BACKGROUND: During total knee arthroplasty surgery, second metatarsal shaft axis is consider as a reference, but its position through the ankle joint is unclear.
OBJECTIVE: To establish a new laser aiming reproducible standard full-length lower limb radiography, to use the method to evaluate the relationship between the second metatarsal shaft axis and the center of the ankle in healthy southern Han Chinese adults.
METHODS: All subjects were divided into 3 groups: ① The new method was adopted to mark skin by same tester who guided the filming position of patients. ② The new method was adopted to mark skin by different testers. ③ Routine radiography was used as control without mark. Twice radiography was done for each subject.
RESULTS AND CONCLUSION: There was no difference of the testers in the group 1 and group 2 (P=0.729), but had difference in the group 1 and group 3 (P=0.017). Absolute value in two radiography of the groups 1 and 2 was lower than that of the group 3,  repeatability in the groups 1 and 2 was higher than the group 3. Using the new method, the ratio of the distance from the second metatarsal shaft axis to the medial and lateral ends of the transverse axis of the ankle was 1.06±0.882. The view that the second metatarsal shaft axis passes the center of the ankle is acceptable clinically.