لخّصلي

Although each loading mode has been considered sepa- rately, living bone is seldom loaded in only one mode.The shear stress was low throughout the stride, denoting minimal torsional loading produced by slight external and internal rotation of the tibia in an alternat- ing pattern.In vivo measurement of the strains on the anteromedial surface of a human adult tibia during walk- ing and jogging demonstrates the complexity of the load- ing patterns during these common physiologic activities (Lanyon et al., 1975).Stress values calculated from these strain measurements by Carter (1978) showed that during normal walking, the stresses were compressive dur- ing heel strike, tensile during the stance phase, and again compressive during push-off (Fig.During jogging, the stress pattern was quite differ- ent (Fig.2-32A).

Although each loading mode has been considered sepa- rately, living bone is seldom loaded in only one mode. Loading of bone in vivo is complex for two principal reasons: Bones are constantly subjected to multiple indeterminate loads, and their geometric structure is irregular. In vivo measurement of the strains on the anteromedial surface of a human adult tibia during walk- ing and jogging demonstrates the complexity of the load- ing patterns during these common physiologic activities (Lanyon et al., 1975). Stress values calculated from these strain measurements by Carter (1978) showed that during normal walking, the stresses were compressive dur- ing heel strike, tensile during the stance phase, and again compressive during push-off (Fig. 2-32A). Values for shear stress were relatively high in the later portion of the gait cycle, denoting significant torsional loading. This torsional loading was associated with external rota- tion of the tibia during stance and push-off.
During jogging, the stress pattern was quite differ- ent (Fig. 2-32B). The compressive stress predominating at toe strike was followed by high tensile stress during push-off. The shear stress was low throughout the stride, denoting minimal torsional loading produced by slight external and internal rotation of the tibia in an alternat- ing pattern. The increase in speed from slow walking to jogging increased both the stress and the strain on the tibia (Lanyon et al., 1975). This increase in strain with greater speed was confirmed in studies of locomotion in sheep, which demonstrated a fivefold increase in strain values from slow walking to fast trotting