Scanning Electron Microscopic Observation of Transverse (Harris) Lines in the Femur and Tibia of Anatomy Cadavers.

Abstract

To investigate the occurrence of transverse lines in long bones of adults, we studied 27 cadavers (14 males and 13 females) used for teaching anatomy, and took a roentgenogram of the femur and tibia. After confirming the presence of a transverse line, a cross-sectional sample was examined macroscopically, and by soft X-ray and scanning electron microscopy. The following results were obtained: 1) According to roentgenograms, transverse (Harris') lines were observed in 40.7% of the distal half of the femur and in 29.6% of the proximal half of the tibia. These showed a strong tendency for bilateral symmetry as is characteristic of transverse lines and the frequency was much higher than previous reports suggested. 2) Macroscopic examination of the bone cross-sections at the level of the transverse line showed membranous structures of various morphologies, ranging from complete interruption of the medullary space to a washer-like appearance, or the structures were formed by joined trabeculae. The frequency of detection may vary according to the observation method. 3) In scanning electron micrographs, matrix fibers were observed on the surface of trabeculae. The transverse lines were clearly formed from osteoblasts. No marked difference in structure was observed between the transverse line trabeculae and the compact bone. 4) From these facts, we considered that further studies are necessary to examine the age-related changes of the transverse lines and the significance of their presence in adults.