Lozano Rocio, Howell Stephen M, Hull Maury L
Department of Biomedical Engineering, University of California, Davis , Davis , CA , USA.
Department of Mechanical Engineering, University of California, Davis , Davis , CA , USA.
Comput Methods Biomech Biomed Engin. 2019 Nov;22(14):1144-1152. doi: 10.1080/10255842.2019.1644503. Epub 2019 Jul 26.
Closely approximating the functional flexion-extension (FE) axis of the tibiofemoral joint in 3D models of the femur is important when computing joint motions which are physiologic. The objectives were to 1) develop methods to approximate the functional FE axis based on fitting circles, a tapered cylinder, and spheres to the posterior condyles, 2) determine the repeatability and reproducibility of each method, and 3) determine limits of agreement between pairs of axes. For each method, the respective axis was determined in forty 3D bone models of the distal femur. Varus-valgus angles and internal-external axial angles were computed relative to standard planes. Repeatability and reproducibility were comparable for the tapered cylinder-based and sphere-based methods and better than that for the circle-based method. Limits of agreement were tightest when comparing the sphere-based and tapered cylinder-based axes. However, limits of agreement for the internal-external axial angle were wide at +3.6° to -3.9° whereas limits of agreement were tighter at +1.4° to -0.7° for the varus-valgus angle. The tapered cylinder-based and sphere-based methods offer advantages of better repeatability and reproducibility over the circle-based method. However, the sphere-based and tapered cylinder-based axes are not interchangeable owing to wide limits of agreement for the internal-external axial angle. The tapered cylinder-based axis is preferred intuitively over the sphere-based axis because the spheres require fitting in both the sagittal and coronal planes whereas the tapered cylinder requires fitting in the sagittal plane only which is the plane of motion in flexion-extension.
在股骨三维模型中紧密逼近胫股关节的功能屈伸（FE）轴，对于计算生理性关节运动非常重要。目的是：1）基于将圆、锥形圆柱体和球体拟合到后髁来开发逼近功能FE轴的方法；2）确定每种方法的可重复性和再现性；3）确定各轴对之间的一致性界限。对于每种方法，在四十个远端股骨的三维骨模型中确定相应的轴。相对于标准平面计算内翻-外翻角度和内外轴向角度。基于锥形圆柱体和基于球体的方法的可重复性和再现性相当，且优于基于圆的方法。比较基于球体和基于锥形圆柱体的轴时，一致性界限最窄。然而，内外轴向角度的一致性界限在+3.6°至-3.9°之间较宽，而内翻-外翻角度的一致性界限在+1.4°至-0.7°之间较窄。基于锥形圆柱体和基于球体的方法比基于圆的方法具有更好的可重复性和再现性优势。然而，由于内外轴向角度的一致性界限较宽，基于球体和基于锥形圆柱体的轴不可互换。直观上，基于锥形圆柱体的轴比基于球体的轴更受青睐，因为球体需要在矢状面和冠状面进行拟合，而锥形圆柱体仅需要在矢状面进行拟合，矢状面是屈伸运动的平面。
