The impact of body-mass index on the frontal knee alignment estimation using three-dimensional reconstruction based on movement analysis

Background: We evaluated the influence of the body-mass index (BMI) on the estimation of the static frontal knee alignment (FKA) using three-dimensional (3D) reconstruction method based on movement analysis.

Methods: Two-hundred nineteen knees (120 individuals with end-stage osteoarthritis) were analyzed. The validity of the 3D method was evaluated under comparison with a reference method based on weight bearing full-leg length radiography. Extensive statistical analyses (Pearson's correlation, one-way ANOVA, linear regression, boxplot diagram) over four groups of BMI (normal, overweight, obese class I and obese classes II and III) were performed.

Results: For BMI below 25 kg/m², the validity of the 3D method was confirmed. For BMI over 25 kg/m², there was an increasing error of the 3D method, especially for the obese groups affected with a large varus alignment.

Conclusions: In a biomechanical context of movement analysis, the results of the study suggest that the 3D method may represent a satisfying alternative to the full-leg radiograph method with limitations regarding to BMI over 25 kg/m².