The Arthritis Institute at Good Samaritan Hospital, 637 S Lucas Avenue, 5th Floor, Los Angeles, CA 90017, USA.
Clin Orthop Relat Res. 2011 Feb;469(2):429-36. doi: 10.1007/s11999-010-1554-7.
Offset in THA correlates to abductor muscle function, wear, and impingement. Femoral offset after THA is not independent of the cup center of rotation (COR) so hip offset, a combination of femoral offset and change in hip COR, becomes the important measurement.
QUESTIONS/PURPOSES: We therefore asked whether hip offset in arthritic hips would correlate with cup COR; whether offset could always be balanced within 6 mm of contralateral normal hips; and whether hip length could also be kept within 6 mm.
We compared hip offset of arthritic and contralateral normal hips on radiographs in 82 patients (82 hips) who had THA. We used computer navigation in all patients with the aim of reconstructing the hip offset and to compare hip offset change to the quantitative change of the hip COR.
The preoperative radiographic change to equalize the offset ranged from -12 to +21 mm (mean, 1.5); postoperatively the change was 1.4 ± 6.4 mm and was within ± 6 mm in 78 of 82 hips. As COR displaced superiorly from 3 to 6+ mm the offset had to be substantially increased. Only with COR 0-3 mm superior and 0-5 mm medial was offset always within 5 mm.
Hip offset reconstruction was directly related to the position of the hip COR, and navigation allowed quantitative control of offset and hip length.
THA 中的偏心距与外展肌功能、磨损和撞击有关。THA 后的股骨偏心距并不独立于杯中心旋转（COR），因此髋部偏心距（股骨偏心距与髋 COR 变化的组合）成为重要的测量指标。
问题/目的：因此，我们询问了关节炎髋关节的髋部偏心距是否与杯 COR 相关；是否可以在 6mm 范围内平衡对侧正常髋关节的偏心距；以及髋长是否也可以保持在 6mm 范围内。
我们比较了 82 例（82 髋）接受 THA 的关节炎和对侧正常髋关节的 X 线片上的髋部偏心距。我们在所有患者中使用计算机导航，旨在重建髋部偏心距，并比较髋部偏心距变化与髋 COR 的定量变化。
术前为了使偏心距相等，放射学上的改变范围从-12 到+21mm（平均 1.5mm）；术后改变为 1.4±6.4mm，82 髋中有 78 髋在±6mm 范围内。随着 COR 从 3 到 6+mm 向上移位，偏心距必须大大增加。只有当 COR 向上 0-3mm 和向内 0-5mm 时，偏心距才总是在 5mm 范围内。
髋部偏心距重建与髋 COR 的位置直接相关，导航允许对偏心距和髋长进行定量控制。
