Paleohistopathology of a Harris line

Identification of Harris lines (HLs), a non-specific indicator of bone growth disruption, is usually achieved radiographically. Histological methods have only been implemented to explore the underlying processes of HL formation in longitudinal sections of animal bone. No prior study has examined HL histopathology in a human skeletal specimen. Here, a first insight into HL formation, from transverse sections in a human distal tibia, is provided. Results will aid understanding about the nature of HL, and its identification from histology.

Distinct HLs were identified macroscopically, and from a radiograph, in a left distal tibia taken from an adult male dating to the British Medieval period. Multiple transverse sections were taken through the HL, and also from trabecular bone regions located immediately proximal and distal to the HL. Thin sections of undecalcified bone were produced following standard histological procedures. Slides were examined under a high-powered microscope at 20x, 40x, and 60x using polarized light. Images were captured using a digital microscope camera and imaging software, and later assembled into montages.

Trabeculae proximal and distal to the HL exhibited no abnormal growth, displaying numerous osteocyte lacunae and a healthy lamellar structure. However, the microanatomy of the HL was characterised by three main features: 1) non-lamellar appearance, 2) lack of osteocyte lacunae, 3) presence of irregular bundle-like canals oriented in multiple directions. These histopathological features indicate an abnormal manner of bone deposition, implying that trapping of osteoblasts does not take place during HL formation. Pictorial and descriptive records of tibial HL histopathology are provided.