The authors have no acknowledgments.

The study was approved by the ethics committee of our institution (reference 2020-277-1). Patients signed the CT scan informed consent.
1. Downloading the CT images
<ol>
	<li>Gain access to a picture archiving and communication system (PACS). 
	NOTE: Each software package has a different way of accessing a PACS, but all of them have a way to download a study in the DICOM format. If there is a question regarding how this is done, ask the system administrator of the cente...

<ol>
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A., Ansari, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Femoral+derotational+osteotomy+using+a+modified+intramedullary+nail+technique.">Femoral derotational osteotomy using a modified intramedullary nail technique.</a> Techniques in Orthopaedics. 33 (4), 267-270 (2018).</li><li>Stambough, J. B., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Knee+pain+and+activity+outcomes+after+femoral+derotation+osteotomy+for+excessive+femoral+anteversion.">Knee pain and activity outcomes after femoral derotation osteotomy for excessive femoral anteversion.</a> Journal of Pediatric Orthopedics. 38 (10), 503-509 (2018).</li><li>Murphy, S. B., Simon, S. R., Kijewski, P. K., Wilkinson, R. H., Griscom, N. T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Femoral+anteversion.">Femoral anteversion.</a> Journal of Bone and Joint Surgery. 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C., Kumta, S., Geel, N. V., Demol, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=One-step+reconstruction+with+a+3D-printed,+biomechanically+evaluated+custom+implant+after+complex+pelvic+tumor+resection.">One-step reconstruction with a 3D-printed, biomechanically evaluated custom implant after complex pelvic tumor resection.</a> Computed Aided Surgery. 20 (1), 14-23 (2015).</li><li>Fang, C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Surgical+applications+of+three-dimensional+printing+in+the+pelvis+and+acetabulum:+From+models+and+tools+to+implants.">Surgical applications of three-dimensional printing in the pelvis and acetabulum: From models and tools to implants.</a> Der Unfallchirurg. 122 (4), 278-285 (2019).</li><li>Upex, P., Jouffroy, P., Riouallon, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Application+of+3D+printing+for+treating+fractures+of+both+columns+of+the+acetabulum:+Benefit+of+pre-contouring+plates+on+the+mirrored+healthy+pelvis.">Application of 3D printing for treating fractures of both columns of the acetabulum: Benefit of pre-contouring plates on the mirrored healthy pelvis.</a> Orthopaedics &amp; Traumatology, Surgery &amp; Research. 103 (3), 331-334 (2017).</li><li>Xie, L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Three-dimensional+printing+assisted+ORIF+versus+conventional+ORIF+for+tibial+plateau+fractures:+A+systematic+review+and+meta-analysis.">Three-dimensional printing assisted ORIF versus conventional ORIF for tibial plateau fractures: A systematic review and meta-analysis.</a> International Journal of Surgery. 57, 35-44 (2018).</li><li>Scorcelletti, M., Reeves, N. D., Rittweger, J., Ireland, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Femoral+anteversion:+Significance+and+measurement.">Femoral anteversion: Significance and measurement.</a> Journal of Anatomy. 237 (5), 811-826 (2020).</li><li>Seitlinger, G., Moroder, P., Scheurecker, G., Hofmann, S., Grelsamer, R. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+contribution+of+different+femur+segments+to+overall+femoral+torsion.">The contribution of different femur segments to overall femoral torsion.</a> The American Journal of Sports Medicine. 44 (7), 1796-1800 (2016).</li><li>Kaiser, P., Attal, R., Kammerer, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Significant+differences+in+femoral+torsion+values+depending+on+the+CT+measurement+technique.">Significant differences in femoral torsion values depending on the CT measurement technique.</a> Archives of Orthopaedic and Trauma Surgery. 136 (9), 1259-1264 (2016).</li><li>Schmaranzer, F., Lerch, T. D., Siebenrock, K. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Differences+in+femoral+torsion+among+various+measurement+methods+increase+in+hips+with+excessive+femoral+torsion.">Differences in femoral torsion among various measurement methods increase in hips with excessive femoral torsion.</a> Clinical Orthopaedics and Related Research. 477 (5), 1073-1083 (2019).</li><li>Sanchis-Alfonso, V., Domenech-Fernandez, J., Ferras-Tarrago, J., Rosello-A&#241;on, A., Teitge, R. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+incidence+of+complications+after+derotational+femoral+and/or+tibial+osteotomies+in+patellofemoral+disorders+in+adolescents+and+active+young+patients:+A+systematic+review+with+meta-analysis.">The incidence of complications after derotational femoral and/or tibial osteotomies in patellofemoral disorders in adolescents and active young patients: A systematic review with meta-analysis.</a> Knee Surgery, Sports Traumatology, Arthroscopy. 30 (10), 3515-3525 (2022).</li></ol>

