Abstract
BackgroundPrecise measurement of lateral femoral bowing is important to achieve postoperative lower limb alignment. We aimed to investigate factors that affect the precision of the radiographic lateral femoral bowing (RLFB) angle using three-dimensional (3D) models and whether the angle affects surgery design.MethodsForty femurs in total were divided into two groups based on their preoperative RLFB angle. The flexion contracture angle, preoperative and postoperative RLFB angles, and intersection angle between the mechanical and anatomical axes were compared. The angle between the arc and sagittal planes, varus and valgus angles, and intersection angle between the mechanical and anatomical axes were measured on a 3D model.ResultsThere was no significant between-group difference in 3D model measurements of the angle between the arc and sagittal planes (p = 0.327). There was no significant difference between the mechanical and anatomical axes measured by both imaging modalities (p > 0.258). When the RLFB was >5°, the flexion contracture angle and radiographic femoral bowing angle were positively correlated (r = 0.535, p < 0.05). Distal femur varus and valgus angles significantly differed between the two groups (p = 0.01). After total knee arthroplasty, the radiographic femoral bowing angle decreased significantly. When the cases’ radiographic femoral bowing angle is larger and the angle between the arc and sagittal planes is smaller as measured in 3D models, the angle between the arc and coronal planes is larger.ConclusionThe radiographic femoral bowing angle does not reflect the actual size of lateral femoral bowing, does not greatly affect surgery design, and is greatly affected by flexion contracture deformity. A RLFB angle larger than 15° indicates real lateral femoral bowing.
Highlights
Precise measurement of lateral femoral bowing is important to achieve postoperative lower limb alignment
Akamatsu et al reported that computed tomography (CT)-based measurements of lateral femoral bowing are much smaller than radiographybased measurements [7]
Few studies have investigated the factors affecting the difference between the lateral femoral bowing angle measured on radiographs and 3D models and whether femoral lateral bowing measured on radiographs affects the angle between the mechanical and anatomical axes measured on 3D models
Summary
Precise measurement of lateral femoral bowing is important to achieve postoperative lower limb alignment. We aimed to investigate factors that affect the precision of the radiographic lateral femoral bowing (RLFB) angle using three-dimensional (3D) models and whether the angle affects surgery design. Preoperative planning based on long-leg weight-bearing anterior radiography aims to restore the alignment [3]. Precise femoral alignment relies on accurate femoral resection which depends on the angle between the mechanical and anatomical axes measured on a preoperative long-leg weight-bearing anterior. Li et al Journal of Orthopaedic Surgery and Research (2017) 12:92 design should rely on both radiographic measurement of lateral femoral bowing and 3D measurements [6, 9]. Few studies have investigated the factors affecting the difference between the lateral femoral bowing angle measured on radiographs and 3D models and whether femoral lateral bowing measured on radiographs affects the angle between the mechanical and anatomical axes measured on 3D models
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