Hyaline cartilage surface study with an environmental scanning electron microscope. An experimental study

To obtain images of the articular surface of fresh osteochondral grafts using an environmental scanning electron microscope (ESEM). To evaluate and compare the main morphological aspects of the chondral surface of the fresh grafts. To develop a validated classification system on the basis of the images obtained via the ESEM. The study was based on osteochondral fragments from the internal condyle of the knee joint of New Zealand rabbits, corresponding to fresh chondral surface. One hundred images were obtained via the ESEM and these were classified by two observers according to a category system. The Kappa index and the corresponding confidence interval (CI) were calculated. Of the samples analysed, 62–72% had an even surface. Among the samples with an uneven surface 17–22% had a hillocky appearance and 12–16% a knobbly appearance. As regards splits, these were not observed in 92–95% of the surfaces; 4–7% showed superficial splits and only 1% deep splits. In 78–82% of cases no lacunae in the surface were observed, while 17–20% showed filled lacunae and only 1–2% presented empty lacunae. The study demonstrates that the ESEM is useful for obtaining and classifying images of osteochondral grafts.