning, driven by the growing use of 3D imaging to support patient-specific treatment planning. Our customers are at the forefront of new research that deepens our understanding of complex anatomical structures and the interactions between medical devices and the human body. These findings are increasingly being applied into clinical practice, where 3D techniques are now widely used to plan surgeries, design custom cutting guides, and reduce the risk of long-term implant problems through tailored models based off patient data. Below are some of the most recent highlights from our customers working in these areas.
Improving Femoral Torsion Evaluation in Infants Through Analysis of Variability and Reliability in Two-Dimensional and Three-Dimensional Imaging Measurements of the Femoral Neck Axis
Chambers, T.T., Melendez, V., Anderson, A.E., Huayamave, V., 2025. Improving Femoral Torsion Evaluation in Infants Through Analysis of Variability and Reliability in Two-Dimensional and Three-Dimensional Imaging Measurements of the Femoral Neck Axis. ASME Journal of Medical Diagnostics, 8:3: 03101.
The femoral neck-shaft angle (α) measurement. (a) Projection of the femur onto the coronal plane, (b) projection onto the sagittal plane, and (c) 3D generated model. The femoral neck axis was defined as the line connecting the femoral head center (FHC—red) with the center of the femoral neck (FNC—blue). The femoral shaft axis was defined as the line connecting a center point on the proximal femoral shaft (FS1) with a center point on the distal femoral shaft (FS2). (Image by Chambers et al. / CC BY 4.0 / Resized from original).
Context
“The femoral neck axis serves as a critical parameter in evaluating hip joint health, particularly in the pediatric population. Commonly used metrics for evaluating femoral torsion, such as the femoral neck-shaft and femoral anteversion angles, rely heavily on precise definitions of the position and orientation of the femoral neck axis. Current measurement methods employing radiographs and performing two-dimensional (2D) measurements on computed tomography (CT) scans are susceptible to errors due to their reliance on reader experience and the inherent limitations in 2D measurements. We hypothesized that utilizing volumetric data would mitigate these errors and enable more accurate and reproducible measurements of the femoral neck axis using the femoral anteversion and femoral neck-shaft angles. To test this hypothesis, we analyzed a historical collection of postmortem infant femoral and pelvic bones (28 hips) aged 0 to 6.5 months, with an average estimated age of 4.68 ± 1.80 months. Our findings revealed an average neck-shaft angle of 128.00 ± 4.92 deg and femoral anteversion angle of 35.56 ± 11.68 deg across all femurs, consistent with literature values. These measurements obtained from volumetric image data were found to be repeatable and reliable compared to conventional methods. Our study suggests that the proposed methodology offers a standardized approach for obtaining repeatable and reproducible measurements, thus potentially enhancing diagnostic accuracy and clinical decision-making in assessing hip developmental conditions in pediatric patients.”
Use of Simpleware Software
“Volumetric anatomical models were generated from the CT of the femurs using Synopsys Simpleware ScanIP, a medical image processing software. All generated 3D models were constructed using a semi-automatic segmentation approach called thresholding, which generates a binary segmentation by separating a grayscale image into two regions based on the selected threshold value. A threshold value of −50 Hounsfield Units was selected for all decedents. All measurements in the current study were performed inSynopsys Simpleware ScanIP by two observers following the same protocol.”
“For the femoral neck, a region of interest (ROI) was selected using paint tools in Synopsys Simpleware ScanIP by “painting” all visible regions of the femoral neck. The geometric center was determined from the center of the sphere completely enclosed by the selected ROI. The ROI was selected as two sections of the femoral shaft, one at a proximal (FS1) point and another at a distal point (FS2). The inner best-fit spheres were computed for each section such that the sphere fit inside each ROI, and the line connecting the center of the two spheres was defined as the femoral shaft axis.”
Outcomes and Impact
“Our study aimed to evaluate infant femoral torsion by exploring the variability of the femoral neck axis through the femoral neck-shaft and anteversion angles using three-dimensional measurements. These angles serve as vital metrics for evaluating hip joint health. By employing a 3D approach, we sought to mitigate some of the variability in femoral neck axis measurements induced by patient positioning. Our findings align with existing literature values and demonstrate the accuracy and reliability of our 3D methodology compared to other conventional methods. Importantly, our approach offers the potential to achieve repeatable and reproducible measurements across different observers. Further research and validation studies are warranted to fully establish the clinical utility and applicability of our approach in diverse patient populations and clinical settings. In summary, our study contributes to advancing the understanding and measurement of femoral neck axis parameters, offering a valuable tool for clinicians and researchers in the fields of orthopedics and pediatric hip health.”
