Fig 1.
HKA: hip-knee-ankle angle; Fs: a point bisecting the width of the femoral shaft at the lower junction of the lesser trochanter and the shaft; Fd: a point bisecting the width of the shaft 10 cm proximal to the knee joint; Fp: a point bisecting the width of the shaft at junction of the proximal third and the midsection; Fm: a point bisecting the width of the shaft at junction of the midsection and the distal third; Fc: a point bisecting the width of the femoral shaft midway between Fs and Fd; NSA: neck-shaft angle; FBA: femoral bowing angle; mMDFA: mechanical medial distal femoral angle; aMDFA: anatomic medial distal femoral angle.
Fig 2.
Three morphology changes effect the mMDFA.
Proximal deformation (NSA changes): a decreasing NSA leads to a decreasing mMDFA; Femoral bowing (FBA changes): an increasing FBA leads to a decreasing mMDFA. Distal deformation (aMDFA changes): a decreasing aMDFA leads to a decreasing mMDFA.
Table 1.
Intraclass correlation coefficient(ICC) of measurements.
Table 2.
Statistical description of variables.
Table 3.
Mean values of groups.
Fig 3.
Relations between variables (Female).
mMDFA: mechanical medial distal femoral angle; FBA: femoral bowing angle; NSA: neck-shaft angle; aMDFA: anatomic medial distal femoral angle.
Table 4.
Pearson correlation test between variables (female).
Table 5.
Pearson correlation test between variables (male).
Table 6.
Regression test between variables.
Fig 4.
With increasing age, the FBA increased, then the NSA and the aMDFA increased, which finally led to a decreased mMDFA.
A. Female, 37 years old, NSA = 133°, FBA = 0°, aMDFA = 96°, mMDFA = 94°. B. Female, 54 years old, NSA = 133°, FBA = 4°, aMDFA = 98°, mMDFA = 90°. C. Female, 63 years old, NSA = 138°, FBA = 7°, aMDFA = 99°, mMDFA = 88°. D. The proximal and distal deformities caused by femur bowing are very similar to the geometric changes in a curling book.