Morphological classification of spinal tendon-to-bone entheses: developmental and regional variation from fetus to adult - A comparative and descriptive anatomohistological study

Details

Supervisors

Chretien, Antoine

Faculty

Faculté des sciences de la motricité

Degree label

Master [120] en sciences de la motricité, orientation générale, à finalité spécialisée: kinésithérapie musculo-squelettique

Abstract

enBackground: Tendon-to-bone (TTB) entheses vary according to anatomical location and mechanical loading, but spinal entheses remain poorly described, especially across development. Objective: This study aimed to classify human spinal TTB entheses in fetal and adult specimens and to describe developmental and regional histological variations. Methods: A comparative descriptive histological study was performed on three fetal and two adult human specimens. Sections were stained with Toluidine Blue, Safranin O, and Sirius Red. Entheses were classified using three criteria: Safranin O positivity, presence of a tidemark, and presence of chondrocyte-like cells. In adults, normalized calcified fibrocartilage thickness and normalized Safranin O positive thickness were quantified. Results: All fetal entheses (n = 55) were classified as fibrous, whereas all adult entheses (n = 32) were classified as fibrocartilaginous, regardless of spinal region. In adults, normalized calcified fibrocartilage thickness and normalized Safranin O positive thickness were highest in the thoracic region and lowest in the lumbar region, with marked inter-muscular variability. Conclusion: Spinal entheses showed a developmental transition from fibrous organization in fetal specimens to fibrocartilaginous organization in adults. Adult regional differences, especially in the thoracic spine, suggest site-specific structural adaptation.