The most important finding of this study is that 3D technology allows the planning of proximal external derotational femoral osteotomy. This technology can simulate the surgery that is to be performed on a specific patient on the computer. It is a simple, reproducible, and free technique that uses software adaptable to most computers. The only technical problem may be that the 3D builder software works only with the Windows operating system. The major limitation is the learning curve. This protocol is still in the prelim...

Anterior knee pain (AKP) is a common clinical issue among adolescents and young adults. There is a growing body of evidence that increased femoral anteversion (FAV) plays an important role in the genesis of AKP1,2,3,4,5,6,7,8,9,10,11. In addition, this same evidence suggests that a derotational femoral osteotomy is beneficial for these patients, as good clinical results have been reported1,2,3,4,5,6,7,8,9,10,11. However, this type of surgery is not widely used in daily clinical practice among orthopedic surgeons, especially in the cases of adolescents and young active patients with anterior knee pain27, because the many controversial aspects generate uncertainty. For example, it has been observed that sometimes the correction obtained after the osteotomy is not what was previously planned. That is, there is not always a 1:1 ratio between the amount of rotation planned when performing the osteotomy and the amount of FAV corrected. This finding has not been studied to date. Therefore, it is the subject of the present paper. To explain the discrepancy between the magnitude of the rotation performed with the osteotomy and the magnitude of the correction of FAV, it was hypothesized that the axis of rotation of the osteotomy and the axis of rotation of the femur may not coincide.
One of the main problems to be addressed is accurately locating the femoral axis of rotation and the axis of rotation of the osteotomy. The first femoral axis is the femoral axis measured on the CT scan at the time of the patient&#39;s diagnosis, while the second femoral axis is the femoral axis measured after performing the osteotomy. Over the last decade, 3D technology has become increasingly important in preoperative planning, especially in orthopedic surgery and traumatology, for simplifying and optimizing surgical techniques15,16. The development of 3D technology has supported the creation of anatomical biomodels based on 3D imaging tests such as CT, in which customized prosthetic implants can be adapted17,18,19 and osteosynthesis plates can be molded in the case of fractures20,21,22. Additionally, 3D planning has already been used in previous studies to analyze the origin of the deformity in unilateral torsional alterations of the femur14. Currently, there are several software programs that are completely free and adaptable to most computers and 3D printers on the market, making this technology easily accessible to most surgeons in the world. This 3D planning allows for the accurate calculation of the initial axis of rotation of the femur and the axis of rotation of the femur after the intertrochanteric osteotomy has been performed. The main purpose of this study is to demonstrate that the axis of rotation of the femoral intertrochanteric osteotomy and the axis of rotation of the femur do not coincide. This 3D technology makes it possible to visualize this discrepancy between the axes and correct it through an adjustment of the osteotomy. The ultimate goal is to stimulate greater interest from orthopedic surgeons in this type of surgery.
This protocol with a 3D methodology is conducted in four fundamental steps. First, CT images are downloaded, and the 3D biomodel is created from the DICOM (Digital Imaging and Communication in Medicine) files of the CT scan. Higher-quality CT scans allow for better biomodels but mean the patient receives more ionizing radiation. For surgical planning with biomodels, the quality of conventional CT is sufficient. The DICOM image of a CT scan consists of a folder with many different files, with one file for each CT cut made. Each of these files contains not only the CT cut&#39;s graphical information but also the metadata (data associated with the image). To open the image, it is essential to have a folder with all the files of the series (the CT). The biomodel is extracted from the totality of the files.
Second, to obtain the 3D biomodel, it is necessary to download the 3D Slicer computer program, an open-source program with many utilities. Furthermore, this is the most widely used computer software in international 3D laboratories and has the advantage of being completely free of cost and downloadable from its main page. As this software is an X-ray image viewer, the DICOM image must be imported into the program.
Third, the first biomodel obtained with 3D Slicer will not match with the definitive one, because there will be regions such as the CT table or bones and soft parts nearby that are of no interest. The biomodel is &#34;cleaned&#34; almost automatically with the 3D design software, MeshMixer, which can also be downloaded directly from its official website for free. Finally, femoral anteversion is calculated, and the osteotomy is simulated using another free software from the Windows Store, 3D Builder.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>3D Builder</td>
			<td>Microsoft Corporation, Washington, USA</td>
			<td></td>
			<td>open-source program; https://apps.microsoft.com/store/detail/3d-builder/9WZDNCRFJ3T6?hl=en-us&#38;gl=us</td>
		</tr>
		<tr>
			<td>3D Slicer</td>
			<td>3D Slicer Harvard Medical School, Massachusetts, USA</td>
			<td></td>
			<td>open-source program; https://download.slicer.org</td>
		</tr>
		<tr>
			<td>MeshMixer&#160;</td>
			<td>Autodesk Inc&#160;</td>
			<td></td>
			<td>open-source program; https://meshmixer.com/download.html</td>
		</tr>
	</tbody>
</table>

