Scanning electron microscopic observation of transverse (Harris) lines in the femur and tibia of anatomy cadavers

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 pres ence of a transverse line, a cross-sectional sample was examined macroscopi cally, and by soft X-ray and scanning electron microscopy. The following re sults were obtained: 1) According to roentgenograms, transverse (Harris') l ines 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 bilater al 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 membrano us structures of various morphologies, ranging from complete interruption o f the medullary space to a washer-like appearance, or the structures were f ormed by joined trabeculae. The frequency of detection may vary according t o the observation method. 3) in scanning electron micrographs, matrix fiber s were observed on the surface of trabeculae. The transverse lines were cle arly formed from osteoblasts. No marked difference in structure was observe d between the transverse line trabeculae and the compact bone. 4) From thes e facts, we considered that further studies are necessary to examine the ag e-related changes of the transverse lines and the significance of their pre sence in adults.