Effects of controlled stress and micromovement on fracture healing

Objective To study the effects of axial stress stimuli on the healing of the fracture ends at different stages. Methods Thirty-two grey goats were randomized into 4 groups, in which stresses of 0 (control group), 1/6 (group A), 1/3 (group B) and 1/2 (group C) of their body weight were applied re-spectively. Transverse osteotomy at the middle shaft of the femur was performed in all groups. The goats were sacrificed in batch at 4 and 8 weeks after operation separately for histological observation and measurement of the callus area at the fracture ends. Results At 4 and 8 weeks after operation, more callus formed and the periosteum callus area at the fracture ends was significantly larger in Groups A, B and C than in the control group (P<0.05). In the former groups, more bony callus aligned in the axial direction and the bony callus was dense with obvious spongy transformation of cortical bone. More callus at the fracture ends was observed,more bony callus aligned in the axial direction and the bony callus was dense with obvious spongy transformation of cortical bone in groups B and C than in group A. There was no significant difference in periosteum callus area at the fourth week but obvious difference at the eighth week. There was no significant difference in callus at the fracture ends between groups B and C. Conclusions As stress at the fracture ends can improve the callus formation, it can be strengthened to enhance the effect. The strengthened stress at the fracture ends, however, may increase incidence of angnlation deformity during fracture healing. Key words: Fracture healing;  Stress, mechanical;  Histological techniques;  Microvement