Application Of Three-dimensional CT Reconstruction Simulation For Treatment Of Malignant Bone Tumors Around The Acetabulum

Objective: Pelvis is the predilection site of malignant primary bone tumors. The malignant tumors around the acetabulum locate deeply with complex anatomic structure; meanwhile these tumors often reach a considerable size and invade extensively before becoming obvious. Therefore, surgical treatment of malignant primary bone tumors around the acetabulum is a challenge. CT scans and MRI are obtained for patients suffering from the disease. The CT images are then imported into Mimics to build a 3D digital model; the MRI images uploaded into Mimics to determinate the border of the tumor. Using the software for the visualization, menstruation, analysis and simulation of surgical procedures, surgeons can determine the details of planes and angles of the resection. Also the hip joint center can be located in the model. Ultimately the specific anatomic geometry in the model could be used in the preoperative planning.Methods: From April 2008 to May 2008, an 18 year-old-female with malignant primary bone tumors around the acetabulum were analyzed before surgical intervention at our hospital. The tumors involved the zone II of Enneking classification. Histo-pathological records of aspiration-needle biopsy are Ewing's sarcoma. The Third Clinical Hospital of Hebei medical University provides Mimics software (Materialise Interactive Medical Image Control System Software, Materialise, Belgium). All imaging was carried out on a multislice helical CT scanner (Volume Zoom Sensation 64, Siemens, Erlangen, Germany) with a 0.5-second gantry rotation. The scanning parameters were as follows: 120 Kv, 250 mA, slice thickness 0.6mm, increment 0.7 mm. The preoperative CT scans (DICOM) are uploaded into the Mimics software. Models for the simulation are produced semiautomatically using the modulars of the software. The first part of this process is determination of the threshold that specifies desired densities which define bones. Then use the tools of the software to modify every slice, especially where small details are not separated automatically. After this procedure, the simulation model can be built. MRI images are then imported into Mimics to determinate the border of the tumor. Comparing to the similar reconstructed 2D CT layer, the border of tumor can be determined and measured by direct observation. Make the 2D marked points convert to the solid 3D points on the model with help of the CAD system. Then use the virtual plan, developed in the preoperative phase, to define the osteotomy planes using the system. The ultimate clinical surgical osteotomy points track the points that the simulative surgical osteotomy planes and the linear anatomic landmarks intersect. The remaining steps in the procedure are all standard operating procedure: perform the osteotomy of the neck of femur, pubis, ischium and illium with help of Mimics on the 3D model. We use the geometric method to determinate of the hip joint center on 2D reformatted image slices (transverse, coronal and sagittal images) and 3D renderings. The Mimics measurement module was used to analyze the data of each component, and to identify their interrelationship.Results:(1)Two cases of malignant primary bone tumors around the acetabulum operations were planed and performed simulative surgery using the software.(2)The results of the simulative osteotomy: The distance between the anatomical landmark (point G) of the pubic osteotomy plane and the left anterior superior iliac spine (point D) is 92.99mm. The distance between G and the superior margin midpoint (point A) of articulation of pubis is 55.62mm. The pubic osteotomy plane is vertical to pectineal line. The distance between the anatomical landmark (point H) of the ischiac osteotomy plane and the left ischiadic spine (point E) is 11.17mm. The ischiac osteotomy plane is vertical to the left greater sciatic notch. The anatomical landmark (point L) of the sacro-iliac osteotomy plane is located on sacrum which is on the same level with posterior superior iliac spine (point F). the distance between L and F is 19.99mm.The sacro-iliac osteotomy plane is from the vertex of the left auricular surface to the L, then change the direction to the caudal end vertical. (3)The results of the determination of the hip joint center (HJC): the distance between the HJC and G is 35.03mm, the distance between the HJC and H is 45.28mm, the distance between the HJC and B is 120.10mm, the distance between the HJC and C is 126.21mm;∠G-HJC-C :85.01°,∠H-HJC-C :66.94°.Conclusion: Using the software for Virtual 3D preoperative Planning and stimulation of the osteotomy, surgeons can plan the details of the surgery. This will enable them to determine a desired cutting. Virtually tumor resections should be planned more precisely, especially the malignant tumors around the acetabulum. The 3-dimensional aspects of the reconstruction could be studied from the various perspectives (dorsal, ventral, oblique) and allowed, therefore, an exact estimation of the operation. Simulated surgery using the software allowed the optimal identification of resection margins. Additionally, since the plan is created preoperatively, the time in the operating room will be reduced, and, therefore, operative risk will also be reduced.