Department of Orthopaedic Surgery, Inselspital Bern, University of Bern, Bern, Switzerland.
Clin Orthop Relat Res. 2019 May;477(5):1073-1083. doi: 10.1097/CORR.0000000000000610.
Correct quantification of femoral torsion is crucial to diagnose torsional deformities, make an indication for surgical treatment, or plan the amount of correction. However, no clear evaluation of different femoral torsion measurement methods for hips with excessive torsion has been performed to date.
QUESTIONS/PURPOSES: (1) How does CT-based measurement of femoral torsion differ among five commonly used measurement methods? (2) Do differences in femoral torsion among measurement methods increase in hips with excessive femoral torsion? (3) What is the reliability and reproducibility of each of the five torsion measurement methods?
Between March and August 2016, we saw 86 new patients (95 hips) with hip pain and physical findings suggestive for femoroacetabular impingement at our outpatient tertiary clinic. Of those, 56 patients (62 hips) had a pelvic CT scan including the distal femur for measurement of femoral torsion. We excluded seven patients (seven hips) with previous hip surgery, two patients (two hips) with sequelae of Legg-Calvé-Perthes disease, and one patient (one hip) with a posttraumatic deformity. This resulted in 46 patients (52 hips) in the final study group with a mean age of 28 ± 9 years (range, 17-51 years) and 27 female patients (59%). Torsion was compared among five commonly used assessment measures, those of Lee et al., Reikerås et al., Jarrett et al., Tomczak et al., and Murphy et al. They differed regarding the level of the anatomic landmark for the proximal femoral neck axis; the method of Lee had the most proximal definition followed by the methods of Reikerås, Jarrett, and Tomczak at the base of the femoral neck and the method of Murphy with the most distal definition at the level of the lesser trochanter. The definition of the femoral head center and of the distal reference was consistent for all five measurement methods. We used the method described by Murphy et al. as our baseline measurement method for femoral torsion because it reportedly most closely reflects true anatomic femoral torsion. With this method we found a mean femoral torsion of 28 ± 13°. Mean values of femoral torsion were compared among the five methods using multivariate analysis of variance. All differences between two of the measurement methods were plotted over the entire range of femoral torsion to evaluate a possible increase in hips with excessive femoral torsion. All measurements were performed by two blinded orthopaedic residents (FS, TDL) at two different occasions to measure intraobserver reproducibility and interobserver reliability using intraclass correlation coefficients (ICCs).
We found increasing values for femoral torsion using measurement methods with a more distal definition of the proximal femoral neck axis: Lee et al. (most proximal definition: 11° ± 11°), Reikerås et al. (15° ± 11°), Jarrett et al. (19° ± 11°), Tomczak et al. (25° ± 12°), and Murphy et al. (most distal definition: 28° ± 13°). The most pronounced difference was found for the comparison between the methods of Lee et al. and Murphy et al. with a mean difference of 17° ± 5° (95% confidence interval, 16°-19°; p < 0.001). For six of 10 possible pairwise comparisons, the difference between two methods increased with increasing femoral torsion and decreased with decreasing femoral torsion. We observed a fair-to-strong linear correlation (R range, 0.306-0.622; all p values < 0.05) for any method compared with the Murphy method and for the Reikerås and Jarrett methods when compared with the Tomczak method. For example, a hip with 10° of femoral antetorsion according Murphy had a torsion of 1° according to Reikerås, which corresponds to a difference of 9°. This difference increased to 20° in hips with excessive torsion; for example, a hip with 60° of torsion according to Murphy had 40° of torsion according to Reikerås. All five methods for measuring femoral torsion showed excellent agreement for both intraobserver reproducibility (ICC, 0.905-0.973) and interobserver reliability (ICC, 0.938-0.969).
Because the quantification of femoral torsion in hips with excessive femoral torsion differs considerably among measurement methods, it is crucial to state the applied methods when reporting femoral torsion and to be consistent regarding the used measurement method. These differences have to be considered for surgical decision-making and planning the degree of correction. Neglecting the differences among measurement methods to quantify femoral torsion can potentially lead to misdiagnosis and surgical planning errors.