three-dimensional preoperative virtual planning in derotational proximal femoral osteotomy

Anterior knee pain (AKP) is a common pathology among adolescents and adults. Increased femoral anteversion (FAV) has many clinical manifestations, including AKP. There is growing evidence that increased FAV plays a major role in the genesis of AKP. Furthermore, this same evidence suggests that derotational femoral osteotomy is beneficial for these patients, as good clinical results have been reported. However, this type of surgery is not widely used among orthopedic surgeons.
The first step in attracting orthopedic surgeons to the field of rotational osteotomy is to give them a methodology that simplifies preoperative surgical planning and allows for the previsualization of the results of surgical interventions on computers. To that end, our working group uses 3D technology. The imaging dataset used for surgical planning is based on a CT scan of the patient. This 3D method is open access (OA), meaning it is accessible to any orthopedic surgeon at no economic cost. Furthermore, it not only allows for the quantification of femoral torsion but also for carrying out virtual surgical planning. Interestingly, this 3D technology shows that the magnitude of the intertrochanteric rotational femoral osteotomy does not present a 1:1 relationship with the correction of the deformity. Additionally, this technology allows for the adjustment of the osteotomy so that the relationship between the magnitude of the osteotomy and the correction of the deformity is 1:1. This paper outlines this 3D protocol.

Femoral anteversion can be measured by different methods. Some of them focus on the femoral neck, using the line passing through the center of the neck and one passing through the femoral condyles as references. Others add a third reference point at the lesser trochanter23. Murphy&#39;s method, which is the most reliable in clinical practice because it has the best clinical-radiological relationship, is one such method using a third reference point25,<sup class="...

Watch this Scientific Journal Video about Three-Dimensional Preoperative Virtual Planning in Derotational Proximal Femoral Osteotomy at JoVE.com

Three-Dimensional Preoperative Virtual Planning in Derotational Proximal Femoral Osteotomy

This work presents a detailed surgical planning protocol using 3D technology with free open-source software. This protocol can be used to correctly quantify femoral anteversion and simulate derotational proximal femoral osteotomy for the treatment of anterior knee pain.

Anterior knee pain (AKP) is a common pathology among adolescents and adults. Increased femoral anteversion (FAV) has many clinical manifestations, ...

