Long leg radiographs underestimate the degree of constitutional varus limb alignment and joint line obliquity in comparison with computed tomography: a radiographic study.

Purpose: The purpose of this study was to understand if differences exist between computed tomography (CT) and long leg radiographs (LLR) when defining coronal plane alignment of the lower limb in total knee arthroplasty (TKA). It aimed to identify any such differences between the two imaging modalities by quantifying constitutional limb alignment (arithmetic hip-knee-ankle angle (aHKA), joint line obliquity (JLO) and Coronal Plane Alignment of the Knee (CPAK) type within the same population.

Methods: A retrospective radiographic study compared pre-operative LLR and CT measurements in patients undergoing robotic-assisted TKA.