Snijders T E, Schlösser T P C, van Gaalen S M, Castelein R M, Weinans H, de Gast A
Department of Orthopaedics, Clinical Orthopedic Research Center - mN, Diakonessenhuis Zeist, Zeist, the Netherlands.
Department of Orthopaedics, UMC Utrecht, Utrecht, the Netherlands.
JB JS Open Access. 2018 Jul 12;3(3):e0063. doi: 10.2106/JBJS.OA.17.00063. eCollection 2018 Sep 25.
Acetabular cup orientation plays a key role in implant stability and the success of total hip arthroplasty. To date, the orientation has been measured with different imaging modalities and definitions, leading to lack of consensus on optimal cup placement. A 3-dimensional (3D) concept involving a trigonometric description enables unambiguous definitions. Our objective was to test the validity and reliability of a 3D trigonometric description of cup orientation.
Computed tomographic scans of the pelvis, performed for vascular assessment of 20 patients with 22 primary total hip replacements in situ, were systematically collected. On multiplanar reconstructions, 3 observers independently measured cup orientation retrospectively in terms of coronal inclination, sagittal tilt, and transverse version. The angles measured in 2 planes were used to calculate the angle in the third plane via a trigonometric algorithm. For correlation and reliability analyses, intraobserver and interobserver differences between measured and calculated angles were evaluated with use of the intraclass correlation coefficient (ICC).
Measured and calculated angles had ICCs of 0.953 for coronal inclination, 0.985 for sagittal tilt, and 0.982 for transverse version. Intraobserver and interobserver reliability had ICCs of 0.987 and 0.987, respectively, for coronal inclination; 0.979 and 0.981, respectively, for sagittal tilt; and 0.992 and 0.978, respectively, for transverse version.
The 3D concept with its trigonometric algorithm is a valid and reliable tool for the measurement of cup orientation.
By calculating the transverse version of cups from coronal inclination and sagittal tilt measurements, the trigonometric algorithm enables a 3D definition of cup orientation, regardless of the imaging modality used. In addition, it introduces sagittal tilt that, like pelvic tilt, rotates around the transverse axis.
髋臼杯的方向在植入物稳定性和全髋关节置换术的成功中起着关键作用。迄今为止，已使用不同的成像方式和定义来测量该方向，导致在髋臼杯的最佳放置方面缺乏共识。一个涉及三角描述的三维（3D）概念能够实现明确的定义。我们的目的是测试髋臼杯方向的三维三角描述的有效性和可靠性。
系统收集了20例原位植入22个初次全髋关节置换术患者的骨盆计算机断层扫描图像，用于血管评估。在多平面重建图像上，3名观察者根据冠状面倾斜度、矢状面倾斜度和横断面旋转角度，独立地对髋臼杯方向进行回顾性测量。通过三角算法，利用在两个平面上测量的角度来计算第三个平面上的角度。为了进行相关性和可靠性分析，使用组内相关系数（ICC）评估测量角度与计算角度之间的观察者内和观察者间差异。
冠状面倾斜度的测量角度与计算角度的ICC为0.953，矢状面倾斜度为0.985，横断面旋转角度为0.982。观察者内和观察者间的可靠性方面，冠状面倾斜度的ICC分别为0.987和0.987；矢状面倾斜度分别为0.979和0.981；横断面旋转角度分别为0.992和0.978。
具有三角算法的三维概念是测量髋臼杯方向的有效且可靠的工具。
通过根据冠状面倾斜度和矢状面倾斜度测量值计算髋臼杯的横断面旋转角度，三角算法能够对髋臼杯方向进行三维定义，而与所使用的成像方式无关。此外，它引入了矢状面倾斜度，该倾斜度如同骨盆倾斜度一样，围绕横轴旋转。
