Abstract
Weight-bearing long-leg radiographs are commonly used in orthopaedic surgery. Measured
parameters, however, change when radiographs are conducted in different rotational
positions of the leg. It was hypothesized that rotational errors are regularly present
in long-leg radiographs resulting in wrong measurements. In 100 consecutive long-leg
radiographs conducted according to the method of Paley, rotation was assessed by fibular
overlap. Angular parameters in radiographs (mechanical lateral proximal femoral angle
(mLPFA), mechanical lateral distal femoral angle (mLDFA), angle between the anatomical
and mechanical femoral axis (AMA), mechanical medial proximal tibia angle (mMPTA),
mechanical lateral distal tibial angle (mLDTA), and the mechanical femoral and tibial
axis (mFA–mTA) were measured and deviations related to malrotation calculated. An
average internal rotation of 8 degrees was found in lower limbs showing a range between
29 degrees of internal and 22 degrees of external rotation. As a result, mean differences
before and after rotational correction for measured parameters (mLPFA, mLDFA, AMA,
mMPTA, mLDTA, mFA–mTA) ranged between 0.4 and 1.7 degrees (−2.1; 5.6 95% confidence
interval [CI]). In conclusion, malrotation of lower limbs is regularly present in
long-leg radiographs. As all measured parameters are influenced by malrotation, correct
lower limb rotation needs to be verified.
Keywords
long-leg radiographs - weight-bearing - mMPTA - mLDFA - mLPFA - mLDTA - rotation -
rotational error - limb alignment - deformity
