Anatomical axis validation of lower extremity for different deformities: A radiological study

Abstract

Aim: The aim of this study was to derive a pure, unbiased, reliable and accurate objective relationship between the local knee axis measurements through a short knee anteroposterior roentgenogram and the lower limb axis measurement through an orthoroentgenogram. Patients and Methods: Radiographs of 114 patients (114 knees) were evaluated by two independent raters for measurement of lower limb axis on an orthoroentgenogram and the local knee axis on short knee anteroposterior X-ray, which was derived by cropping the orthoroentgenogram by a blinded radiology assistant. The raters measured at two different time-points separated by an interval of 30-day period. Intra-rater and inter-rater reliabilities were calculated by intra-class correlation coefficients and three models were built to establish the relationships of X-ray anatomical axis with orthoroentgenogram anatomical axis, orthoroentgenogram anatomical axis with orthoroentgenogram mechanical axis and X-ray anatomical axis with orthoroentgenogram mechanical axis. Results: For three different measurements, intra-class correlation coefficients of Rater 2 were higher than 0.90 which shows perfect reliability, while that for Rater 1 was low. Furthermore, first measurements were more consistent than the second measurement. There was a strong positive correlation in all the three models except for varus cases in the last. Conclusion: The standardized correlation derived between the two different techniques for measuring knee alignment is fairly comparable with the studies in the past and would serve as a reliable template for future studies concerning relationships between the two, in addition to helping knee surgeons make more reliable and accurate interpretations through local knee axis measurements.

Non-weight-bearing short knee radiographs to evaluate coronal alignment before total knee arthroplasty

“…In our study, the correlation coefficient for varus knees was 0.650, which is close to Sheehy's (r=0.45). However, Unal et al's findings concerning the relationship to the varus knee were inconsistent with our own, and they found no correlation between the two methods for varus knees (6). Furthermore, we did not find any correlation between the two methods for neutral and valgus knees.…”

“…In this study, we found a strong positive correlation between FTA SKR and HKA (r=0.861). Notably, our Pearson coefficient results were higher than those in other studies (6,7,9). We believe that the more distant reference points of the femur and tibia which were close to the edge of the image could reduce the influence of femoral and tibial anatomical variations and promote the ability of FTA SKR to assess coronal alignment (18).…”

“…In practice, the femorotibial angle (FTA) is always measured on SKRs and is defined as the angle between the axis of the femur and tibia. Even if the hip and ankle joints are unable to be visualized in SKR, MA can still be calculated by putting FTA into the predictive equation (6)(7)(8). Although the application of FTA into the equation has not been widely accepted by the orthopedic community, it remains the best way to predict MA from a limited SKR.…”

Radiographic Evaluation of Pediatric Patients with Patellofemoral Instability

“…While clinical evaluation of limb alignment on examination provides initial screening, subtle deformities can be missed or hidden due to body habitus or ligamentous laxity. The standing orthoroentgenogram [30], a composite, often weight-bearing, lower extremity radiographic image, compliments the clinical limb alignment assessment, allowing a more precise determination of the anatomic and mechanical axes of the lower extremity [25,27,[31][32][33][34].…”