In this protocol, we demonstrate that the axis of rotation of the femoral osteotomy and the axis of rotation of the femur does not coincide. This protocol makes it possible to visualize and correct it. By using the free 3D software in this study, the surgeon can plan the surgery and increase the precision of the osteotomy.This technique is easily reproducible with simple step. We recommend practicing it many times to gain fluency. To begin, import the CT images in the DICOM format by clicking on the DCM icon on the top left corner of the screen, followed by clicking on Import DICOM Files on the left side of the screen.Next, click on Dummy Patient Name on the top right of the screen, and click on Load on the lower right margin. To create a 3D biomodel, in the dropdown menu, choose the Legacy and Editor options. Press OK on the message that appears and wait for a new menu to appear on the left side of the screen.Click on the Threshold Effect icon and move the bar in the lower box until only the bone is painted in the images on the right. This way, select the value of the Hounsfield units to be included in the model. Once the desired paint level is achieved, click on Apply.The selection is marked with the color green here. Select the option Make Model Effect from the side menu, and select Apply, which generates the 3D model in the upper right window. Click on the golden frame.Center the 3D view on the scene to center the image in the window. To save the created 3D biomodel, click on Save in the upper left margin. In the box that appears, uncheck other files, and only select the file Tissue.In the second column in the dropdown menu, select STL. Import the STL image by selecting the Import option in the center of the screen. Look for the Select option in the menu on the left side.Select the thickness of the brush using the Select tool, and double-click on the femur. Use the Select tool to select the part of interest. Look for the options, Modify and Invert in the side menu, and then press the delete button on the keyboard.Then navigate to Edit, Generate Face Groups, and move the bar of Angle Threshold until the different structures have a different color. Next, using the Select tool, double-click on the femur, modify, invert, and press the Delete button on the keyboard. to make a solid model, navigate to Edit, Make Solid, Solid Type, and Accurate.Then maximize the solid accuracy and mesh density values. Select the Export option from the side menu, and select the STL format and the folder to which the biomodel is exported. In the 3D builder software, click on the Insert icon at the top of the screen.Then click on Add to import the biomodel to the scene. Click on Object, then Settle to fix the object to the work plane. To perform the femoral osteotomy, click on Edit and Split from the top menu.When a rectangular cut plane appears, select Keep Both. Use the Move mode button on the bar in the lower margin of the screen to move the cutting plane horizontally and vertically. Use the Rotate mode button on the bar in the lower margin of the screen to rotate the plane around the femur.Put the cutting plane parallel to the x-axis and perpendicular to the Y-axis. Click on Split. To calculate the femoral anteversion, insert the guides by clicking on Insert, Add, and choose the 3MF file.Select only the proximal part of the femur on the right side of the screen, and press Control+X on the keyboard to cut the selection. The femoral diaphysis appears like this. Select the red circular guide and the purple circular guide together, on the right side of the screen.Use the commands in the bottom margin panel to move the guides and put them in the center of the femoral diaphysis. Then use the inferior margin panel commands to adjust the size and ensure that all the edges touch the cortex of the bone. Press Control+V on the keyboard to paste the proximal femur again.Select only the sphere on the right side of the screen and adjust the size, including all the edges touching the bone cortex. Select the proximal femur on the right side and cut it by pressing Control+X on the keyboard. Select only the red plane on the right side of the screen and place it to pass through the center of the sphere and the center of the circular guides.Press Control+V on the keyboard to paste the proximal femur again. To perform the rotational osteotomy of the proximal femur, select the proximal femur, the red circumference, and the sphere on the right side. Make an internal derotational proximal femoral osteotomy of 20 degrees by adding 20 to the pitch using the commands on the panel of the lower margin.To measure the new femoral anteversion, select the proximal femur and the red circumference, and press Control+X on the keyboard to cut these two elements. Select only the red plane and place it to pass through the center of the sphere and the center of the purple circular guide. Paste the proximal femur and the red circumference.To perform the adjustment of the rotational osteotomy, select the femoral diaphysis and the red plane, and press Control+X on the keyboard to cut. Select the proximal femur, the sphere, and the red circumference, and move these three elements en bloc so that the center of the red circumference matches the center of the purple circumference. Recalculate the new femoral anteversion with the adjustment made.The data here detail the values of the femoral anteversion obtained in two groups for the three magnitudes of the rotational osteotomy, 10, 20, and 30 degrees. When the adjustment was made so that the femur's rotation axis and the osteotomy's rotation axis coincided, the relationship between the planned correction and the final correction was a one-to-one ratio in the three correction magnitudes, but the same did not occur in group 1. The most important thing to remember is accuracy in performing the procedure, especially when creating the bone model, selecting only the bone of interest, and performing the osteotomy measurement before and after the adjustment.In the field of rotational deformities of the femur, this technique opens the way to study the region of these deformities and the consequences they have on potential femoral pressure and anterior knee pain.

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828 Views.  Hospital Arnau de Vilanova. In this protocol, we demonstrate that the axis of rotation of the femoral osteotomy and the axis of rotation of the femur does not coincide. This protocol makes it possible to visualize and correct it. By using the free 3D software in this study, the surgeon can plan the surgery and increase the precision of the osteotomy.This technique is easily reproducible with simple step. We recommend practicing it many times to gain fluency. To begin, import the CT images in the DICOM format by c...