Department of Orthopedics, Balgrist University Hospital, University of Zurich, Forchstrasse 340, 8008, Zürich, Switzerland.
Institute for Biomechanics, ETH Zurich, Zurich, Switzerland.
BMC Musculoskelet Disord. 2020 Jun 30;21(1):418. doi: 10.1186/s12891-020-03449-1.
Deformity assessment and preoperative planning of realignment surgery are conventionally based on weight-bearing (WB) radiographs. However, newer technologies such as three-dimensional (3D) preoperative planning and surgical navigation with patient-specific instruments (PSI) rely on non-weight bearing (NWB) computed tomography (CT) data. Additionally, differences between conventional two-dimensional (2D) and 3D measurements are known. The goal of the present study was to systematically analyse the influence of WB and the measurement modality (2D versus 3D) on common WB-dependent measurements used for deformity assessment.
85 lower limbs could be included. Two readers measured the hip-knee-ankle angle (HKA) and the joint line convergence angle (JLCA) in 2D WB and 2D NWB radiographs, as well as in CT-reconstructed 3D models using an already established 3D measurement method for HKA, and a newly developed 3D measurement method for JLCA, respectively. Interrater and intermodality reliability was assessed.
Significant differences between WB and NWB measurements were found for HKA (p < 0.001) and JLCA (p < 0.001). No significant difference could be observed between 2D HKA NWB and 3D HKA (p = 0.09). The difference between 2D JLCA NWB and 3D JLCA was significant (p < 0.001). The intraclass correlation coefficient (ICC) for the interrater agreement was almost perfect for all HKA and 3D JLCA measurements and substantial for 2D JLCA WB and 2D JLCA NWB. ICC for the intermodality agreement was almost perfect between 2D HKA WB and 2D HKA NWB as well as between 2D HKA NWB and 3D HKA, whereas it was moderate between 2D JLCA WB and 2D JLCA NWB and between 2D JLCA NWB and 3D JLCA.
Limb loading results in significant differences for both HKA and JLCA measurements. Furthermore, 2D projections were found to be insufficient to represent 3D joint anatomy in complex cases. With an increasing number of surgical approaches based on NWB CT-reconstructed models, research should focus on the development of 3D planning methods that consider the effects of WB on leg alignment.
传统的畸形评估和矫正手术术前规划都是基于负重位（weight-bearing，WB）X 线片。然而，新的技术，如三维（three-dimensional，3D）术前规划和使用患者特定器械（patient-specific instruments，PSI）的手术导航，都依赖于非负重位（non-weight-bearing，NWB）计算机断层扫描（computed tomography，CT）数据。此外，二维（two-dimensional，2D）和三维（three-dimensional，3D）测量之间的差异也是已知的。本研究的目的是系统分析负重位（weight-bearing，WB）和测量方式（二维 versus 三维）对用于畸形评估的常见依赖于负重位（weight-bearing，WB）的测量的影响。
共纳入 85 条下肢。两名观察者分别在二维负重位（2D WB）和二维非负重位（2D NWB）X 线片以及通过已经建立的用于测量髋关节-膝关节-踝关节角（hip-knee-ankle angle，HKA）的 3D 测量方法和新开发的用于测量关节线会聚角（joint line convergence angle，JLCA）的 3D 测量方法的 CT 重建 3D 模型上测量 HKA 和 JLCA。评估了观察者间和测量方式间的可靠性。
HKA（p<0.001）和 JLCA（p<0.001）的负重位（weight-bearing，WB）和非负重位（non-weight-bearing，NWB）测量值之间存在显著差异。2D NWB HKA 与 3D HKA 之间无显著差异（p=0.09）。2D JLCA NWB 与 3D JLCA 之间的差异具有统计学意义（p<0.001）。HKA 和所有 3D JLCA 测量的观察者间一致性的组内相关系数（intraclass correlation coefficient，ICC）几乎为完美，2D JLCA WB 和 2D JLCA NWB 的 ICC 为高度一致。2D HKA WB 和 2D HKA NWB 之间以及 2D HKA NWB 和 3D HKA 之间的测量方式间一致性的 ICC 几乎为完美，而 2D JLCA WB 和 2D JLCA NWB 之间以及 2D JLCA NWB 和 3D JLCA 之间的 ICC 为中度一致。
肢体负重会导致 HKA 和 JLCA 测量值出现显著差异。此外，在复杂病例中，二维投影被发现不足以代表 3D 关节解剖结构。随着越来越多的手术方法基于非负重位 CT 重建模型，研究应集中于开发考虑负重对腿部对线影响的 3D 规划方法。