Non-invasive Assessment of Cerebral Perfusion Pressure: Applied Towards Preoperative Planning of Aortic Arch Surgery with Selective Antegrade Cerebral Perfusion
Vikström, A., Eklund, A., Johannesdottir, M., Wåhlin, A., Zarrinkoob, L., Malm, J., Appelblad, M., Hellström, J., Holmlund, P., 2025. Non-invasive assessment of cerebral perfusion pressure: Applied towards preoperative planning of aortic arch surgery with selective antegrade cerebral perfusion. Journal of Biomechanics, 179: 112459.
Inlet and outlet boundary configurations as well as resulting pressure distribution for the preoperative and intraoperative simulations for one patient. Preoperatively, inflows Qin and outflows Qout are defined by the MRI-measured flow rates, with the simultaneously measured MAP as reference pressure at the arteries extending from the aortic arch. In the intraoperative simulations, inflow through the right SA is defined by the pressure Pin generated by the heart–lung machine, and outflows are determined by the pressures Pout from Equation (2). For the bSACP configuration, the left CCA inflow is defined by the flow rate QCCA L measured by the M4-device. (Image by Vikström et al. / CC BY 4.0 / Resized from original).
Context
“Selective antegrade cerebral perfusion (SACP) is a protective procedure to ascertain adequate brain perfusion during aortic arch surgeries requiring moderate hypothermic circulatory arrest. SACP entails catheterization of arteries feeding the brain, which can be done bilaterally (bSACP) or unilaterally (uSACP), but there is no consensus on when to use each approach. bSACP may increase the risk of embolization, while uSACP risks hypoperfusion due to insufficient perfusion pressure in the contralateral hemisphere, since a single catheter must perfuse both hemispheres. We developed and tested the feasibility of a new method for predicting cerebral perfusion pressures (CPP) during SACP, which could potentially aid clinicians in preoperatively identifying which SACP approach to use. Feasibility of the method was evaluated in five patients eligible for aortic arch surgery (65 ± 7 years, 3 men). Patients were investigated preoperatively with computed tomography angiography (CTA) and 4D flow magnetic resonance imaging (MRI) to assess patient-specific arterial anatomy and blood flows. From the imaging, computational fluid dynamics (CFD) simulations estimated the patients' vascular resistances. Applying these resistances and intraoperative SACP pressure/flow settings to the model’s boundary conditions allowed for predictions of contralateral CPP during SACP. Predicted pressures were compared to corresponding intraoperative pressure measurements. The method showed promise for predicting contralateral CPP during both uSACP (median error (range): 2.4 (−0.2–18.0) mmHg) and bSACP (0.8 (−3.3–5.4) mmHg). Predictions were most sensitive to collateral artery size. This study showed the feasibility of CPP predictions of SACP, and presents key features needed for accurate modelling.”
Use of Simpleware Software
“Patient-specific vascular trees were segmented from CTA images. Included arteries were those extending from the aortic arch, up to, and including arteries of the CoW and its outgoing cerebral arteries (Fig. 2). Segmentations were made with Synopsys’ Simpleware (ScanIP P-2019.09; Synopsys, Inc., Mountain View, CA, USA). Images were isotropically interpolated to voxels of 0.3 or 0.3125 mm and a bilateral filter was applied, reducing background noise. Initial segmentation consisted of detecting arterial walls with signal intensity thresholding, followed by a gradient-based smoothing filter, Local Surface Correction (search radius: 2 voxels, smoothing radius: 1 voxel). Arterial walls were manually separated from interfering tissues. The final segmentation was smoothed with a volume and topology preserving local smoothing filter, Smart Mask Smoothing (20 iterations). The Local Surface Correction smoothing was deemed too strict in its classification of the arterial wall, resulting in an overly constricted segmentation, and the final segmentation was dilated by one voxel.”
Outcomes and Impact
“Our new method for predicting CPP showed promise as a new technique with potential use in preoperative planning of aortic arch surgery regarding the best choice of SACP technique for individual patients. Basing our model on preoperative imaging and select data from surgery, we tested the feasibility of our method by comparing the predicted against the measured contralateral CPP, which had high agreement for both uSACP and bSACP. Overall, the results motivate continued work and evaluation of the method in a full-scale clinical study.”
Acetabular Home Run Screw Guidance for Transiliac Fixation in Cup Revision Arthroplasty
Wessling, M., Gebert, C., Marei, M., Dudda, M., Streitbuerger, A., Aach, M., Jeys, L., Frieler, S., Koller, D., Hanusrichter, Y., 2025. Acetabular Home Run Screw Guidance for Transiliac Fixation in Cup Revision Arthroplasty. Journal of Clinical Medicine, 14(3), 922.
