Comparative Morphology and Immunohistochemistry of the Adipose Tissues at the Posteromedial Tibial Border and the Heel Fat Pad in the Human

INTRODUCTION: A previous study confirmed the presence of adipose tissue along the posteromedial tibial border. This tissue may be the cause of medial shin pain, such as in medial tibial stress syndrome. However, the morphological and immunohistochemical characteristics of adipose tissue along the posteromedial tibial border remain unclear. In this study, we investigated the morphological and immunohistochemical characteristics of this tissue and compared them to those of the heel fat pad. METHODS: Seven cadavers were fixed in 10% formalin solution, and specimens were sampled from the adipose tissue along the posteromedial tibial border and heel fat pad. RESULTS: Scanning electron microscopy images showed a basket-like fibrous structure surrounding the adipocytes. This fibrous structure formed a three-dimensional network connecting adipocytes in both the posteromedial tibial border and the heel fat pad. The area and perimeter of the adipocytes were not significantly different between the adipose tissue along the posteromedial tibial border and the heel fat pads. Additionally, immunohistochemical staining confirmed that the fibres around the adipocytes were type I and III collagen fibres. These adipose tissues also reacted positively to substance P. CONCLUSION: The morphological and immunohistochemical characteristics of the adipose tissue along the posteromedial tibial border may be a structure adapted to carry mechanical stress. Additionally, the presence of substance P indicated that the adipose tissue along the posteromedial tibial border may be a source of pain, such as that experienced in medial tibial stress syndrome.