Hello, I'm going to present our work on evaluation of articular morphology and congruency using a combination of three-dimensional CT-based bone segmentation and joint surface matting. I'm Shuyuan Li, the corresponding author for this study, and we have nothing to disclose. Evaluation of joint congruency on both X-rays and CT scans has their limitations because neither can give us an accurate representation of the percentage of the bony surface that is covered by articular cartilage. Currently, most joint congruency studies were based on CT findings, which assumes cartilage surface is identical to the bony cartilage surface, but which may not be the truth. Here is an example of using joint gap mapping technique and analyzing the CT scan of the two articulating bones from the bone distance to show the congruency of the joint surface. Here's another technique or method looked into peritelial subluxation, and this paper used measurement of the bony surface congruency to reflect the joint congruency, but this is also may not be the real cartilage coverage. There are some joints in the foot which may only have 20 to 50% of the bone surface covered by cartilage, and this has implications for both surgical planning as well as evaluation of deformities where the severity of joint incongruency may be different from the bony surface subluxation shown on CT scans. So this study was to introduce a novel joint surface mapping technique using three-dimensional surface scanning to determine the articular morphology and congruency, and using 3D segmented and reconstructed articulating bones from CT scans in the bone templates to verify and guide the surface mapping. We used fresh frozen cadaver foot without trauma history nor deformities. We first CT scanned the foot and then used the CT scan images to do 3D segmentation and reconstruction of the calcaneus and cuboid bones. We used the calcaneus and cuboid bones and the calcaneus-cuboid joint as an example to do our descriptive study. And then we dissected the calcaneus and cuboid bones with all soft tissues being removed. Then we used surface scan and 3D reconstruction to reconstruct the two bones as well as the calcaneus-cuboid articular surfaces. It is a 3D laser scanner. And then both the CT and surface mapping reconstructions were imported into GMAGIC software where the reconstructed calcaneus via CT was merged with the reconstructed calcaneus via surface mapping, that is, to piece the two bones together. And the same procedure was applied to the cuboid bone. Cartilage surfaces from the surface mapping reconstruction were outlined on and compared to the bone surfaces underneath. Here is an illustration of what has been done. First of all, we took the foot for CT scan and then used the CT scan images to reconstruct the calcaneus bone. And then we dissected the calcaneus bone out and do 3D surface scanning. And here's a video showing how to surface scan the bone. And then from the CT scan, we reconstructed the cuboid bone. And from the surface scanning data, we also reconstructed the cuboid bone. And you can see they are almost identical. But to make sure they are identical, we merged the surface CT scan bone with the surface scanning reconstructed bone. And you can see they merged together very well. That means we used a CT scan reconstructed bone to test the surface scanning technique and it worked. And then by doing so, we used the surface scanning data to lift up the two articular cartilage surfaces. This one is from the cuboid sign and the white one was from the calcaneus sign. And the results. 3D surface scanning reconstructed bones matched the 3D CT scanning reconstructed bones. And the articular surfaces of the calcaneal cuboid joint were shaped according to the bone contours on both sides. They are similar. That means the cartilage contour and the bone contour from the same side of the bone or joint surface is very similar. But however, the articular surface did not fully match the bone surface on both sides of the joint. And you can see here on the calcaneus side, the bony surface is much larger than the cartilage surface. The same applies to the cuboid side. And you can see on the calcaneus side, only 84% of the bony jaw surface is covered by cartilage. And on the cuboid joint, about 80% or 81% of the bony surface is covered by cartilage. And here, we also did the articular mapping. And on the left side, it is the cartilage surfaces of both the cuboid and the calcaneus bones. And on the right side, it is the bony surfaces of the cuboid side and the calcaneus side in the back. And then we also restored the articulation of the reconstructed two bones. And then we got the calcaneus cuboid joint. And we can see that on the left side, the blue sign shows the uncovered bony surface. And on the right side, the green sign shows the uncovered cartilage surface. And you can see on the dorsolateral corner of the calcaneus and the plantar medial corner of the cuboid, there was uncoverage on both the bony surfaces and the cartilage surfaces. But the articular surfaces or the cartilage surfaces is uncovered at a smaller uncovering level compared to the bony uncoverage. So here's our conclusion. Even with 3D CT segmentation and reconstruction of articulating bones, one has no knowledge of the precise articular surface of a joint. And we have proven that 3D surface scanning is a reliable method to study morphology of the cartilage surface of a joint. We just used the CC joint as an example. But we are going to look into more joints in the foot and ankle. And we have also found that 3D CT reconstruction combined with 3D surface mapping is a useful tool for studying both the bony surface and the cartilage surface of a joint. And this study has implications for treatment of any joint in the foot, which appears subluxated or X-ray or CT scans. But this may represent the normal bony morphology, but not the true cartilage subluxation. And also, articular congruence study under weight-bearing condition is currently under investigation by our research group. The photos we showed just now, they were from non-weight-bearing CT scans. So here are our references.

articular morphology

congruency

three-dimensional CT-based bone segmentation

joint surface matting

joint treatment