Three-dimensional Imaging of Articular Cartilage in Human Using Synchrotron Radiation Micro-computer Tomography

Objective: To investigate the feasibility of detecting microstructure in human articular cartilage with Synchrotron Radiation Micro-Computer Tomography. Methods: Three cylindrical cartilage-bone plugs with approximate 1mm in diameters and 4mm in heights were harvested from the joint of human knee. The three specimens were performed by SR-μCT after being soaked in 4% formalin solution. The original projection images of SR-μCT were processed by phase retrieval, slice and 3D reconstruction. Then we compared the size, shape, orientation of chondrocytes with pathologic pictures and analyzed the differences of orientation of collagen framework between normal and damaged cartilage. Results: The size, shape, distribution of chondrocytes and lacunas can be clearly demonstrated on reconstructed images of SR-μCT. The results were in accordance with pathological pictures. On Maximum intensity projection(MIP) images the orientation of collagen framework was revealed. Collagen fiber structure was in a vertical direction through the cartilage with arcade structure on surface in normal cartilage. And the collagen fibrils were deformed in the vertical direction with their axial low-grade collapse in mild cartilage damage. As to severe cartilage damage, the collagen framework was disordered and there was a severe collapse in axial direction. Conclusion: SR-μCT can demonstrate a true cellular resolution for human articular cartilage and clearly show the three-dimensional structure of collagen framework by selecting appropriate threshold value.