A comparison of five approaches to measurement of anatomic knee alignment from radiographs

Abstract

Objective The recent recognition of the correlation of the hip-knee-ankle angle (HKA) with femur-tibia angle (FTA) on a standard knee radiograph has led to the increasing inclusion of FTA assessments in OA studies due to its clinical relevance, cost effectiveness and minimal radiation exposure. Our goal was to investigate the performance metrics of currently used methods of FTA measurement to determine whether a specific protocol could be recommended based on these results. Methods Inter- and intra-rater reliability of FTA measurements were determined by intraclass correlation coefficient (ICC) of two independent analysts. Minimal detectable differences were determined and the correlation of FTA and HKA was analyzed by linear regression. Differences among methods of measuring HKA were assessed by ANOVA. Results All five methods of FTA measurement demonstrated high precision by inter- and intra-rater reproducibility (ICCs≥0.93). All five methods displayed good accuracy, but after correction for the offset of FTA from HKA, the femoral notch landmark method was the least accurate. However, the methods differed according to their minimal detectable differences; the FTA methods utilizing the center of the base of the tibial spines or the center of the tibial plateau as knee center landmarks yielded the smallest minimal detectable differences (1.25° and 1.72° respectively) Conclusion All methods of FTA were highly reproducible, but varied in their accuracy and sensitivity to detect meaningful differences. Based on these parameters we recommend standardizing measurement angles with vertices at the base of the tibial spines or the center of the tibia and comparing single-point and two-point methods in larger studies.

Sensitivity of different measures of frontal plane alignment to medial and lateral joint space narrowing: From the osteoarthritis initiative

“…Concurrent validity between measurement methods was modest and consistent with previous studies [5][6][7][8][9][10][11]15,26], and correlations were similar when stratifying for sex and JSN. IranpourBoroujeni et al [12] reported correlations with HKA using the traditional FTA method (r ¼ 0.68) and the new FTA method (r ¼ 0.75), which were larger than those reported in the present study.…”

“…Underestimating the magnitude of alignment at both ends of the continuum further highlights the limited utility of this measurement tool, rendering goniometry inadequate for use in a clinical environment. Of the few studies that have evaluated the relationship between goniometry and radiographic alignment, poor consensus has been established [5,6,26]. This inconsistent evidence is most likely an outcome of the relatively large random error and potentially low precision of the goniometer measurement, as well as measurement variability between different studies.…”

The value of the intra-operative clinical mechanical axis measurement in open-wedge valgus high tibial osteotomies

“…Another possible explanation for the difference may also be due to observation errors when evaluating WLR's. This however does not appear to be a problem since HKA angle measurements on standing WLR are relatively reliable with a standard error of less than 1.5° [21].…”

Association of urinary metabolites with radiographic progression of knee osteoarthritis in overweight and obese adults: an exploratory study

“…The baseline KL scores did not differ significantly between the progressors and non-progressors (p=0.36). Because alignment may influence the risk of progression, we measured baseline alignment using the femur-tibia angle measure (method B) reported by McDaniel et al 24 . There was a difference in the mean baseline alignment angle but it was not significant due to the large variability (progressors 0.96±5.06, mean±SD, non-progressors −1.46±3.78; p=0.08).…”