The surface microstructures of cartilage are closely related to its functions. Accurate observation of cartilage surface is key to researching cartilage-related diseases. Traditional observation methods have limitations: conventional optical microscopes have a narrow depth of field and cannot clearly image the uneven cartilage surface; other methods either have low resolution or damage the sample. Ultra depth of field microscopy(UDFM)is a new high-precision method for cartilage surface research. It can non-invasively show clear 3D microstructural details of the cartilage surface without damaging the sample. At present, its application in cartilage surface research is still in the exploration stage, and it is of great significance to use this new method for related research. Fresh porcine knee joints and discarded cartilage tissue from human total knee arthroplasty were utilized to prepare a range of cartilage damage models and sectioned specimens. UDFM was employed to examine the cartilage surface, cross-sections, and lateral profiles at various magnifications (10–2000×), generating both two-dimensional and three-dimensional topographic images. The integrated UDFM software was used for qualitative assessment of surface morphology, cellular architecture, and damage characteristics, as well as for quantitative measurements of height differences, surface roughness, fissure length, and stained area. UDFM provides non-destructive and direct visualization of the authentic three-dimensional morphology and subtle surface damage of articular cartilage, with 3D topographic mapping precisely delineating the depth and extent of lesions. This technology enables continuous, high-resolution observation of the macroscopic appearance, surface microarchitecture, and cellular morphology of cartilage across a broad range of magnifications. In fresh specimens, it reliably reveals in situ paired or clustered chondrocytes. The OPt-SEM special lighting mode further enhances the detection sensitivity for subtle surface damage. UDFM delivers rapid and highly accurate quantitative measurements of surface height differences, roughness, fissure length, and stained area, all with excellent reproducibility. In comparison to conventional techniques, UDFM is straightforward to operate, eliminates the need for complex sample preparation, and preserves the native structure of cartilage, thereby effectively addressing the inherent limitations of stereomicroscopy and scanning electron microscopy. Ultra depth of field microscopy is an efficient, non-destructive, and precise tool for three-dimensional observation of cartilage surfaces, offering high resolution, large depth of field, convenient operation, and strong quantitative capabilities. This technology can comprehensively and authentically reflect the microstructure and damage characteristics of cartilage surfaces, providing a new technical approach and objective quantitative method for basic and clinical cartilage research, early disease diagnosis, and evaluation of repair efficacy, with broad application prospects.
Zhang et al. (Wed,) studied this question.
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