[Importance of vascular and mechanical factors for bone healing.].
The author submits a brief account of contemporary views on the importance of vascular and mechanical factors for healing of bones. Damage of the vascularization after fractures when using conservative treatment and intramedullary and external fixation, does not influence bone healing in a substantial way. In those instances the bone heals by forming a callus with newly formed ample vascularization. On the other hand, in case of osteosynthesis, using a splint with perfect stabilization, the bone heals very slowly by a process of direct healing by haver remodelling. The period of healing is proportional to the extent of bone necrosis. Therefore biological surgery with maximal sparing of periostal vessels is essential. The importance of mechanical factors depends also on the type of healing. The prerequisite of direct healing and healing in the cavity is mechanical rest. Mechanical influences become involved only in the osteoblastic, apposition stage of the remodelling process. During healing by means of a callus mechanical factors play a different role in different stages of development of the callus. In the proliferation stage the mechanical optimum is moderate, so far not accurately quantified motor activity. In the differentiation stage similar mechanisms are involved as during differentiation of the embryonic mesenchymal blastema: traction in the surface layers of the callus leads to desmogenesis, pressure inside the callus to chondrogenesis. The ossification stage calls for mechanical rest. In the final modelling and remodelling stage two basic mechanism of functional adaptation of bone are involved, apposition caused by deformation of the bone marrow and surface reabsorption caused by direct pressure of the adjacent periostium. In the conclusion the authors discuss the importance of mechanical factors in the stress shielding phenomenon, traction osteogenesis and dynamic compression. Key words: bone - healing, vascular and mechanical factors, mechanical factors - bone.
Hert
J
J
Anatomický ústav lékarské fakulty KU, Plzen.