Balcarek Peter, Hosseini Ali Seif Amir, Streit Ulrike, Brodkorb Tobias Franz, Walde Tim Alexander
Arcus Sportklinik, Rastatter Str. 17-19, 75179, Pforzheim, Germany.
Department of Trauma Surgery, Orthopedics and Plastic Surgery, University Medical Center Göttingen, Göttingen, Germany.
Arch Orthop Trauma Surg. 2018 Feb;138(2):267-272. doi: 10.1007/s00402-017-2838-0. Epub 2017 Nov 10.
In total knee arthroplasty the femoral posterior condylar offset (PCO) may serve as a potential branch for correct femoral component positioning. The technique of adjusting the sagittal magnetic resonance imaging (MRI)-scan on which it is measured has not been investigated in previous literature, but may be subject to variances due to knee joint positioning or axial localizer scan angulation. The purpose of this study was to investigate the effect of simulated femur rotation on the accuracy of PCO measurement.
Ten asymptomatic knee joints underwent MRI investigations. A sagittal plane perpendicular to the transepicondylar axis was defined as the true-sagittal plane (tsP). Sagittal images were reformatted in the tsP and angulated by 5° and - 5° in medial and lateral direction. In total each knee received three scans in 0°, 5° and - 5° axial localizer scan angulation. Medial and lateral PCO measurement was performed in each MRI-scan angulation.
Simulated external rotation decreased medial PCO size by 1.7 mm (95% CI 0.5994-3.127) (p = 0.012), and simulated internal rotation increased medial PCO size by 2.1 mm (95% CI 1.142-2.994) (p = 0.001). Lateral PCO size increased by 1.9 mm (95% CI 0.5660-3.412) and decreased by 2.1 mm (95% CI 1.142-2.994) with simulated external and internal rotation, respectively (p = 0.011; p = 0.0007).
This study shows the high sensitivity of medial and lateral PCO measurements to small changes of MRI axial localizer scan angulations simulating minor degrees of internal or external femur rotation. Thus, absolute PCO values should be interpreted with caution if the sagittal image acquisition is not standardized.
在全膝关节置换术中，股骨后髁偏移（PCO）可作为正确放置股骨组件的一个潜在参考指标。以往文献中尚未研究用于测量PCO的矢状面磁共振成像（MRI）扫描的调整技术，但由于膝关节位置或轴向定位扫描角度的不同，该测量可能存在差异。本研究的目的是探讨模拟股骨旋转对PCO测量准确性的影响。
对10个无症状膝关节进行MRI检查。将垂直于髁间轴的矢状面定义为真矢状面（tsP）。矢状面图像在tsP中重新格式化，并分别向内侧和外侧倾斜5°和-5°。每个膝关节总共接受0°、5°和-5°轴向定位扫描角度的三次扫描。在每个MRI扫描角度下进行内侧和外侧PCO测量。
模拟外旋使内侧PCO尺寸减小1.7mm（95%可信区间0.5994 - 3.127）（p = 0.012），模拟内旋使内侧PCO尺寸增加2.1mm（95%可信区间1.142 - 2.994）（p = 0.001）。模拟外旋和内旋时，外侧PCO尺寸分别增加1.9mm（95%可信区间0.5660 - 3.412）和减小2.1mm（95%可信区间1.142 - 2.994）（p = 0.011；p = 0.0007）。
本研究表明，模拟轻微程度的股骨内旋或外旋时，MRI轴向定位扫描角度的微小变化对内侧和外侧PCO测量具有高度敏感性。因此，如果矢状面图像采集未标准化，PCO的绝对值应谨慎解读。
