Intra- and extra-articular differences in the collagen organization of the long head of the m. biceps brachii, clinical relevance? Observational pilot study

Abstract

Abstract Background: The long head of biceps tendon (LHBT) is remarkable due to its anatomical course through the intertubercular groove. This forms an intra- and extra-articular part. The intra-articular part is most prone to tearing, but further investigation is needed. Method: 10 patients undergoing artroscopic shoulder surgery have the LHBT resected, biopsies are taken at regular intervals. These biopsies are examined by light microscopy (LM) and transmission electron microscopy (TEM), for fine and ultra-structural differences in collagen organization. Results: LM showed most degeneration at 2cm distal from origin. During TEM the intra- (1cm distal from origin) and extra-articular (3cm distal from origin) sections were compared considering collagen density. The extra-articular section showed remarkably higher collagen density (215 fibers/µm²), compared with the intra-articular section (161 fibers/µm²). This was not statistically significant. Conclusion: Light microscopy (LM) and transmission electron microscopy (TEM) seem to indicate an increased vulnerability to tearing in the intra-articular aspect of the long head biceps tendon (LHBT). Goal of the research: Linking clinical signs of LHBT pathology to fine and ultra-structural LHBT morphology, by using light and transmission electron microscopy, particularly focused on collagen density. Research question: Are there any intra- and extra-articular differences in the collagen organization of the long head of the m. biceps brachii, and what is their clinical rel