Enthesis of the Calcaneal Tendon ‐ A morphological Analysis
Authors: Hirtler Lena , Tewes Henning 
Published: April 2020

IntroductionThe enthesis of the Achilles tendon (ASE) is an example of a fibrocartilaginous osteotendinous insertion. It shows a complex ultrastructure and is surrounded by various attachment tissues. For various pathologies, caused by degeneration, rheumatoid diseases and excessive strain, the ASE is the site of manifestation. Therefore, the visualization of its ultrastructure is of great clinical interest in order to diagnose diseases early or monitor their course of therapy. Magnetic resonance imaging (MRI) is considered the gold standard for soft tissue imaging and is used in this study in the form of a three‐dimensional MRI‐sequence, capable of generating variable echo times (3D‐vTE‐sequence). To verify the correctness of the results obtained, it is necessary to prepare a corresponding histological compound. Thus, this study serves to design a manufacturing protocol for a holistic histological preparation of the ASE. Additionally, the potential of the 3D‐vTE‐sequence for imaging ultrastructural details of the ASE is to be investigated based on this histological preparation. A special feature of this study is that a holistic, morphological comparison of the ASE is to be achieved by the used techniques, which, to our current knowledge, has not yet been carried out in this form.MethodsIn total five ASE were extracted from post‐mortem donations. Initially, proof of concept was performed with two ASE by using Giemsa stained cutting‐thin section‐technique by Plenk. Subsequently, three further ASE were subjected to MRI using a T2*‐weighted 3D‐vTE‐sequence in a 7 Tesla magnetic resonance tomograph. Measurements with a total of 12 different echo times were performed. Additionalliy, after the cutting‐thin section‐preparation, individually microradiographies (MRG) were manufactured.ResultsThe proof of concept showed satisfactory results regarding the histological imaging of the ASE and its ultrastructure. The holistic, high‐resolution images of the MRI‐examination showed ultrastructural details of the ASE, which correlated morphologically with the depiction of the ASE in the cutting‐thin section‐preparations. At the same time, some ultrastructural details are not reflected in MRI. The same applies in some cutting‐thin section‐preparations of the ASE: Due to artifact formation and other reasons, not all components of the ultrastructure can be determined. The MRG provided reliable information about the architecture of the bone tissue and were additionally used for the comparison between MRI and histological compounds. Seite | 7ConclusionThe used cutting‐thin section‐technique by Plenk and the 3D vTE MRI‐sequence showed great potential for the holistic representation of ASE and its ultrastructure. Nevertheless, certain deficits can be identified in both forms of presentation. Regarding to the detailed reproduction of the ultrastructure, the cutting‐thin section‐technique by Plenk is superior to the used MRI‐sequence. The manufactured MRG warranted a detailed depiction of the hard tissue architecture and have been useful for the performed holistic comparison. For further trials of this kind, it is necessary to take alternative depiction techniques into account to check their potential and compare it with the techniques used in this study.