PMC7315311_01
Radiographs of the pelvis (AP in (a) and Lequesne view in (b)) showing signs of hip dysplasia.
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MRI (coronal cut) of the right hip showing dysplasia and a hypertrophic labrum torn at its base.
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Magnetic resonance imaging (MRI) contributed to the diagnosis of a typical hyperplasic torn labrum (Figure 2).
The pelvis with positioned osteotomes and the extruded guide (in green).
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This selection was then separated to create a new object, which was extruded into a constant direction to produce a 10 mm thick object, named the Guide (Figure 3).
Images of the acetabular fragment in different projections (rotations).
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This, too, was saved as a separate object (Figure 4).
Images of the acetabular fragment superimposed to the pelvis after rotation and space repositioning.
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fig5
Then, we rotated the acetabular fragment over the center of the femoral head in order to restore normal radiographic parameters (Figure 5).
Image of the repositioned acetabular fragment, femur, and pelvis, with the ray casting technique, to simulate the transparency of the structures as in radiographs. The center edge angle (a) and Tonnis angle (b) were measured in both hips.
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fig6
At the end, we took screenshots of the images and measured the usual radiographic parameters in order to confirm adequate correction and provided the surgeon with visual feedback during surgery (Figure 6).
Final guide printed in ABS plastic (pelvic and abdominal faces).
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fig7
A1, GTMax, Brazil) using a pure, colorless 1.75 mm Acrylonitrile Butadiene Styrene (ABS) plastic (GTMax, Brazil) (Figure 7). After visual inspection for flaws, actual surgical chisels were tested through the slots for compatibility.
Surgical guide held in place (iliac fossa) with a reduction clamp, and a perfect fit can be noticed.
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Perfect fit was obtained according to plan (Figure 8).
Picture of a straight osteotome inserted into the pubic slot ready to be driven through the bone. Notice the screw securing the guide to the bone.
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Hence, a straight osteotome (measuring 2.9 x 10 x 200 mm) was introduced into the pubic slot of the guide, and after fluoroscopic confirmation of the position, was hammered into the bone creating the iliopubic bone cut (Figure 9).
Fluoroscopic images of the iliac and posterior column osteotomes being driven through the bone (a) and the extension of the posterior column cut up to the ischium cut (b).
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The osteotome was inserted down to the incomplete ischium cut (Figure 10).
Picture of the acetabular fragment repositioned in space. Note that the planned rotation of the fragment is 5.9  in the longitudinal axis, 28  in the anterior-posterior axis, and 14  in the laterolateral axis.
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fig11
Measurement of the center edge angle (a and b) and the Tonnis angle (c and d), for both the planned (a and c) and actual radiographs (b and d). The obtained center edge angle is equal to as planned, and the Tonnis angle is 2  less than as planned.
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Radiographs were taken and showed that the correction was as planned for both the center edge (difference = 0 ) and Tonnis angles (difference = 2 ) (Figure 12).