Semi-automated histomorphometric quantification of acetabular labral surface roughness

Histopathologic surface changes, including fibrillation, fraying, undulation, and disruption, are important indicators of tissue wear and acetabular labral degeneration. Surface assessment, however, commonly relies on descriptive or semiquantitative grading and may be partly observer-dependent when applied to naturally curved fibrocartilaginous surfaces. This study developed and evaluated a semi-automated histomorphometric workflow for quantifying acetabular labral articular surface roughness using histologic images. Sixteen human hemipelves from nine embalmed cadavers were divided into eight anatomical segments and grouped into superior, anterior, inferior, and posterior quadrants. Sections were stained with haematoxylin and eosin and Safranin O/Fast Green, scanned at high resolution, and analysed using Fiji/ImageJ and Python. The labral articular surface was isolated, skeletonised into a one-pixel-wide line, and exported as coordinates. A specimen-specific LOWESS-smoothed reference contour was generated, and roughness percentage was calculated from the mean absolute pointwise deviation between the original and smoothed profiles. Roughness percentage did not differ significantly across anatomical quadrants. In contrast, it differed significantly across histopathologic surface severity levels, with severely degenerated surfaces showing higher values than normal, mild, and moderate surfaces. Intra- and inter-observer reliability was excellent, with intraclass correlation coefficients of 0.994 and 0.962, respectively. This workflow provides a reproducible quantitative extension to conventional histopathologic grading with potential future application to other curved, load-bearing fibrocartilaginous tissues.