Quantitative investigations on newly-built bone and defects. Its time-dependent changes of morphological and biomechanical properties.

Bone growth in drillholes in sheep tibiae were examined morphologically and biomechanically after 4, 6, 9, and 12 weeks. Selected bone specimens were removed from the defective areas and used to determine the strength and, with the aid of microradiographs, the volume of new bone. Strength as well as volume of new bone increased in the defects within the healing time. However, the strength of the newly-formed bone reached only 20% of the strength of normal cortical bone. This is caused by the random structure of new bone which, despite the repair of the defect and the nearly normal mineralization, is not yet adapted to the adjacent normal cortical bone.