Davda Kinner, Smyth Niall, Cobb Justin P, Hart Alister J
Imperial College, Charing Cross Hospital , London , UK ;
Acta Orthop. 2015;86(4):485-90. doi: 10.3109/17453674.2015.1017791. Epub 2015 Feb 12.
2D analysis of metal-on-metal (MoM) hip arthroplasty (HA) has been conducted in several large series on conventional radiographs with the use of Ein Bild Roentegen Analyse (EBRA) software, but there have been no comparisons with 3D analysis in the literature. The main aim of this study was to quantify the agreement in measurements of cup version of large-diameter MoM hips obtained by EBRA and by 3D computed tomography (3D-CT). The secondary aim was to quantify the agreement for cup inclination. Lastly, we wanted to determine the inter- and intra-observer reliability of both methods.
87 MoM hips in 81 patients were analyzed for cup inclination and version in 2D on conventional radiographs using EBRA software. The results were compared with 3D measurements using CT.
Cup version was underestimated by EBRA when compared to 3D-CT, by 6° on average with the pelvis supine and by 8° on average with the pelvis orientated to the anterior pelvic plane (APP). For inclination, the mean difference was no more than 1°. 53% of hips were within a 10° safe zone of 45° inclination and 20° version when measured by 3D-CT with the pelvis supine (and 54% with the pelvis in the APP). The proportion was only 24% when measured by EBRA. Inter- and intra-observer reliability of cup version is poorer using 2D analysis than when using 3D-CT.
Errors in version in 2D were due to the difficulty in delineating the cup rim, which was obscured by a large-diameter metal head of the same radio-opacity. This can be overcome with 3D analysis. The present study demonstrates that measurements using EBRA have poor agreement and are less reliable than those with 3D-CT when measuring cup version and inclination in MoM hips.
已使用艾因·比尔德伦琴分析（EBRA）软件在传统X线片上对多个大型金属对金属（MoM）髋关节置换术（HA）系列进行了二维分析，但文献中尚无与三维分析的比较。本研究的主要目的是量化通过EBRA和三维计算机断层扫描（3D-CT）获得的大直径MoM髋关节髋臼外展角测量值的一致性。次要目的是量化髋臼倾斜度的一致性。最后，我们想确定两种方法的观察者间和观察者内可靠性。
使用EBRA软件在传统X线片上对81例患者的87个MoM髋关节进行二维髋臼倾斜度和外展角分析。将结果与使用CT的三维测量结果进行比较。
与3D-CT相比，EBRA低估了髋臼外展角，骨盆仰卧时平均低估6°，骨盆朝向骨盆前平面（APP）时平均低估8°。对于倾斜度，平均差异不超过1°。3D-CT测量骨盆仰卧位时，53%的髋关节髋臼倾斜度在45°、外展角在20°的10°安全区内（骨盆处于APP时为54%）。而EBRA测量时该比例仅为24%。二维分析时髋臼外展角的观察者间和观察者内可靠性比三维CT分析时更差。
二维分析中外展角的误差是由于难以勾勒髋臼边缘，其被具有相同X线不透射性的大直径金属股骨头遮挡。这可通过三维分析克服。本研究表明，在测量MoM髋关节的髋臼倾斜度和外展角时，使用EBRA的测量一致性较差且不如三维CT可靠。