Exemplary illustration of the measured angles and entry point. (a) The AP angle, which reflects the lateral deviation from the midline in anterior view of the pelvis. (b) The lateral angle of the transiliac fixation in lateral view of the pelvis. (c) The entry point of the screw in the surgeon’s view, in this case 112. (Image by Wessling et al. / CC BY 4.0 / Resized from original).
Context
“The growing incidence of acetabular revisions has highlighted the importance of achieving reliable fixation to the remaining bone. Proximal transiliac fixation (TIF) of pelvic implants is becoming an increasingly common approach for managing extensive bone defects. This study seeks to provide guidance on TIF implantation by analyzing the optimal screw placement in partial pelvic replacements for acetabular defects.
Between 2014 and 2024, a cohort of 96 consecutive patients (65 females and 31 males) who underwent customized partial pelvic replacement (PPR) with transiliac fixation (TIF) were examined. The angle and entry point of the ideal TIF were determined using preoperative three-dimensional planning and compared with potential influencing factors.
All PPRs were successfully implanted, with an average TIF length of 77 mm. The mean anteroposterior angle for TIF was 18° medially and 27° dorsally.
Analysis of the entry point showed concentration around the second radius and between the eleven o’clock and one o’clock positions. The AP angle is notably affected by gender and height. Considering the precision of human judgment, a recommendation for TIF placement would be 20° medial and 30° dorsal deviation, with the entry point around the twelve o’clock position and the second ring from the center of the cup.”
Use of Simpleware Software
“The three-dimensional dataset created during planning using Geomagic Freeform Plus (Version 2019.2.50, 3D-Systems, Moerfelden-Walldorf, Germany) and Simpleware ScanIP Medical (Version R-2020.09, Synopsys, Sunnyvale, CA, USA) was standardized in an anterior, lateral, and isometric (surgeon’s view) view.”
Outcomes and Impact
“The TIF “home run screw” is one of the most important methods for the proximal securing of pelvic reconstruction in revision arthroplasty. As a guideline for placement, the entry point should be placed at approximately twelve o’clock, and on the second radius from the center. The angle of the home run screw should deviate approximately 20° medially and 30° dorsally. It does not appear necessary to adjust the angles for the risk factors examined.”
Understanding the Variability of the Proximal Femoral Canal: A Computational Modeling Study
Ramesh, A., Henckel, J., Hart, A., Di Laura, A., 2024. Understanding the Variability of the Proximal Femoral Canal: A Computational Modeling Study. Journal of Orthopaedic Research, 43(1), 173-182.
(Top row) The segmentations of the femoral canal for five of the cases used in this study, within the external geometry of the proximal femur, reveal noticeable variability. (Bottom row) Coronal, sagittal, and axial views of the mean shape which was computed mathematically from the total 64 canals on which the statistical shape modeling was built. (Image by Ramesh et al. / CC BY 4.0 / Resized from original).
Context
“Statistical shape modeling (SSM) offers the potential to describe the morphological differences in similar shapes using a compact number of variables. Its application in orthopedics is rapidly growing. In this study, an SSM of the intramedullary canal of the proximal femur was built, with the aim to better understanding the complexity of its shape which may, in turn, enhance the preoperative planning of total hip arthroplasty (THA). This includes the prediction of the prosthetic femoral version (PFV) which is known to be highly variable amongst patients who have undergone THA. The model was built on three dimensional (3D) models of 64 femoral canals which were generated from pelvic computed tomography images including the proximal femur in the field of view. Principal component analysis (PCA) was performed on the mean shape derived from the model and each segmented canal. Five prominent modes of variations representing approximately 84% of the total 3D variations in the population of shapes were found to capture variability in size, proximal torsion, intramedullary femoral anteversion, varus/valgus orientation, and distal femoral shaft twist/torsion, respectively. It was established that the intramedullary femoral canal is highly variable in its size, shape, and orientation between different subjects. PCA-driven SSM is beneficial for identifying patterns and extracting valuable features of the femoral canal.”
Use of Simpleware Software
“The DICOM CT images were imported into Simpleware ScanIP Medical (Version 2022.3; Synopsys Inc.). Three dimensional (3D) models of the patient's intramedullary femoral canal were generated from each CT scan, using a semi-automatic segmentation method. This involved a Boolean subtraction of a segmented model of the proximal femoral bone (with a cavity in regions representing the femoral canal), from a “completely filled” proximal femur, resulting in a segmentation of solely the canal. The default Hounsfield Unit (HU) values for a bone range from 230 to 3020 HU. This was used for the threshold-based segmentation for all cases. The same individual performed all segmentations for consistency in the workflow.”
