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3D Modeling & 3D Printing Can Enhance THA Analysis, Classification, & Surgical Planning

The Digital Presentation On-line System, or EPOS, is the European Society of Radiology‘s digital database for scientific displays. A bunch of researchers revealed in EPOS about their work utilizing 3D modeling and 3D printing instruments to diagnose, classify, and perform surgical planning for fixing periprosthetic acetabular fractures, that are a tough, however widespread, complication of whole hip arthroplasty (THA).

“Periprosthetic acetabular fractures are associated to traumatic occasions and pathologic underlining circumstances that cut back the structural integrity of supporting bone[1] and sometimes are related to aseptic loosening, periprosthetic osteolysis and extreme bone loss[2],” the researchers wrote.

“Evaluation based mostly on customary radiographs alone will not be appropriate to reliably detect the residual stability of the implant and measure the extent of the fracture and pelvic bone loss [3].”

3D Modeling & 3D Printing Can Enhance THA Analysis, Classification, & Surgical Planning

Fig. 1: (a) Anterior–posterior (AP) pelvis and (b) lateral view of proper hip radiographs confirmed delicate indicators of periacetabular osteolysis with out proof of implant loosening and acetabular fracture.

They state that in terms of defining a fracture sample, CT scanning is “the gold customary,” which is unquestionably the case when a 3D digital rendering is required to assist with surgical pre-planning.

3D modeling software program based mostly on CT scans permits clinicians to get exact photos of “tridimensional reconstructions of the bony floor” by just about eradicating metallic implants with segmentation. Different analytic instruments embody measuring remaining bone inventory, evaluating implant stability, and characterizing the fracture, and 3D photos will also be used to 3D print anatomical fashions for surgical planning and simulation functions.

The researchers stated their paper would present that bone high quality and fracture morphology evaluation might be improved with 3D modeling software program, and reveal how helpful 3D modeling and 3D printing are for the diagnostic technique of periprosthetic acetabular fracture round THA, in addition to making life-size fashions for pre-op implant templating, simulation, and sizing.

3D Modeling & 3D Printing Can Enhance THA Analysis, Classification, & Surgical Planning

Fig. 2: CT scan of pelvis. (a) Coronal view exhibits barely medially protruded acetabular cup; (b) sagittal view of the hip revealed posterior wall fracture of the acetabulum. The tridimensional reconstruction of the fracture is seen (c), however its extension is hidden by picture artifacts.

They used the case of a 75-year-old lady who got here to an ER after a home trauma incident. The affected person had a historical past of extreme coxarthrosis in her proper hip, which had been handled a decade earlier than utilizing cementless THA. Docs took AP radiographs of her pelvis, and a cross-leg view of her hip, and noticed no indicators of fracture or loosening across the acetabulum or the stem. Nonetheless, a “CT scan of the pelvis with MAR protocol” confirmed that the posterior wall of the acetabulum did have a fracture, although the acetabular cup wasn’t displaced.

Materialise Mimics software program was used to create a 3D digital mannequin of the pelvis based mostly on CT scan information. The bone was differentiated from surrounding mushy tissue and the affected person’s prosthetic implants via segmentation.

3D Modeling & 3D Printing Can Enhance THA Analysis, Classification, & Surgical Planning

Fig. three: Tridimensional photos elaborated with 3D modeling software program. (a,b) Total pelvis with acetabular cup retained. Femurs and femoral stem have been eliminated throughout segmentation. (c,d) Bone high quality map exhibits areas with regular bone high quality (inexperienced) and areas with low bone high quality and thickness (pink). (e,f) Measurements of the bone defect space and fracture extension.

“The primary part is thresholding, which incorporates all voxels whose density is inside a specified vary of Hounsfield Unit (HU) values. We used a masks with a HU vary from 130 to 1750 with a purpose to exclude metallic and ceramic implants and embody each cancellous and cortical bone,” the researchers defined.

“The ultimate segmentation, with the removing of sentimental tissues and artifacts, was manually carried out utilizing extra instruments of the software program (Fig. three a,b). Ultimately, each femurs and steel implants have been digitally faraway from the corresponding pelvis and a 3D picture of the remoted area of curiosity (ROI) was created.”

A bone high quality map with a shade gradient was used for the acetabulum, in response to cortical and general bone thickness of the assorted areas. Measures of the fracture’s space, form, and spatial location have been analyzed later, together with “the acetabular bone loss and the middle of rotation, in comparison with the contralateral acetabulum.”

Lastly, a life-size mannequin of the affected person’s complete pelvis was 3D printed on a Type 3L system.

3D Modeling & 3D Printing Can Enhance THA Analysis, Classification, & Surgical Planning

Fig. four: (a) 3D printed life-size plastic mannequin of the whole pelvis. (b,c) Specific of the medial wall and posterior column fracture.

After analyzing the 3D photos and the 3D printed mannequin, they re-classified the posterior wall fracture as an incomplete posterior column and medial wall acetabular fracture. Moreover, the fracture was discovered to be “spontaneous,” with lower than 50% lack of bone inventory. Lastly, the bone high quality map decided world bone loss, displaying poor high quality in each the posterior and medial partitions. The 3D printed mannequin was additionally used to carry out pre-op templating.

“The remedy technique was chosen in response to the algorithm proposed by Simon et al. [14, 15, 16], which recommend the acetabular revision surgical procedure bridging or distracting the fracture, with out fracture fixation,” the researchers defined.

3D Modeling & 3D Printing Can Enhance THA Analysis, Classification, & Surgical Planning

Fig. 5: (a) Postoperative AP radiograph of the pelvis and (b,c) CT scan of the pelvis at three months post-op exhibits good implant positioning and full fracture therapeutic.

AP radiographs taken of the pelvis and proper hip post-op confirmed that the implant was “well-positioned and glued.” Three months later, a CT scan was taken of the affected person’s pelvis, which confirmed “bone integration of the trabecular cup” and full fracture therapeutic “with callus formation.” A 3D digital mannequin constructed utilizing DICOM photos confirmed this.

3D Modeling & 3D Printing Can Enhance THA Analysis, Classification, & Surgical Planning

Fig. 6: 3D modeling digital reconstruction. The posterior column and medial wall of the acetabulum have been restored.

“Using 3D modeling software program confirmed that periprosthetic acetabular fractures might be higher addressed, in comparison with plain radiograph and CT scans,” the researchers concluded.

“3D modeling software program present extra measurement instruments which permit the volumetric evaluation of bone defects and bone high quality evaluation.”

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