Level IV, diagnostic study.
正确量化股骨扭转对于诊断扭转畸形、确定手术指征或计划矫正程度至关重要。然而，迄今为止，尚未对存在过度扭转的髋关节进行不同股骨扭转测量方法的明确评估。
问题/目的：（1）五种常用测量方法中，基于 CT 的股骨扭转测量有何不同？（2）测量方法之间的股骨扭转差异是否会随着股骨扭转的增加而增大？（3）五种扭转测量方法的可靠性和可重复性如何？
2016 年 3 月至 8 月期间，我们在我们的门诊三级诊所中看到了 86 名新的髋关节疼痛患者（95 髋）和体格检查提示股骨髋臼撞击症。其中，56 名患者（62 髋）接受了包括股骨远端在内的骨盆 CT 扫描，以测量股骨扭转。我们排除了 7 名（7 髋）曾接受过髋关节手术的患者、2 名（2 髋）Legg-Calvé-Perthes 病后遗症患者和 1 名（1 髋）创伤后畸形患者。这导致最终研究组有 46 名患者（52 髋），平均年龄 28 ± 9 岁（范围，17-51 岁），27 名女性患者（59%）。我们比较了 Lee 等、Reikerås 等、Jarrett 等、Tomczak 等和 Murphy 等五种常用评估方法的扭转情况。它们在近端股骨颈轴的解剖标志水平上有所不同；Lee 等方法的定义最接近股骨颈的基底部，其次是 Reikerås 等、Jarrett 等和 Tomczak 等方法，Murphy 等方法的定义最接近小转子的水平。五种测量方法的股骨头中心和远端参考定义均保持一致。我们使用 Murphy 等的方法作为我们的基线股骨扭转测量方法，因为它据报道最能反映真实的解剖股骨扭转。使用该方法，我们发现股骨扭转平均为 28 ± 13°。使用方差分析多变量比较五种方法之间的股骨扭转平均值。将两种测量方法之间的所有差异绘制在整个股骨扭转范围内，以评估在存在过度股骨扭转的髋关节中差异是否增加。所有测量均由两名盲法骨科住院医师（FS、TDL）在两个不同的场合进行，以使用组内相关系数（ICC）测量观察者内的可重复性和观察者间的可靠性。
我们发现，随着近端股骨颈轴定义更为远端的测量方法的使用，股骨扭转值逐渐增大：Lee 等（最接近股骨颈的定义：11° ± 11°）、Reikerås 等（15° ± 11°）、Jarrett 等（19° ± 11°）、Tomczak 等（25° ± 12°）和 Murphy 等（最远端的定义：28° ± 13°）。Lee 等方法和 Murphy 等方法之间的比较差异最大，平均差异为 17° ± 5°（95%置信区间，16°-19°；p < 0.001）。对于 10 种可能的两两比较中的 6 种，两种方法之间的差异随着股骨扭转的增加而增加，随着股骨扭转的减少而减少。与 Murphy 方法相比，任何方法与 Reikerås 和 Jarrett 方法相比，都与 Murphy 方法具有良好到较强的线性相关性（R 范围，0.306-0.622；所有 p 值均<0.05）。例如，根据 Murphy 方法，具有 10°股骨前扭转的髋关节，根据 Reikerås 方法，其扭转为 1°，对应差异为 9°。这种差异在存在过度扭转的髋关节中增加到 20°；例如，根据 Murphy 方法，扭转为 60°的髋关节，根据 Reikerås 方法，其扭转为 40°。五种股骨扭转测量方法在观察者内重复性（ICC，0.905-0.973）和观察者间可靠性（ICC，0.938-0.969）方面均具有优异的一致性。
由于在存在过度股骨扭转的髋关节中，股骨扭转的量化在测量方法之间存在显著差异，因此在报告股骨扭转时，必须说明所应用的方法，并在使用的测量方法上保持一致。手术决策和计划矫正程度都需要考虑这些差异。忽视量化股骨扭转的测量方法之间的差异可能导致误诊和手术计划错误。
IV 级，诊断研究。
