Department of Orthopaedics, Charité-University Medicine, Berlin, Germany.
Int Orthop. 2011 Jul;35(7):981-7. doi: 10.1007/s00264-010-1047-z. Epub 2010 Jun 13.
Adequate stem alignment is essential for the success of Total Hip Arthroplasty (THA) to avoid dislocation and impingement. One factor that has not been sufficiently investigated so far is the stem tilting in the sagittal plane, which has an influence on the position of the centre of the femoral head and thus also on prosthesis torsion. We aimed to evaluate sagittal stem position using 3D-CTs in patients with THA and to develop a mathematical-geometrical model to simulate the functional correlation between sagittal stem tilting and the influence on functional anteversion. Thirty patients with THA underwent a CT-scan. By 3D-reconstruction of the CT-data, femoral-/prosthesis-axis, torsion and sagittal tilt were determined. In accordance with the position of the femoral and prosthesis axes, the rotatory (rAV) (surgically adjusted) and functional (depending on sagittal tilt) anteversion (fAV) was measured. A three dimentional-coordinate transformation was also performed using the Euler-angles to derive a mathematical-geometrical correlation between sagittal stem tilting and corresponding influence on anteversion. The mean rAV was 8° (-11.6-26°), the fAV 18° (6.2-37°), and the difference 10° (8.8-18°). The mean degree of stem tilting was 5.2° (0.7-9°) anterior towards the femoral axis. The individually measured parameters are reflected in the mathematical-geometrical model. Depending on the extent of the sagittal deviation, a clear influence on the torsion emerges. For example, a stem implanted at a 15° anteverted angle with a sagittal tilt by two degrees towards anterior results in a fAV of 20°. A clear association between the sagittal stem alignment and the impact on the fAV was demonstrated. Hence, the rotatory anteversion intended by the surgeon may be functionally significantly different. This might pose an increased risk of dislocation or impingement. The sagittal tilt of the prosthesis should therefore be considered in the context of impingement and dislocation diagnosis. In this respect, we recommend a 3D-analysis of stem alignment.
人工髋关节置换术（THA）的成功需要充分的股骨柄对线，以避免脱位和撞击。到目前为止，一个尚未得到充分研究的因素是矢状面中的股骨柄倾斜，这会影响股骨头中心的位置，从而也会影响假体的扭转。我们旨在通过 3D-CT 评估 THA 患者的矢状面股骨柄位置，并建立一个数学几何模型来模拟矢状面股骨柄倾斜与功能前倾角影响之间的功能相关性。30 例 THA 患者接受 CT 扫描。通过 CT 数据的 3D 重建，确定了股骨/假体轴、扭转和矢状倾斜。根据股骨和假体轴的位置，测量了旋转（rAV）（手术调整）和功能（取决于矢状倾斜）前倾角（fAV）。还使用欧拉角进行了三维坐标变换，以得出矢状面股骨柄倾斜与相应前倾角影响之间的数学几何相关性。rAV 的平均值为 8°（-11.6-26°），fAV 的平均值为 18°（6.2-37°），差异为 10°（8.8-18°）。股骨柄倾斜的平均程度为 5.2°（0.7-9°）朝向股骨轴前方。个体测量的参数反映在数学几何模型中。根据矢状偏差的程度，明显会对扭转产生影响。例如，植入矢状面倾斜 2 度向前的 15°前倾角的股骨柄会导致 fAV 为 20°。证明了矢状面股骨柄对线与对 fAV 的影响之间存在明显的关联。因此，外科医生期望的旋转前倾角在功能上可能有很大差异。这可能会增加脱位或撞击的风险。因此，在撞击和脱位诊断中应考虑假体的矢状倾斜。在这方面，我们建议对股骨柄对线进行 3D 分析。
