INTRODUCTION
The physiological function of the human wrist is strictly dependent on
the complex anatomy of the carpal bones and the ligaments providing
stability to these bones (Andersson, 2017). The human scapholunate
interosseous ligament (SLIL) is a C-shape structure connecting the
scaphoid and lunate carpal bones, and it is considered as the primary
stabilizer of the scapholunate joint (Johnson et al., 2013). SLIL
disruption due to trauma or degeneration is considered the most common
cause of carpal instability, which can significantly compromise hand
function and lead to wrist arthrosis (Kitay & Wolfe, 2012; Wolff &
Wolfe, 2016). The regenerative capability of the human SLIL is very
limited, and injuries in this structure cannot heal by themselves and
typically require surgical treatment (Mullikin et al., 2020). Although,
numerous surgical procedures have been described (Lui et al., 2019;
Mullikin et al., 2020), reconstruction of the dorsal component of the
SLIL is the usual surgical treatment for SLIL injuries, underestimating
the biomechanical role of the membranous and palmar portions of this
structure (Naqui et al., 2018).
Despite its key role in carpal physiology, the exact structure and
composition of the human SLIL are not fully understood. The gross
morphology of the SLIL was originally defined by Berger and cols.
(Berger, 1996), who described three major zones in the human SLIL: the
dorsal, membranous, and palmar regions. The dorsal region is
transversely oriented, whereas the palmar region is oblique, allowing
significant relative movement between the two bones (Sokolow & Saffar,
2001). Numerous reports focused on the study of the SLIL from the
anatomical, kinematical and biomechanical standpoints (Kitay & Wolfe,
2012; Rajan & Day, 2015; Wolff & Wolfe, 2016).
Histologically, the human SLIL is thought to be composed of collagen
fascicles infiltrated by loosely organized connective tissue, as it is
the case of most other intraarticular ligaments, although the SLIL could
also share some similarities with human fibrocartilage (Berger, 1996;
Sokolow & Saffar, 2001). However, the detailed histological structure
of the human SLIL remains to be elucidated.
In the present work, we carried out a comprehensive histological
characterization of the human SLIL using an array of histochemical and
immunohistochemical methods in order to determine the main extracellular
matrix molecules and cells which form part of this ligament.