The University of Sydney, Sydney Musculoskeletal Health and The Kolling Institute, Northern Clinical School, Faculty of Medicine and Health and the Northern Sydney Local Health District, Sydney, NSW, Australia.
Central Clinical School, Sydney Medical School, Faculty of Medicine and Health, the University of Sydney, Sydney, Australia.
Clin Orthop Relat Res. 2023 Oct 1;481(10):1928-1936. doi: 10.1097/CORR.0000000000002650. Epub 2023 Apr 18.
The accurate measurement of pelvic tilt is critical in hip and spine surgery. A sagittal pelvic radiograph is most often used to measure pelvic tilt, but this radiograph is not always routinely obtained and does not always allow the measurement of pelvic tilt because of problems with image quality or patient characteristics (such as high BMI or the presence of a spinal deformity). Although a number of recent studies have explored the correlation between pelvic tilt and the sacro-femoral-pubic angle using AP radiographs (SFP method), which aimed to estimate pelvic tilt without a sagittal radiograph, disagreement remains about whether the SFP method is sufficiently valid and reproducible for clinical use.
QUESTIONS/PURPOSES: The purpose of this meta-analysis was to evaluate the correlation between SFP and pelvic tilt in the following groups: (1) overall cohort, (2) male and female cohort, and (3) skeletally mature and immature cohorts (young and adult groups, defined as patients older or younger than 20 years). Additionally, we assessed (4) the errors of SFP-estimated pelvic tilt angles and determined (5) measurement reproducibility using the intraclass correlation coefficient.
This meta-analysis was reported in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines and registered in PROSPERO (record ID: CRD42022315673). PubMed, Embase, Cochrane, and Web of Science were screened in July 2022. The following keywords were used: sacral femoral pubic, sacro femoral pubic, or SFP. The exclusion criteria were nonresearch articles such as commentaries or letters and studies that only investigated relative pelvic tilt rather than absolute pelvic tilt. Although the included studies had different patient recruitment strategies, study quality-wise, they all used an adequate amount of radiographs for landmark annotation and applied a correlation analysis for the relationship between the SFP angle and pelvic tilt. Thus, no risk of bias was found. Participant differences were mitigated via subgroup and sensitivity analyses to remove outliers. Publication bias was assessed using the p value of a two-tailed Egger regression test for the asymmetry of funnel plots, as well as the Duval and Tweedie trim and fill method for potential missing publications to impute true correlations. The extracted correlation coefficients r were pooled using the Fisher Z transformation with a significance level of 0.05. Nine studies were included in the meta-analysis, totaling 1247 patients. Four studies were used in the sex-controlled subgroup analysis (312 male and 460 female patients), and all nine studies were included in the age-controlled subgroup analysis (627 adults and 620 young patients). Moreover, a sex-controlled subgroup analysis was conducted in two studies with only young cohorts (190 young male patients and 220 young female patients).
The overall pooled correlation coefficient between SFP and pelvic tilt was 0.61, with high interstudy heterogeneity (I 2 = 76%); a correlation coefficient of 0.61 is too low for most clinical applications. The subgroup analysis showed that the female group had a higher correlation coefficient than the male group did (0.72 versus 0.65; p = 0.03), and the adult group had a higher correlation coefficient than the young group (0.70 versus 0.56; p < 0.01). Three studies reported erroneous information about the measured pelvic tilt and calculated pelvic tilt from the SFP angle. The mean absolute error was 4.6° ± 4.5°; in one study, 78% of patients (39 of 50) were within 5° of error, and in another study, the median absolute error was 5.8º, with the highest error at 28.8° (50 female Asian patients). The intrarater intraclass correlation coefficients ranged between 0.87 and 0.97 for the SFP angle and between 0.89 and 0.92 for the pelvic tilt angle, and the interrater intraclass correlation coefficients ranged between 0.84 and 1.00 for the SFP angle and 0.76 and 0.98 for the pelvic tilt angle. However, large confidence intervals were identified, suggesting considerable uncertainty in measurement at the individual radiograph level.
This meta-analysis of the best-available evidence on this topic found the SFP method to be unreliable to extrapolate sagittal pelvic tilt in any patient group, and it was especially unreliable in the young male group (defined as patients younger than age 20 years). Correlation coefficients generally were too low for clinical use, but we remind readers that even a high correlation coefficient does not alone justify clinical application of a metric such as this, unless further subgroup analyses find low error and low heterogeneity, which was not the case here. Further ethnicity-segregated subgroup analyses with age, sex, and diagnosis controls could be useful in the future to determine whether there are some subgroups in which the SFP method is useful.
