Effect of femoral bowing angle on the lower limb alignment in different positions based on CT three-dimensional reconstruction / 中国组织工程研究

ABSTRACT

BACKGROUND: Measuring result of the lower limb alignment is often influenced by various factors, such as femoral bowing angle (FBA) in different positions.OBJECTIVE: To measure the FBA and femoral valgus correction angle (VCA) in different positions after CT reconstruction of lower limb model, and simulating X-ray examination, and to explore the rule of FBA affecting lower limb alignment.METHODS: Twenty patients undergoing CT angiography of lower extremity artery were enrolled, three-dimensional reconstruction of low limb was established on Mimics13.0 software based on CT data, and the FBA in standard posture was determined. All patients were divided into groups A (FBA > 2°), B (2° > FBA > 0°), C (0° > FBA > -2°) and D (FBA <-2°) (n=5 per group). Then each model was revolved through the vertical axis from 20° of internal rotation to 20° of external rotation by 2° for one motion, and 21 three-dimensional images were transformed into two-dimensional images to obtain the X-ray images of low limb. FBA and VCA in different positions were measured.RESULTS AND CONCLUSION: (1) The outcome measurements showed that FBA tended to be decreased in internal rotation and increased in external rotation. (2) VCA tended to be increased in external rotation and decreased in internal rotation. (3) FBA was positively correlated with VCA in the different positions (P < 0.01). (4) These results suggest that FBA can be altered with rotation and even expose influence on VCA. The bigger FBA is, the more influence on the lower limb alignment. Therefore, it is advisable to conduct the full length X-ray of lower limb in a standard posture, especially for the patients with larger FBA.