Quantifying Complex Micro‐Topography of Degenerated Articular Cartilage Surface by Contrast‐Enhanced Micro‐Computed Tomography and Parametric Analyses

One of the earliest changes in osteoarthritis (OA) is a surface discontinuity of the articular cartilage (AC), and these surface changes become gradually more complex with OA progression. We recently developed a contrast enhanced micro‐computed tomography (μCT) method for visualizing AC surface in detail. The present study aims to introduce a μCT analysis technique to parameterize these complex AC surface features and to demonstrate the feasibility of using these parameters to quantify degenerated AC surface. Osteochondral plugs (n = 35) extracted from 19 patients undergoing joint surgery were stained with phosphotungstic acid and imaged using μCT. The surface micro‐topography of AC was analyzed with developed method. Standard root mean square roughness (R_q) was calculated as a reference, and the Area Under Curve (AUC) for receiver operating characteristic analysis was used to compare the acquired quantitative parameters with semi‐quantitative visual grading of μCT image stacks. The parameters quantifying the complex micro‐topography of AC surface exhibited good sensitivity and specificity in identifying surface continuity (AUC: 0.93, [0.80 0.99]), fissures (AUC: 0.94, [0.83 0.99]) and fibrillation (AUC: 0.98, [0.88 1.0]). Standard R_q was significantly smaller compared with the complex roughness (CR_q) already with mild surface changes with all surface reference parameters − continuity, fibrillation, and fissure sum. Furthermore, only CR_q showed a significant difference when comparing the intact surface with lowest fissure sum score. These results indicate that the presented method for evaluating complex AC surfaces exhibit potential to identify early OA changes in superficial AC and is dynamic throughout OA progression.