Hunter Collin D R, Rosenthal Reece M, Froerer Devin L, Ihn Hansel E, Khalil Ameen Z, Featherall Joseph, Ernat Justin J, Maak Travis G, Aoki Stephen K
Department of Orthopaedics, University of Utah, Salt Lake City, Utah, USA.
Orthop J Sports Med. 2025 May 22;13(5):23259671251335982. doi: 10.1177/23259671251335982. eCollection 2025 May.
Accurate measurement of posterior tibial slope (PTS) is for understanding knee biomechanics and stability, as well as in planning surgical procedures. The validated methodology for measuring PTS requires outline visualization of 15 cm distal to the proximal tibia, a cutoff that is not always met on standard lateral knee radiographs.
PURPOSE/HYPOTHESIS: The goal of this study was to critically evaluate whether using a 10-cm anatomic axis on conventional lateral knee radiographs is comparable with the established 15-cm standard. The authors hypothesized that a shortened 10-cm anatomic axis would yield comparable results to the conventional 15-cm method.
Cohort study (diagnosis); Level of evidence, 3.
Lateral knee radiographs were reviewed until a cohort of 100 patients was identified where ≥15 cm of the tibial shaft distal to the joint line could be measured. PTS was calculated using both the conventional 15-cm proximal anatomic axis (15-PTS) and the proposed modified 10-cm axis (10-mPTS). Measurement reliability and agreement were quantitatively assessed via intraclass correlation coefficients (ICCs) and Bland-Altman analysis, respectively. Paired tests and linear regression were performed to evaluate the equivalence of methods. Additionally, a second set of 100 lateral knee radiographs was randomly selected to determine a percentage of radiographs that could be measured ≥15 cm below the joint line.
There was a statistically significant congruence between the 10-mPTS and 15-PTS techniques (ICC, 0.92; < .001). The mean PTS discrepancy was statistically significant at 0.94°, with a 95% CI ranging from 0.78° to 1.0°. Both methods demonstrated high inter- and intrarater reliability (ICCs > 0.90). On 61% of standard lateral knee radiographs queried, we were unable to visualize 15 cm of the proximal tibia.
The 10-mPTS method exhibits <1° of deviation compared with the conventional 15-PTS approach, establishing it as a practical and reliable alternative for assessing PTS on lateral knee radiographs, particularly when visualization of 15 cm distally is not possible.
准确测量胫骨后倾坡度（PTS）有助于理解膝关节生物力学和稳定性，也有助于手术方案的制定。经过验证的PTS测量方法需要显示胫骨近端以下15厘米的轮廓，但在标准的膝关节侧位X线片上，这一要求并非总能满足。
目的/假设：本研究的目的是严格评估在传统膝关节侧位X线片上使用10厘米的解剖轴是否与既定的15厘米标准具有可比性。作者假设缩短至10厘米的解剖轴将产生与传统15厘米方法相当的结果。
队列研究（诊断）；证据等级，3级。
回顾膝关节侧位X线片，直至确定100例患者的队列，这些患者的关节线远端胫骨轴可测量长度≥15厘米。使用传统的15厘米近端解剖轴（15-PTS）和提议的改良10厘米轴（10-mPTS）计算PTS。分别通过组内相关系数（ICC）和Bland-Altman分析对测量可靠性和一致性进行定量评估。进行配对t检验和线性回归以评估方法的等效性。此外，随机选择另一组100张膝关节侧位X线片，以确定关节线以下可测量长度≥15厘米的X线片百分比。
10-mPTS和15-PTS技术之间存在统计学上的显著一致性（ICC，0.92；P <.001）。PTS平均差异在统计学上显著，为0.94°，95%置信区间为0.78°至1.0°。两种方法均显示出较高的观察者间和观察者内可靠性（ICC > 0.90）。在61%的标准膝关节侧位X线片中，我们无法看到近端胫骨15厘米的长度。
与传统的15-PTS方法相比，10-mPTS方法的偏差小于1°，这使其成为评估膝关节侧位X线片上PTS的一种实用且可靠的替代方法，特别是在无法看到远端15厘米的情况下。
