The Study Of Synchronization Between Calcium Sulphate Cement Degradation And New Bone Formation With External Mechanical Regulation

[Objective]A major challenge faced in the bone materials of weight-bearing without internal fixture support is the mismatch of material degradation and new bone formation, leading to weakening or even failure of the overall bony structure. The purpose of this study was to evaluate if calcium sulphate cement degradation and new bone formation could be better synchronized by external mechanical force.[Methods]Thirty 12-week old female Sprague Dawley rats were anesthetized by 10% chloral hydrate intraperitoneally. A hole of 3 mm in diameter and length was drilled into the left leg on the lateral side of the distal femur. Afterwards, calcium sulphate cement(CSC) scaffolds were implanted inside the holes. The rats were equally divided into two testing groups and a control. In the testing groups, the mechanical force was applied through a treadmill exercise. The exercise started at day 7 postoperatively for 30 consecutive days. One group was at a constant speed 8 m/min for 45 min/day. The other had a regulating mechanical force: an ascending treadmill speed from 8 m/min to 24 m/min with the increment of 8 m/min in every 10 days. In the control, the rats were restricted in the cages. Among the 30 animals, 21(7 for each group) were used for the micro-CT imaging in vivo and biomechanical test, and 9(3 for each group) were for the histologic study.[Results]An ascending force in line with calcium sulphate cement degradation could achieve bone healing in 37 days with ultimate load to failure of 87.00±7.30 N, similar to that of intact femur(80.46±2.79 N, p=0.369). In contrast, the healing process under either a constant force or no force was not synchronized well with significant residual defect areas of 1.47±0.44 mm3 and 4.08±0.89 mm3(p<0.001), and weaker ultimate loads to failure of 69.56±4.74 N and 59.17±7.48 N, respectively(p<0.001). The histologic results at day 37 confirmed the Micro-CT finding of better synchronization by the regulating force.[Conclusion]Our results suggest that the mechanical regulation approach deserves further investigation and may potentially offer a clinical strategy to improve synchronization.