Outcomes and Impact
“The intersubject anatomical variability in proximal femoral canal shapes for a population of 64 patients was assessed in the present study, using PCA-based SSM. This mathematical model provides a valuable tool for analyzing and characterizing geometric shape variations in the femoral canal. The large variations in the size, shape, and orientation of the femoral canals can be holistically captured by a series of PC modes. The 3D models used in this study have shown to be highly variable in terms of these aspects. Since the femoral version was identified as a key changing characteristic, it provides evidence that the variability commonly found in the achieved PFV is largely due to the canal shape into which the stem is fitted.”
Development of a Methodology for In Vitro and In Silico Simulation of Transcatheter Aortic Valve Replacement using 3D-printed Valve Frames
Zhao, X., Eren, O.C., Molyneux, Anthony, Geekie, L., Curzen, N., Bressloff, N.W., 2025. Development of a Methodology for In Vitro and In Silico Simulation of Transcatheter Aortic Valve Replacement using 3D-printed Valve Frames. Computers in Biology and Medicine, 186: 109690.
(a) Auto-segmented leaflets; (b) manually segmented, gap-free leaflets in Synopsys Simpleware software; (c) the smoothed aortic wall model used in 3D printing; (d) one of the smoothed leaflets used in 3D printing; (e) top and (f) perspective views of the final aortic root model. (Image by Zhao et al. / CC BY 4.0 / Resized from original).
Context
“Transcatheter aortic valve implantation (TAVI) is experiencing continued growth as an option for the treatment of aortic stenosis. Both in vitro and in silico methods have proven reliable in assessing the performance of TAVI devices, which can be used in procedure planning and prototyping new concepts. 3D printing of TAVI frames has the potential for revolutionizing frame designs by making it possible to create more complex geometries. However, the mechanical performance of additively manufactured frames, in terms of crimping and deployment into an aortic root, needs to be verified if such frames are to provide a plausible and reliable method for benchtop testing.
Having previously established a suitable set of process parameters for laser powder bed fusion (LPBF) manufacture of TAVI frames based on the SAPIEN S3 design, the deployment of such a frame into a patient-specific, 3D printed aortic root phantom was undertaken and assessed using a high resolution CT scan of the result. In parallel, a full computational model was developed to simulate the same deployment procedure and validated against the in vitro study. Further, an interesting case study was setup using this approach to assess deployment of the LPBF frame into the same aortic root phantom but with two of the leaflets fused together.
The LPBF-manufactured frame had sufficient radial strength to fully open the leaflets within the aortic root phantom and anchor the frame in place for both fused and non-fused leaflet cases. There was good agreement between the in vitro and in silico tests in terms of frame position with an average nodal position error of 0.37 mm and 1.29 mm for non-fused and fused cases respectively. Similarly, the frame diameter difference between the in vitro and in silico deployments were 1.01% for the non-fused and 3.17% for the fused cases.
Manufacture of a SAPIEN S3 type heart valve frame using LPBF has been shown to provide a viable procedure for producing frames for testing and assessment when crimped and deployed into a model of an aortic root. Further, the validated in silico model developed in this study can be used to computationally design and test novel frame concepts to be manufactured by LPBF.”
Use of Simpleware Software
“The aortic root model was segmented from patient specific CT data of an 83-year-old male patient. Simpleware ScanIP (Synopsys Inc., US) was used to segment the aortic root wall, leaflets, and plaques into separate models. However, following segmentation, the leaflets were not continuous, as shown in Fig. 1a. There were also gaps between the leaflets and the aortic root wall and the model needed to be consolidated to allow the 3D printing of the aortic root. The segmented masks of the leaflets were manually closed as shown in Fig. 1b. The improved models were exported to a CAD package, Rhino 7 (McNeel & Associates, US), to generate smoother surfaces on all parts. Fig. 1c–f depicts the final models used for the 3D printing of the aortic root.”
Outcomes and Impact
“In conclusion, this study presented the successful deployment of LPBF-manufactured frames into 3D printed patient-specific aortic root phantoms with fused and non-fused valve leaflets, evidencing their suitability for testing and/or assessing the performance of prosthetic heart valve frames, albeit with the omission of prosthetic leaflets and skirt. These in vitro deployments were computationally reconstructed via high resolution CT scans and compared against in silico deployments of the same scenarios, showing good agreement. Through this validation, these in silico models can be used in future computational development and testing of novel frames manufactured via LPBF.”
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