Level III, diagnostic study.
在髋关节和脊柱手术中，准确测量骨盆倾斜至关重要。通常使用矢状骨盆 X 光片来测量骨盆倾斜，但由于图像质量或患者特征（如高 BMI 或脊柱畸形）的问题，并非总是常规获取此 X 光片，并且并非总是可以测量骨盆倾斜。尽管最近有许多研究使用前后位 X 光片（SFP 法）探讨了骨盆倾斜与骶髂耻股角之间的相关性，旨在无需矢状位 X 光片的情况下估计骨盆倾斜，但对于 SFP 法是否足以用于临床使用，其有效性和可重复性仍存在争议。
本荟萃分析的目的是评估以下各组 SFP 与骨盆倾斜之间的相关性：（1）总体队列，（2）男性和女性队列，以及（3）骨骼成熟和不成熟队列（年轻和成年组，定义为年龄大于或小于 20 岁的患者）。此外，我们评估了（4）SFP 估计的骨盆倾斜角度的误差，并使用组内相关系数确定了（5）测量的可重复性。
本荟萃分析按照系统评价和荟萃分析的首选报告项目（PRISMA）指南进行报告，并在 PROSPERO（记录 ID：CRD42022315673）中进行了注册。2022 年 7 月，我们对 PubMed、Embase、Cochrane 和 Web of Science 进行了筛选。使用了以下关键词：骶髂耻股，骶髂耻股，或 SFP。排除标准是非研究性文章，如评论或信函，以及仅研究相对骨盆倾斜而不是绝对骨盆倾斜的研究。尽管纳入的研究有不同的患者招募策略，但在研究质量方面，它们都使用了足够数量的 X 光片进行地标注释，并应用相关分析来研究 SFP 角度与骨盆倾斜之间的关系。因此，没有发现偏倚风险。通过亚组和敏感性分析来减轻参与者差异，以消除异常值。使用双尾 Egger 回归检验漏斗图的不对称性来评估发表偏倚，并使用 Duval 和 Tweedie 修剪和填充方法来评估潜在的缺失出版物，以估算真实的相关性。提取的相关系数 r 使用 Fisher Z 变换进行汇总，显著性水平为 0.05。共纳入 9 项研究，总计 1247 名患者。其中 4 项研究用于性别对照亚组分析（312 名男性和 460 名女性患者），所有 9 项研究均纳入年龄对照亚组分析（627 名成年患者和 620 名年轻患者）。此外，还对仅包含年轻队列的两项研究进行了性别对照亚组分析（190 名年轻男性患者和 220 名年轻女性患者）。
SFP 和骨盆倾斜之间的总体汇总相关系数为 0.61，具有高度的组间异质性（I 2 = 76%）；0.61 的相关系数对于大多数临床应用来说太低了。亚组分析显示，女性组的相关系数高于男性组（0.72 与 0.65；p = 0.03），成年组的相关系数高于年轻组（0.70 与 0.56；p < 0.01）。有 3 项研究报告了有关测量骨盆倾斜和从 SFP 角度计算骨盆倾斜的错误信息。平均绝对误差为 4.6°±4.5°；在一项研究中，50 名患者中有 78%（39 名）的误差在 5°以内，另一项研究中，中位数绝对误差为 5.8°，最高误差为 28.8°（50 名亚洲女性）。SFP 角度的组内相关系数范围为 0.87 至 0.97，骨盆倾斜角度的组内相关系数范围为 0.89 至 0.92，SFP 角度的组间相关系数范围为 0.84 至 1.00，骨盆倾斜角度的组间相关系数范围为 0.76 至 0.98。然而，置信区间较大，表明在个体 X 光片水平上的测量存在相当大的不确定性。
本荟萃分析对该主题的最佳可用证据进行了评估，发现 SFP 方法在任何患者群体中都不可靠，无法推断矢状位骨盆倾斜，尤其是在年轻男性组（定义为年龄小于 20 岁的患者）中。相关系数通常太低，无法用于临床应用，但我们提醒读者，即使相关系数很高，也不能单独证明这样的指标（如 SFP 方法）可以用于临床，除非进一步的亚组分析发现误差低且异质性低，但在本研究中并未发现这种情况。未来可能需要进一步进行种族隔离的亚组分析，结合年龄、性别和诊断控制，以确定 SFP 方法在哪些亚组中有用。
III 级，诊断研究。
