Histology of a Harris line in a human distal tibia.

Identification and diagnosis of Harris lines (HLs) is usually achieved using radiography. To date, histological methods have been mainly implemented in research exploring the underlying processes of HL deposition using longitudinal sections taken from animal bone. Here, a new insight into HL formation is provided following transverse histological sectioning in a human specimen. A distinct HL was identified macroscopically, and from a radiograph, in a left distal tibia taken from an adult human male. Transverse sections were taken through the HL, and also from trabeculae immediately superior and inferior to the HL. Thin sections were produced following standard histological procedures. Micrographs were captured using a digital microscope camera. Trabeculae immediately superior and inferior to the HL displayed no indication of abnormal growth, exhibiting abundant osteocyte lacunae and a lamellar structure. However, the micro-anatomy of the HL was characterised by the following three main features: (1) non-lamellar appearance, (2) a complete lack of osteocyte lacunae, and (3) presence of irregularly distributed tubular structures. These three histological features indicate a specific process of bone deposition, implying that trapping of osteoblasts may not take place during HL formation. Pictorial and descriptive records of HL histology are provided, aiding current understanding about the nature of HL, its identification from histology, and serving as a reference point for future comparative research.